CYME is now part of the Energy Automation Solutions (“EAS”) group within Cooper Power Systems
Posted on December 5, 2008
Cooper announces the acquisition of CYME International. “This acquisition complements Cooper Power Systems’ ability to provide utility customers with comprehensive smartgrid solutions to improve power quality, reliability and efficiency in their transmission and distribution networks,” said Cooper Industries Chairman and Chief Executive Officer Kirk S. Hachigian.
“This is a natural integration of two companies who know that the smart grid is a business driver for utilities,” adds Marc Coursol, President and CEO of CYME. Press Release.
CYME International T&D is a world-class Power Engineering Solutions provider with an established reputation for customer responsiveness and technical expertise. Solutions stand behind thousands of T&D projects in over 100 countries around the world.
CYME offers an extensive line of Power Engineering Software that feature some of the most advanced analysis tools for transmission, distribution and industrial power systems.
Saturday, December 27, 2008
Tuesday, December 23, 2008
Reference platform for simplifying 'smart' electric power metering
Paper source from: http://dataweek.co.za/news.aspx?pklNewsId=19121&pklCategoryID=46
Supplied by avnet kopp
www.avnet.co.za
Tel +27 (0)11 809 6100
Fax +27 (0)11 444 1706
Email sales@avnet.co.za
STMicroelectronics has introduced a reference design platform for the electronic power meter market. Electronic energy meters are replacing traditional electromechanical meters because their versatility and low-cost allows manufacturers to implement many features that were impractical with the older mechanical designs.
For example, an electronic design can protect against meter tampering and theft of service. It can also measure and record energy usage at different times of the day, so utilities can bill based on time of usage. Also, automatic meter reading (AMR) can be enabled, transmitted information to the utility over a power line communications link.The reference platform provides a modular solution that can be adapted by software to meet particular needs.
It comprises two PCBs, one dedicated to the mains power measurement functions and one implementing sophisticated computational and supervisory functions. The measurement board supports all current measurement technologies, from the most accurate Rogowski coils to inexpensive shunt resistors. It can monitor both Live and Neutral current for tamper detection and complies with international standards for metering equipment (AC).
The Measurement Board is based on ST's STPM01 power metering chip, which includes all necessary signal conditioning, processing, data conversion, input/output signals and voltage reference. The STPM01 can be used as a standalone device in 1-phase kWh meters or as a peripheral in microprocessor-based 1- or 3-phase energy meters, in which case active, reactive and apparent energy, Vrms, Irms, instantaneous voltage and current, and line frequency readings are available through the SPI bus. The Control Board is based on an ST7 microcontroller and is supplied with a library of C-code software, with many additional software routines (available free from the ST website).
The microcontroller communicates with the STMP01 ASSP via SPI interface, allowing easy customisation of metering functions with included PC software. The reference design also includes the M41ST87 realtime clock chip, a 256 Kbit serial SPI bus EEPROM and a dedicated 32-character alphanumeric LCD with on-glass driver.
Supplied by avnet kopp
www.avnet.co.za
Tel +27 (0)11 809 6100
Fax +27 (0)11 444 1706
Email sales@avnet.co.za
STMicroelectronics has introduced a reference design platform for the electronic power meter market. Electronic energy meters are replacing traditional electromechanical meters because their versatility and low-cost allows manufacturers to implement many features that were impractical with the older mechanical designs.
For example, an electronic design can protect against meter tampering and theft of service. It can also measure and record energy usage at different times of the day, so utilities can bill based on time of usage. Also, automatic meter reading (AMR) can be enabled, transmitted information to the utility over a power line communications link.The reference platform provides a modular solution that can be adapted by software to meet particular needs.
It comprises two PCBs, one dedicated to the mains power measurement functions and one implementing sophisticated computational and supervisory functions. The measurement board supports all current measurement technologies, from the most accurate Rogowski coils to inexpensive shunt resistors. It can monitor both Live and Neutral current for tamper detection and complies with international standards for metering equipment (AC).
The Measurement Board is based on ST's STPM01 power metering chip, which includes all necessary signal conditioning, processing, data conversion, input/output signals and voltage reference. The STPM01 can be used as a standalone device in 1-phase kWh meters or as a peripheral in microprocessor-based 1- or 3-phase energy meters, in which case active, reactive and apparent energy, Vrms, Irms, instantaneous voltage and current, and line frequency readings are available through the SPI bus. The Control Board is based on an ST7 microcontroller and is supplied with a library of C-code software, with many additional software routines (available free from the ST website).
The microcontroller communicates with the STMP01 ASSP via SPI interface, allowing easy customisation of metering functions with included PC software. The reference design also includes the M41ST87 realtime clock chip, a 256 Kbit serial SPI bus EEPROM and a dedicated 32-character alphanumeric LCD with on-glass driver.
Monday, December 15, 2008
Overview: Online Measurements of Transformer Fault Gases
Thomas, Waters, B.S. Chemist
Kristin Williamson, M.S. Chemist
Dr. Douglas Ritchie, PhD Physicist
SERVERON, INC
The dissolved gas analysis technique (DGA) is well known to the transformer engineering community. Equally well known are some of the limitations of this method for analyzing transformer fault gases (H2, O2, CO, CO2, CH4, C2H2, C2H4, C2H6). Further, it is widely knownthat knowledge of the concentrations of these gases dissolved in oil (especially the combustible gases) is critical to safe transformer operation and management.
Serveron has developed and deployed an online system that eliminates most of the aforementioned limitations and a system that provides near real time information on transformer gassing, with an ability to access this data from a remote location.
FUNDAMENTALS
If the transformer is a conservator design, there of course is no headspace. In these cases the analysis must be done by direct contact with the oil in the transformer main body. However, in the case of a headspace transformer, one has a choice. Measurements can be made utilizing a sample of gas taken from the headspace (especially if the transformer has a leak tight or low leakheadspace) or the measurements can be made from the oil.
Both will provide data on existing transformer fault gases. This paper presents data taken from a headspace transformer simultaneously outfitted with both types of analysis equipment – a headspace analyzer and an oilphase analyzer.
The questions of merit that are addressed in this paper are:
· Details on the instrumentation utilized
· Details concerning the subject transformer
· A clear description of the installations used to gather these measurements
· Precision measurements of gas-in-gas (transformed to oil equivalents) for all eight fault gases
· Precision measurements of gas-in-oil for all eight fault gases
· Comparisons of the two measurement techniques, with conclusions as to any differences seen between the two types of instrumentation, and conclusions about the dynamics oftransformer fault gases.
for INSTRUMENTATION UTILIZED and DATA ANALYSIS please visit EPRI or
http://www.bplglobal.net/eng/knowledge-center/download.aspx?id=206
SERVERON (EPRI Substation Equipment Diagnostics Conference (2/2001))
Kristin Williamson, M.S. Chemist
Dr. Douglas Ritchie, PhD Physicist
SERVERON, INC
The dissolved gas analysis technique (DGA) is well known to the transformer engineering community. Equally well known are some of the limitations of this method for analyzing transformer fault gases (H2, O2, CO, CO2, CH4, C2H2, C2H4, C2H6). Further, it is widely knownthat knowledge of the concentrations of these gases dissolved in oil (especially the combustible gases) is critical to safe transformer operation and management.
Serveron has developed and deployed an online system that eliminates most of the aforementioned limitations and a system that provides near real time information on transformer gassing, with an ability to access this data from a remote location.
FUNDAMENTALS
If the transformer is a conservator design, there of course is no headspace. In these cases the analysis must be done by direct contact with the oil in the transformer main body. However, in the case of a headspace transformer, one has a choice. Measurements can be made utilizing a sample of gas taken from the headspace (especially if the transformer has a leak tight or low leakheadspace) or the measurements can be made from the oil.
Both will provide data on existing transformer fault gases. This paper presents data taken from a headspace transformer simultaneously outfitted with both types of analysis equipment – a headspace analyzer and an oilphase analyzer.
The questions of merit that are addressed in this paper are:
· Details on the instrumentation utilized
· Details concerning the subject transformer
· A clear description of the installations used to gather these measurements
· Precision measurements of gas-in-gas (transformed to oil equivalents) for all eight fault gases
· Precision measurements of gas-in-oil for all eight fault gases
· Comparisons of the two measurement techniques, with conclusions as to any differences seen between the two types of instrumentation, and conclusions about the dynamics oftransformer fault gases.
for INSTRUMENTATION UTILIZED and DATA ANALYSIS please visit EPRI or
http://www.bplglobal.net/eng/knowledge-center/download.aspx?id=206
SERVERON (EPRI Substation Equipment Diagnostics Conference (2/2001))
Saturday, December 13, 2008
Comprehensive Links for transformer standard index
MSC provides indexed standards about transformers, which could be a good reference for standards index overview.
From the MSC link pages, both Chinese and English are arranged in columns, with simple description. vistors can view international standards index, such as IEC, IEEE, and national standards index, such as NF, EN, ANSI,BS,DIN,GB,JIS and so on.
Some of the latest standards index collected here are:
ANSI C12.9-2005
Test Switches for Transformer-Rated Meters
ANSI/IEEE C57.12.01-2005
Standard General Requirements for Dry-Type Distribution and Power Transformers Including Those with Solid-Cast and/or Resin Encapsulated Windings
ANSI/IEEE C57.125-2005
Guide for Failure Investigation, Documentation, and Analysis for Power Transformers and Shunt Reactors
ANSI/IEEE C57.13-2003
Standard Requirements for Instrument Transformers
ANSI/IEEE C57.13.2-2005
Standard Conformance Test Procedure for Instrument Transformers
ANSI/IEEE C57.13.6-2005
Standard for High Accuracy Instrument Transformers
ANSI/IEEE C57.94-2000
Recommended Practice for Installation, Application, Operation, and Maintenance of Dry-Type General-Purpose Distribution and Power Transformers
ASTM A 1009-2005
Standard Specification for Soft Magnetic MnZn Ferrite Core Materials for High Frequency (10 kHz-1 MHz) Power Transformer and Filter Inductor Applications
UL 1876-2001
Isolating signal and feedback transformers for use in electronic equipment
IEC 60044-1 Edition 1.2-2003
Instrument transformers - Part 1: Current transformers
IEC 60076-5-2006
Power transformers - Part 5: Ability to withstand short circuit
IEC/TS 60076-14-2004
Power transformers - Part 14: Design and application of liquid-immersed power transformers using high-temperature insulation materials
ANSI/IEEE C57.119-2002
Recommended Practice for Performing Temperature Rise Tests on Oil Immersed Power Transformers at Loads Beyond Nameplate Ratings
To view comprehensive index, please visit MSC links.
From the MSC link pages, both Chinese and English are arranged in columns, with simple description. vistors can view international standards index, such as IEC, IEEE, and national standards index, such as NF, EN, ANSI,BS,DIN,GB,JIS and so on.
Some of the latest standards index collected here are:
ANSI C12.9-2005
Test Switches for Transformer-Rated Meters
ANSI/IEEE C57.12.01-2005
Standard General Requirements for Dry-Type Distribution and Power Transformers Including Those with Solid-Cast and/or Resin Encapsulated Windings
ANSI/IEEE C57.125-2005
Guide for Failure Investigation, Documentation, and Analysis for Power Transformers and Shunt Reactors
ANSI/IEEE C57.13-2003
Standard Requirements for Instrument Transformers
ANSI/IEEE C57.13.2-2005
Standard Conformance Test Procedure for Instrument Transformers
ANSI/IEEE C57.13.6-2005
Standard for High Accuracy Instrument Transformers
ANSI/IEEE C57.94-2000
Recommended Practice for Installation, Application, Operation, and Maintenance of Dry-Type General-Purpose Distribution and Power Transformers
ASTM A 1009-2005
Standard Specification for Soft Magnetic MnZn Ferrite Core Materials for High Frequency (10 kHz-1 MHz) Power Transformer and Filter Inductor Applications
UL 1876-2001
Isolating signal and feedback transformers for use in electronic equipment
IEC 60044-1 Edition 1.2-2003
Instrument transformers - Part 1: Current transformers
IEC 60076-5-2006
Power transformers - Part 5: Ability to withstand short circuit
IEC/TS 60076-14-2004
Power transformers - Part 14: Design and application of liquid-immersed power transformers using high-temperature insulation materials
ANSI/IEEE C57.119-2002
Recommended Practice for Performing Temperature Rise Tests on Oil Immersed Power Transformers at Loads Beyond Nameplate Ratings
To view comprehensive index, please visit MSC links.
Carry out tests on power transformers
Abstracted standard from NZQA.
Purpose
People credited with this unit standard are able to: prepare for testing of power transformers for maintenance and/or acceptance; set up testequipment; carry out tests; interpret test results and complete compliance documentation; and place in, or return equipment to service.
Domain Electricity Supply - Testing
Status Registered
Status date 19 May 2006
Date version published 19 May 2006
Planned review date 31 December 2011
Entry information Recommended: Unit 14287, Use and maintain test instruments used within the high voltage electrical industry; Unit 14294, Carry out insulating oil sampling and voltage breakdown tests; or demonstrate equivalent knowledge and skills. Accreditation Evaluation of documentation and visit by NZQA and industry.
Standard setting body (SSB) Electricity Supply Industry Training Organisation Accreditation and Moderation Action Plan (AMAP) reference 0120This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Standard setting body (SSB) Electricity Supply Industry Training Organisation
© New Zealand Qualifications Authority 2006
To access the full standard.
Purpose
People credited with this unit standard are able to: prepare for testing of power transformers for maintenance and/or acceptance; set up testequipment; carry out tests; interpret test results and complete compliance documentation; and place in, or return equipment to service.
Domain Electricity Supply - Testing
Status Registered
Status date 19 May 2006
Date version published 19 May 2006
Planned review date 31 December 2011
Entry information Recommended: Unit 14287, Use and maintain test instruments used within the high voltage electrical industry; Unit 14294, Carry out insulating oil sampling and voltage breakdown tests; or demonstrate equivalent knowledge and skills. Accreditation Evaluation of documentation and visit by NZQA and industry.
Standard setting body (SSB) Electricity Supply Industry Training Organisation Accreditation and Moderation Action Plan (AMAP) reference 0120This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Standard setting body (SSB) Electricity Supply Industry Training Organisation
© New Zealand Qualifications Authority 2006
To access the full standard.
Tuesday, December 9, 2008
IET Activities Diagnosis Of The Condition Of Electric Components Using Transfer Funktions (transformer analyze)
by Søren Damsgaard Mikkelsen
RÉSUMÉ
In this report the performance of transfer functions in diagnosis of faults and ageing phenomena in components in electrical power systems has been tested. The basic principles of transfer function based diagnosis are explained in the following:
A low voltage test signal is applied to the device to be analyzed through a coupling circuit. This input signal is measured together with an output signal from the component and the obtained digitized data areused in a computer to calculate a dynamic input/output model of the device - the transfer function.
The calculated transfer function is subsequently compared with a reference model obtained when the device was new to determine whether differences has emerged. The differences, if they appear, are the key to evaluate the condition of the component and predict the time to breakdown.
Two transformer types are used as test basis in the research work....
The first step in the investigation is to survey the incipient failures and ageing phenomena to be detected by transfer functions.
Based on a systematic description of the most commonly appearing failures intransformers and ZnO surge arresters in electrical power systems a common pattern of symptoms for allthese irregularities is given.For transformers in electrical power systems four characteristic symptoms of incipient failures and ageing phenomena are set up:
a. Raised eddy current/magnetic losses.
b. Displaced turns/windings.
c. Decomposed or stressed winding insulation.
d. Acid, moisture and sludge in the insulating oil.
For ZnO surge arresters a single symptom is set up:a. Increased leakage current. These symptoms are the basic symptoms to be detected by transfer functions, if the method is going to be an effective tool in diagnosis of transformers and ZnO surge arresters in electrical power systems.
The second step in the research work is to set up the basic theoretical models describing the transformer and the ZnO surge arrester dynamic. An important demand for a descriptive model to be used in diagnosis is that - the model is closely connected to the physical operation of the component.
A mathematical description like a s-domain transfer function is thus less suited for diagnosis purposes than an equivalent circuit with RLC parameters related directly to the physical operation of specific parts within the component. Two basic equivalent circuit configurations describing the dynamic of single phase transformers and ZnO surge arresters, respectively, are set up for the project.The third step in the research work is to find the identification methods to identify the dynamic behaviourof transformers and ZnO surge arrester.
The most important demand for an identification method to be used in diagnosis is that- the identification result is stable and reproducible under unchanged conditions, i.e. the stochastic deviation of the identified model is small.
Basically, the available identification methods can be divided in two groups: non-parametric methods and parametric methods.The non-parametric identification methods determine a non-parametric model of the device under test.
The non-parametric model is usually a frequency domain model showing the amplitude gain and phasedisplacement of the component versus frequency. Such a frequency domain model forms together with an equivalent circuit a nearly complete basis to evaluate the dynamic (like the existence of resonant frequencies, impedance level, phase angle etc.) of a component.
The two most commonly used methods to determine the frequency response of a device is frequency sweep analysis and FFT analysis.
Both methods are thoroughly tested in this project by impedance identifications performed on the two singlephase transformer types and in the leakage region of the two ZnO surge arrester types. The result of these fundamental modelling tests are:- Frequency sweep analysis gives highly stable and reproducible models of transformers as well as of ZnO surge arresters.- FFT analysis gives stable and reproducible models of transformers, while the dynamic range of the available test equipment is too small to obtain reliable results on ZnO devices in the leakage region.
The parametric identification methods determines the parameter values of a parametric component model. The parametric model can be an equivalent circuit with RLC parameters or a general s-domain transfer function with a suitable number of coefficients. Several methods to solve the problem ofparameter identification in a given model from recorded test data are available.
In this project LeastSquares method is tested by impedance identifications performed on transformers and in the leakage andnormal operation region of ZnO surge arresters. The results of the these preliminary identification testsare:- Parametric identification gives stable and reproducible results on transformers and on ZnO surgearresters in the normal operation region. Contrary to this are the results of parametric identification in leakage region of ZnO arresters useless due to the same reason as stated for FFT analysis, i.e.limitations in the test equipment.
Three different identification methods are thus concluded to produce stable and reproducible results on transformers: frequency sweep analysis, FFT analysis and parametric identification.Two identification methods are similarly determined to give satisfactory results on ZnO surge arresters:frequency sweep analysis in the leakage region and parametric identification in the normal operation region.
The final but very important step in the research work is to determine the relation between the identified models and the condition of the devices concerned.Two test series are performed on the available transformers: sensitivity tests and ageing tests. The former test series is used to determine the sensitivity of the identified models to the condition of the insulating oil/grease, the magnetic circuit and the winding insulation. The latter test series is performed inorder to see whether or not the dynamic model of a transformer changes due to ageing phenomena andto determine whether or not it is possible to detect a development towards breakdown.
A single test series is performed on the available ZnO surge arresters: ageing tests. As the performed ageing tests on transformers, the ageing test series on ZnO surge arresters serves the purpose of investigating the development in the identified models towards breakdown.
The following results are obtained via the performed tests:- Detection of faults and ageing phenomena in a transformer is possible from the transfer function implied that changes in the lumped winding capacitances, the total losses, the reluctance of the core orthe geometry of the windings occurs.
However, a complete and precise condition evaluation of a transformer from the transfer function is impossible to obtain. The number of parameters included in the dynamic transfer function is thus insufficient.- Detection of faults and ageing phenomena in a ZnO surge arrester is also possible. However, in this situation it is the question, whether or not it is reasonable to use the described relatively complicated method.
A much simpler alternative is thus proposed in the project based on the experiences gained.
To view the full abstract.
To order the paper:
http://www.iet.aau.dk/
RÉSUMÉ
In this report the performance of transfer functions in diagnosis of faults and ageing phenomena in components in electrical power systems has been tested. The basic principles of transfer function based diagnosis are explained in the following:
A low voltage test signal is applied to the device to be analyzed through a coupling circuit. This input signal is measured together with an output signal from the component and the obtained digitized data areused in a computer to calculate a dynamic input/output model of the device - the transfer function.
The calculated transfer function is subsequently compared with a reference model obtained when the device was new to determine whether differences has emerged. The differences, if they appear, are the key to evaluate the condition of the component and predict the time to breakdown.
Two transformer types are used as test basis in the research work....
The first step in the investigation is to survey the incipient failures and ageing phenomena to be detected by transfer functions.
Based on a systematic description of the most commonly appearing failures intransformers and ZnO surge arresters in electrical power systems a common pattern of symptoms for allthese irregularities is given.For transformers in electrical power systems four characteristic symptoms of incipient failures and ageing phenomena are set up:
a. Raised eddy current/magnetic losses.
b. Displaced turns/windings.
c. Decomposed or stressed winding insulation.
d. Acid, moisture and sludge in the insulating oil.
For ZnO surge arresters a single symptom is set up:a. Increased leakage current. These symptoms are the basic symptoms to be detected by transfer functions, if the method is going to be an effective tool in diagnosis of transformers and ZnO surge arresters in electrical power systems.
The second step in the research work is to set up the basic theoretical models describing the transformer and the ZnO surge arrester dynamic. An important demand for a descriptive model to be used in diagnosis is that - the model is closely connected to the physical operation of the component.
A mathematical description like a s-domain transfer function is thus less suited for diagnosis purposes than an equivalent circuit with RLC parameters related directly to the physical operation of specific parts within the component. Two basic equivalent circuit configurations describing the dynamic of single phase transformers and ZnO surge arresters, respectively, are set up for the project.The third step in the research work is to find the identification methods to identify the dynamic behaviourof transformers and ZnO surge arrester.
The most important demand for an identification method to be used in diagnosis is that- the identification result is stable and reproducible under unchanged conditions, i.e. the stochastic deviation of the identified model is small.
Basically, the available identification methods can be divided in two groups: non-parametric methods and parametric methods.The non-parametric identification methods determine a non-parametric model of the device under test.
The non-parametric model is usually a frequency domain model showing the amplitude gain and phasedisplacement of the component versus frequency. Such a frequency domain model forms together with an equivalent circuit a nearly complete basis to evaluate the dynamic (like the existence of resonant frequencies, impedance level, phase angle etc.) of a component.
The two most commonly used methods to determine the frequency response of a device is frequency sweep analysis and FFT analysis.
Both methods are thoroughly tested in this project by impedance identifications performed on the two singlephase transformer types and in the leakage region of the two ZnO surge arrester types. The result of these fundamental modelling tests are:- Frequency sweep analysis gives highly stable and reproducible models of transformers as well as of ZnO surge arresters.- FFT analysis gives stable and reproducible models of transformers, while the dynamic range of the available test equipment is too small to obtain reliable results on ZnO devices in the leakage region.
The parametric identification methods determines the parameter values of a parametric component model. The parametric model can be an equivalent circuit with RLC parameters or a general s-domain transfer function with a suitable number of coefficients. Several methods to solve the problem ofparameter identification in a given model from recorded test data are available.
In this project LeastSquares method is tested by impedance identifications performed on transformers and in the leakage andnormal operation region of ZnO surge arresters. The results of the these preliminary identification testsare:- Parametric identification gives stable and reproducible results on transformers and on ZnO surgearresters in the normal operation region. Contrary to this are the results of parametric identification in leakage region of ZnO arresters useless due to the same reason as stated for FFT analysis, i.e.limitations in the test equipment.
Three different identification methods are thus concluded to produce stable and reproducible results on transformers: frequency sweep analysis, FFT analysis and parametric identification.Two identification methods are similarly determined to give satisfactory results on ZnO surge arresters:frequency sweep analysis in the leakage region and parametric identification in the normal operation region.
The final but very important step in the research work is to determine the relation between the identified models and the condition of the devices concerned.Two test series are performed on the available transformers: sensitivity tests and ageing tests. The former test series is used to determine the sensitivity of the identified models to the condition of the insulating oil/grease, the magnetic circuit and the winding insulation. The latter test series is performed inorder to see whether or not the dynamic model of a transformer changes due to ageing phenomena andto determine whether or not it is possible to detect a development towards breakdown.
A single test series is performed on the available ZnO surge arresters: ageing tests. As the performed ageing tests on transformers, the ageing test series on ZnO surge arresters serves the purpose of investigating the development in the identified models towards breakdown.
The following results are obtained via the performed tests:- Detection of faults and ageing phenomena in a transformer is possible from the transfer function implied that changes in the lumped winding capacitances, the total losses, the reluctance of the core orthe geometry of the windings occurs.
However, a complete and precise condition evaluation of a transformer from the transfer function is impossible to obtain. The number of parameters included in the dynamic transfer function is thus insufficient.- Detection of faults and ageing phenomena in a ZnO surge arrester is also possible. However, in this situation it is the question, whether or not it is reasonable to use the described relatively complicated method.
A much simpler alternative is thus proposed in the project based on the experiences gained.
To view the full abstract.
To order the paper:
http://www.iet.aau.dk/
Selected feature of TTR application notes (power tranformer test)
APPLICATIONS
The TTR applies voltage to the high voltage winding of a transformer and accurately measures the resulting voltagefrom the low voltage winding. In addition to turns ratio,the unit measures excitation current, phase angle deviation between the high and low voltage windings and percentratio error.
Transformer Turns Ratio
Transformer turns ratio is the ratio of the number of turnsin the high-voltage winding to that in the low-voltagewinding. Complexity in the measured ratio versusnameplate ratio occurs with most three phase power transformers because multipliers such as √3 are required tomatch the measured ratio to the nameplate ratio. The three-phase TTR automatically applies the multiplier in a form which allows the operator a direct comparison to the nameplate (or expected) ratio. The TTR’s built-in calculator displays the % error versus nameplate for each tap and each winding, without the need of a computer or software.
Exciting Current
The TTR provides accurate measurement of exciting current (to 0.1 mA) which can help provide information about the condition of a transformer’s core. Unwanted circulating currents or unintentional grounds can increase the exciting current and indicate a problem.
Phase Angle Deviation and its Application
The phase angle deviation, displayed in either degrees(minutes) or radians, is the phase relationship between the voltage signal applied to the high voltage winding and the voltage signal extracted from the low voltage winding.The phase deviation together with ratio error can be used as a low cost method of verifying accuracy class of alltypes of PTs and CTs at “zero burden.”The phase deviation between the high and low side of atransformer is generally very small. If there is deteriorationor damage in the transformer core, however, the phase deviation can change significantly. The three-phase TTR can measure this phase relationship with the resolution of 0.1 minutes (equal to 1/600 of a degree), which is necessary to detect problems.
To view the comprehensive technical parameters and features, click here.
To view more information at www.megger.com
The TTR applies voltage to the high voltage winding of a transformer and accurately measures the resulting voltagefrom the low voltage winding. In addition to turns ratio,the unit measures excitation current, phase angle deviation between the high and low voltage windings and percentratio error.
Transformer Turns Ratio
Transformer turns ratio is the ratio of the number of turnsin the high-voltage winding to that in the low-voltagewinding. Complexity in the measured ratio versusnameplate ratio occurs with most three phase power transformers because multipliers such as √3 are required tomatch the measured ratio to the nameplate ratio. The three-phase TTR automatically applies the multiplier in a form which allows the operator a direct comparison to the nameplate (or expected) ratio. The TTR’s built-in calculator displays the % error versus nameplate for each tap and each winding, without the need of a computer or software.
Exciting Current
The TTR provides accurate measurement of exciting current (to 0.1 mA) which can help provide information about the condition of a transformer’s core. Unwanted circulating currents or unintentional grounds can increase the exciting current and indicate a problem.
Phase Angle Deviation and its Application
The phase angle deviation, displayed in either degrees(minutes) or radians, is the phase relationship between the voltage signal applied to the high voltage winding and the voltage signal extracted from the low voltage winding.The phase deviation together with ratio error can be used as a low cost method of verifying accuracy class of alltypes of PTs and CTs at “zero burden.”The phase deviation between the high and low side of atransformer is generally very small. If there is deteriorationor damage in the transformer core, however, the phase deviation can change significantly. The three-phase TTR can measure this phase relationship with the resolution of 0.1 minutes (equal to 1/600 of a degree), which is necessary to detect problems.
To view the comprehensive technical parameters and features, click here.
To view more information at www.megger.com
Problems on Transformer/LT coil evaluation
Abstracted from Agilent Effective Transformer/LF Coil TestingApplication Note 1305-3
Transformers and LF coils are used in power supplies, digital networks (forexample, ADSL) and various communication instruments to step up (or down)an AC voltage or for impedance conversion or filtering purposes. Thoughproduction of transformers is increasing year after year, there are problems thatQA test efficiency and production test throughput cannot be easily improvedbecause several different measurement instruments and setups need to be usedfor testing various transformer parameters. This application note introduces thecost-effective solutions to the transformer parameter measurements by usingthe Agilent 4263B LCR Meter.
Current Problems onTransformer/LF CoilEvaluation
The primary parameters that need to be known for transformer/LF coils areself-inductance, dc resistance, turns ratio and inter-winding capacitance.Conventional low-cost LCR meters have the following shortcomings when usedfor transformer/LF coil evaluation.
1. DC resistance of primary and secondary windings cannot be measured withLCR meters. (The DC resistance measurement requires using a separate testinstrument such as a multimeter.)
2. The turns ratio, a key transformer parameter, cannot be measured with LCRmeters.
3. The transformer parameters cannot be measured at 100 kHz because manylow-cost LCR meters do not cover high frequencies up to 100 kHz.
4. The test signal level is automatically selected according to the measurementrange, the test signal level cannot be user-defined for a specified level.
5. Total test throughput on production lines cannot be maximized because ofslow measurement
speed.
6. The connections of a transformer to the instrument (test fixture) must bechanged to measure parameters for the primary and secondary windings.The required connection changes make it difficult to enhance themeasurement efficiency.
To read more about solutions from Agilent.
Transformers and LF coils are used in power supplies, digital networks (forexample, ADSL) and various communication instruments to step up (or down)an AC voltage or for impedance conversion or filtering purposes. Thoughproduction of transformers is increasing year after year, there are problems thatQA test efficiency and production test throughput cannot be easily improvedbecause several different measurement instruments and setups need to be usedfor testing various transformer parameters. This application note introduces thecost-effective solutions to the transformer parameter measurements by usingthe Agilent 4263B LCR Meter.
Current Problems onTransformer/LF CoilEvaluation
The primary parameters that need to be known for transformer/LF coils areself-inductance, dc resistance, turns ratio and inter-winding capacitance.Conventional low-cost LCR meters have the following shortcomings when usedfor transformer/LF coil evaluation.
1. DC resistance of primary and secondary windings cannot be measured withLCR meters. (The DC resistance measurement requires using a separate testinstrument such as a multimeter.)
2. The turns ratio, a key transformer parameter, cannot be measured with LCRmeters.
3. The transformer parameters cannot be measured at 100 kHz because manylow-cost LCR meters do not cover high frequencies up to 100 kHz.
4. The test signal level is automatically selected according to the measurementrange, the test signal level cannot be user-defined for a specified level.
5. Total test throughput on production lines cannot be maximized because ofslow measurement
speed.
6. The connections of a transformer to the instrument (test fixture) must bechanged to measure parameters for the primary and secondary windings.The required connection changes make it difficult to enhance themeasurement efficiency.
To read more about solutions from Agilent.
Thursday, December 4, 2008
Review of Several Free Electric Power Forums
Review of Electric Power Forums
I take this is the best one of online forum. the website hosts large amout of subjects within industrial engineering, which attracts many visitors to show their problems. It also very good as you don't need to sign in before you browse the question and answers. Almost everything is open for guest visitors except when you want to start a new tread.
Most of the time it is ranked No.1 on Google or Yahoo search list, it centrals on Electricity and Electrical Energy, for exchange of policy and technical information.
You can register for email notification of recent published news, they send you news almost every day, but I think most of them are advertizing or news information, which is very useful for marketing managers or product researchers looking for new products.
Over the past two years, I have visited several electric power forums for problem solving, information collections and discussion. It might be happened that there exists lot of people looking for solutions but they may feel puzzled by large amout of data Googled or Yahooled by search engines.
I hope this brief review will be any help to reduce times cost for researchers, engineers...
I take this is the best one of online forum. the website hosts large amout of subjects within industrial engineering, which attracts many visitors to show their problems. It also very good as you don't need to sign in before you browse the question and answers. Almost everything is open for guest visitors except when you want to start a new tread. Most of the time it is ranked No.1 on Google or Yahoo search list, it centrals on Electricity and Electrical Energy, for exchange of policy and technical information.You can register for email notification of recent published news, they send you news almost every day, but I think most of them are advertizing or news information, which is very useful for marketing managers or product researchers looking for new products.
Note: You need sign in to look for further information.
3. PSAT forum (world famous but subject-limited and only for members)
Actually it is a Yahoo Group that discuss information through mail lists. Even Though it is for membership sharing insights, the PSAT is opensource for everyone, and it is easy to join in the group. It is really powerful, full of intelligence mainly for academic research, but there also groups engineering technicians for soft-applications, below is brief introduction of PSAT.
PSAT is a Matlab toolbox for electric power system analysis and control. The command line version of PSAT is also GNU Octave compatible. PSAT includes power flow, continuation power flow, optimal power flow, small signal stability analysis and time domain simulation. All operations can be assessed by means of graphical user interfaces (GUIs) and a Simulink-based library provides an user-friendly tool for network design.
Note: The PSAT source code can be downloaded from here.
4. Forumelectric http://www.forumelectric.com/
With multisubject platform, posted over one thousand articles and hundreds of subjects.
I am not a register but views the Q&A, it really holds many interesting subjects.
Wednesday, December 3, 2008
Defects in Nonceramic Insulators: Can They be Detected in a Timely Manner?
Introduction: There are a multitude of designs, materials, formulations, and manufacturing processes that are used presently for nonceramic insulators. While this beneficial in terms of offering choices for the users, this also means that in case of problems, failure patterns could be different. It is fairly well known that most problems in NCI result originate from interfaces. The critical interfaces in this type of insulator are between the rod and housing, between hardware-rod-housing and different sheds of housing if unit is not manufactured in a single piece.
The presence of corona at the interfaces leads to sheath damage exposing the fiberglass rod, tracking the rod, thereby leading to insulator failure through interfacial flashover, rod burning and brittle fracture. Also, the presence of any contamination like water, salts, and dirt can intensify the field at those locations. Fig. 1 shows a picture of a failed NCI. It can be seen that the first few sheds have suffered corona cutting. Some degradation in the form of tracking and erosion is also visible. If the damage to the insulator is not in the line of sight, then this may not be identified as a problem during routine line inspection by road or helicopter patrols until the unit fails. The challenge is to identify such insulators at an early stage of degradation whe n there is still time to act.
Understanding the electric field distribution plays a vital role in insulator design and also can be useful for detecting internal defects. In ceramic insulators the voltage distribution is relatively more linear due to the presence of intermediate metal parts. The material does not degrade with corona, hence corona is not usually a problem in ceramic insulators. However in NCI’s the voltage distribution is highly non-uniform as shown in Fig. 2, and can give rise to corona. Corona rings are normally used for NCI at voltages above 230 kV in order to reduce the electric field near the line end.
There have been several recent publications that concluded that there is no fool-proof method for early detection of defects in nonceramic insulators. Among the methods examined were partial discharge detection, infrared thermography, corona and audible noise detection, leakage current measurement and electric field measurement. In the utility environment the electric field technique is being increasingly used as a diagnostic tool to ident ify defective porcelain units. Their use on nonceramic insulators appears to be the logical step. What types and degrees off defects can be detected by such a measurement? This study was undertaken to answer this question. The electric field distribution of a healthy insulator was taken as the reference.
Types of Defects Modeled: Several types of defects that can occur on a NCI were modeled. The various types of defects that are considered difficult to detect but critical are incorporated on to the healthy model and simulated. The size, position and conductivity of such defects are varied. The field values for locations close to the defect along the path of the probe are noted down. These values are then compared with the values obtained in the healthy cases. The presently used electric field probes are sensitive for field values above 2 kV/m. Hence defects that produce a difference of 2 kV/m and above are considered detectable while others were considered undetectable. The differences in field values thus obtained are plotted as a function of the shed number. A logarithmic trend line is fitted to the above plot for a better perception of the defect detection possibilities.
Various types of defects such as those occurring on the shed, shank, interface, external tracks from end fittings and tracks occurring on the rod sheath interface were considered. Most of the external defects could be observed during careful visual inspection. However, defects that occur inside the housing are not visible. Hence such defects are modeled for electric field distortion studies to verify the possibility of detecting such defects using field probes as shown in Table 1. A defect that occurs for the distance between any two consecutive sheds is named as the single shed defect. A single shed defect will have the shape of a cylinder with a 9.2 cm height and 5 mm diameter. A diagrammatic representation of various types of single shed defects modeled is as shown in Fig. 3. Similarly two-shed and three shed defects are simulated and analyzed.
It is likely that corona cuts or any other deformities in the insulator will give rise to corona, especially under humid conditions. The work reported last year showed that a combination of location specifics and quantitative data like brightness can provide useful information on making decisions such as problematic corona or nonproblematic corona. This should be explored further.
Conclusions:
The defect detection is position dependant and has the best possibility of being detected if it is closer to the high voltage electrode.Larger and longer defects produce higher field changes hence they are more easily detected than the smaller ones. The change in field value observed depends on the type of the defect. More conductive the defect is, greater is the possibility of detecting it. The range of the field probe can be greatly enhanced if measurements are taken radially instead of conventional axial measurements.
S. Gorur and S. Sivasubramaniyam Department of Electrical Engineering, Arizona State University, Tempe, AZ, USA
This work was performed under a PSERC funded project at Arizona State University
The presence of corona at the interfaces leads to sheath damage exposing the fiberglass rod, tracking the rod, thereby leading to insulator failure through interfacial flashover, rod burning and brittle fracture. Also, the presence of any contamination like water, salts, and dirt can intensify the field at those locations. Fig. 1 shows a picture of a failed NCI. It can be seen that the first few sheds have suffered corona cutting. Some degradation in the form of tracking and erosion is also visible. If the damage to the insulator is not in the line of sight, then this may not be identified as a problem during routine line inspection by road or helicopter patrols until the unit fails. The challenge is to identify such insulators at an early stage of degradation whe n there is still time to act.
Understanding the electric field distribution plays a vital role in insulator design and also can be useful for detecting internal defects. In ceramic insulators the voltage distribution is relatively more linear due to the presence of intermediate metal parts. The material does not degrade with corona, hence corona is not usually a problem in ceramic insulators. However in NCI’s the voltage distribution is highly non-uniform as shown in Fig. 2, and can give rise to corona. Corona rings are normally used for NCI at voltages above 230 kV in order to reduce the electric field near the line end.
There have been several recent publications that concluded that there is no fool-proof method for early detection of defects in nonceramic insulators. Among the methods examined were partial discharge detection, infrared thermography, corona and audible noise detection, leakage current measurement and electric field measurement. In the utility environment the electric field technique is being increasingly used as a diagnostic tool to ident ify defective porcelain units. Their use on nonceramic insulators appears to be the logical step. What types and degrees off defects can be detected by such a measurement? This study was undertaken to answer this question. The electric field distribution of a healthy insulator was taken as the reference.
Types of Defects Modeled: Several types of defects that can occur on a NCI were modeled. The various types of defects that are considered difficult to detect but critical are incorporated on to the healthy model and simulated. The size, position and conductivity of such defects are varied. The field values for locations close to the defect along the path of the probe are noted down. These values are then compared with the values obtained in the healthy cases. The presently used electric field probes are sensitive for field values above 2 kV/m. Hence defects that produce a difference of 2 kV/m and above are considered detectable while others were considered undetectable. The differences in field values thus obtained are plotted as a function of the shed number. A logarithmic trend line is fitted to the above plot for a better perception of the defect detection possibilities.
Various types of defects such as those occurring on the shed, shank, interface, external tracks from end fittings and tracks occurring on the rod sheath interface were considered. Most of the external defects could be observed during careful visual inspection. However, defects that occur inside the housing are not visible. Hence such defects are modeled for electric field distortion studies to verify the possibility of detecting such defects using field probes as shown in Table 1. A defect that occurs for the distance between any two consecutive sheds is named as the single shed defect. A single shed defect will have the shape of a cylinder with a 9.2 cm height and 5 mm diameter. A diagrammatic representation of various types of single shed defects modeled is as shown in Fig. 3. Similarly two-shed and three shed defects are simulated and analyzed.
It is likely that corona cuts or any other deformities in the insulator will give rise to corona, especially under humid conditions. The work reported last year showed that a combination of location specifics and quantitative data like brightness can provide useful information on making decisions such as problematic corona or nonproblematic corona. This should be explored further.
Conclusions:
The defect detection is position dependant and has the best possibility of being detected if it is closer to the high voltage electrode.Larger and longer defects produce higher field changes hence they are more easily detected than the smaller ones. The change in field value observed depends on the type of the defect. More conductive the defect is, greater is the possibility of detecting it. The range of the field probe can be greatly enhanced if measurements are taken radially instead of conventional axial measurements.
S. Gorur and S. Sivasubramaniyam Department of Electrical Engineering, Arizona State University, Tempe, AZ, USA
This work was performed under a PSERC funded project at Arizona State University
UGM,4-5-6 May,2009
UGM, 4-5-6 May, 2009
REGISTER NOW
The 6th UGM - UV inspection users group meeting will take place in Las Vegas NV USA during May 4th to May 6th, 2009. Attendees from all over the world are invited to participate and share their accumulated knowledge and exprience with the growing UV inspectors community.
The luxurious Tuscany Suites & Casino was selected to host the meeting, with special reduced rates for the group members. During the meetings breakfast, lunch and coffee breaks will be served. An informal dinner party is schedulled in the evening where spouses are welcome to attend.
The agenda will include lectures by keyspeakers, presentations by veteran users, tutorials by Ofil's engineers. The proceedings CD of the event will be given to attendees.
The five previous events were very successful and the list of users who register is getting filled up quickly. Space is limited and it is therefore recommended to reserve a seat in advance, and the earlier - the better.
To register download the form >>
Fill the form and fax it to Ofil1.888.950.5557 (USA toll free) +972.8.940.7873 (Israel)
Should you have any question or special request, please write to Hannah Barzilay - the UGM coordinator.
The objectives of the meetings
Expand aspects of using the UV inspection technology
Review, discuss and understand implications of corona discharge on lines, insulators substation components and grid hardware
Study from experts
Link between utilities, researchers, academy and industry
See what has been achieved by peers from around the world
Hands-on workshop
Who attends?
Potential users familiar with IR and Ultrasound inspection techniques wishing to learn about UV inspection
UV inspection users who want to expand their knowledge and understanding of corona
Users wishing to exchange information and know-how with colleagues
Utility executives
Electrical engineers, services providers, technicians, high voltage laboratory researchers, T&D engineers, predictive maintenance designers etc.
Researchers in search for projects and hot subjects
REGISTER NOW
The 6th UGM - UV inspection users group meeting will take place in Las Vegas NV USA during May 4th to May 6th, 2009. Attendees from all over the world are invited to participate and share their accumulated knowledge and exprience with the growing UV inspectors community.
The luxurious Tuscany Suites & Casino was selected to host the meeting, with special reduced rates for the group members. During the meetings breakfast, lunch and coffee breaks will be served. An informal dinner party is schedulled in the evening where spouses are welcome to attend.
The agenda will include lectures by keyspeakers, presentations by veteran users, tutorials by Ofil's engineers. The proceedings CD of the event will be given to attendees.
The five previous events were very successful and the list of users who register is getting filled up quickly. Space is limited and it is therefore recommended to reserve a seat in advance, and the earlier - the better.
To register download the form >>
Fill the form and fax it to Ofil1.888.950.5557 (USA toll free) +972.8.940.7873 (Israel)
Should you have any question or special request, please write to Hannah Barzilay - the UGM coordinator.
The objectives of the meetings
Expand aspects of using the UV inspection technology
Review, discuss and understand implications of corona discharge on lines, insulators substation components and grid hardware
Study from experts
Link between utilities, researchers, academy and industry
See what has been achieved by peers from around the world
Hands-on workshop
Who attends?
Potential users familiar with IR and Ultrasound inspection techniques wishing to learn about UV inspection
UV inspection users who want to expand their knowledge and understanding of corona
Users wishing to exchange information and know-how with colleagues
Utility executives
Electrical engineers, services providers, technicians, high voltage laboratory researchers, T&D engineers, predictive maintenance designers etc.
Researchers in search for projects and hot subjects
Tuesday, December 2, 2008
GIS Insulation Accident Concern
GIS (Gas-Insulated Switchgear) characterizes with many merits such as high reliability,easy-maintenance, small volume, and receives widely application in the world.
Even though, due to testing devices and techniques, there are still quite large amout of GIS never undergo strict fields test for earlier applications. it happens that insulation problem is still an improtant issue for fields maintenance, from which it aroses many methods to conduct insulation experiment, such as chemical analyzing method, pulse, ultrasonic and UHF method.
From the experience, there are certain kind of defect, which can not be anyharm and not easy to detect, will exemplify themselves in the later years, especially when CB operates, partial discharge occures that may result in large accident and maintenance has to be in power-off conditions so as to lead to large economic loss.
There are some insulation faults happened in Guangdong province, China:
Jiangmen 500kVGIS, DayaWan 400kVGIS, Shenzhen Huanggang station220kVGIS, ShajiaoA power plant220kVGIS.
Especially for Shajiao A plant, in the year of 1989, a 220kVGIS N.3 faults result in loss of 32GW.h.
Edited by J.Zh
IEEETM Center
Even though, due to testing devices and techniques, there are still quite large amout of GIS never undergo strict fields test for earlier applications. it happens that insulation problem is still an improtant issue for fields maintenance, from which it aroses many methods to conduct insulation experiment, such as chemical analyzing method, pulse, ultrasonic and UHF method.
From the experience, there are certain kind of defect, which can not be anyharm and not easy to detect, will exemplify themselves in the later years, especially when CB operates, partial discharge occures that may result in large accident and maintenance has to be in power-off conditions so as to lead to large economic loss.
There are some insulation faults happened in Guangdong province, China:
Jiangmen 500kVGIS, DayaWan 400kVGIS, Shenzhen Huanggang station220kVGIS, ShajiaoA power plant220kVGIS.
Especially for Shajiao A plant, in the year of 1989, a 220kVGIS N.3 faults result in loss of 32GW.h.
Edited by J.Zh
IEEETM Center
On-site Sensitivity Verification for UHF PD Detection in GIS（NOTES）
Necessity of UHF Sensitivity Check
A article features with on-line check of Sensitivity, which rises an important issue.
S. Meijer1*, J.J. Smit11
Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands
In industry, partial discharge technology related to switchgear has been operational for many years. Partial discharge testing has been conducted on both new high voltage switchgear in the laboratory setup, as well as several older HV installations in the utility grid. The results clearly indicate that partial discharge analysis of HV switchgear is an excellent online tool to assess its dielectriccondition. “Dielectric windows” present on existing GIS offer the possibility to pick-up the signals by means of external couplers.In order to check the sensitivity or to prove the possibility to detect a certain PD level, a sensitivity check procedure has beenpublished by Cigre several years ago.
This procedure was mainly focusing on new equipment in which internal sensors are beinginstalled in the factory. In this case, it is possible to make comparison tests in the laboratory between the UHF technique andaccording to the IEC 60270 to get a relation between both readings.For older GIS with PD couplers retrofitted or using externalsensors, usually the laboratory step required in this sensitivity check procedure is not possible due to lack of spare parts. In this contribution, a solution to perform the laboratory test on-site is described.
Proceedings of the International Conference on
Electrical Engineering and InformaticsInstitut Teknologi Bandung, Indonesia
June 17-19, 2007
A article features with on-line check of Sensitivity, which rises an important issue.
S. Meijer1*, J.J. Smit11
Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands
In industry, partial discharge technology related to switchgear has been operational for many years. Partial discharge testing has been conducted on both new high voltage switchgear in the laboratory setup, as well as several older HV installations in the utility grid. The results clearly indicate that partial discharge analysis of HV switchgear is an excellent online tool to assess its dielectriccondition. “Dielectric windows” present on existing GIS offer the possibility to pick-up the signals by means of external couplers.In order to check the sensitivity or to prove the possibility to detect a certain PD level, a sensitivity check procedure has beenpublished by Cigre several years ago.
This procedure was mainly focusing on new equipment in which internal sensors are beinginstalled in the factory. In this case, it is possible to make comparison tests in the laboratory between the UHF technique andaccording to the IEC 60270 to get a relation between both readings.For older GIS with PD couplers retrofitted or using externalsensors, usually the laboratory step required in this sensitivity check procedure is not possible due to lack of spare parts. In this contribution, a solution to perform the laboratory test on-site is described.
Proceedings of the International Conference on
Electrical Engineering and InformaticsInstitut Teknologi Bandung, Indonesia
June 17-19, 2007
Why place more efforts on magnetizing characteristics for CT than VT?
Technical Notes of Instrument TransformersThe Role that Magnetizing Impedance Plays
Instrument Transformer is special transformer, due to its operation condition, the equivalent circuit differes with respect to tranfer parameters.
Difference in equivalent circuit between CT and VT
1.VT. due to its operation limit, the secondary voltage runs rarely out of the limit value (80%~120), even in fault conditions, protection equipment will prevent them long keep in the state of out-limit. so it is reasonable to assume that the magnetizing impedance during operation is constant with respect to protection, and linear with respect to metering.Also, as VT is connected in paralle with power lines, only voltage is considered. the magnetizing impedance has very little influence on the burden voltage.
2.CT, secondary current is considered, its operation range is (1%~120%,to say,S class), magnetizing impedance varies significantly thus bypass secondary current from the burden, and affect the state value from primary being transfered to secondary. especially in fault conditions, such as primary line short-circuit, magnetizing impedance is a very important parameters to be considered.
In consideration of metering accuracy:
Both CT and VT characterize their error graph by nonlinearity of magnetizing impedance (MI). In principle, MI bypasses burden current, which influence the voltage drop on secondary lines and thus affecting the signal supplied to the burden.
MI is an interesting parameter that still attracts big conern, both for metering and protections.
J.ZH
IEEETM Central Sources
IEEETM Central Sources
Monday, December 1, 2008
Capacitive voltage sensor for measuring very fast transient overvoltages in GIS
What is the role that capacitive voltage sensor plays in GIS transient studies?
Masafumi Yashima, Hideo Fujinami, Tadasu Takuma§
Central Research Institute of Electric Power Industry
A reliable technique is needed for accurate measurement of very fast transient overvoltages such as disconnector-induced surges occurring in GIS which have very steep front and high-frequency oscillation. Recently, capacitive voltage sensors with very short response times have been proposed for this purpose. However, few studies have been made on the dielectric properties of materials used for a low-voltage-side capacitor, as well as the frequency bandwidth of the measuring system.
In this paper a thin mica plate is proposed for a low-voltage-side capacitor which has a surface coated with silver on both sides. This material has been shown to have stable and high static capacitance up to a high-frequency range. A quantitative estimate also is given for the frequency bandwidth of the measuring system. Furthermore, a practical-scale sensor of this type has been developed which can successfully measure simulated disconnector-induced surges of several hundred kilovolts under similar conditions in GIS.
Full Paper can be bought from Wiley Interscience.
I am wondering if and how it can be used for online condition assessment...
Discussion welcomed.
Masafumi Yashima, Hideo Fujinami, Tadasu Takuma§
Central Research Institute of Electric Power Industry
A reliable technique is needed for accurate measurement of very fast transient overvoltages such as disconnector-induced surges occurring in GIS which have very steep front and high-frequency oscillation. Recently, capacitive voltage sensors with very short response times have been proposed for this purpose. However, few studies have been made on the dielectric properties of materials used for a low-voltage-side capacitor, as well as the frequency bandwidth of the measuring system.
In this paper a thin mica plate is proposed for a low-voltage-side capacitor which has a surface coated with silver on both sides. This material has been shown to have stable and high static capacitance up to a high-frequency range. A quantitative estimate also is given for the frequency bandwidth of the measuring system. Furthermore, a practical-scale sensor of this type has been developed which can successfully measure simulated disconnector-induced surges of several hundred kilovolts under similar conditions in GIS.
Full Paper can be bought from Wiley Interscience.
I am wondering if and how it can be used for online condition assessment...
Discussion welcomed.
Retrofit and Field Test of Large Power Transformers with Fiber Optic Partial Discharge Sensors(Project Notes)
A tow-year project initiated by EPRI in 2006 has focus attention on Extending the useful life of power transformer so as to increasing the life of the power transmission and distribution infrastructure.
Central of the project features with effective transformer diagnostics and condition assessment.
The project aims to process data from testing in-tank, fiber optic partial discharge sensors and developing better transformer tank penetration methods for sensor insertion.
The project includes:
1. Develop a method and then manufacture and test prototypes of a cost-effective penetrator mechanism and sensor system suitable for retrofit into transformers
2. Obtain proof-of-concept of internal fiber optic pd sensors in an operating transformer with known pd
3. Establish an initial database to characterize the pd signals to the type of fault.
Abstracted and Summarized from EPRI
Central of the project features with effective transformer diagnostics and condition assessment.
The project aims to process data from testing in-tank, fiber optic partial discharge sensors and developing better transformer tank penetration methods for sensor insertion.
The project includes:
1. Develop a method and then manufacture and test prototypes of a cost-effective penetrator mechanism and sensor system suitable for retrofit into transformers
2. Obtain proof-of-concept of internal fiber optic pd sensors in an operating transformer with known pd
3. Establish an initial database to characterize the pd signals to the type of fault.
Abstracted and Summarized from EPRI
SF6 Insulated equipment Online Safety Issue
Online safety diagnostics of SF6 insulated equipment (Notes)
SF6 Gas is widely used in electric power industry, the internal metal kernel, dust and moisture content, are major reasons that lead to GIS fault. When there is conductive material within equipment, partial discharge produces abnormal noise, vibration and discharges with small light, in the phenomena of decomposition of SF6 gases.
Partial Discharge (PD) rises big concern for GIS, GCB and GIT.
Major Techniques employed for PD.
1. measuring electromagnetic wave to locate and judge the pd level.
2. UHF measurement and location.
3. High-frequency earthy current testing.
4. Sound tranmission and vibration test.
5. Chemical method, to analyze composition of sf6 Gases (HF/SO2/SOF2)
Actually there exists no effective method that can fix the problem well. There are both benefits and defects. among the methods, UHF is most popular at the present, but it is still difficult to measure the pd level and the cost is relative high.
Two extra research that complements the method
1. GIS discharge model or function( within or outside GIS)
2. Discharge Data Process to identify faults.
Also there are research that employs ultrasonic fault detection method which seldom sees the application.
J.ZH
Simplified Notes from
IEEETM Central Source
SF6 Gas is widely used in electric power industry, the internal metal kernel, dust and moisture content, are major reasons that lead to GIS fault. When there is conductive material within equipment, partial discharge produces abnormal noise, vibration and discharges with small light, in the phenomena of decomposition of SF6 gases.
Partial Discharge (PD) rises big concern for GIS, GCB and GIT.
Major Techniques employed for PD.
1. measuring electromagnetic wave to locate and judge the pd level.
2. UHF measurement and location.
3. High-frequency earthy current testing.
4. Sound tranmission and vibration test.
5. Chemical method, to analyze composition of sf6 Gases (HF/SO2/SOF2)
Actually there exists no effective method that can fix the problem well. There are both benefits and defects. among the methods, UHF is most popular at the present, but it is still difficult to measure the pd level and the cost is relative high.
Two extra research that complements the method
1. GIS discharge model or function( within or outside GIS)
2. Discharge Data Process to identify faults.
Also there are research that employs ultrasonic fault detection method which seldom sees the application.
J.ZH
Simplified Notes from
IEEETM Central Source
The Role short circuit impedance plays in Power Transformer Assessment
Short Circuit Impedance (SCI) refers to equivalent impedance from one side of Power Transformer (PT) with another side being short-circuited.
The main part of SCI is inductive value, so sometimes it can approximates to leakage inductance.
When testing the SCI, allow one side (ofen secondary) winding be short-circuited, and applies test voltage from another side winding (ofen primary), and then measure the impedance using VA or PQ method.
SCI can be used for frequency response test, with the help of equivalent model, to analyze defect of PT, such as winding deformation, internal insulation and core characteristics.
To analyze the data
Three phase comparision of impedance, periodic comparison and historic comparison are methods usually used to comprehensively characterize structural information of PT.
Also from a point of view to assess PT operation conditions, SCI is an improtant factor that help make medium or long time maintenance decisions.
J.ZH
Notes of Pusala Technology
成都普莎拉科技有限公司
IEEETM Central Source
The main part of SCI is inductive value, so sometimes it can approximates to leakage inductance.
When testing the SCI, allow one side (ofen secondary) winding be short-circuited, and applies test voltage from another side winding (ofen primary), and then measure the impedance using VA or PQ method.
SCI can be used for frequency response test, with the help of equivalent model, to analyze defect of PT, such as winding deformation, internal insulation and core characteristics.
To analyze the data
Three phase comparision of impedance, periodic comparison and historic comparison are methods usually used to comprehensively characterize structural information of PT.
Also from a point of view to assess PT operation conditions, SCI is an improtant factor that help make medium or long time maintenance decisions.
J.ZH
Notes of Pusala Technology
成都普莎拉科技有限公司
IEEETM Central Source
How to enlarge leakage inductance for experiment
Leakage Inductance Issue
It is determined by structure of transformers, not easy for change. a possible way is adding inductance in series with the primary (high voltage side), so as to increase the voltage that applies on the transformers.
The principle behind this the series inductance be in series with equivalent capacitance, but it requires that the insulated voltage level of series inductance should be high enough.
Also increase the gap between winding and core, or between different windings can also enlarge leakage inductance.
Leakage inductance is supposed to be controlled in low value with consideration of applications. And in practice it is not easy to measure and assume, but most of the study and application consider that to be a constant value (due to what kind of use)
IEEETM Notes
It is determined by structure of transformers, not easy for change. a possible way is adding inductance in series with the primary (high voltage side), so as to increase the voltage that applies on the transformers.
The principle behind this the series inductance be in series with equivalent capacitance, but it requires that the insulated voltage level of series inductance should be high enough.
Also increase the gap between winding and core, or between different windings can also enlarge leakage inductance.
Leakage inductance is supposed to be controlled in low value with consideration of applications. And in practice it is not easy to measure and assume, but most of the study and application consider that to be a constant value (due to what kind of use)
IEEETM Notes
Sunday, November 30, 2008
Sulfur Hexafluoride (SF6) Insulating Gas Leak Detection with an IR Imaging Camera
For years, electric utility transmission thermographers have wanted a camera that could spot leaking sulfur hexafluoride, SF6. As an insulating gas, SF6 is widely used by the electric power industry in high voltage circuit breakers to prevent arcing. Early efforts met with limited success through the use of imagers that required active scanning with infrared lasers. The resulting systems were somewhat cumbersome and required specific conditions which limited their utility. Now there is an IR camera that can spot SF6 in very small amounts and is a completely passive system, requiring no infrared laser but for the smallest leaks. This paper gives a brief history of SF6 as an insulating gas, problems caused by leaking SF6, the theory behind the IR camera, and why it works as well as it does. Additionally, we present some sample findings from both the laboratory and actual operating circuit breakers in high voltage systems that use SF6.
Read the whole article
Discussion welcomed.
Read the whole article
Discussion welcomed.
A Novel, Compact Instrument for the Measurement and Evaluation of Relaxation Currents conceived for On-Site Diagnosis of Electric Power Apparatus
A Novel, Compact Instrument for the Measurement and Evaluation of Relaxation Currents conceived for On-Site Diagnosis of Electric Power Apparatus
Abstract: Ageing of insulation materials and systems may well be detected by quantitative measurements of their dielectric response. Such measurements can be performed in the frequency or time domain. In this contribution, a novel type of equipment based on relaxation current measurements is introduced which is designed for on-site tests of high voltage power apparatus. The Introduction outlines the reasons for the development. Then, the technique of the instrument is briefly explained. Finally, some examples of on-site measurements on power transformers are presented and post-processing and interpretation of the results is demonstrated.
The measurements presented in this paper have been carried out in due course of the project "Insulation diagnosis of power transformers", performed at the High Voltage Laboratory of the Swiss Federal Institute of Technology [12]. This project was financially supported from "Projekt und Studienfonds der Elektrizitätswirtschaft" (PSEL Project No. 65).
View full paper from Alff
Discussion welcomed.
Abstract: Ageing of insulation materials and systems may well be detected by quantitative measurements of their dielectric response. Such measurements can be performed in the frequency or time domain. In this contribution, a novel type of equipment based on relaxation current measurements is introduced which is designed for on-site tests of high voltage power apparatus. The Introduction outlines the reasons for the development. Then, the technique of the instrument is briefly explained. Finally, some examples of on-site measurements on power transformers are presented and post-processing and interpretation of the results is demonstrated.
The measurements presented in this paper have been carried out in due course of the project "Insulation diagnosis of power transformers", performed at the High Voltage Laboratory of the Swiss Federal Institute of Technology [12]. This project was financially supported from "Projekt und Studienfonds der Elektrizitätswirtschaft" (PSEL Project No. 65).
View full paper from Alff
Discussion welcomed.
Low voltage short circuit impedance measurement
Low voltage short-circuit impedance measurement
The low voltage short -circuit impedance measurement by means of a low voltage three phase power source can be performed because the impedance valuedoes not depend on the applied voltage.The low voltage short-circuit impedance measurement requires utilization of highly accurate instrumentation on the one side, and elimination of the errors caused by the fluctuations of low voltage power networks due to welding equipment, etc., on the other.In order to carry out these measurements a diagram developed. The diagram uses data acquisition and processing system (DAQ) that enables evaluation of the measured data, the short-circuitimpedance variation curve plotting on the spot, as well as the subsequent processing obtained data. The processing system also corrects the data with the supplyvoltage frequency variation.
Furthermore:
The short-circuit impedance measurement between allthe winding pairs and by each position of the on-load tapchanger is imperiously necessary for:
- verifying the observance of the technical conditions,the designed ones included;
- verifying the possible nonconformities in thewinding manufacturing;
- verifying the behavior of the winding operation onsite (the measurement is performed in agreement with thenorms in force);
- carrying out the system calculations and the short circuitones (including the correct protection regulation);
- verifying the loading of the same type, as well as a of different type transformer units.
The short-circuit impedance measurement can beperformed by connecting the measurement installation to a low voltage (380/220V) source provided that highly accurate instrumentation enabling the automatic data processing is used.
Taken from a paper:
Power Transformer Units Condition Assessment Using VirtualInstrumentation
Discussion welcomed.
The low voltage short -circuit impedance measurement by means of a low voltage three phase power source can be performed because the impedance valuedoes not depend on the applied voltage.The low voltage short-circuit impedance measurement requires utilization of highly accurate instrumentation on the one side, and elimination of the errors caused by the fluctuations of low voltage power networks due to welding equipment, etc., on the other.In order to carry out these measurements a diagram developed. The diagram uses data acquisition and processing system (DAQ) that enables evaluation of the measured data, the short-circuitimpedance variation curve plotting on the spot, as well as the subsequent processing obtained data. The processing system also corrects the data with the supplyvoltage frequency variation.
Furthermore:
The short-circuit impedance measurement between allthe winding pairs and by each position of the on-load tapchanger is imperiously necessary for:
- verifying the observance of the technical conditions,the designed ones included;
- verifying the possible nonconformities in thewinding manufacturing;
- verifying the behavior of the winding operation onsite (the measurement is performed in agreement with thenorms in force);
- carrying out the system calculations and the short circuitones (including the correct protection regulation);
- verifying the loading of the same type, as well as a of different type transformer units.
The short-circuit impedance measurement can beperformed by connecting the measurement installation to a low voltage (380/220V) source provided that highly accurate instrumentation enabling the automatic data processing is used.
Taken from a paper:
Power Transformer Units Condition Assessment Using VirtualInstrumentation
Discussion welcomed.
Advanced Online Moisture Measurements in Power transformers
Advanced Online Moisture Measurementsin Power Transformers
Maik Koch, Stefan Tenbohlen and Tobias Stirl*
University of Stuttgart, IEH, Pfaffenwaldring 47, 70569 Stuttgart, Germany* Areva Energietechnik GmbH, Activity Schorch Transformers, Rheinstrasse 73,41065 Mönchengladbach, Germany
Abstract – This paper investigates new approaches to determinewater in oil-paper-insulated power transformers.Moisture diffusion and equilibrium are described in termsof water potential. Measurement methods for water in oilpaper insulations were compared. Since the conventionalapplication of moisture equilibrium diagrams leads to erroneousresults, diagrams adapted to the moisture absorptioncapacity and ageing state of the involved materials werecreated. An advanced representation of equilibrium diagramsusing relative moisture in oil leads to much betterresults. Beyond this the moisture determination as activewater in oil and cellulose provides easy, accurate and continuousmeasurements and reflects directly the destructivepotential of water in oil paper insulations. Its integration inonline monitoring systems is shown.
SUMMARY:Main motivation for this investigation was to determinewater in oil-paper-insulated transformers accurateand continuously using equilibrium processes.- Moisture diffusion and equilibrium depends on thehighest possible entropy. This leads to the simple rule,that the relative moisture content CW,rel in adjacent materials becomes identical.
- The ability to dissolve water changes especially withageing of oil. Ageing products such as alcohols, aldehydes,ketones and acids are able to coalesce with waterand therefore increase water solubility.
- Ageing shifts the array of equilibrium curves towardsoil because of its intense increased water solubilitythereby that of cellulose decreases slightly.
- The old method to derive moisture in cellulose (in %)from moisture in oil (in ppm) via equilibrium diagramsis effected by substantial errors.
- Better results can be obtained, if moisture in oil relativeto saturation level (in %) is used instead of moisturein oil by weight (in ppm).
- Moisture relative to saturation or water activity is easy,continually and accurate measurable. Online monitoringsystems can derive moisture in paper from relativemoisture in oil using equilibrium diagrams adapted tothe moisture absorption capacity of paper.
- Active water or relative humidity directly reflects the destructive potential of water. It is therefore muchmore meaningful than the conventionally used waterrelated to weight. Thus water activity is a sufficient indicationfor water in oil paper insulations. Water activityin paper and pressboard is immediately derivable from relative moisture in oil.
To view the full paper
Discussion,Comment are welcomed.
Maik Koch, Stefan Tenbohlen and Tobias Stirl*
University of Stuttgart, IEH, Pfaffenwaldring 47, 70569 Stuttgart, Germany* Areva Energietechnik GmbH, Activity Schorch Transformers, Rheinstrasse 73,41065 Mönchengladbach, Germany
Abstract – This paper investigates new approaches to determinewater in oil-paper-insulated power transformers.Moisture diffusion and equilibrium are described in termsof water potential. Measurement methods for water in oilpaper insulations were compared. Since the conventionalapplication of moisture equilibrium diagrams leads to erroneousresults, diagrams adapted to the moisture absorptioncapacity and ageing state of the involved materials werecreated. An advanced representation of equilibrium diagramsusing relative moisture in oil leads to much betterresults. Beyond this the moisture determination as activewater in oil and cellulose provides easy, accurate and continuousmeasurements and reflects directly the destructivepotential of water in oil paper insulations. Its integration inonline monitoring systems is shown.
SUMMARY:Main motivation for this investigation was to determinewater in oil-paper-insulated transformers accurateand continuously using equilibrium processes.- Moisture diffusion and equilibrium depends on thehighest possible entropy. This leads to the simple rule,that the relative moisture content CW,rel in adjacent materials becomes identical.
- The ability to dissolve water changes especially withageing of oil. Ageing products such as alcohols, aldehydes,ketones and acids are able to coalesce with waterand therefore increase water solubility.
- Ageing shifts the array of equilibrium curves towardsoil because of its intense increased water solubilitythereby that of cellulose decreases slightly.
- The old method to derive moisture in cellulose (in %)from moisture in oil (in ppm) via equilibrium diagramsis effected by substantial errors.
- Better results can be obtained, if moisture in oil relativeto saturation level (in %) is used instead of moisturein oil by weight (in ppm).
- Moisture relative to saturation or water activity is easy,continually and accurate measurable. Online monitoringsystems can derive moisture in paper from relativemoisture in oil using equilibrium diagrams adapted tothe moisture absorption capacity of paper.
- Active water or relative humidity directly reflects the destructive potential of water. It is therefore muchmore meaningful than the conventionally used waterrelated to weight. Thus water activity is a sufficient indicationfor water in oil paper insulations. Water activityin paper and pressboard is immediately derivable from relative moisture in oil.
To view the full paper
Discussion,Comment are welcomed.
Saturday, November 29, 2008
Asset Management and Condition Maintenance
The effectiveness of expending maintenance resources can vary dramatically depending on the target and timing of the maintenance activities. The state-of-the-art in maintenance management offers at least three basic approaches for making maintenance management decisions:
(1) condition-based maintenance (CBM) initiates a maintenance activity when datafrom equipment monitors indicates a need;
(2) reliability centered maintenance (RCM) prioritizes maintenance activities based on quantification of likelihood and consequence of equipment failures; and
(3) optimization techniques offer methods for maximizing effectiveness of the maintenance activities subject to constraints on economic resources, available maintenance crews, and restricted time intervals.
A comprehensive and cost-effective system-wide maintenance allocation and scheduling system
Based on automated integration of condition monitoring with an RCM-based optimized scheduler. The maintenance allocation and scheduling system can reduce maintenance costs while increasing equipment reliability. It can also (1) extend equipment life; (2) cut costs for substation design, refurbishment and construction; and (3) ensure high levels of health and safety for operation and maintenance personnel, the public, and the environment.
The effect of a specified maintenance task can be quantified basedon the cumulative reduction in system risk obtained from it.
1. Mid-term maintenance selection and scheduling: Algorithms and related software applications were created for selecting and scheduling transmission-related maintenancetasks over a budget and labor-constrained time period (e.g., a year) such that the effect ofthose resources are optimized.
2. Long-term maintenance scheduling: an approach for planning longterm policies associated with inspecting and maintaining power transformers and circuit breakers. Results of this approach serve to provide a list of candidate maintenance tasks as input to the mid-term scheduler.
3. Data integration: A novel data integration method created to avoid the need to aggregate data into a centralized warehouse but rather to allow users to query multiple, related data sources simultaneously.
4. Software design approach: Multiagent systems use messaging to facilitate communication between software applications, provide for long-term maintain ability of the software system, and are particularly effective when data and applications are highly distributed as they are in the asset management problem ..
abstracted from
PSERC FINAL PROJECT REPOET 2006
www.pserc.org
(1) condition-based maintenance (CBM) initiates a maintenance activity when datafrom equipment monitors indicates a need;
(2) reliability centered maintenance (RCM) prioritizes maintenance activities based on quantification of likelihood and consequence of equipment failures; and
(3) optimization techniques offer methods for maximizing effectiveness of the maintenance activities subject to constraints on economic resources, available maintenance crews, and restricted time intervals.
A comprehensive and cost-effective system-wide maintenance allocation and scheduling system
Based on automated integration of condition monitoring with an RCM-based optimized scheduler. The maintenance allocation and scheduling system can reduce maintenance costs while increasing equipment reliability. It can also (1) extend equipment life; (2) cut costs for substation design, refurbishment and construction; and (3) ensure high levels of health and safety for operation and maintenance personnel, the public, and the environment.
The effect of a specified maintenance task can be quantified basedon the cumulative reduction in system risk obtained from it.
1. Mid-term maintenance selection and scheduling: Algorithms and related software applications were created for selecting and scheduling transmission-related maintenancetasks over a budget and labor-constrained time period (e.g., a year) such that the effect ofthose resources are optimized.
2. Long-term maintenance scheduling: an approach for planning longterm policies associated with inspecting and maintaining power transformers and circuit breakers. Results of this approach serve to provide a list of candidate maintenance tasks as input to the mid-term scheduler.
3. Data integration: A novel data integration method created to avoid the need to aggregate data into a centralized warehouse but rather to allow users to query multiple, related data sources simultaneously.
4. Software design approach: Multiagent systems use messaging to facilitate communication between software applications, provide for long-term maintain ability of the software system, and are particularly effective when data and applications are highly distributed as they are in the asset management problem ..
abstracted from
PSERC FINAL PROJECT REPOET 2006
www.pserc.org
Recursive Least Squares Method in Parameters Identification
Recursive Least Squares Method in Parameters Identification of DC Motors Models
Dedicated to Professor Mili´c Stoji´c on the occasion of his 65th birthdayRadojka Krneta, Sanja Anti´c, and Danilo Stojanovi´c
Abstract: The procedure of parameters identification of DC motor model using a method of recursive least squares is described in this paper. To identify the system an experimental measuring of signals was carrying out at input - supply of voltage and output of the system for identification - motor angle speed. For the needs of the experiment, a system has been configured with a motor and an optical encoder whose output is connected with the counter input of acquisition card LCK-6013 which overa block connector CB-68LP makes a connection with a computer. The speed of the motor measured by optical encoder is compared with the speed of identified system inorder to confirm the quality of the motor model's parameters estimation.
Conclusion:This paper has investigated the issues involved in applying Recursive Least Squares method in parameters identification of DC motor models. The issues have been considered both theoretically and experimentally. The experimental work was performed on a DC motor with an optical encoder as an output of the system. The validity of the proposed method was shown by simulation an experiments. By comparing a graphic of real motor speed and a graphics of speed of investigated models in a Z and S domains it can be concluded that a satisfying quality of DCmotor parameters identification has been achieved.
FACTA UNIVERSITATIS (NIS)
SER.: ELEC. ENERG. vol. 18, no. 3, December 2005, 467-478
Dedicated to Professor Mili´c Stoji´c on the occasion of his 65th birthdayRadojka Krneta, Sanja Anti´c, and Danilo Stojanovi´c
Abstract: The procedure of parameters identification of DC motor model using a method of recursive least squares is described in this paper. To identify the system an experimental measuring of signals was carrying out at input - supply of voltage and output of the system for identification - motor angle speed. For the needs of the experiment, a system has been configured with a motor and an optical encoder whose output is connected with the counter input of acquisition card LCK-6013 which overa block connector CB-68LP makes a connection with a computer. The speed of the motor measured by optical encoder is compared with the speed of identified system inorder to confirm the quality of the motor model's parameters estimation.
Conclusion:This paper has investigated the issues involved in applying Recursive Least Squares method in parameters identification of DC motor models. The issues have been considered both theoretically and experimentally. The experimental work was performed on a DC motor with an optical encoder as an output of the system. The validity of the proposed method was shown by simulation an experiments. By comparing a graphic of real motor speed and a graphics of speed of investigated models in a Z and S domains it can be concluded that a satisfying quality of DCmotor parameters identification has been achieved.
FACTA UNIVERSITATIS (NIS)
SER.: ELEC. ENERG. vol. 18, no. 3, December 2005, 467-478
Transformer winding defects identification based on a high frequency method
Transformer winding defects identification based on a high frequency method
frequency response analysis method is most frequently used technique employed to detecting fault of inductive apparatus. expecially for faults that are not so much significant but may enlarge in a certain period of time.
Below is an abstract from an article, I find that is a good representation of similar method.
Abstract. The transformer diagnostic methods are systematically being improved and extended due to growing requirements for reliability of power systems in terms of uninterrupted power supply and avoidance of blackouts. Those methods are also driven by longer lifetime of transformers and demand for reduction of transmission and distribution costs. Hence, the detection of winding faults in transformers, both in exploitation or during transportation is an important aspect of power transformer failure prevention. The frequency response analysis method (FRA), more and more frequently used in electric power engineering, has been applied for investigations and signature analysis based on the admittance and transfer function. The paper presents a novel approach to the identification of typical transformer winding problems such as axial or radial movements or turn-to-turn faults. The proposed transfer function discrimination (TFD) criteria are based on the derived transfer function ratios, manifesting higher sensitivity.
Print publication: Issue 9 (September 2007)Received 27 December 2006, in final form 8 June 2007Published 20 July 2007
Marek Florkowski1 and Jakub Furgał21 ABB Corporate Research, 31-038 Kraków, ul. Starowiślna 13A, Poland2 Electrical Power Institute, AGH University of Science and Technology 30-059 Kraków, al. Mickiewicza 30, PolandE-mail: marek.florkowski@pl.abb.com and furgal@uci.agh.edu.pl
In consideration of the basic techniques for the defects identification, I am also very interested in the frequency-vary power source, of how much power output should be considered in order to assure the accuracy of test....
Discuss welcomed.
frequency response analysis method is most frequently used technique employed to detecting fault of inductive apparatus. expecially for faults that are not so much significant but may enlarge in a certain period of time.
Below is an abstract from an article, I find that is a good representation of similar method.
Abstract. The transformer diagnostic methods are systematically being improved and extended due to growing requirements for reliability of power systems in terms of uninterrupted power supply and avoidance of blackouts. Those methods are also driven by longer lifetime of transformers and demand for reduction of transmission and distribution costs. Hence, the detection of winding faults in transformers, both in exploitation or during transportation is an important aspect of power transformer failure prevention. The frequency response analysis method (FRA), more and more frequently used in electric power engineering, has been applied for investigations and signature analysis based on the admittance and transfer function. The paper presents a novel approach to the identification of typical transformer winding problems such as axial or radial movements or turn-to-turn faults. The proposed transfer function discrimination (TFD) criteria are based on the derived transfer function ratios, manifesting higher sensitivity.
Print publication: Issue 9 (September 2007)Received 27 December 2006, in final form 8 June 2007Published 20 July 2007
Marek Florkowski1 and Jakub Furgał21 ABB Corporate Research, 31-038 Kraków, ul. Starowiślna 13A, Poland2 Electrical Power Institute, AGH University of Science and Technology 30-059 Kraków, al. Mickiewicza 30, PolandE-mail: marek.florkowski@pl.abb.com and furgal@uci.agh.edu.pl
In consideration of the basic techniques for the defects identification, I am also very interested in the frequency-vary power source, of how much power output should be considered in order to assure the accuracy of test....
Discuss welcomed.
Estimation of Partial Discharge Parameters
Estimation of Partial Discharge Parameters in GIS Using Acoustic Emission Techniques A Theoretical Approach
DOI No:
10.1142/S0218396X98000260
Source:
Journal of Computational Acoustics, Vol. 6, No. 4 (1998) 403-419
Author(s):
Nandini GuptaDepartment of High-Voltage Engineering, Indian Institute of Science, Bangalore-560 012, IndiaT. S. RamuDepartment of High-Voltage Engineering, Indian Institute of Science, Bangalore-560 012, India
History:
Received 15 October 1996Revised 2 September 1997
Abstract:
Electrical discharge activity within an electrical power apparatus has detrimental effects on the insulating components of the system, and thus its prognosis and diagnosis are of utmost importance. Traditional electrical methods have been replaced by newer techniques such as acoustic detection. Among these, acoustic methods possess certain inherent advantages, especially where complex electrical systems like GIS are involved. The major concerns therein are the estimation of the magnitude of the discharge level as well as location of the source of discharge. The present work addresses, on a theoretical basis, problems connected with identification, measurement and location of electrical discharges, in particular in GIS. Models for the inception and propagation of p.d. within GIS have been proposed. This study, based essentially on a numerical simulation model, corroborates many of the experimental findings reported in the existing literature, and in addition attempts to suggest newer directions in magnitude estimation and location of p.d.
DOI No:
10.1142/S0218396X98000260
Source:
Journal of Computational Acoustics, Vol. 6, No. 4 (1998) 403-419
Author(s):
Nandini GuptaDepartment of High-Voltage Engineering, Indian Institute of Science, Bangalore-560 012, IndiaT. S. RamuDepartment of High-Voltage Engineering, Indian Institute of Science, Bangalore-560 012, India
History:
Received 15 October 1996Revised 2 September 1997
Abstract:
Electrical discharge activity within an electrical power apparatus has detrimental effects on the insulating components of the system, and thus its prognosis and diagnosis are of utmost importance. Traditional electrical methods have been replaced by newer techniques such as acoustic detection. Among these, acoustic methods possess certain inherent advantages, especially where complex electrical systems like GIS are involved. The major concerns therein are the estimation of the magnitude of the discharge level as well as location of the source of discharge. The present work addresses, on a theoretical basis, problems connected with identification, measurement and location of electrical discharges, in particular in GIS. Models for the inception and propagation of p.d. within GIS have been proposed. This study, based essentially on a numerical simulation model, corroborates many of the experimental findings reported in the existing literature, and in addition attempts to suggest newer directions in magnitude estimation and location of p.d.
INSTRUMENT TRANSFORMER ACCURACY TESTING BY DFT METHOD
Slobodan Škundrić, Dragan Kovačević, Slobodan Mikičić
Electrical Engineering Institute “Nikola Tesla”, Belgrade, Yugoslavia
Abstract -Instrument transformer accuracy testing bythe method based on integration of DFT and virtualinstrument concept, composed of standard hardware(osciloscope, PC) and specific software is outlined. Thestructure of the realized virtual instrument for accuracy testof current transformer by DFT method is shown. Themethod has experimentally verified and compared withmeasurements made with the classical complex Hohlecompensator.
Conclusion:
The main advantages of the VI-DFTmethod are that strong, flexible and standard hardware combined withpowerful, flexible and easily changeable software, resulting,compared to the classical concept in improvedperformances, reduced cost and time of development.The experimental test performed on the realised systemshow the validity of the followed approach and very gooddegree of coicidence with classical instruments.The concept proposed and the hardware and softwarestructures presented are strong enough to support laboratoryand on-site, standard and non standard, accuracy testing ofinstrument transformer.
To view detailed information:
http://www.imeko.org/publications/wc-2003/PWC-2003-TC4-113.pdf
Comments welcomed.
Electrical Engineering Institute “Nikola Tesla”, Belgrade, Yugoslavia
Abstract -Instrument transformer accuracy testing bythe method based on integration of DFT and virtualinstrument concept, composed of standard hardware(osciloscope, PC) and specific software is outlined. Thestructure of the realized virtual instrument for accuracy testof current transformer by DFT method is shown. Themethod has experimentally verified and compared withmeasurements made with the classical complex Hohlecompensator.
Conclusion:
The main advantages of the VI-DFTmethod are that strong, flexible and standard hardware combined withpowerful, flexible and easily changeable software, resulting,compared to the classical concept in improvedperformances, reduced cost and time of development.The experimental test performed on the realised systemshow the validity of the followed approach and very gooddegree of coicidence with classical instruments.The concept proposed and the hardware and softwarestructures presented are strong enough to support laboratoryand on-site, standard and non standard, accuracy testing ofinstrument transformer.
To view detailed information:
http://www.imeko.org/publications/wc-2003/PWC-2003-TC4-113.pdf
Comments welcomed.
Measuring storm-restoration performance （Abstract from EEI Report)
Measuring storm-restoration performance
测量飓风恢复绩效
One of the challenges in attempting to compare past and present utility storm-restoration performance is that no two storms are the same.Ice storms can cause vastly different types of damage—depending on whether they hit whenleaves are still on trees, the thickness of the ice, how high the accompanying winds are andwhether the ice damages transmission lines as well as distribution lines.Similarly no two hurricanes are the same. One hurricane might wreak havoc on a utilitysystem with its high winds, while another creates considerable damage from flooding, andanother does both. Because of these differences, it is unrealistic to compare storms and utilityresponses to them without considering the wide variety of factors that can impact a utility’sstorm-restoration activities.The other major challenge of evaluating whether utility responses are getting better or worseis obtaining good data on utility storm-restoration activities. The industry does not have astandardized method for evaluating post-storm restoration effectiveness. Hence, there is noconsistent method of collecting data on utility storm-restoration activities.Most data regarding storm damage is collected and maintained by individual utilities, and isused primarily for tracking costs and preparing “major storm reports” for state public utilitycommissions. Once again, there is no formal or informal standard for preparing these reports,either at the regional or national level.To address this lack of comparable data, EEI designed a special survey to collectinformation on utility storm-restoration activities over at least a 10-year period of time.
Storm Restoration Survey Results
1) In recent years, survey respondents have improved the rate at which they are ableto restore power to customers following a major storm event.
3) The number of restoration workers deployed after major storms has decreasedfairly dramatically in recent years as the number of customers restored per workerhas risen.
4) Based on equipment damage, recent storms do not appear to have been any moreor less severe.
4) Based on equipment damage, recent storms do not appear to have been any moreor less severe.
Summary
These storm reports help clarify the tremendous impact of major storms on utility systems,and illustrate the huge effort utilities undertake to restore their systems as quickly as possible.The summaries indicate favorable performance trends when the companies’ most recent stormrestoration efforts are compared with previous significant storms.The North Carolina Utilities Commission reached similar conclusions regarding the DukePower and Progress Energy storm-restoration efforts. In its final report on the 2002 Ice Storm,the commission found no discernable increase in outage duration. The report illustrated howmuch more quickly Duke and Progress Energy customers were restored in 2002 than in theaftermath of a 1996 Ice Storm.The North Carolina Commission concluded that the companies’ restoration efforts were“diligent, effective and well managed as a whole.”10 The Maryland Public Service Commissionis currently evaluating BG&E’s storm report as well as those of the other Maryland utilities thataffected by Hurricane Isabel.
Taken from EEI (Edison Electric Institute) 2004 report 'Utility Storm RestorationResponse'
测量飓风恢复绩效
One of the challenges in attempting to compare past and present utility storm-restoration performance is that no two storms are the same.Ice storms can cause vastly different types of damage—depending on whether they hit whenleaves are still on trees, the thickness of the ice, how high the accompanying winds are andwhether the ice damages transmission lines as well as distribution lines.Similarly no two hurricanes are the same. One hurricane might wreak havoc on a utilitysystem with its high winds, while another creates considerable damage from flooding, andanother does both. Because of these differences, it is unrealistic to compare storms and utilityresponses to them without considering the wide variety of factors that can impact a utility’sstorm-restoration activities.The other major challenge of evaluating whether utility responses are getting better or worseis obtaining good data on utility storm-restoration activities. The industry does not have astandardized method for evaluating post-storm restoration effectiveness. Hence, there is noconsistent method of collecting data on utility storm-restoration activities.Most data regarding storm damage is collected and maintained by individual utilities, and isused primarily for tracking costs and preparing “major storm reports” for state public utilitycommissions. Once again, there is no formal or informal standard for preparing these reports,either at the regional or national level.To address this lack of comparable data, EEI designed a special survey to collectinformation on utility storm-restoration activities over at least a 10-year period of time.
Storm Restoration Survey Results
1) In recent years, survey respondents have improved the rate at which they are ableto restore power to customers following a major storm event.
3) The number of restoration workers deployed after major storms has decreasedfairly dramatically in recent years as the number of customers restored per workerhas risen.
4) Based on equipment damage, recent storms do not appear to have been any moreor less severe.
4) Based on equipment damage, recent storms do not appear to have been any moreor less severe.
Summary
These storm reports help clarify the tremendous impact of major storms on utility systems,and illustrate the huge effort utilities undertake to restore their systems as quickly as possible.The summaries indicate favorable performance trends when the companies’ most recent stormrestoration efforts are compared with previous significant storms.The North Carolina Utilities Commission reached similar conclusions regarding the DukePower and Progress Energy storm-restoration efforts. In its final report on the 2002 Ice Storm,the commission found no discernable increase in outage duration. The report illustrated howmuch more quickly Duke and Progress Energy customers were restored in 2002 than in theaftermath of a 1996 Ice Storm.The North Carolina Commission concluded that the companies’ restoration efforts were“diligent, effective and well managed as a whole.”10 The Maryland Public Service Commissionis currently evaluating BG&E’s storm report as well as those of the other Maryland utilities thataffected by Hurricane Isabel.
Taken from EEI (Edison Electric Institute) 2004 report 'Utility Storm RestorationResponse'
Current Transformer definition and principle（Continued from KAPPA)
Current transformers
Principle of operation
Definitions
Standards
Tests
Typical Specifications
Principle of operation
A current transformer is defined as "as an instrument transformer in which the secondary current is substantially proportional to the primary current (under normal conditions of operation) and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections." This highlights the accuracy requirement of the current transformer but also important is the isolating function, which means no matter what the system voltage the secondary circuit need be insulated only for a low voltage.
The current transformer works on the principle of variable flux. In the "ideal" current transformer, secondary current would be exactly equal (when multiplied by the turns ratio) and opposite to the primary current. But, as in the voltage transformer, some of the primary current or the primary ampere-turns is utilized for magnetizing the core, thus leaving less than the actual primary ampere turns to be "transformed" into the secondary ampere-turns. This naturally introduces an error in the transformation. The error is classified into two-the current or ratio error and the phase error.
Kappa CT s are designed to minimise the errors using the best quality electrical steels for the core of the transformer. Both toroidal (round) and rectangular CT s are manufactured.
Definitions
Rated primary current: The value of current which is to be transformed to a lower value. In CT parlance, the "load" of the CT refers to the primary current.
Rated secondary current: The current in the secondary circuit and on which the performance of the CT is based. Typical values of secondary current are 1 A or 5 A. In the case of transformer differential protection, secondary currents of 1/ root 3 A and 5/ root 3 A are also specified.
Rated burden: The apparent power of the secondary circuit in Volt-amperes expressed at the rated secondary current and at a specific power factor (0.8 for almost all standards)
Accuracy class: In the case of metering CT s, accuracy class is typically, 0.2, 0.5, 1 or 3. This means that the errors have to be within the limits specified in the standards for that particular accuracy class. The metering CT has to be accurate from 5% to 120% of the rated primary current, at 25% and 100% of the rated burden at the specified power factor. In the case of protection CT s, the CT s should pass both the ratio and phase errors at the specified accuracy class, usually 5P or 10P, as well as composite error at the accuracy limit factor of the CT.
Composite error: The rms value of the difference between the instantaneous primary current and the instantaneous secondary current multiplied by the turns ratio, under steady state conditions.
Accuracy limit factor: The value of primary current upto which the CT complies with composite error requirements. This is typically 5, 10 or 15, which means that the composite error of the CT has to be within specified limits at 5, 10 or 15 times the rated primary current.
Short time rating: The value of primary current (in kA) that the CT should be able to withstand both thermally and dynamically without damage to the windings, with the secondary circuit being short-circuited. The time specified is usually 1 or 3 seconds.
Instrument security factor (factor of security): This typically takes a value of less than 5 or less than 10 though it could be much higher if the ratio is very low. If the factor of security of the CT is 5, it means that the composite error of the metering CT at 5 times the rated primary current is equal to or greater than 10%. This means that heavy currents on the primary are not passed on to the secondary circuit and instruments are therefore protected. In the case of double ratio CT's, FS is applicable for the lowest ratio only.
Class PS/ X CT: In balance systems of protection, CT s with a high degree of similarity in their characteristics are required. These requirements are met by Class PS (X) CT s. Their performance is defined in terms of a knee-point voltage (KPV), the magnetizing current (Imag) at the knee point voltage or 1/2 or 1/4 the knee-point voltage, and the resistance of the CT secondary winding corrected to 75C. Accuracy is defined in terms of the turns ratio.
Knee point voltage: That point on the magnetizing curve where an increase of 10% in the flux density (voltage) causes an increase of 50% in the magnetizing force (current).
Summation CT: When the currents in a number of feeders need not be individually metered but summated to a single meter or instrument, a summation current transformer can be used. The summation CT consists of two or more primary windings which are connected to the feeders to be summated, and a single secondary winding, which feeds a current proportional to the summated primary current. A typical ratio would be 5+5+5/ 5A, which means that three primary feeders of 5 are to be summated to a single 5A meter.
Core balance CT (CBCT): The CBCT, also known as a zero sequence CT, is used for earth leakage and earth fault protection. The concept is similar to the RVT. In the CBCT, the three core cable or three single cores of a three phase system pass through the inner diameter of the CT. When the system is fault free, no current flows in the secondary of the CBCT. When there is an earth fault, the residual current (zero phase sequence current) of the system flows through the secondary of the CBCT and this operates the relay. In order to design the CBCT, the inner diameter of the CT, the relay type, the relay setting and the primary operating current need to be furnished.
Interposing CT's (ICT's) : Interposing CT's are used when the ratio of transformation is very high. It is also used to correct for phase displacement for differential protection of transformers.
Taken from KAPPA electricals.
Principle of operation
Definitions
Standards
Tests
Typical Specifications
Principle of operation
A current transformer is defined as "as an instrument transformer in which the secondary current is substantially proportional to the primary current (under normal conditions of operation) and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections." This highlights the accuracy requirement of the current transformer but also important is the isolating function, which means no matter what the system voltage the secondary circuit need be insulated only for a low voltage.
The current transformer works on the principle of variable flux. In the "ideal" current transformer, secondary current would be exactly equal (when multiplied by the turns ratio) and opposite to the primary current. But, as in the voltage transformer, some of the primary current or the primary ampere-turns is utilized for magnetizing the core, thus leaving less than the actual primary ampere turns to be "transformed" into the secondary ampere-turns. This naturally introduces an error in the transformation. The error is classified into two-the current or ratio error and the phase error.
Kappa CT s are designed to minimise the errors using the best quality electrical steels for the core of the transformer. Both toroidal (round) and rectangular CT s are manufactured.
Definitions
Rated primary current: The value of current which is to be transformed to a lower value. In CT parlance, the "load" of the CT refers to the primary current.
Rated secondary current: The current in the secondary circuit and on which the performance of the CT is based. Typical values of secondary current are 1 A or 5 A. In the case of transformer differential protection, secondary currents of 1/ root 3 A and 5/ root 3 A are also specified.
Rated burden: The apparent power of the secondary circuit in Volt-amperes expressed at the rated secondary current and at a specific power factor (0.8 for almost all standards)
Accuracy class: In the case of metering CT s, accuracy class is typically, 0.2, 0.5, 1 or 3. This means that the errors have to be within the limits specified in the standards for that particular accuracy class. The metering CT has to be accurate from 5% to 120% of the rated primary current, at 25% and 100% of the rated burden at the specified power factor. In the case of protection CT s, the CT s should pass both the ratio and phase errors at the specified accuracy class, usually 5P or 10P, as well as composite error at the accuracy limit factor of the CT.
Composite error: The rms value of the difference between the instantaneous primary current and the instantaneous secondary current multiplied by the turns ratio, under steady state conditions.
Accuracy limit factor: The value of primary current upto which the CT complies with composite error requirements. This is typically 5, 10 or 15, which means that the composite error of the CT has to be within specified limits at 5, 10 or 15 times the rated primary current.
Short time rating: The value of primary current (in kA) that the CT should be able to withstand both thermally and dynamically without damage to the windings, with the secondary circuit being short-circuited. The time specified is usually 1 or 3 seconds.
Instrument security factor (factor of security): This typically takes a value of less than 5 or less than 10 though it could be much higher if the ratio is very low. If the factor of security of the CT is 5, it means that the composite error of the metering CT at 5 times the rated primary current is equal to or greater than 10%. This means that heavy currents on the primary are not passed on to the secondary circuit and instruments are therefore protected. In the case of double ratio CT's, FS is applicable for the lowest ratio only.
Class PS/ X CT: In balance systems of protection, CT s with a high degree of similarity in their characteristics are required. These requirements are met by Class PS (X) CT s. Their performance is defined in terms of a knee-point voltage (KPV), the magnetizing current (Imag) at the knee point voltage or 1/2 or 1/4 the knee-point voltage, and the resistance of the CT secondary winding corrected to 75C. Accuracy is defined in terms of the turns ratio.
Knee point voltage: That point on the magnetizing curve where an increase of 10% in the flux density (voltage) causes an increase of 50% in the magnetizing force (current).
Summation CT: When the currents in a number of feeders need not be individually metered but summated to a single meter or instrument, a summation current transformer can be used. The summation CT consists of two or more primary windings which are connected to the feeders to be summated, and a single secondary winding, which feeds a current proportional to the summated primary current. A typical ratio would be 5+5+5/ 5A, which means that three primary feeders of 5 are to be summated to a single 5A meter.
Core balance CT (CBCT): The CBCT, also known as a zero sequence CT, is used for earth leakage and earth fault protection. The concept is similar to the RVT. In the CBCT, the three core cable or three single cores of a three phase system pass through the inner diameter of the CT. When the system is fault free, no current flows in the secondary of the CBCT. When there is an earth fault, the residual current (zero phase sequence current) of the system flows through the secondary of the CBCT and this operates the relay. In order to design the CBCT, the inner diameter of the CT, the relay type, the relay setting and the primary operating current need to be furnished.
Interposing CT's (ICT's) : Interposing CT's are used when the ratio of transformation is very high. It is also used to correct for phase displacement for differential protection of transformers.
Taken from KAPPA electricals.
Technical information on Instrument Transformers
Technical information On Instrument Transformers
For those who are interested in basic ideas of instrument transfomrers
Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. Their role in electrical systems is of primary importance as they are a means of "stepping down" the current or voltage of a system to measurable values, such as 5A or 1A in the case of a current transformers or 110V or 100V in the case of a voltage transformer. This offers the advantage that measurement and protective equipment can be standardized on a few values of current and voltage.
Voltage transformers
Current transformers
Kappa has published a reference manual on instrument transformers
Voltage transformers
Principle of operation
Definitions
Standards
Tests
Typical Specifications
Principle of operation
The standards define a voltage transformer as one in which "the secondary voltage is substantially proportional to the primary voltage and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections."
This, in essence, means that the voltage transformer has to be as close as possible to the "ideal" transformer. In an "ideal" transformer, the secondary voltage vector is exactly opposite and equal to the primary voltage vector, when multiplied by the turns ratio.
In a "practical" transformer, errors are introduced because some current is drawn for the magnetization of the core and because of drops in the primary and secondary windings due to leakage reactance and winding resistance. One can thus talk of a voltage error,which is the amount by which the voltage is less than the applied primary voltage ,and the phase error, which is the phase angle by which the reversed secondary voltage vector is displaced from the primary voltage vector.
To read more
For those who are interested in basic ideas of instrument transfomrers
Instrument transformers are used for measurement and protective application, together with equipment such as meters and relays. Their role in electrical systems is of primary importance as they are a means of "stepping down" the current or voltage of a system to measurable values, such as 5A or 1A in the case of a current transformers or 110V or 100V in the case of a voltage transformer. This offers the advantage that measurement and protective equipment can be standardized on a few values of current and voltage.
Voltage transformers
Current transformers
Kappa has published a reference manual on instrument transformers
Voltage transformers
Principle of operation
Definitions
Standards
Tests
Typical Specifications
Principle of operation
The standards define a voltage transformer as one in which "the secondary voltage is substantially proportional to the primary voltage and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections."
This, in essence, means that the voltage transformer has to be as close as possible to the "ideal" transformer. In an "ideal" transformer, the secondary voltage vector is exactly opposite and equal to the primary voltage vector, when multiplied by the turns ratio.
In a "practical" transformer, errors are introduced because some current is drawn for the magnetization of the core and because of drops in the primary and secondary windings due to leakage reactance and winding resistance. One can thus talk of a voltage error,which is the amount by which the voltage is less than the applied primary voltage ,and the phase error, which is the phase angle by which the reversed secondary voltage vector is displaced from the primary voltage vector.
To read more
Low voltage method characterize calibration for Instrument Transformer
Portable Electromagnetizing Instrument Transformer tester (calibrator) assumes first that there is no significant change of mechanical parameter.
Then it employs electric parameter to map the error model, and compute its error graph. all the error data is obtained from simulated test, including test power source and phatom electronic load, so as to lower down the test power significantly.
Because the simulation signal is applied from the secondary with primary being open circuited, the simulating voltage should assure that insulation between windings should not be damaged, which places high requirement for accurate measurement of feedback current from the secondary in response with the drive voltage.
But actually the feedback current can be as low as serveral miniamp, it is not easy to carry on accurate test without noise undercontrol.
From this point of view, frequency-response analyzing technique being used to complement that defect and focus attention on filters.
Data tested from simulation can be used to re-modify the original model that representing the error characteristics, among which one significant value is leakage inductance, a parameter not easy for direct measurement.
Then it employs electric parameter to map the error model, and compute its error graph. all the error data is obtained from simulated test, including test power source and phatom electronic load, so as to lower down the test power significantly.
Because the simulation signal is applied from the secondary with primary being open circuited, the simulating voltage should assure that insulation between windings should not be damaged, which places high requirement for accurate measurement of feedback current from the secondary in response with the drive voltage.
But actually the feedback current can be as low as serveral miniamp, it is not easy to carry on accurate test without noise undercontrol.
From this point of view, frequency-response analyzing technique being used to complement that defect and focus attention on filters.
Data tested from simulation can be used to re-modify the original model that representing the error characteristics, among which one significant value is leakage inductance, a parameter not easy for direct measurement.
IEEETM website be blocked in China
IEEETM Can not be visited in China at the present, including its Chinese version Pusala, as it shares the same IP address.
The most recently published information will be copied to this blog.
IEEETM is also planning to establish a product panel that unfolds new tech and products from IEEETM (Pusala China), So customers in China can view the information as it is a different IP address.
Furthermore, IEEETM is considering transfer the server to load Pusala China website in 2009.
The most recently published information will be copied to this blog.
IEEETM is also planning to establish a product panel that unfolds new tech and products from IEEETM (Pusala China), So customers in China can view the information as it is a different IP address.
Furthermore, IEEETM is considering transfer the server to load Pusala China website in 2009.
Monday, November 24, 2008
Technical & Product Summary
IEEETM aims at serving the electric power industry with innovative Solutions and Instruments.
For detailed information about technical principle and how to process useful data to derive test report, please refer to Guidance of Technical Application Book published by Pusala Technology, Chengdu China.
Solutions:
IEEETM collaborates with automation Research Institute of Guangxi University and Electric Lab of Sichuan University of Technology & Science for Soft-solutions in the electric power system. Main focus of the work is towards minimizing the economic investment and at the same time ensuring certain level of security.
Condition-Based Maintenance (CBM)
CBM is an advanced maintenance method that attracts increasing interests by power Utilities. It bases its theory and method on assorting condition data that collected directly or indirectly from fields test or monitoring, then assesses possible cost and safety problem to rank maintenance activities and make middle or long time decisions.
Note: Simulation data will be adjusted to local regulation and experience.
Know what is CBM in more detail
Risk Assessment System (RAS)
Features with comprehensive arithmetic that combines optimal theory, power flow and modeling technique, it focus on decision making that reduces patent risk and maximize income when satisfying certain level of security and stability.
Notes: Large Scale computation is required.
Get views about system reliability
For detailed information about technical principle and how to process useful data to derive test report, please refer to Guidance of Technical Application Book published by Pusala Technology, Chengdu China.
Solutions:
IEEETM collaborates with automation Research Institute of Guangxi University and Electric Lab of Sichuan University of Technology & Science for Soft-solutions in the electric power system. Main focus of the work is towards minimizing the economic investment and at the same time ensuring certain level of security.
Condition-Based Maintenance (CBM)
CBM is an advanced maintenance method that attracts increasing interests by power Utilities. It bases its theory and method on assorting condition data that collected directly or indirectly from fields test or monitoring, then assesses possible cost and safety problem to rank maintenance activities and make middle or long time decisions.
Note: Simulation data will be adjusted to local regulation and experience.
Know what is CBM in more detail
Risk Assessment System (RAS)
Features with comprehensive arithmetic that combines optimal theory, power flow and modeling technique, it focus on decision making that reduces patent risk and maximize income when satisfying certain level of security and stability.
Notes: Large Scale computation is required.
Get views about system reliability
Sunday, November 23, 2008
State estimation technique obtained from CCVT transient studies
CCVT (coupling capacitor voltage transformer)
电容式电压互感器
is widely used in Electric Power Industries.
due to its complex structure and operation principle, the transient characteristics have attracted attention from all over the world to study what is affecting the transfer functions.
among the past research, serveral famous methods are undertaken:
a) off-line or lab test by applying operation voltage to the primary to simulate working conditions.
b) online measurement from the secondary.
c) off-line or lab test from the secondary, take advantage of parameter identification.
IEEETM has been conducting research and experiment parameter studies in order to obtain accurate parameter of transfer function, which will be used for online fault forcast.
Also in order to make the project feasible, online monitoring has to combine with offline data in order to adjust internal parameter by iteration techniques, as a way to analyze transfer characteristics.
Traditionally, there is much cost to test a CCVT by offline test, as it requires a standard transformer and high voltage power source, there may be some portable way of testing the CCVT which also guarantee the test accuracy.
So, a possible way is to apply test signal from the secondary, in reference with a mathematical model to iterate parameters.
Among the techniques, safety issues and noise problem should be taken into consideration.
This project is open for discussions.
Vieena Apple
IEEETM center
电容式电压互感器
is widely used in Electric Power Industries.
due to its complex structure and operation principle, the transient characteristics have attracted attention from all over the world to study what is affecting the transfer functions.
among the past research, serveral famous methods are undertaken:
a) off-line or lab test by applying operation voltage to the primary to simulate working conditions.
b) online measurement from the secondary.
c) off-line or lab test from the secondary, take advantage of parameter identification.
IEEETM has been conducting research and experiment parameter studies in order to obtain accurate parameter of transfer function, which will be used for online fault forcast.
Also in order to make the project feasible, online monitoring has to combine with offline data in order to adjust internal parameter by iteration techniques, as a way to analyze transfer characteristics.
Traditionally, there is much cost to test a CCVT by offline test, as it requires a standard transformer and high voltage power source, there may be some portable way of testing the CCVT which also guarantee the test accuracy.
So, a possible way is to apply test signal from the secondary, in reference with a mathematical model to iterate parameters.
Among the techniques, safety issues and noise problem should be taken into consideration.
This project is open for discussions.
Vieena Apple
IEEETM center
American National Standard for voltage ratings
From www.ien.com
American National Standard For Electric Power Systems and Equipment -- Voltage Ratings
Rosslyn, VA, January 16, 2007 -- The National Electrical Manufacturers Association (NEMA) has published ANSI C84.1-2006, American National Standard for Electric Power Systems and Equipment -- Voltage Ratings (60 Hertz).
This standard establishes nominal voltage ratings and operating tolerances for 60 Hz electric power systems above 100 volts. It also makes recommendations to other standardizing groups with respect to voltage ratings for equipment used on power systems and for utilization devices connected to such systems. ANSI C84.1-2006 includes preferred voltage ratings up to and including 1200 kV maximum system voltage.
In defining maximum system voltage, voltage transients and temporary overvoltages caused by abnormal system conditions such as faults, loads, and rejection are excluded. However, voltage transients and temporary overvoltages may affect equipment operating performance and may be considered in the individual product standards.
The standard was expanded to cover voltages from 230-1,200 kV, and the requirements from the Institute of Electrical and Electronics Engineers, Inc (IEEE) 1312, which covered these higher voltages, were incorporated into the C84.1 revision.....
American National Standard For Electric Power Systems and Equipment -- Voltage Ratings
Rosslyn, VA, January 16, 2007 -- The National Electrical Manufacturers Association (NEMA) has published ANSI C84.1-2006, American National Standard for Electric Power Systems and Equipment -- Voltage Ratings (60 Hertz).
This standard establishes nominal voltage ratings and operating tolerances for 60 Hz electric power systems above 100 volts. It also makes recommendations to other standardizing groups with respect to voltage ratings for equipment used on power systems and for utilization devices connected to such systems. ANSI C84.1-2006 includes preferred voltage ratings up to and including 1200 kV maximum system voltage.
In defining maximum system voltage, voltage transients and temporary overvoltages caused by abnormal system conditions such as faults, loads, and rejection are excluded. However, voltage transients and temporary overvoltages may affect equipment operating performance and may be considered in the individual product standards.
The standard was expanded to cover voltages from 230-1,200 kV, and the requirements from the Institute of Electrical and Electronics Engineers, Inc (IEEE) 1312, which covered these higher voltages, were incorporated into the C84.1 revision.....
Introduction
This blog site is an open discussing panel for technical problem within industry aera.
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IEEETM technical center
Contact: opensource@ieeetm.com
www.ieeetm.com
Supported by
IEEETM technical center
Contact: opensource@ieeetm.com
www.ieeetm.com
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