by Kevin K. Tseng, M.ASCE, (Assistant Professor, Dept. of Civil and Environmental Engineering, Vanderbilt Univ., Nashville, TN 37235.) and Liangsheng Wang, (Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Vanderbilt Univ., Nashville, TN 37235.)
Journal of Engineering Mechanics, Vol. 131, No. 1, January 2005, pp. 58-64, (doi 10.1061/(ASCE)0733-9399(2005)131:1(58))
Abstract:
A structural damage identification technique based on the impedance method is presented in this paper using smart piezoelectric transducer (PZT) patches. A modeling framework is developed to determine the structural impedance response and the dynamic output forces of PZT patches from the electric admittance measurements. A damage identification scheme for solving the nonlinear optimization problem is proposed to locate and quantify the structural damage through the minimization of the discrepancy between the structural impedance response and the numerically computed frequency response. The proposed technique does not use modal analysis or model reduction, and only the electric admittance measurements of PZT patches and the analytical system matrices are required. A beam example has been employed to illustrate the effectiveness of the proposed algorithm numerically. Furthermore, the influence of the measurement noise on the results has been investigated.
From ASCE Publications.
Tuesday, September 1, 2009
Paper recommendation: Research Article The dielectric behavior of outdoor high-voltage polymeric insulation due to environmental aging
Application of Dielectric Spectroscopy in HV insulation
ABSTRACT
Most of breakdowns are caused by aging effects of high-voltage insulation used within these components, and there is still a need of suitable tools to diagnose such systems non-destructively and reliably in the field. Several methods have been published in the last decade for which reliable diagnostics are claimed. One of these methods is based on changes of the dielectric properties of the insulation. Dielectric spectroscopy provides information on molecular dynamics and free charge carriers and it is sensitive to the insulation morphology, that is crystallinity, oxidation, additives, and impurities (ions and dipolar molecules). The measurement of dielectric constants and dielectric losses in frequency domain help to quantify the chemical and physical changes in the bulk of polymer due to aging. The results of frequency domain measurements in this contribution show that the effects of aging of insulators can be analyzed by this method. This paper demonstrates the use of a dielectric spectroscopy technique for monitoring the effect of different aging on silicone rubber, ethylene-propylene diene monomer (EPDM), and blend of silicone-EPDM and new polymeric alloy. New polymeric alloy is found to be suitable for humid environment and shows good hydro-thermal resistance compared to other polymers; also it is cheaper than other materials.
Copyright © 2006 John Wiley & Sons, Ltd.
The dielectric behavior of outdoor high-voltage polymeric insulation due to environmental aging
M. Ehsani 1 *, G. R. Bakhshandeh 1, J. Morshedian 1, H. Borsi 2, E. Gockenbach 2, A. A. Shayegani 3
1Department of Polymer Processing, Iran Polymer and Petrochemical Institute (IPPI), P.O. Box.14965/115, Tehran, Iran
2Institute of Electric Power Systems, Division of High Voltage Engineering, Schering Institute, University of Hannover, Callinstr. 25A, D-30167, Hannover, Germany
3High Voltage Laboratory, Electrical and Computer Engineering Department, University of Tehran, P.O. Box 14395-515, Tehran, Iran
*Correspondence to M. Ehsani, Department of Polymer Processing, Iran Polymer and Petrochemical Institute (IPPI), P.O. Box.14965/115, Tehran, Iran.
Funded by: Ministry of Energy of Iran
KEYWORDS
dissipation factor • permittivity • dielectric spectroscopy • polarization
ABSTRACT
Most of breakdowns are caused by aging effects of high-voltage insulation used within these components, and there is still a need of suitable tools to diagnose such systems non-destructively and reliably in the field. Several methods have been published in the last decade for which reliable diagnostics are claimed. One of these methods is based on changes of the dielectric properties of the insulation. Dielectric spectroscopy provides information on molecular dynamics and free charge carriers and it is sensitive to the insulation morphology, that is crystallinity, oxidation, additives, and impurities (ions and dipolar molecules). The measurement of dielectric constants and dielectric losses in frequency domain help to quantify the chemical and physical changes in the bulk of polymer due to aging. The results of frequency domain measurements in this contribution show that the effects of aging of insulators can be analyzed by this method. This paper demonstrates the use of a dielectric spectroscopy technique for monitoring the effect of different aging on silicone rubber, ethylene-propylene diene monomer (EPDM), and blend of silicone-EPDM and new polymeric alloy. New polymeric alloy is found to be suitable for humid environment and shows good hydro-thermal resistance compared to other polymers; also it is cheaper than other materials.
Copyright © 2006 John Wiley & Sons, Ltd.
The dielectric behavior of outdoor high-voltage polymeric insulation due to environmental aging
M. Ehsani 1 *, G. R. Bakhshandeh 1, J. Morshedian 1, H. Borsi 2, E. Gockenbach 2, A. A. Shayegani 3
1Department of Polymer Processing, Iran Polymer and Petrochemical Institute (IPPI), P.O. Box.14965/115, Tehran, Iran
2Institute of Electric Power Systems, Division of High Voltage Engineering, Schering Institute, University of Hannover, Callinstr. 25A, D-30167, Hannover, Germany
3High Voltage Laboratory, Electrical and Computer Engineering Department, University of Tehran, P.O. Box 14395-515, Tehran, Iran
*Correspondence to M. Ehsani, Department of Polymer Processing, Iran Polymer and Petrochemical Institute (IPPI), P.O. Box.14965/115, Tehran, Iran.
Funded by: Ministry of Energy of Iran
KEYWORDS
dissipation factor • permittivity • dielectric spectroscopy • polarization
Reading Recommendation: Application of low frequency dielectric spectroscopy to estimate condition of mineral oil
Paper about dielectric spectroscopy application in HV equipment & materials.
Abstract
Conventional loss factor and capacitance measurements are used to determine condition of insulating liquid. In the new IEC 61620 standard capacitance and conductance are measured at low voltage and low frequency with square wave method to over come some difficulties of the conventional method. Nowadays low frequency dielectric spectroscopy becomes a powerful diagnostics tools for high voltage apparatus and utilities provide spectroscopy measurement system for diagnosis of their power apparatus. In this paper is shown that the space charge polarization can be observed with low frequency spectroscopy for insulating liquids. Increase of capacitance at low frequency can be defined as a new parameter and help to accurate determination of state of insulating liquid. Space charge polarization of insulating liquids can influence the result of dielectric spectroscopy of liquid impregnated insulation system too and must be considered for better interpretation of spectroscopy results.
Shayegani, A.A. Borsi, H. Gockenbach , E. Mohseni, H. Div. of High Voltage Eng., Hannover Univ., Germany;
This paper appears in: Dielectric Liquids, 2005. ICDL 2005. 2005 IEEE International Conference on
Publication Date: 26 June-1 July 2005
On page(s): 285- 288
ISSN: ISBN: 0-7803-8954-9
INSPEC Accession Number: 8565526
Digital Object Identifier: 10.1109/ICDL.2005.1490082
Current Version Published: 2005-08-01
Abstract
Conventional loss factor and capacitance measurements are used to determine condition of insulating liquid. In the new IEC 61620 standard capacitance and conductance are measured at low voltage and low frequency with square wave method to over come some difficulties of the conventional method. Nowadays low frequency dielectric spectroscopy becomes a powerful diagnostics tools for high voltage apparatus and utilities provide spectroscopy measurement system for diagnosis of their power apparatus. In this paper is shown that the space charge polarization can be observed with low frequency spectroscopy for insulating liquids. Increase of capacitance at low frequency can be defined as a new parameter and help to accurate determination of state of insulating liquid. Space charge polarization of insulating liquids can influence the result of dielectric spectroscopy of liquid impregnated insulation system too and must be considered for better interpretation of spectroscopy results.
Shayegani, A.A. Borsi, H. Gockenbach , E. Mohseni, H. Div. of High Voltage Eng., Hannover Univ., Germany;
This paper appears in: Dielectric Liquids, 2005. ICDL 2005. 2005 IEEE International Conference on
Publication Date: 26 June-1 July 2005
On page(s): 285- 288
ISSN: ISBN: 0-7803-8954-9
INSPEC Accession Number: 8565526
Digital Object Identifier: 10.1109/ICDL.2005.1490082
Current Version Published: 2005-08-01
Monday, August 31, 2009
ResearchNews:Effects of "Natural" Water and "Added" Water on Microwave Dielectric Properties of Shelled Corn for Sensing Density and Moisture Content
Authors
Trabelsi, Samir
Nelson, Stuart
Lewis, Micah
Submitted to: Journal of Microwave Power and Electromagnetic Energy
Publication Type: Peer Reviewed Journal Publication
Acceptance Date: July 8, 2009 Publication Date: July 8, 2009
Publisher's URL: http://www.impi.org/meetings/symposium/
Citation: Trabelsi, S., Nelson, S.O., Lewis, M.A. 2009. Effects of "Natural" Water and "Added" Water oon Microwave Dielectric Properties of Shelled Corn for Sensing Density and Moisture Content. Journal of Microwave Power and Electromagnetic Energy.
Interpretive Summary:
The electrical characteristics of grain known as dielectric properties are used by electronic grain moisture meters for rapid determination of moisture content. Moisture content is important in determining the potential for safe storage of grain, and it must be measured whenever a grain lot is sold. Recent research has shown that measurements on grain at microwave frequencies offer advantages for moisture testing compared to the lower radio frequencies currently used by commercial grain moisture meters. This research has also shown that the moisture content of grain can be rapidly obtained from microwave measurements that determine the dielectric properties of the grain independent of fluctuations in the bulk density (packing) of the grain, which causes errors in the moisture content indicated by currently used moisture meters if it is not taken into account. Therefore the microwave sensing of grain moisture content shows promise for on-line monitoring of moisture in grain and seed. Questions have been raised as to whether dielectric properties of grain of high moisture contents at harvest are different from those of the same grain to which water has been added, after drying, to bring it back to the original moisture level. In this study, microwave dielectric properties of shelled, yellow-dent hybrid field corn were measured at harvest and as the corn dried down to normal storage levels. Then, water was added to hybrid corn lots of normal storage moisture levels and the dielectric properties were measured as moisture content was increased to levels for corn at harvest. Comparing results of the measurements showed that there was no appreciable difference between the natural-moisture and added moisture-lots of shelled corn. Thus, the customary method for adding moisture in research studies does not introduce any complications in research on microwave methods for sensing moisture content in corn. The new information is useful to engineers developing new moisture meters and it will therefore contribute to the goal of providing high quality and healthful products for consumers.
Technical Abstract:
Dielectric properties of samples of shelled corn of ¿natural¿ water content and those prepared by adding water were measured in free space at microwave frequencies and 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 9 GHz show no difference between the samples with ¿natural¿ water and those in which water was added artificially. Bulk densities and moisture contents predicted from calibration equations expressed in terms of dielectric properties of both natural and added water samples agreed closely, and standard errors were less than 1% moisture content and 5% for bulk density.
From http://www.ars.usda.gov
Trabelsi, Samir
Nelson, Stuart
Lewis, Micah
Submitted to: Journal of Microwave Power and Electromagnetic Energy
Publication Type: Peer Reviewed Journal Publication
Acceptance Date: July 8, 2009 Publication Date: July 8, 2009
Publisher's URL: http://www.impi.org/meetings/symposium/
Citation: Trabelsi, S., Nelson, S.O., Lewis, M.A. 2009. Effects of "Natural" Water and "Added" Water oon Microwave Dielectric Properties of Shelled Corn for Sensing Density and Moisture Content. Journal of Microwave Power and Electromagnetic Energy.
Interpretive Summary:
The electrical characteristics of grain known as dielectric properties are used by electronic grain moisture meters for rapid determination of moisture content. Moisture content is important in determining the potential for safe storage of grain, and it must be measured whenever a grain lot is sold. Recent research has shown that measurements on grain at microwave frequencies offer advantages for moisture testing compared to the lower radio frequencies currently used by commercial grain moisture meters. This research has also shown that the moisture content of grain can be rapidly obtained from microwave measurements that determine the dielectric properties of the grain independent of fluctuations in the bulk density (packing) of the grain, which causes errors in the moisture content indicated by currently used moisture meters if it is not taken into account. Therefore the microwave sensing of grain moisture content shows promise for on-line monitoring of moisture in grain and seed. Questions have been raised as to whether dielectric properties of grain of high moisture contents at harvest are different from those of the same grain to which water has been added, after drying, to bring it back to the original moisture level. In this study, microwave dielectric properties of shelled, yellow-dent hybrid field corn were measured at harvest and as the corn dried down to normal storage levels. Then, water was added to hybrid corn lots of normal storage moisture levels and the dielectric properties were measured as moisture content was increased to levels for corn at harvest. Comparing results of the measurements showed that there was no appreciable difference between the natural-moisture and added moisture-lots of shelled corn. Thus, the customary method for adding moisture in research studies does not introduce any complications in research on microwave methods for sensing moisture content in corn. The new information is useful to engineers developing new moisture meters and it will therefore contribute to the goal of providing high quality and healthful products for consumers.
Technical Abstract:
Dielectric properties of samples of shelled corn of ¿natural¿ water content and those prepared by adding water were measured in free space at microwave frequencies and 23 oC. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 9 GHz show no difference between the samples with ¿natural¿ water and those in which water was added artificially. Bulk densities and moisture contents predicted from calibration equations expressed in terms of dielectric properties of both natural and added water samples agreed closely, and standard errors were less than 1% moisture content and 5% for bulk density.
From http://www.ars.usda.gov
Theory and Application of Dielectric Spectroscopy
Wikipedia Defines the Dielectric spectroscopy (sometimes called impedance spectroscopy) as measures the dielectric properties of a medium as a function of frequency.It is based on the interaction of an external field with the electric dipole moment of the sample, often expressed by permittivity.
"Dielectric spectroscopy can provide information about the segmental mobility of a polymer by probing its dielectric properties. The complex dielectric properties, the loss factor(e") and the relative permittivity(e'), are determined by performing several isothermal scans as a function of frequency. An alternating current(Vrms=0.005-1.1 volts) external electric field is applied across the DUT(Device Under Test) in a capacitor plate configuration. The applied alternating electric field interacts with the electric dipole moments of the DUT."
"Each dielectric mechanism effect has a characteristic relaxation frequency. As the frequency becomes larger, the slower mechanisms drop off. This in turn leaves only the faster mechanisms to contribute to the dielectric storage."
"Dielectric relaxation is the result of a movement of dipoles or electric charges due to a changing electric field in the frequency range of 10^2-10^10 Hz. This mechanism is a relatively slow process when compared with electronic transitions or molecular vibrations which have frequencies above 10^12 Hz. Only when sufficient time is allowed after the application of an electric field for the orientation to attain equilibrium will the maximum polarization, corresponding to the highest observable dielectric constant, be realized in a material."
Dielectric spectroscopymeter
In dielectric spectroscopy the current flowing through a sample cell containing a colloidal suspension and the voltage across this cell are measured as a function of frequency. From this data one can obtain the impedance of the solution as a function of frequency. The impedance can then be separated into the frequency dependent conductivity and relative permittivity of the solution. A schematic of a dielectric spectrometer is given below.
An oscillatory field applied to a colloidal suspension changes the distribution of ions in the electrostatic double layer, as well as the neutral region just outside of the double layer. The applied field polarizes the double layer when time scales of ionic transport processes are fast compared with the period of the oscillatory field. High polarization is manifested as a relative dielectric permittivity that may be much greater than that of the suspending medium. If we increase the frequency of the applied field, the polarization and relative dielectric permittivity decrease and the latter eventually approaches that of the suspending medium. This process, dielectric relaxation, can therefore indicate the time scales of ionic transport processes near particle surfaces.
Dielectric spectroscopy characterizes the dynamics of double layer relaxation and yields more information per measurement than static methods such as electrophoresis. Full interpretation of dielectric models requires the use of colloidal electrodynamics. These models usually rely upon electrostatic parameters that are obtained through electrokinetic methods. Thus the availability of both electrokinetic and dielectric techniques offer an advantage for reconciling and interpreting measurements of particle surface structure and electrochemistry.
http://www.psrc.usm.edu/mauritz/dilect.html
2. wikipedia. http://en.wikipedia.org/wiki/Dielectric_spectroscopy
3. Division of Information Technology, Engineering and the EnvironmentLaser Light Scattering and Materials Science Group.
http://www.unisa.edu.au/laser/Research/Dielec.asp
4. Dielectric Spectroscopy: Choosing the Right Approach, Sep 2, 2008By: A. Mathur, K. Sundara-Rajan, G. Rowe, A. V. MamishevPharmaceutical TechnologyVolume 9, Issue 32, pp. 8293
"Dielectric spectroscopy can provide information about the segmental mobility of a polymer by probing its dielectric properties. The complex dielectric properties, the loss factor(e") and the relative permittivity(e'), are determined by performing several isothermal scans as a function of frequency. An alternating current(Vrms=0.005-1.1 volts) external electric field is applied across the DUT(Device Under Test) in a capacitor plate configuration. The applied alternating electric field interacts with the electric dipole moments of the DUT."
"Each dielectric mechanism effect has a characteristic relaxation frequency. As the frequency becomes larger, the slower mechanisms drop off. This in turn leaves only the faster mechanisms to contribute to the dielectric storage."
"Dielectric relaxation is the result of a movement of dipoles or electric charges due to a changing electric field in the frequency range of 10^2-10^10 Hz. This mechanism is a relatively slow process when compared with electronic transitions or molecular vibrations which have frequencies above 10^12 Hz. Only when sufficient time is allowed after the application of an electric field for the orientation to attain equilibrium will the maximum polarization, corresponding to the highest observable dielectric constant, be realized in a material."
Dielectric spectroscopymeter
In dielectric spectroscopy the current flowing through a sample cell containing a colloidal suspension and the voltage across this cell are measured as a function of frequency. From this data one can obtain the impedance of the solution as a function of frequency. The impedance can then be separated into the frequency dependent conductivity and relative permittivity of the solution. A schematic of a dielectric spectrometer is given below.
An oscillatory field applied to a colloidal suspension changes the distribution of ions in the electrostatic double layer, as well as the neutral region just outside of the double layer. The applied field polarizes the double layer when time scales of ionic transport processes are fast compared with the period of the oscillatory field. High polarization is manifested as a relative dielectric permittivity that may be much greater than that of the suspending medium. If we increase the frequency of the applied field, the polarization and relative dielectric permittivity decrease and the latter eventually approaches that of the suspending medium. This process, dielectric relaxation, can therefore indicate the time scales of ionic transport processes near particle surfaces.Dielectric spectroscopy characterizes the dynamics of double layer relaxation and yields more information per measurement than static methods such as electrophoresis. Full interpretation of dielectric models requires the use of colloidal electrodynamics. These models usually rely upon electrostatic parameters that are obtained through electrokinetic methods. Thus the availability of both electrokinetic and dielectric techniques offer an advantage for reconciling and interpreting measurements of particle surface structure and electrochemistry.
Other application:
The range of potential applications of dielectric spectroscopy is quite broad. Virtually any physical process change leads to changes in dielectric properties of samples. Process variability is a primary concern for the pharmaceutical industry (1). Exposure to mechanical and thermal stress can cause a change in the physical properties of pharmaceuticals. Such variations are important to control because physical properties generally determine the efficacy of the drug...There are two major properties of dielectric spectroscopy that are typically varied to suit the desired application: the spatial distribution of the interrogation field and the interrogation frequency range....Direct sensing or preconcentrators? There are many cases in which gas or liquid analytes must be sensed in small concentrations close to, or below, the detection threshold of a dielectric spectroscopy measurement device. Direct sensing is simpler than preconcentration; however, direct sensing is not always possible. Preconcentration should be performed in the following cases:
When the analyte is at a concentration at or below the measurement threshold
To select an analyte of interest from a mixture of gases or liquids....
Single frequency or spectroscopy? Relaxation processes in dielectric spectroscopy are very similar to relaxation processes in the optical regime. However, the interrogation frequencies used in dielectric spectroscopy are lower than optical frequencies, so this technique studies molecular interactions such as polymer reconfiguration within a matrix, percolation processes, and moisture diffusion. A major advantage of dielectric spectroscopy is that it can be performed over a wide band of measurement frequencies. The lowest boundary for frequency in existing dielectric spectroscopy is around 1 μHz, and the highest is in THz range. It is rarely practical to go to such extremes; most practical industrial measurements are accomplished in the range from 1 Hz to 100 MHz...
Further reading
A significant amount of literature is available that describes the theoretical aspects of dielectric behavior, algorithms, and signal processing methods used for the processsing of dielectric data and sensor design for dielectric measurements. One of the earliest models describing the frequency dependence of dielectric behavior was proposed by Debye (43). Jonscher describes dielectric relaxation emphasizing solids materials (44). Dielectric spectroscopy also has been explored in detail for polymeric materials (36). An understanding of dielectric behavior for engineers is presented by Coelho (45). Specifically for pharmaceuticals, a comprehensive review of applications is provided by Craig (14). MacDonald provides a review of methods for measurement of dielectric properties (46). A number of algorithms have been proposed for calibration and correlating data to physical property distributions (47–49). Rapid advancements in microtechnology have resulted in an increase in the number and complexity of electrode structures available for dielectric measurements. Notable references for sensor design are also available (50–56). A comprehensive overview of interdigital dielectric sensors is provided by Sundara-Rajan (57). A detailed review of currently available dielectric spectroscopic systems can be found at www.ee.washington.edu/research/seal/pharmatech/ .
Get more from pharmtech.
Reference.
1. author Beau Lambert (Partially From His Master's Research)http://www.psrc.usm.edu/mauritz/dilect.html
2. wikipedia. http://en.wikipedia.org/wiki/Dielectric_spectroscopy
3. Division of Information Technology, Engineering and the EnvironmentLaser Light Scattering and Materials Science Group.
http://www.unisa.edu.au/laser/Research/Dielec.asp
4. Dielectric Spectroscopy: Choosing the Right Approach, Sep 2, 2008By: A. Mathur, K. Sundara-Rajan, G. Rowe, A. V. MamishevPharmaceutical TechnologyVolume 9, Issue 32, pp. 8293
Sunday, August 30, 2009
For Explorers&Designers: USB bus-powered DAQ module
USB-7202 mulifunction Test&Measurement Module
USB bus-powered DAQ module with eight, 16-bit analog inputs and eight digital I/O lines; 
for Message-Based DAQ - Designed for OEMs
Key Highlights
8 channels of 16-bit analog input
100 kS/s max total throughput (200 kS/s Burst Mode), 50 kS/s on any one channel
8 digital I/O lines
One 32-bit event counter
Simultaneous sampling (1 A/D converter per input)
Stackable 3.55" x 3.75" board dimensions
Simple messaging protocol
Develop on one computing platform, deploy on many with out-of-the-box support for Windows® and Linux®
Small software footprint
Included accessories: USB cable and a CD containing the MC7000 DAQ Software API, USB-7000 Series Firmware Architecture, a Windows® installer file (msi), and a Zip file containing installation files for Linux® operating systems
Read "Message Based DAQ" Whitepaper
for Message-Based DAQ - Designed for OEMsKey Highlights
8 channels of 16-bit analog input
100 kS/s max total throughput (200 kS/s Burst Mode), 50 kS/s on any one channel
8 digital I/O lines
One 32-bit event counter
Simultaneous sampling (1 A/D converter per input)
Stackable 3.55" x 3.75" board dimensions
Simple messaging protocol
Develop on one computing platform, deploy on many with out-of-the-box support for Windows® and Linux®
Small software footprint
Included accessories: USB cable and a CD containing the MC7000 DAQ Software API, USB-7000 Series Firmware Architecture, a Windows® installer file (msi), and a Zip file containing installation files for Linux® operating systems
Read "Message Based DAQ" Whitepaper
Product Specifications - PDF printable
Product User's Manual - PDF printable
Overview taken from www.mccdaq.com
The USB-7202 is part of the USB-7000 series of data acquisition products, designed specifically for Message-based DAQ (MBD), Measurement Computing’s new O/S-independent protocol that allows DAQ devices to be programmed with simple text-based messages.MBD is a well-defined protocol that permits the programming of DAQ devices using simple text-based messages. The MBD protocol greatly simplifies driver and application development, because all DAQ operations are programmed through a common command interface, which is composed of a consistent, extensible firmware interface and an open-source, cross-platform API.The USB-7202 has eight single-ended 16-bit analog inputs and provides one A/D converter per channel, allowing simultaneous sampling over all 8 inputs.
The USB-7202 offers continuous single-channel sample rates up to 50 kS/s, and multiple-channel continuous sampling rates up to 100 kS/s total. A burst mode is also provided which allows four channels to be sampled at 50 kS/s each, total aggregate up to 200 kS/s, for up to 32,768 total samples. Input ranges of ±10V, ±5V, ±2V and ±1V are software selectable, and each channel may be set at any of the four ranges, independent of other channels. It also includes a 32-bit event counter. Included accessories: USB cable and a CD containing the MC7000 DAQ Software API, USB-7000 Series Firmware Architecture, a Windows® installer file (msi), and a Zip file containing installation files for Linux operating systems
More products: www.mccdaq.com
Books Recommendation: Computational methods for electric power systems
Wondered about how to analyze,compute critic parameter and to model mathematiclly of a system serving various kinds of decision making?
Some of the latest books drive attention for both researcher & engineeris in those areas.
1. Computational methods for electric power systems
By Mariesa Cro
below is abstracted Book overview
The sheer size of today's power grid and the increasingly stressed conditions under which power systems operate demand the use of computers for analysis and simulations. Yet commercial software packages often fail or give erroneous results when used to simulate stressed systems. To correctly interpret the results, it is therefore imperative that power engineers understand the underlying numerical algorithms of the software.Computational Methods for Electric Power Systems provides a comprehensive study of the various computational methods that form the basis of many analytical studies of power systems. It presents the analytical background of the algorithms used in many commercially available software packages, thereby enabling readers to make more informed decisions in their use of the software and correctly interpret their results. The book furnishes a well-balanced discussion of the theory and applications of the algorithms and supports them with instructional examples and illustrations.As more and more demands are placed on the nation's power systems, predicting and updating the operating status of a network through systems analysis becomes increasingly important. This book builds the background necessary to successfully perform that analysis and prepares readers to cope with any difficulties they may encounter in practice.
Brief comment.
I have completed reading this book and find a quite clear structure of compuation methods towards traditional analysis and plan towards optimization or decision making.
Aslo, some of the related books can be a deepening minds for study&research.
2. Applied mathematics for restructured electric power systems: optimization ... By Joe H. Chow, Felix F. Wu, James A. Momoh
Book overview
Applied Mathematics for Restructured Electric Power Systems: Optimization, Control, and Computational Intelligence consists of chapters based on work presented at a National Science Foundation workshop organized in November 2003. The theme of the workshop was the use of applied mathematics to solve challenging power system problems. The areas included control, optimization, and computational intelligence. In addition to the introductory chapter, this book includes 12 chapters written by renowned experts in their respected fields. Each chapter follows a three-part format: (1) a description of an important power system problem or problems, (2) the current practice and/or particular research approaches, and (3) future research directions. Collectively, the technical areas discussed are voltage and oscillatory stability, power system security margins, hierarchical and decentralized control, stability monitoring, embedded optimization, neural network control with adaptive critic architecture, control tuning using genetic algorithms, and load forecasting and component prediction. This volume is intended for power systems researchers and professionals charged with solving electric and power system problems.
3. New Computational Methods in Power System Reliability
By David Elmakias
Book overview
Power system reliability is in the focus of intensive study due to its critical role in providing energy supply to the modern society. This book is not aimed at providing the overview of the state of the art in power system reliability. On the contrary, it describes application of some new specific techniques: universal generating function method and its combination with Monte Carlo simulation and with random processes methods, Semi-Markov and Markov reward models and genetic algorithm. The book can be considered as complementary to power system reliability textbooks. It is suitable for different types of readers. It primarily addresses practising reliability engineers and researchers who have an interest in reliability and performability analysis of power systems. It can also be used as a textbook for senior undergraduate or graduate courses in electrical engineering.
Some of the books can be previewed on Google Books or Amazon website.
Some of the latest books drive attention for both researcher & engineeris in those areas.
1. Computational methods for electric power systems
By Mariesa Cro
below is abstracted Book overview
The sheer size of today's power grid and the increasingly stressed conditions under which power systems operate demand the use of computers for analysis and simulations. Yet commercial software packages often fail or give erroneous results when used to simulate stressed systems. To correctly interpret the results, it is therefore imperative that power engineers understand the underlying numerical algorithms of the software.Computational Methods for Electric Power Systems provides a comprehensive study of the various computational methods that form the basis of many analytical studies of power systems. It presents the analytical background of the algorithms used in many commercially available software packages, thereby enabling readers to make more informed decisions in their use of the software and correctly interpret their results. The book furnishes a well-balanced discussion of the theory and applications of the algorithms and supports them with instructional examples and illustrations.As more and more demands are placed on the nation's power systems, predicting and updating the operating status of a network through systems analysis becomes increasingly important. This book builds the background necessary to successfully perform that analysis and prepares readers to cope with any difficulties they may encounter in practice.
Brief comment.
I have completed reading this book and find a quite clear structure of compuation methods towards traditional analysis and plan towards optimization or decision making.
Aslo, some of the related books can be a deepening minds for study&research.
2. Applied mathematics for restructured electric power systems: optimization ... By Joe H. Chow, Felix F. Wu, James A. Momoh
Book overview
Applied Mathematics for Restructured Electric Power Systems: Optimization, Control, and Computational Intelligence consists of chapters based on work presented at a National Science Foundation workshop organized in November 2003. The theme of the workshop was the use of applied mathematics to solve challenging power system problems. The areas included control, optimization, and computational intelligence. In addition to the introductory chapter, this book includes 12 chapters written by renowned experts in their respected fields. Each chapter follows a three-part format: (1) a description of an important power system problem or problems, (2) the current practice and/or particular research approaches, and (3) future research directions. Collectively, the technical areas discussed are voltage and oscillatory stability, power system security margins, hierarchical and decentralized control, stability monitoring, embedded optimization, neural network control with adaptive critic architecture, control tuning using genetic algorithms, and load forecasting and component prediction. This volume is intended for power systems researchers and professionals charged with solving electric and power system problems.
3. New Computational Methods in Power System Reliability
By David Elmakias
Book overview
Power system reliability is in the focus of intensive study due to its critical role in providing energy supply to the modern society. This book is not aimed at providing the overview of the state of the art in power system reliability. On the contrary, it describes application of some new specific techniques: universal generating function method and its combination with Monte Carlo simulation and with random processes methods, Semi-Markov and Markov reward models and genetic algorithm. The book can be considered as complementary to power system reliability textbooks. It is suitable for different types of readers. It primarily addresses practising reliability engineers and researchers who have an interest in reliability and performability analysis of power systems. It can also be used as a textbook for senior undergraduate or graduate courses in electrical engineering.
Some of the books can be previewed on Google Books or Amazon website.
Free information about current transformer application
"Many times, the designer wishes to generate a DC signal from an AC current transformer for input to a PLC or data acquisition system, or even as part of a current or motor controller. Creating DC from an AC source creates problems with diode voltage drops and the variances over temperature and current. The following circuit provides an accurate method for creating this DC signal."
CRMagnetics provide very good reference material about current transformer (CT) on the web, with clear illustration of circuits and some computation methods.
Free software for unit converter as isslustrated in the above graph.
From CR MAGNETICS, INC.
http://www.crmagnetics.com/newprod/freesoftware.asp
From CR MAGNETICS, INC.
http://www.crmagnetics.com/newprod/freesoftware.asp
It is quite useful for beginnners and engineers.
Saturday, August 29, 2009
Very Low Frequency-Application in Power equipment
In Wiki, very low frequency being explained:
"Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 kHz to 30 kHz. "
In the area of electric engineering, VLF commonly refers to frequencies below or equal to 0.1Hz.
Very low frequency(VLF) method is now expanding its application in electric power engineering area, two recently announced products are:
a. transformer moisture analyzing system, where VLF plays very important role.
b. cable insulation and dielectric loss test, where VLF reduces the weight and power compared with traditional methods.
"Very low frequency or VLF refers to radio frequencies (RF) in the range of 3 kHz to 30 kHz. "
In the area of electric engineering, VLF commonly refers to frequencies below or equal to 0.1Hz.
Very low frequency(VLF) method is now expanding its application in electric power engineering area, two recently announced products are:
a. transformer moisture analyzing system, where VLF plays very important role.
b. cable insulation and dielectric loss test, where VLF reduces the weight and power compared with traditional methods.
Friday, August 28, 2009
Free download-Freecal for Test and Measurement
FreeCal - GPIB Instrument Automation for Metrology Test and Measurement
By Scott Page
FreeCal is a free 100% .NET suite of utilities and instrument drivers for controlling multiple instruments in a Test and Measurement environment.
Features
Base instrument libraries for Signal Generators, Spectrum Analyzers, Network Analyzers, Power Meters, Function Generators, Universal and RF/Microwave Counters, Attenuator/Switch Drivers, EEPROM Power Sensors, Digital Multimeters and any other type of instrument that can be controlled remotely. All categories have specific instruments that have been coded for compatibility (due to the fact that all instruments have their own specific language for communication).
Charts/graphs are integrated into the code with the use of ZedGraph: A flexible charting library for .NET (Thanks to JChampion for ZedGraph, many sleepless nights have been avoided developing an integrated charting library).
Procedures for Power Sensors, Signal Generators, Spectrum Analyzers and Network Analyzer Calibration Kits have already been developed (so far most of them partially completed due to time), but they are not difficult to create as you will see in the examples below.
Several conversion functions included to aid in the development and presentation of data: Frequency conversion from one range to another (i.e. MHz to GHz), Amplitude and Time conversions are also included as a base for almost all formulas and instrument communication.
I recently started construction of a visual editor that allows "drag and drop" style test creation. It is included in the source and can be found in the demo under the Tools menu.
Integrates with MySQL using the MySQL.NET Connector. I have created a number of data classes that ease the task of saving result data to a MySQL database.
Various forms have been created for several of the instrument categories, like Network Analyzers. One of the most difficult tasks in RF/Microwave is downloading and manipulating data from the Agilent 8500 Series NWA, so I spent a lot of time writing the NWA data transfer classes.
Because every instrument has its own tolerances and capabilities, the drivers have been written to include all of this (any missing information is easily added as it is all structure based).
Instrument drivers and procedures are written with a "One Procedure Any Instrument" mindset. You can write one procedure that can calibrate any instrument of the same category. This is due to each instrument driver including the specifications for each test.
To get detail and download:
http://www.codeproject.com/KB/dotnet/FreeCal.aspx?msg=1710490
By Scott Page
FreeCal is a free 100% .NET suite of utilities and instrument drivers for controlling multiple instruments in a Test and Measurement environment.
Features
Base instrument libraries for Signal Generators, Spectrum Analyzers, Network Analyzers, Power Meters, Function Generators, Universal and RF/Microwave Counters, Attenuator/Switch Drivers, EEPROM Power Sensors, Digital Multimeters and any other type of instrument that can be controlled remotely. All categories have specific instruments that have been coded for compatibility (due to the fact that all instruments have their own specific language for communication).
Charts/graphs are integrated into the code with the use of ZedGraph: A flexible charting library for .NET (Thanks to JChampion for ZedGraph, many sleepless nights have been avoided developing an integrated charting library).
Procedures for Power Sensors, Signal Generators, Spectrum Analyzers and Network Analyzer Calibration Kits have already been developed (so far most of them partially completed due to time), but they are not difficult to create as you will see in the examples below.
Several conversion functions included to aid in the development and presentation of data: Frequency conversion from one range to another (i.e. MHz to GHz), Amplitude and Time conversions are also included as a base for almost all formulas and instrument communication.
I recently started construction of a visual editor that allows "drag and drop" style test creation. It is included in the source and can be found in the demo under the Tools menu.
Integrates with MySQL using the MySQL.NET Connector. I have created a number of data classes that ease the task of saving result data to a MySQL database.
Various forms have been created for several of the instrument categories, like Network Analyzers. One of the most difficult tasks in RF/Microwave is downloading and manipulating data from the Agilent 8500 Series NWA, so I spent a lot of time writing the NWA data transfer classes.
Because every instrument has its own tolerances and capabilities, the drivers have been written to include all of this (any missing information is easily added as it is all structure based).
Instrument drivers and procedures are written with a "One Procedure Any Instrument" mindset. You can write one procedure that can calibrate any instrument of the same category. This is due to each instrument driver including the specifications for each test.
To get detail and download:
http://www.codeproject.com/KB/dotnet/FreeCal.aspx?msg=1710490
Online CT Diagonistics Without Contact of Primary
Online CT Diagnostics Without Contact of Primary
by swipower @ 2009-08-01 – 08:08:53
The research started from year 2006 and initiated project in year 2007. a sample product being finished in the end of year 2008.
Features:
Internal Insulation Diagnostics
Exciting magnetics shortcomings
Potential Faults
Burden Influence
Trends data analysis
Portable Design
Avoid High Voltage Contact
Application Background:
Current Transformer, Voltage Transformer, Secondary wirings and Electronic energy meters are components of metering loop, among which high-voltage electronic energy meter is online calibrated periodically 6 to 12 months, and even shorter in some substations. But Current Transformer (CT) keeps running for several years until a power off accuracy calibration, metering loss will be difficult to compensate if error runs out of limits. Traditional methods employ offline comparison techniques to verify the accuracy and healthy condition of current transformer, which requires large amount of efforts on both labor and time. Power utilities also try their best to get family data that relates to accuracy or potential fault in order to avoid or decrease sudden power losses. Most common adopted techniques are active ratio, phase error test, burden measurement and harmonics. But burden measurement can only determine if secondary load is within allowed limit, which is just one of several factors that affect metering error. Ratio and phase error measurement require operator to contact primary high-voltage line for an online verification, which adds extra danger and in most cases infeasible. Harmonics gives results which are not easy for decision making of whether CT is running healthily. TM01 is an innovative CT analyzer that focuses on active composite error for metering verification and potential faults that cannot be detected through traditional ways. It also features on low-voltage injection methods that avoid high-voltage contact. Test methods are well in accordance with IEEE CT application Guide and IEC standards.
Active CT background
Factors that influence CT metering error (under active conditions):
1. Turns ratio
2. Load conditions (primary and secondary)
3. DC magnetizing (Remanence)
4. Magnetizing Characteristics
Factors that influence CT operation (Fault):
1. Primary short circuit or abnormal impedance
2. Insulation (Turn to Turn) breakdown
3. Secondary burden (multipoint grounding, joint corrosion, burden out of limit)
4. DC magnetizing (Remanence)
5. Mechanical problem (Gap, vibration)
Major Function of TM-01-X Online CT Analyzer(Also named active ct analyzer,admittance response analyzer)
¨ Active composite error test (going to be announced)
¨ Active magnetizing characteristics test
¨ Active internal wiring insulation analysis
¨ Active loop impedance (admittance) test
¨ Active load/current characteristics
¨ Fault characteristics and trends analysis
¨ Current Harmonics(Optional)
Application Area
¨ Onsite accuracy verification without need to contact primary line
¨ Internal wiring short-circuit/insulation abnormality
¨ DC magnetizing (Remanence abnormal)
¨ Permeability decrease
¨ Contact point corrosion
¨ Multipoint ground/ ground abnormality
¨ Primary line to ground insulation abnormality
¨ Wiring displacement/vibration
¨ Linea (magnetizing) zone Assessment
Major technical parameter
¨ Primary current influence: less than 1.5%
¨ System voltage level: Any but best for 35kV and above
¨ Secondary current: Rated 5A/1A
¨ Ratio: unlimited but accuracy will go down for very low ratio CT.
¨ Rated burden: 0-200VA
¨ Composite error: 0.2%F.S (Upgradable to 0.1%F.S)
¨ Instability: 0.05%
¨ Admittance: 0.001～999.999mS
¨ Harmonics: 50th (Optional)
¨ Temperature: 0～55
¨ System Language: English (German is optional)
¨ Weight: about 4kg.
TM01 Configuration:
1.TM01-A Potential Fault DetectActive Frequency Response Analyzer (AFRA)
2.TM01-B Onsite Accuracy VerificationActive (Composite) Error Analyzer (ACEA)
Contact: Email: swipower@yahoo.com
Taken From: www.diagnostics.blogs.se
by swipower @ 2009-08-01 – 08:08:53
The research started from year 2006 and initiated project in year 2007. a sample product being finished in the end of year 2008.
Features:
Internal Insulation Diagnostics
Exciting magnetics shortcomings
Potential Faults
Burden Influence
Trends data analysis
Portable Design
Avoid High Voltage Contact
Application Background:
Current Transformer, Voltage Transformer, Secondary wirings and Electronic energy meters are components of metering loop, among which high-voltage electronic energy meter is online calibrated periodically 6 to 12 months, and even shorter in some substations. But Current Transformer (CT) keeps running for several years until a power off accuracy calibration, metering loss will be difficult to compensate if error runs out of limits. Traditional methods employ offline comparison techniques to verify the accuracy and healthy condition of current transformer, which requires large amount of efforts on both labor and time. Power utilities also try their best to get family data that relates to accuracy or potential fault in order to avoid or decrease sudden power losses. Most common adopted techniques are active ratio, phase error test, burden measurement and harmonics. But burden measurement can only determine if secondary load is within allowed limit, which is just one of several factors that affect metering error. Ratio and phase error measurement require operator to contact primary high-voltage line for an online verification, which adds extra danger and in most cases infeasible. Harmonics gives results which are not easy for decision making of whether CT is running healthily. TM01 is an innovative CT analyzer that focuses on active composite error for metering verification and potential faults that cannot be detected through traditional ways. It also features on low-voltage injection methods that avoid high-voltage contact. Test methods are well in accordance with IEEE CT application Guide and IEC standards.
Active CT background
Factors that influence CT metering error (under active conditions):
1. Turns ratio
2. Load conditions (primary and secondary)
3. DC magnetizing (Remanence)
4. Magnetizing Characteristics
Factors that influence CT operation (Fault):
1. Primary short circuit or abnormal impedance
2. Insulation (Turn to Turn) breakdown
3. Secondary burden (multipoint grounding, joint corrosion, burden out of limit)
4. DC magnetizing (Remanence)
5. Mechanical problem (Gap, vibration)
Major Function of TM-01-X Online CT Analyzer(Also named active ct analyzer,admittance response analyzer)
¨ Active composite error test (going to be announced)
¨ Active magnetizing characteristics test
¨ Active internal wiring insulation analysis
¨ Active loop impedance (admittance) test
¨ Active load/current characteristics
¨ Fault characteristics and trends analysis
¨ Current Harmonics(Optional)
Application Area
¨ Onsite accuracy verification without need to contact primary line
¨ Internal wiring short-circuit/insulation abnormality
¨ DC magnetizing (Remanence abnormal)
¨ Permeability decrease
¨ Contact point corrosion
¨ Multipoint ground/ ground abnormality
¨ Primary line to ground insulation abnormality
¨ Wiring displacement/vibration
¨ Linea (magnetizing) zone Assessment
Major technical parameter
¨ Primary current influence: less than 1.5%
¨ System voltage level: Any but best for 35kV and above
¨ Secondary current: Rated 5A/1A
¨ Ratio: unlimited but accuracy will go down for very low ratio CT.
¨ Rated burden: 0-200VA
¨ Composite error: 0.2%F.S (Upgradable to 0.1%F.S)
¨ Instability: 0.05%
¨ Admittance: 0.001～999.999mS
¨ Harmonics: 50th (Optional)
¨ Temperature: 0～55
¨ System Language: English (German is optional)
¨ Weight: about 4kg.
TM01 Configuration:
1.TM01-A Potential Fault DetectActive Frequency Response Analyzer (AFRA)
2.TM01-B Onsite Accuracy VerificationActive (Composite) Error Analyzer (ACEA)
Contact: Email: swipower@yahoo.com
Taken From: www.diagnostics.blogs.se
Thursday, August 27, 2009
Open Tech.Group about electronic&electric power Engineering
This group is open for anyone who likes to share or discuss technical trends or products within the electronic & electric area.
Wednesday, May 13, 2009
变压器局放检测方法简评
变压器局放检测
电力变压器局部放电检测方法有脉冲电流法、DGA法、超声波法、RIV法、光测法、射频检测法和化学方法等。
脉冲电流法
它是通过检测阻抗接入到测量回路中来检测。检测变压器套管末屏接地线、外壳接地线、中性点接地线、铁芯接地线以及绕组中由于局放引起的脉冲电流，获得视在放电量。脉冲电流法是研究最早、应用最广泛的一种检测方法，IEC-60270为IEC于2000年正式公布的局放测量标准。脉冲电流法通常被用于变压器出厂时的型式试验以及其他离线测试中，其离线测量灵敏度高。脉冲电流法的问题在于以下几方面：其抗干扰能力差，无法有效应用于现场的在线监测；对于变压器类具有绕组结构的设备在标定时产生很大的误差；由于检测阻抗和放大器对测量的灵敏度、准确度、分辨率以及动态范围等都有影响，因此当试样的电容量较大时，受耦合阻抗的限制，测试仪器的测量灵敏度受到一定限制；测量频率低、频带窄，包含的信息量少。
DGA法。
DGA法是通过检测变压器油分解产生的各种气体的组成和浓度来确定故障（局放、过热等）状态。该方法目前已广泛应用于变压器的在线故障诊断中，并且建立起模式识别系统可实现故障的自动识别，是当前在变压器局放检测领域非常有效的方法。但是DGA法具有两个缺点：油气分析是一个长期的监测过程，因而无法发现突发性故障；该方法无法进行故障定位。
超声波法
超声波法是通过检测变压器局放产生的超声波信号来测量局放的大小和位置。超声传感器的频带约为70～150千赫兹（或300千赫兹），以避开铁芯的铁磁噪声和变压器的机械振动噪声。由于超声波法受电气干扰小以及可以在线测量和定位，因而人们对超声波法的研究较深入。但目前该方法存在着很大的问题：目前的超声传感器灵敏度很低，无法在现场有效地测到信号；传感器的抗电磁干扰能力较差。因此，超声检测主要用于定性地判断局放信号的有无，以及结合脉冲电流法或直接利用超声信号对局放源进行物理定位。在电力变压器的离线和在线检测中，它是主要的辅助测量手段。
RIV法
局部放电会产生无线电干扰的现象很早就被人们所认识。例如人们常采用无线电电压干扰仪来检测由于局放对无线电通讯和无线电控制的干扰，并已制定了测量方法的标准。用RIV表来检测局放的测量线路与脉冲电流直测法的测量电路相似。此外，还可以利用一个接收线圈来接收由于局放而发出的电磁波，对于不同测试对象和不同的环境条件，选频放大器可以选择不同的中心频率（从几万赫兹到几十万赫兹），以获得最大的信噪比。这种方法已被用于检查电机线棒和没有屏蔽层的长电缆的局放部位。
光测法
光测法利用局放产生的光辐射进行检测。在变压器油中，各种放电发出的光波长不同，研究表明通常在500～700mm之间。在实验室利用光测法来分析局放特征及绝缘劣化等方面已经取得了很大进展，但是由于光测法设备复杂昂贵、灵敏度低，且需要被检测物质对光是透明的，因而在实际中无法应用。
射频检测法
利用罗果夫斯基线圈从变压器中性点处测取信号，测量的信号频率可以达到3万千赫兹，大大提高了局放的测量频率，同时测试系统安装方便，检测设备不改变电力系统的运行方式。但对于三相电力变压器，得到的信号是三相局放信号的总和，无法进行分辨，且信号易受外界干扰。随着数字滤波技术的发展，射频检测法在局放在线检测中得到了较广泛的应用。
高压设备局放检测的发展方向
随着科技的发展，特别是信号分析技术如神经网络、指纹分析、专家系统、模糊诊断和分形等都越来越多地应用到变压器局放检测中，对通过脉冲电流法按照IEC270标准测量得到数据，进行模式识别和绝缘寿命评估，推动了局放检测技术的发展。超高频检测方法从一开始就是从数字化技术起步的，通过将成功的传统方法移植到超高频检测之中，实现局放的连续在线监测和自动识别的研究正在取得快速的进展，上述超高频法存在的问题是目前很多相关研究单位需要解决的课题。笔者认为，任何一种方法都有一定的应用范围，有些问题它可以解决，有一些则不能解决。当前通信技术的发展使人们充分认识到，在线监测是个跨学科、综合性的研究领域，多种方法相结合，综合运行目前各种技术和知识，构建统一的、综合的在线监测平台，将是未来局放在线监测的发展方向。
目前，超高频方法的研究也面临着一些问题，由于测量机理与脉冲电流法不同，因此无法进行视在放电量的标定，而目前大多数工程人员已经习惯于通过视在放电量来反映局放的严重程度，IEC规定有关局放的变压器产品出厂标准中，其指标也是通过局放量的阈值来规定的。目前的研究表明，即使在局放源到传感器之间的传播路径不变的情况下，脉冲电流法的视在局放量与超高频方法所测得的脉冲信号幅值之间也没有确定的对应关系，这就更加大了应用该方法进行局放定量的难度；此外，由于变压器内部绝缘结构的复杂性，局放产生的电磁波在内部的传播将存在大量的散射、折反射以及衰减，因而传播特性研究和局放源定位工作将注定是难度很大而且充满挑战的。
来源：中国自动化仪表网
电力变压器局部放电检测方法有脉冲电流法、DGA法、超声波法、RIV法、光测法、射频检测法和化学方法等。
脉冲电流法
它是通过检测阻抗接入到测量回路中来检测。检测变压器套管末屏接地线、外壳接地线、中性点接地线、铁芯接地线以及绕组中由于局放引起的脉冲电流，获得视在放电量。脉冲电流法是研究最早、应用最广泛的一种检测方法，IEC-60270为IEC于2000年正式公布的局放测量标准。脉冲电流法通常被用于变压器出厂时的型式试验以及其他离线测试中，其离线测量灵敏度高。脉冲电流法的问题在于以下几方面：其抗干扰能力差，无法有效应用于现场的在线监测；对于变压器类具有绕组结构的设备在标定时产生很大的误差；由于检测阻抗和放大器对测量的灵敏度、准确度、分辨率以及动态范围等都有影响，因此当试样的电容量较大时，受耦合阻抗的限制，测试仪器的测量灵敏度受到一定限制；测量频率低、频带窄，包含的信息量少。
DGA法。
DGA法是通过检测变压器油分解产生的各种气体的组成和浓度来确定故障（局放、过热等）状态。该方法目前已广泛应用于变压器的在线故障诊断中，并且建立起模式识别系统可实现故障的自动识别，是当前在变压器局放检测领域非常有效的方法。但是DGA法具有两个缺点：油气分析是一个长期的监测过程，因而无法发现突发性故障；该方法无法进行故障定位。
超声波法
超声波法是通过检测变压器局放产生的超声波信号来测量局放的大小和位置。超声传感器的频带约为70～150千赫兹（或300千赫兹），以避开铁芯的铁磁噪声和变压器的机械振动噪声。由于超声波法受电气干扰小以及可以在线测量和定位，因而人们对超声波法的研究较深入。但目前该方法存在着很大的问题：目前的超声传感器灵敏度很低，无法在现场有效地测到信号；传感器的抗电磁干扰能力较差。因此，超声检测主要用于定性地判断局放信号的有无，以及结合脉冲电流法或直接利用超声信号对局放源进行物理定位。在电力变压器的离线和在线检测中，它是主要的辅助测量手段。
RIV法
局部放电会产生无线电干扰的现象很早就被人们所认识。例如人们常采用无线电电压干扰仪来检测由于局放对无线电通讯和无线电控制的干扰，并已制定了测量方法的标准。用RIV表来检测局放的测量线路与脉冲电流直测法的测量电路相似。此外，还可以利用一个接收线圈来接收由于局放而发出的电磁波，对于不同测试对象和不同的环境条件，选频放大器可以选择不同的中心频率（从几万赫兹到几十万赫兹），以获得最大的信噪比。这种方法已被用于检查电机线棒和没有屏蔽层的长电缆的局放部位。
光测法
光测法利用局放产生的光辐射进行检测。在变压器油中，各种放电发出的光波长不同，研究表明通常在500～700mm之间。在实验室利用光测法来分析局放特征及绝缘劣化等方面已经取得了很大进展，但是由于光测法设备复杂昂贵、灵敏度低，且需要被检测物质对光是透明的，因而在实际中无法应用。
射频检测法
利用罗果夫斯基线圈从变压器中性点处测取信号，测量的信号频率可以达到3万千赫兹，大大提高了局放的测量频率，同时测试系统安装方便，检测设备不改变电力系统的运行方式。但对于三相电力变压器，得到的信号是三相局放信号的总和，无法进行分辨，且信号易受外界干扰。随着数字滤波技术的发展，射频检测法在局放在线检测中得到了较广泛的应用。
高压设备局放检测的发展方向
随着科技的发展，特别是信号分析技术如神经网络、指纹分析、专家系统、模糊诊断和分形等都越来越多地应用到变压器局放检测中，对通过脉冲电流法按照IEC270标准测量得到数据，进行模式识别和绝缘寿命评估，推动了局放检测技术的发展。超高频检测方法从一开始就是从数字化技术起步的，通过将成功的传统方法移植到超高频检测之中，实现局放的连续在线监测和自动识别的研究正在取得快速的进展，上述超高频法存在的问题是目前很多相关研究单位需要解决的课题。笔者认为，任何一种方法都有一定的应用范围，有些问题它可以解决，有一些则不能解决。当前通信技术的发展使人们充分认识到，在线监测是个跨学科、综合性的研究领域，多种方法相结合，综合运行目前各种技术和知识，构建统一的、综合的在线监测平台，将是未来局放在线监测的发展方向。
目前，超高频方法的研究也面临着一些问题，由于测量机理与脉冲电流法不同，因此无法进行视在放电量的标定，而目前大多数工程人员已经习惯于通过视在放电量来反映局放的严重程度，IEC规定有关局放的变压器产品出厂标准中，其指标也是通过局放量的阈值来规定的。目前的研究表明，即使在局放源到传感器之间的传播路径不变的情况下，脉冲电流法的视在局放量与超高频方法所测得的脉冲信号幅值之间也没有确定的对应关系，这就更加大了应用该方法进行局放定量的难度；此外，由于变压器内部绝缘结构的复杂性，局放产生的电磁波在内部的传播将存在大量的散射、折反射以及衰减，因而传播特性研究和局放源定位工作将注定是难度很大而且充满挑战的。
来源：中国自动化仪表网
Wednesday, April 29, 2009
中等规模生物质气化发电技术(项目推荐）
项目简介：
生物质气化发电技术是洁净利用生物质能的有效方法之一，它可以在不产生污染的情况下把生物质能转化为电能，达到从低品位能源获取高品位能源的目的，是最有前途的可再生能源技术之一。 因地制宜地利用丰富的生物质资源，建立分散、独立的离网或并网生物质分布式电站不仅可以弥补电力供应的不足，而且可以有效减少环境污染和温室气体排放，所以它也是一种重要的环保技术。
以农业废弃物和木材废弃物为主的生物质资源分布分散，收集和运输困难，不适合采用大规模燃烧技术，而中等规模的生物质气化发电技术（400—6000kW）在发展中国家具有独特的优势，也具备进入市场竞争的条件。中国科学院广州能源研究所研究开发的中等规模生物质气化发电技术达到了同类技术的国际先进水平，性价比处于国际领先水平，该技术共申请国家专利9项，已在中国、台湾和东南亚等国家推广应用，取得了显著的经济、社会和环境效益。生物质气化发电技术先后获得“九五”国家重点科技攻关计划优秀成果奖、广东省科技进步二等奖、上海国际工业博览会银奖、广东省优秀专利奖。2005年10月，在由联合国教科文组织发起的全球可再生能源领域最具投资价值的十大领先技术评选中该技术获得“蓝天奖”，再一次证明了生物质气化发电技术在国际上的影响力。
适用范围及应用条件：
该生物质气化发电技术应用范围广，灵活性好，根据用户不同需要，发电规模可选择在200-5000kW之间。用于处理碾米厂的谷壳，家具厂、人造板厂和造纸厂的木屑、边角料、树皮，为工厂提供电力，也适用于处理林场及农场的枝桠材、秸杆、稻草、稻壳等，为缺电农村地区和企业供电。同时，由于该项目属于环保技术，对消除污染，减少CO2的排放有重要的意义，有条件享受国家政府的相关优惠政策，有很好的市场前景和巨大的推广潜力。
主要技术性能及指标：
生物质气化发电技术采用循环流化床气化炉，把生物质废弃物，包括木料、秸秆、稻草、甘蔗渣等转换为可燃气体。这些可燃气体经过除尘除焦等净化工序后，再送到气体内燃机进行发电。为进一步提高系统效率，可利用气化系统和内燃机产生的余热，通过余热锅炉和蒸汽轮机实现联合循环发电。
该技术主要特点如下：
(1)采用循环流化床气化炉为燃气发生装置，利用气体内燃机代替燃气轮机，采用简单可靠的燃气净化方法。整个系统具有原料适应性好，处理规模大，负荷适应能力强，发电效率高等特点；
(2)采用新型专利技术，有效解决了燃气净化中的难题；采用特种菌种和好氧、厌氧相结合的方法处理焦油污水，实现气化发电系统中焦油污水循环利用；
(3)建立的5MW生物质气化及联合循环发电优化系统示范工程，克服了传统IGCC技术在发展中国家利用的限制，大大降低了技术难度和系统成本，设备全部国产化。
这些特点保证了气化发电系统的综合性能稳定可靠，单位投资和运行成本都较低的特点，系统达到以下技术经济指标：
以原料价格200元/吨计，简单生物质气化发电系统（400－3000kW）发电效率达到16－20％，单位投资：4000－4500元/kW，单位原料耗量：1.35kg/kWh，发电运行成本：0.35-0.45元/kWh；联合循环生物质气化发电系统（5MW）发电效率达28%，单位投资：6500元/千瓦，单位原料耗量1kg/kWh，发电运行成本<0.35元/ kWh。
已应用情况：
在全面分析市场需求的情况下，成功开发了400kW到5000kW的系列生物质气化发电装置，提高了整个技术的成套性和实用性，为推广应用奠定了良好的基础。自2000以来，该技术在中国、台湾和东南亚国家推广，已经成为国际上应用最多的中小型生物质气化发电系统。目前已签订和在建生物质气化发电项目共32项，总装机容量34 MW，累计合同额达8021.82万元，间接经济效益3400万元，新增产值 1.02亿元，取得了显著的经济效益；年减排CO2 约27.5万吨，环境效益显著。
该技术的推广应用为根本解决中国农村普遍存在的而又始终无法根治的“秸秆问题”提供了有效的利用途径。例如：一个3000kW的生物质发电站，年处理秸秆约2万吨，相当于2万亩的秸秆。电站以200元/吨的价格向农民收购秸秆，每亩地可增加产出50-100元；电站可解决90－150人的就业机会；生物质发电直接成本中的秸秆成本和人工成本约为0.35-0.4元/度电，直接转化为当地农民收入。如果每个县建设5万kW的生物质电站，每年可为农民增收1亿多元，其推广应用的社会效益非常显著。
已具备的推广应用条件：
目前本成果由广州能源所属下科技公司——广州中科华源科技有限公司负责实施与市场开发。广州中科华源科技有限公司是由中国科学院广州能源研究所生物质能研究室投资成立，专业从事生物质能利用技术开发、节能技术产品开发与销售的高新技术企业，现有员工50多人，其中专职研究人员3名，高工3名， 工程师10多名,技术力量雄厚，主要专业技术与产品有：循环流化床生物质气化炉、生物质气化发电装置、生物质气化集中供气装置、医疗垃圾焚烧炉，具备生物质能电站设计、建设和施工的能力。
生物质气化发电技术是洁净利用生物质能的有效方法之一，它可以在不产生污染的情况下把生物质能转化为电能，达到从低品位能源获取高品位能源的目的，是最有前途的可再生能源技术之一。 因地制宜地利用丰富的生物质资源，建立分散、独立的离网或并网生物质分布式电站不仅可以弥补电力供应的不足，而且可以有效减少环境污染和温室气体排放，所以它也是一种重要的环保技术。
以农业废弃物和木材废弃物为主的生物质资源分布分散，收集和运输困难，不适合采用大规模燃烧技术，而中等规模的生物质气化发电技术（400—6000kW）在发展中国家具有独特的优势，也具备进入市场竞争的条件。中国科学院广州能源研究所研究开发的中等规模生物质气化发电技术达到了同类技术的国际先进水平，性价比处于国际领先水平，该技术共申请国家专利9项，已在中国、台湾和东南亚等国家推广应用，取得了显著的经济、社会和环境效益。生物质气化发电技术先后获得“九五”国家重点科技攻关计划优秀成果奖、广东省科技进步二等奖、上海国际工业博览会银奖、广东省优秀专利奖。2005年10月，在由联合国教科文组织发起的全球可再生能源领域最具投资价值的十大领先技术评选中该技术获得“蓝天奖”，再一次证明了生物质气化发电技术在国际上的影响力。
适用范围及应用条件：
该生物质气化发电技术应用范围广，灵活性好，根据用户不同需要，发电规模可选择在200-5000kW之间。用于处理碾米厂的谷壳，家具厂、人造板厂和造纸厂的木屑、边角料、树皮，为工厂提供电力，也适用于处理林场及农场的枝桠材、秸杆、稻草、稻壳等，为缺电农村地区和企业供电。同时，由于该项目属于环保技术，对消除污染，减少CO2的排放有重要的意义，有条件享受国家政府的相关优惠政策，有很好的市场前景和巨大的推广潜力。
主要技术性能及指标：
生物质气化发电技术采用循环流化床气化炉，把生物质废弃物，包括木料、秸秆、稻草、甘蔗渣等转换为可燃气体。这些可燃气体经过除尘除焦等净化工序后，再送到气体内燃机进行发电。为进一步提高系统效率，可利用气化系统和内燃机产生的余热，通过余热锅炉和蒸汽轮机实现联合循环发电。
该技术主要特点如下：
(1)采用循环流化床气化炉为燃气发生装置，利用气体内燃机代替燃气轮机，采用简单可靠的燃气净化方法。整个系统具有原料适应性好，处理规模大，负荷适应能力强，发电效率高等特点；
(2)采用新型专利技术，有效解决了燃气净化中的难题；采用特种菌种和好氧、厌氧相结合的方法处理焦油污水，实现气化发电系统中焦油污水循环利用；
(3)建立的5MW生物质气化及联合循环发电优化系统示范工程，克服了传统IGCC技术在发展中国家利用的限制，大大降低了技术难度和系统成本，设备全部国产化。
这些特点保证了气化发电系统的综合性能稳定可靠，单位投资和运行成本都较低的特点，系统达到以下技术经济指标：
以原料价格200元/吨计，简单生物质气化发电系统（400－3000kW）发电效率达到16－20％，单位投资：4000－4500元/kW，单位原料耗量：1.35kg/kWh，发电运行成本：0.35-0.45元/kWh；联合循环生物质气化发电系统（5MW）发电效率达28%，单位投资：6500元/千瓦，单位原料耗量1kg/kWh，发电运行成本<0.35元/ kWh。
已应用情况：
在全面分析市场需求的情况下，成功开发了400kW到5000kW的系列生物质气化发电装置，提高了整个技术的成套性和实用性，为推广应用奠定了良好的基础。自2000以来，该技术在中国、台湾和东南亚国家推广，已经成为国际上应用最多的中小型生物质气化发电系统。目前已签订和在建生物质气化发电项目共32项，总装机容量34 MW，累计合同额达8021.82万元，间接经济效益3400万元，新增产值 1.02亿元，取得了显著的经济效益；年减排CO2 约27.5万吨，环境效益显著。
该技术的推广应用为根本解决中国农村普遍存在的而又始终无法根治的“秸秆问题”提供了有效的利用途径。例如：一个3000kW的生物质发电站，年处理秸秆约2万吨，相当于2万亩的秸秆。电站以200元/吨的价格向农民收购秸秆，每亩地可增加产出50-100元；电站可解决90－150人的就业机会；生物质发电直接成本中的秸秆成本和人工成本约为0.35-0.4元/度电，直接转化为当地农民收入。如果每个县建设5万kW的生物质电站，每年可为农民增收1亿多元，其推广应用的社会效益非常显著。
已具备的推广应用条件：
目前本成果由广州能源所属下科技公司——广州中科华源科技有限公司负责实施与市场开发。广州中科华源科技有限公司是由中国科学院广州能源研究所生物质能研究室投资成立，专业从事生物质能利用技术开发、节能技术产品开发与销售的高新技术企业，现有员工50多人，其中专职研究人员3名，高工3名， 工程师10多名,技术力量雄厚，主要专业技术与产品有：循环流化床生物质气化炉、生物质气化发电装置、生物质气化集中供气装置、医疗垃圾焚烧炉，具备生物质能电站设计、建设和施工的能力。
Tuesday, April 28, 2009
Texas Instruments EZ430-RF2500 SEH at Digi-Key
from Digi-Key Corporation
From Digi-Key, the eZ430-RF2500-SEH is a complete Solar Energy Harvesting development kit to help create a perpetually powered wireless sensor network based on the ultra-low-power MSP430 microcontroller.
The Solar Energy Harvester module includes a high-efficiency solar (2.25x2.25") panel optimized for operating indoors under low-intensity fluorescent lights, which provide enough power to run a wireless sensor application with no additional batteries. Inputs are also available for external energy harvesters such as thermal, piezoelectric, or another solar panel.
The system also manages and stores additional energy in a pair of thin-film rechargeable EnerChips from Cymbet which are capable of delivering enough power for 400+ transmissions. The EnerChips act as an energy buffer that stores the energy while the application is sleeping and has light available to harvest. The batteries are environmentally friendly and can be recharged thousands of times. They also have a very low self discharge, which is vital for a no-power, energy harvesting system.
The eZ430-RF2500 is used to run the energy harvesting application. It is a complete USB-based MSP430 wireless development tool and provides all the hardware and software necessary to use the MSP430F2274 microcontroller and CC2500 2.4-GHz wireless transceiver. It includes a USB debugging interface that allows for real-time, in-system debugging and programming for the MSP430, and it is also the interface to transfer data to a PC from your wireless system.
The integrated temperature and RF signal strength indicators can be used to monitor the environment, and many external sensors can be used to collect additional data. User's Guide
The eZ430-RF2500-SEH Sensor Monitor is a complete open source application that includes an example energy-aware project to test your hardware and may be used as a framework for your energy harvesting project. Firmware is provided for the MSP430 as well as a PC demo application to display the data samples from your wireless network.
Features:
- Efficient solar energy harvesting module for the eZ430-RF2500
Battery-less operation
Works in low ambient light
400+ transmissions in dark
Adaptable to any RF network or sensor input
Inputs available for external harvesters (thermal, piezo, 2nd solar panel, etc.)
USB debugging and programming interface with application backchannel to PC
18 available analog and communications input/output pins
Highly integrated, ultra-low-power MSP430 MCU with 16-MHz performance
Two green and red LEDs for visual feedback
Interruptible push button for user feedback
Alternative Energy - Standards and Electrical Safety Testing of Solar Modules
QuadTech Products Ideal forAlternative Energy Manufacturers
With the current U.S. administration focused on alternative energy, green initiatives like solar and wind power are a priority for manufacturers- a topic QuadTech has extensive knowledge in.
For example, QuadTech's 6000 Plus is an ideal product for manufacturers performing power inverter testing for hipot, ground bond and even dielectric withstand testing- a requirement for compliance and production testing of solar modules.
QuadTech recently released their 31000 AC Programmable Power Sources, a solid product line for testing inverters at a wide variety of voltages and frequencies.
Taken from Quadtech.
Saturday, April 25, 2009
电科院“互感器现场检定技术”通过鉴定
文章来源：中国电力新闻网
2009年3月23日，中国电机工程学会在武汉主持召开“电力互感器现场检定试验技术与装置研究”项目的技术鉴定会。
国网电科院计量所
“电力互感器现场检定试验技术与装置研究”通过技术鉴定
2009年3月23日，中国电机工程学会在武汉主持召开“电力互感器现场检定试验技术与装置研究”项目的技术鉴定会。鉴定委员会由来自武汉大学、华中科技大学和多家省电科院、湖北省计量院的多位教授、专家组成。鉴定委员会专家分别听取项目的研制报告、技术报告、效益分析报告、用户报告、测试报告和查新报告，审查了相关技术资料，一致同意通过鉴定。
由国网电科院计量测试技术研究所完成的“电力互感器现场检定试验技术与装置研究”项目针对国内外高电压等级、大电流、超长距离全封闭GIS（组合电器）中电流互感器安装完毕后无法在现场进行检定试验的技术难题，研究了现场试验方法，开发研制了全套检测装置。项目研制的集成化、模块式、积木式大电流升流系统，能根据现场实际工况灵活配置，实现了各种工况下GIS电流互感器现场试验电流达到120%设备额定电流。项目完成了世界首台串联式工频标准电压互感器的研制，其结构上采用上下级叠加，由两台500kV单级SF6气体绝缘电压互感器串联组成且叠加放置，具有结构合理、体积小、质量轻、运输方便，性能稳定的特点。并且基于串联式电压互感器上下级电压的可加性，提出了采用半绝缘互感器电压加法对电压互感器进行量值溯源的方法。项目的研究成果成功应用在我国1000kV特高压交流试验示范工程、西北750kV输变电工程中，验证了其理论方法正确，技术先进，使用灵活，适应性和可操作性强。鉴定委员会一致认为：该项目在特高压/超高压电力互感器现场检定技术上填补了国内空白，其研究及应用成果达到国际领先水平。
2009年3月23日，中国电机工程学会在武汉主持召开“电力互感器现场检定试验技术与装置研究”项目的技术鉴定会。
国网电科院计量所
“电力互感器现场检定试验技术与装置研究”通过技术鉴定
2009年3月23日，中国电机工程学会在武汉主持召开“电力互感器现场检定试验技术与装置研究”项目的技术鉴定会。鉴定委员会由来自武汉大学、华中科技大学和多家省电科院、湖北省计量院的多位教授、专家组成。鉴定委员会专家分别听取项目的研制报告、技术报告、效益分析报告、用户报告、测试报告和查新报告，审查了相关技术资料，一致同意通过鉴定。
由国网电科院计量测试技术研究所完成的“电力互感器现场检定试验技术与装置研究”项目针对国内外高电压等级、大电流、超长距离全封闭GIS（组合电器）中电流互感器安装完毕后无法在现场进行检定试验的技术难题，研究了现场试验方法，开发研制了全套检测装置。项目研制的集成化、模块式、积木式大电流升流系统，能根据现场实际工况灵活配置，实现了各种工况下GIS电流互感器现场试验电流达到120%设备额定电流。项目完成了世界首台串联式工频标准电压互感器的研制，其结构上采用上下级叠加，由两台500kV单级SF6气体绝缘电压互感器串联组成且叠加放置，具有结构合理、体积小、质量轻、运输方便，性能稳定的特点。并且基于串联式电压互感器上下级电压的可加性，提出了采用半绝缘互感器电压加法对电压互感器进行量值溯源的方法。项目的研究成果成功应用在我国1000kV特高压交流试验示范工程、西北750kV输变电工程中，验证了其理论方法正确，技术先进，使用灵活，适应性和可操作性强。鉴定委员会一致认为：该项目在特高压/超高压电力互感器现场检定技术上填补了国内空白，其研究及应用成果达到国际领先水平。
电容式触控传感器方案
欧姆龙与瑞萨签署协议共同开发电容式触控传感器方案
文章来源：科讯网
日前，欧姆龙与瑞萨科技签署协议，将共同开发电容式触控传感器解决方案，并将应用于下一代的人机界面。
目前，触控屏幕正逐渐广泛地应用于各式各样的产品，包括家用电器、视听设备、办公设备、游戏机、行动电话及可携式音乐播放机等。欧姆龙拥有独家的串联电容式分割比对系统，也就是以串联方式连接至传感器电极之电容器的电容变化量转变成电压，而面板的触控/非触控状态则是透过测量放电持续时间而决定。采用此系统的触控传感器可提供快速响应能力及高噪声容忍度。
根据协议，瑞萨将于其R8C系列16位微控制器(MCU)产品内整合欧姆龙的触控传感器技术，并提供各种领域的触控传感器解决方案，包括家用电器及行动装置。
由于提供多种封装及内存配置的选择，因此在消费性16位MCU市场上瑞萨拥有极高的占有率，针对经过验证的欧姆龙触控传感器技术硬件版本，使用者透过触控侦测电路装置的方式加以建构，并将其整合至瑞萨R8C系列MCU产品之后，将获得以下好处：
提升系统效能──将执行系统控制的MCU及触控侦测电路装置整合至单一芯片，不需提供电流给独立的外部芯片，即可启动此功能并提升噪声容忍度。如此将可改善触控传感器的灵敏度，提供更精确的触控侦测。
降低系统功耗──采用单芯片整合有助于降低功耗。即使处于低功耗模式，仍可支持低频率(4MHz/5MHz)运作期间的触控侦测。对于以电池运作的产品，可大幅延长(例如游戏机、计算机及行动电话等)其电池寿命。
小型尺寸，低总体成本──采用单芯片整合后，不需再提供电流给大量的外部外围装置(例如电容器及电阻器等)，因此可以使用更小型的印刷电路板。由于能够透过MCU及部分电容器和电阻器建构整个系统，因此可以减少装置的数量，降低总体成本并提升可靠度。
瑞萨科技成立于2003年4月1日，它结合了日立与三菱电机在半导体领域上的丰富经验和专业知识，配合全球二万七千名员工的无限创意，将为人类创造出更舒适美好的生活。
文章来源：科讯网
日前，欧姆龙与瑞萨科技签署协议，将共同开发电容式触控传感器解决方案，并将应用于下一代的人机界面。
目前，触控屏幕正逐渐广泛地应用于各式各样的产品，包括家用电器、视听设备、办公设备、游戏机、行动电话及可携式音乐播放机等。欧姆龙拥有独家的串联电容式分割比对系统，也就是以串联方式连接至传感器电极之电容器的电容变化量转变成电压，而面板的触控/非触控状态则是透过测量放电持续时间而决定。采用此系统的触控传感器可提供快速响应能力及高噪声容忍度。
根据协议，瑞萨将于其R8C系列16位微控制器(MCU)产品内整合欧姆龙的触控传感器技术，并提供各种领域的触控传感器解决方案，包括家用电器及行动装置。
由于提供多种封装及内存配置的选择，因此在消费性16位MCU市场上瑞萨拥有极高的占有率，针对经过验证的欧姆龙触控传感器技术硬件版本，使用者透过触控侦测电路装置的方式加以建构，并将其整合至瑞萨R8C系列MCU产品之后，将获得以下好处：
提升系统效能──将执行系统控制的MCU及触控侦测电路装置整合至单一芯片，不需提供电流给独立的外部芯片，即可启动此功能并提升噪声容忍度。如此将可改善触控传感器的灵敏度，提供更精确的触控侦测。
降低系统功耗──采用单芯片整合有助于降低功耗。即使处于低功耗模式，仍可支持低频率(4MHz/5MHz)运作期间的触控侦测。对于以电池运作的产品，可大幅延长(例如游戏机、计算机及行动电话等)其电池寿命。
小型尺寸，低总体成本──采用单芯片整合后，不需再提供电流给大量的外部外围装置(例如电容器及电阻器等)，因此可以使用更小型的印刷电路板。由于能够透过MCU及部分电容器和电阻器建构整个系统，因此可以减少装置的数量，降低总体成本并提升可靠度。
瑞萨科技成立于2003年4月1日，它结合了日立与三菱电机在半导体领域上的丰富经验和专业知识，配合全球二万七千名员工的无限创意，将为人类创造出更舒适美好的生活。
Friday, April 24, 2009
Inductance Analyzer 3255B
Within the coil winding industry Wayne Kerr's reputation for quality, performance and accuracy are second to none. The introduction of the 3255B Inductance Analyzer maintains this tradition.
By using the latest technology, and combining the most used measurement functions into an easy to use portable unit, the Wayne Kerr 3255B has brought improved accuracy, performance and even greater value for money to the inductance test market.
Key Features include:
Wide frequency range (20Hz - 500kHz)
Fast measurement speed (up to 20 measurements per second)
0.25% basic accuracy
Up to 125Amps of DC bias current
Binning function
Multi-frequency mode
Comprehensive measurement functions - including Z, L, C, Rac, Phase, Q, D, Rdc & Turns Ratio
Straight forward intuitive operation
Print test results
IEEE488 control using FREE LabVIEW™ driver
By using the latest technology, and combining the most used measurement functions into an easy to use portable unit, the Wayne Kerr 3255B has brought improved accuracy, performance and even greater value for money to the inductance test market.
Key Features include:
Wide frequency range (20Hz - 500kHz)
Fast measurement speed (up to 20 measurements per second)
0.25% basic accuracy
Up to 125Amps of DC bias current
Binning function
Multi-frequency mode
Comprehensive measurement functions - including Z, L, C, Rac, Phase, Q, D, Rdc & Turns Ratio
Straight forward intuitive operation
Print test results
IEEE488 control using FREE LabVIEW™ driver
Murata’s Digital Panel Meters at Digi-Key
From Digi-Key, for more than 35 years, the Murata Power Solutions / Datel offering of digital panel meters has been recognized as the industry's most versatile and affordable meters. While the ACA5-20RM and ACA-20RM-ALM ammeters offer current measurement to 500A, the DMS-20PC and DMS-20RM provide precision voltage measurement from ±200mV to ±200V.
General Purpose Voltmeters
DATEL voltmeters are a good solution for applications requiring a precise readout of AC or DC voltages.
Typical mounting options include 12-pin DIPs and traditional bezel/case assemblies which simplify panel mounting
AC-input options include average or rms-responding inputs
Self-powered, 2-wire models contain only two connections since they are powered directly from the signal they are measuring, making them ideal for new installations or as modern replacements for analog panel meters
Digital options include 3½ or 4½ digit, LED or LCD displays which can be operated from AC (85-264V) or DC (+5V to +40V) power sources
For harsh environments, users can choose from several bezel options that feature rubber gaskets and secure threaded metal fasteners.
Ammeters
For measuring AC or DC currents, DATEL ammeters feature easy set up and installation, and typically require no additional components or user set up. Average responding or true-rms inputs can measure currents up to 100A with a built in current transformer and up to 2000A with external 5A CTs.
AC ammeters with built-in current transformers (CTs) greatly simplify current measurement applications. Most installations require just three connections: two for supplying operating power, and one for the current being measured. All models feature easy-to-read LED displays and sturdy terminal block connections.
DC ammeters are available with built-in shunts capable of measuring currents from 200uA to 20A. For higher currents, models are specifically designed to accept inputs from external 50mV DC shunts, enabling these models to measure up to 2000Adc.
General Purpose Voltmeters
DATEL voltmeters are a good solution for applications requiring a precise readout of AC or DC voltages.
Typical mounting options include 12-pin DIPs and traditional bezel/case assemblies which simplify panel mounting
AC-input options include average or rms-responding inputs
Self-powered, 2-wire models contain only two connections since they are powered directly from the signal they are measuring, making them ideal for new installations or as modern replacements for analog panel meters
Digital options include 3½ or 4½ digit, LED or LCD displays which can be operated from AC (85-264V) or DC (+5V to +40V) power sources
For harsh environments, users can choose from several bezel options that feature rubber gaskets and secure threaded metal fasteners.
Ammeters
For measuring AC or DC currents, DATEL ammeters feature easy set up and installation, and typically require no additional components or user set up. Average responding or true-rms inputs can measure currents up to 100A with a built in current transformer and up to 2000A with external 5A CTs.
AC ammeters with built-in current transformers (CTs) greatly simplify current measurement applications. Most installations require just three connections: two for supplying operating power, and one for the current being measured. All models feature easy-to-read LED displays and sturdy terminal block connections.
DC ammeters are available with built-in shunts capable of measuring currents from 200uA to 20A. For higher currents, models are specifically designed to accept inputs from external 50mV DC shunts, enabling these models to measure up to 2000Adc.
6kW Regenerative DC Electronic Load
PLZ6000R is a DC electronic load that regenerates load power to the AC line. Regular electronic loads consume load power by having semiconductor devices convert it into heat. By contrast, PLZ6000R converts load power into reusable electric power, rather than converting it into heat as is typically done, and feeds this power to the AC line, thereby substantially reducing the amount of waste energy. PLZ6000R is an environment-friendly electronic load that can contribute significantly to your energy saving efforts.
Features
Power regeneration efficiency of up to 90% (at rated power)The use of a proprietary switching technology (patent pending) provides high power regeneration efficiency - from 85% or more at one-third of rated power (2000 W) to a maximum of 90% or more. This energy saving feature greatly reduces the electronic load's environment impact on your plant and it is not necessary to equip special cooling system such as water cooling method to supress the heat generation.
No necessity of special cooling system such as water cooling method
Aging and evaluation testing for DC/DC converters and various types of power supplies
Evaluation and durability testing for alternators and motor generators
Discharge testing for different types of batteries (lead, lithium, and assembled batteries)
Dummy load testing for equipment powered by natural energy (solar cells and wind power generation)
Evaluation testing for fuel cells and stacks
[Note] This product is intended for in-plant power generation only. (It does not feed its generated power back to the electric power system.) This product cannot be used unless 5.4 kW or more of power is consumed by each power distribution system per one unit.
Features
Power regeneration efficiency of up to 90% (at rated power)The use of a proprietary switching technology (patent pending) provides high power regeneration efficiency - from 85% or more at one-third of rated power (2000 W) to a maximum of 90% or more. This energy saving feature greatly reduces the electronic load's environment impact on your plant and it is not necessary to equip special cooling system such as water cooling method to supress the heat generation.
No necessity of special cooling system such as water cooling method
Aging and evaluation testing for DC/DC converters and various types of power supplies
Evaluation and durability testing for alternators and motor generators
Discharge testing for different types of batteries (lead, lithium, and assembled batteries)
Dummy load testing for equipment powered by natural energy (solar cells and wind power generation)
Evaluation testing for fuel cells and stacks
[Note] This product is intended for in-plant power generation only. (It does not feed its generated power back to the electric power system.) This product cannot be used unless 5.4 kW or more of power is consumed by each power distribution system per one unit.
To view more.
Good things come in small packages
PicoScope 5000 PC Oscilloscopes have been designed to take up very little of your valuable desk space. The innovative anti-slip case design means that the PicoScope 5000 PCOs can be used either horizontally or vertically — ideal when desk space is at a premium.
Unlike traditional benchtop oscilloscopes, PicoScope 5000 PC Oscilloscopes are lightweight and small enough to be carried in the same bag as your laptop, but for added protection you can use the supplied tough carry case. Despite the compact design, the case can safely store and protect your oscilloscope, leads, probes and power supply — there’s even enough room for the user manual and software.
A PicoScope 5000 PC Oscilloscope comes with everything you need to start taking measurements with the minimum of fuss and effort. The PicoScope 5000 PCO is supplied in a tough carry case that includes a USB cable, two 250 MHz x1/x10 oscilloscope probes, PicoScope oscilloscope software and a universal power adaptor that allows you to use your oscilloscope almost anywhere in the world.
All you need in an oscilloscope
With class-leading bandwidth, sampling rate and memory depth, and an array of advanced high end features, PicoScope 5000 PC Oscilloscopes give you the features and performance you need without compromise. An ideal direct replacement to benchtop oscilloscopes, PicoScope 5000 oscilloscopes are easy-to-use and cost-effective. The PicoScope 5204 is the vanguard of PC Oscilloscope design, whilst for those on a budget, the PicoScope 5203 has all the performance of the 5204 but with a smaller, though still impressive, 32 megasamples of memory.
Unlike traditional benchtop oscilloscopes, PicoScope 5000 PC Oscilloscopes are lightweight and small enough to be carried in the same bag as your laptop, but for added protection you can use the supplied tough carry case. Despite the compact design, the case can safely store and protect your oscilloscope, leads, probes and power supply — there’s even enough room for the user manual and software.
A PicoScope 5000 PC Oscilloscope comes with everything you need to start taking measurements with the minimum of fuss and effort. The PicoScope 5000 PCO is supplied in a tough carry case that includes a USB cable, two 250 MHz x1/x10 oscilloscope probes, PicoScope oscilloscope software and a universal power adaptor that allows you to use your oscilloscope almost anywhere in the world.
All you need in an oscilloscope
With class-leading bandwidth, sampling rate and memory depth, and an array of advanced high end features, PicoScope 5000 PC Oscilloscopes give you the features and performance you need without compromise. An ideal direct replacement to benchtop oscilloscopes, PicoScope 5000 oscilloscopes are easy-to-use and cost-effective. The PicoScope 5204 is the vanguard of PC Oscilloscope design, whilst for those on a budget, the PicoScope 5203 has all the performance of the 5204 but with a smaller, though still impressive, 32 megasamples of memory.
PicoScope 5000 oscilloscopes are supplied with PicoScope 6 oscilloscope software which allows you to use your PicoScope PCO as an oscilloscope, spectrum analyzer and meter. PicoScope 6 is just as easy to use as its predecessor and makes the same efficient use of screen space, but is now even more responsive and has a more modern user interface. New features in the software include draggable axis, improved zoom tools and a waveform replay tool which automatically records the last 32 waveforms.
To view more details.
Friday, April 17, 2009
TVA Locates Faulty Equipment
By Ralph McKosky, Mark Goff and Joseph Graziano, Tennessee Valley Authority
Antenna-array technology is used to locate partial-discharge signature of equipment that goes bad
Tennessee Valley Authority has had to Deal with Pollution Problems on Insulators and lightning arresters at its Paradise Fossil Plant Switchyard. Particulates from the combustion process have caused insulator pollution. The worst case is when this pollution leads to an insulator flashover, resulting in a protection relay and circuit breaker operating to mitigate the problem. TVA (Knoxville, Tennessee, U.S.) has changed its plant blow-down operations and now periodically washes the insulators. These steps have minimized but not solved the problem.
Working with the Electric Power Research Institute's (Palo Alto, California, U.S.) Substation Task Force and the University of Strathclyde (Glasgow, Scotland), TVA and other utilities are developing an antenna-array system to continuously monitor partial-discharge (PD) activity in a substation as an effective way to locate possible faults. TVA is using a PD system that was developed by the Institute for Energy and Environment at the University of Strathclyde. The antenna-array system constantly listens for all discharge activity within its range. The antenna-array PD system was demonstrated successfully by National Grid in the United Kingdom.
The antenna-array PD system measures radio-frequency (RF) signals to detect and locate PD. To accomplish this, the antenna-array PD system uses four specially designed omni-directional disk-cone antennas, a high-speed wide-band digitizing oscilloscope, custom software and algorithms to record and analyze the RF sources. The technology detects and captures the discharge and then computes the time-of-flight data to locate the source of PD. This is done by finding the solution of nonlinear equations.
The goal of the project is for the system to screen and identify suspected problems such as incipient faults and insulator pollution issues. With this knowledge, TVA could schedule insulator washing before a flashover risk occurs or take action to replace or repair high-voltage equipment showing internal PD.
In December 2005, TVA installed an antenna array in a wireless sensor lab of a Paradise mobile field trailer. Since that time, the utility has been tracking two different sources of PD. On average, 2000 PD impulses have been recorded a day. One source had a more energetic level of PD activity; the other source just seemed less energetic.
On May 18, 2006, TVA took a 69-kV bus off-line to install sensors for another research project (on wireless back-scatter sensors). During the outage, power-system operations, transmission operations and maintenance personnel performed a follow-up power-factor retest on the B-phase voltage transformer (VT).
The retest showed a sharp increase of the power factor; hence, it was decided to replace the VT during this outage. Once the 69-kV bus was back in service, the less energetic of the previously tracked discharges disappeared. The post-processed data after analysis was then plotted on a substation overview. A closer look at the data revealed that the source that seemed to have disappeared coincided with the replaced VT.
To read more, click here.
Antenna-array technology is used to locate partial-discharge signature of equipment that goes bad
Tennessee Valley Authority has had to Deal with Pollution Problems on Insulators and lightning arresters at its Paradise Fossil Plant Switchyard. Particulates from the combustion process have caused insulator pollution. The worst case is when this pollution leads to an insulator flashover, resulting in a protection relay and circuit breaker operating to mitigate the problem. TVA (Knoxville, Tennessee, U.S.) has changed its plant blow-down operations and now periodically washes the insulators. These steps have minimized but not solved the problem.
Working with the Electric Power Research Institute's (Palo Alto, California, U.S.) Substation Task Force and the University of Strathclyde (Glasgow, Scotland), TVA and other utilities are developing an antenna-array system to continuously monitor partial-discharge (PD) activity in a substation as an effective way to locate possible faults. TVA is using a PD system that was developed by the Institute for Energy and Environment at the University of Strathclyde. The antenna-array system constantly listens for all discharge activity within its range. The antenna-array PD system was demonstrated successfully by National Grid in the United Kingdom.
The antenna-array PD system measures radio-frequency (RF) signals to detect and locate PD. To accomplish this, the antenna-array PD system uses four specially designed omni-directional disk-cone antennas, a high-speed wide-band digitizing oscilloscope, custom software and algorithms to record and analyze the RF sources. The technology detects and captures the discharge and then computes the time-of-flight data to locate the source of PD. This is done by finding the solution of nonlinear equations.
The goal of the project is for the system to screen and identify suspected problems such as incipient faults and insulator pollution issues. With this knowledge, TVA could schedule insulator washing before a flashover risk occurs or take action to replace or repair high-voltage equipment showing internal PD.
In December 2005, TVA installed an antenna array in a wireless sensor lab of a Paradise mobile field trailer. Since that time, the utility has been tracking two different sources of PD. On average, 2000 PD impulses have been recorded a day. One source had a more energetic level of PD activity; the other source just seemed less energetic.
On May 18, 2006, TVA took a 69-kV bus off-line to install sensors for another research project (on wireless back-scatter sensors). During the outage, power-system operations, transmission operations and maintenance personnel performed a follow-up power-factor retest on the B-phase voltage transformer (VT).
The retest showed a sharp increase of the power factor; hence, it was decided to replace the VT during this outage. Once the 69-kV bus was back in service, the less energetic of the previously tracked discharges disappeared. The post-processed data after analysis was then plotted on a substation overview. A closer look at the data revealed that the source that seemed to have disappeared coincided with the replaced VT.
To read more, click here.
Thursday, April 16, 2009
Ultrasonic Detector with Phased Array Imaging
The EPOCH 1000 Series Digital Ultrasonic Flaw Detectors combines the highest level of performance for conventional portable flaw detection with the power of phased array imaging. The EPOCH 1000, 1000iR and 1000i feature a new horizontal case style with full VGA display, knob and navigation arrows for parameter adjustment, and full EN12668‑1 compliance. The advanced conventional ultrasonic functionality of the EPOCH 1000 series is augmented in the EPOCH 1000i with phased array imaging capabilities.
Key Features:
Available with Phased Array Imaging Package
EN12668-1 compliant
Over 30 digital receiver filter selections
6 kHz pulse repetition rate for high speed scanning
Automatic phased array probe recognition
Intuitive wedge delay and sensitivity calibration for all focal laws
Programmable analog/alarm outputs
IP66 environmental rating for harsh environments
Horizontal design with navigation panel and knob parameter adjustment
Digital high dynamic range receiver
Full VGA sunlight readable display
ClearWave™ Visual Enhancement Package for conventional A-scan interpretation
Reference and measurement cursors
Standard dynamic DAC/TVG
Standard onboard DGS/AVG
Advanced Ultrasound, Upgradable to Phased Array
The EPOCH 1000, EPOCH 1000iR, and EPOCH 1000i provide advanced conventional ultrasound capabilities for both the standard and advanced level inspector. These portable instruments can also be integrated into small systems for high speed scanning and single channel imaging. They come standard with a host of high performance features, including a 6 kHz maximum Pulse Rate Frequency (PRF) with single-shot measurements for accurate high speed scanning applications, tunable square wave pulser with PerfectSquare™ technology, and comprehensive digital filter sets for exceptional signal-to-noise clarity.
Rugged. Portable. Meets the Demands of the Toughest Inspection Environments!
The EPOCH 1000 Series is designed to meet the IP66 environmental rating. Tested for shock, vibration, explosive atmosphere, and wide temperature range, these instruments can withstand operation in harsh inspection conditions. Some of the EPOCH 1000 Series' other key physical features include:
Large, full VGA (640x480) resolution color transflective display for optimum viewing in low or bright lighting conditions
Rugged rubber handle for easy carrying
Durable instrument-mounted D-rings for chest harness use
Front and rear stands for table-top or steep inclined viewing
USB Client and Host ports for PC communication, direct printing and communication with peripheral devices
VGA output for presentations, training, and remote instrument monitoring
Programmable analog outputs, alarm outputs, and RS-232 communication
Standard internal, rechargeable lithium ion battery
Key Features:
Available with Phased Array Imaging Package
EN12668-1 compliant
Over 30 digital receiver filter selections
6 kHz pulse repetition rate for high speed scanning
Automatic phased array probe recognition
Intuitive wedge delay and sensitivity calibration for all focal laws
Programmable analog/alarm outputs
IP66 environmental rating for harsh environments
Horizontal design with navigation panel and knob parameter adjustment
Digital high dynamic range receiver
Full VGA sunlight readable display
ClearWave™ Visual Enhancement Package for conventional A-scan interpretation
Reference and measurement cursors
Standard dynamic DAC/TVG
Standard onboard DGS/AVG
Advanced Ultrasound, Upgradable to Phased Array
The EPOCH 1000, EPOCH 1000iR, and EPOCH 1000i provide advanced conventional ultrasound capabilities for both the standard and advanced level inspector. These portable instruments can also be integrated into small systems for high speed scanning and single channel imaging. They come standard with a host of high performance features, including a 6 kHz maximum Pulse Rate Frequency (PRF) with single-shot measurements for accurate high speed scanning applications, tunable square wave pulser with PerfectSquare™ technology, and comprehensive digital filter sets for exceptional signal-to-noise clarity.
Rugged. Portable. Meets the Demands of the Toughest Inspection Environments!
The EPOCH 1000 Series is designed to meet the IP66 environmental rating. Tested for shock, vibration, explosive atmosphere, and wide temperature range, these instruments can withstand operation in harsh inspection conditions. Some of the EPOCH 1000 Series' other key physical features include:
Large, full VGA (640x480) resolution color transflective display for optimum viewing in low or bright lighting conditions
Rugged rubber handle for easy carrying
Durable instrument-mounted D-rings for chest harness use
Front and rear stands for table-top or steep inclined viewing
USB Client and Host ports for PC communication, direct printing and communication with peripheral devices
VGA output for presentations, training, and remote instrument monitoring
Programmable analog outputs, alarm outputs, and RS-232 communication
Standard internal, rechargeable lithium ion battery
FUTEK offers Load Cell with USB Output
FUTEK Advanced Sensor Technology, Inc. is pleased to present its LSB200 S-Beam Jr. Load Cell with a brand new USB Digital Interface with 16 bits resolution. With this improvement, FUTEK has once again shown its innovation by becoming one of the first Sensor manufacturers to offer a USB type solution for Strain Gage Based Load Cells. FUTEK's USB Sensor Solution provides an easy "Plug & Play" with basic software making the System Integration even simpler.
The Miniature S Beam Load Cell has become one of the signature products in the FUTEK Load Cell Series. This model is widely used in Medical Bag Weighing Applications as well as automated feed back control and inline processing applications. The perfect mixture of size, accuracy and of course the assurance of an overload protection feature makes this one of our most sought after models. With a height of only 0.75", the LSB200 Miniature S Beam Load Cell is a great selection where tight environments or space is a challenge. The Standard LSB200 Miniature S Beam Load Cell model has female threads, comes in 2024 Aluminum construction (10 gram - 10 lb) or 17-4 Stainless Steel (25 lbs – 100lbs), and a 5 ft 29 AWG 4 conductor shielded silicone cable. It is also available in metric threads.
With all of its design features the Miniature S Beam Load Cell has a high accuracy with a Nonlinearity of ±0.1%, deflection of 0.005" nominal and an operating temperature of -60° F to 200° F. Similar to our entire Load Cell product line this model is manufactured in the U.S. and uses metal foil strain gauge technology.
Product Highlights:
Compact sized S-Beam Load Cell
Available in both Aluminum or Stainless Steel
USB output in 16 bits resolution
External Matched output option available
Built In Overload Protection
Metric Threads Available
In both Tension & Compression
Utilizes Metal Foil Strain Gauge Technology
Weight: 0.3 oz (aluminum) / 0.9 oz (Steel)
FUTEK also offers Donut Load Cells, Pancake Load Cells, and In Line Load Cells as additional solutions in the Load Cell line. In addition to our Load Cells, FUTEK carries over 400 products covering various Pressure Sensors, Torque Sensors, Force Sensors and related Instruments.
From www.globalspec.com
The Miniature S Beam Load Cell has become one of the signature products in the FUTEK Load Cell Series. This model is widely used in Medical Bag Weighing Applications as well as automated feed back control and inline processing applications. The perfect mixture of size, accuracy and of course the assurance of an overload protection feature makes this one of our most sought after models. With a height of only 0.75", the LSB200 Miniature S Beam Load Cell is a great selection where tight environments or space is a challenge. The Standard LSB200 Miniature S Beam Load Cell model has female threads, comes in 2024 Aluminum construction (10 gram - 10 lb) or 17-4 Stainless Steel (25 lbs – 100lbs), and a 5 ft 29 AWG 4 conductor shielded silicone cable. It is also available in metric threads.
With all of its design features the Miniature S Beam Load Cell has a high accuracy with a Nonlinearity of ±0.1%, deflection of 0.005" nominal and an operating temperature of -60° F to 200° F. Similar to our entire Load Cell product line this model is manufactured in the U.S. and uses metal foil strain gauge technology.
Product Highlights:
Compact sized S-Beam Load Cell
Available in both Aluminum or Stainless Steel
USB output in 16 bits resolution
External Matched output option available
Built In Overload Protection
Metric Threads Available
In both Tension & Compression
Utilizes Metal Foil Strain Gauge Technology
Weight: 0.3 oz (aluminum) / 0.9 oz (Steel)
FUTEK also offers Donut Load Cells, Pancake Load Cells, and In Line Load Cells as additional solutions in the Load Cell line. In addition to our Load Cells, FUTEK carries over 400 products covering various Pressure Sensors, Torque Sensors, Force Sensors and related Instruments.
From www.globalspec.com
Monday, April 13, 2009
电能计量装置现场分析（标准）系统
STANDARD ANALYSIS SYSTEM FOR METERING SETS
产品应用背景
基于电能计量装置远程监测系统、电能计量装置综合误差监测系统的应用，解决针对现场运行的高精度标准电能表、CT回路导纳、CT变比及长期运行互感器PT/CT负载变化的影响效果的校验及检验问题。例如：监测系统改变了CT/PT二次负荷后对传变的电流/电压信号的影响程度。所有的测试均可在带电状态进行，无需升流和信号源装置，即能根据需求针对电能计量装置的相关部件进行测试、校验。该套系统可用于电能计量装置远程校验监测系统、综合误差监测系统在安装投入前的现场情况考察和试验，估算系统接入的经济损失，确保现场条件符合要求。也可用于带电已运行系统相关参数的测试、验收、周期性检验等。
摘自：成都普莎拉科技有限公司 了解更多
产品应用背景
基于电能计量装置远程监测系统、电能计量装置综合误差监测系统的应用，解决针对现场运行的高精度标准电能表、CT回路导纳、CT变比及长期运行互感器PT/CT负载变化的影响效果的校验及检验问题。例如：监测系统改变了CT/PT二次负荷后对传变的电流/电压信号的影响程度。所有的测试均可在带电状态进行，无需升流和信号源装置，即能根据需求针对电能计量装置的相关部件进行测试、校验。该套系统可用于电能计量装置远程校验监测系统、综合误差监测系统在安装投入前的现场情况考察和试验，估算系统接入的经济损失，确保现场条件符合要求。也可用于带电已运行系统相关参数的测试、验收、周期性检验等。
摘自：成都普莎拉科技有限公司 了解更多
Thursday, April 9, 2009
Research Helps Protect Against Lightning Damage
Research Helps Protect Against Lightning Damage
Studies Benefit Utilities, Manufacturers and Consumers
Atlanta (February 4, 2009) —Firing bolts of lightning at expensive electrical equipment is all in a day’s work at NEETRAC – the National Electric Energy Testing Research and Applications Center. The goal for the lightning research and other testing done by the center is to improve reliability for the nation’s electric energy transmission and distribution system.
The 2.2 million-volt impulse generator needed to produce artificial lightning is just one part of the test gear used to evaluate utility industry equipment that ranges from wooden poles and aluminum transmission lines to transformers and switches. Part of Georgia Tech’s School of Electrical and Computer Engineering, the center is supported by 32 equipment manufacturers and utility companies that provide nearly 60 percent of the electricity used in the United States.
A major part of the work is ensuring reliability during the lightning storms that threaten utilities and their customers.
“Lightning is electricity of the wrong sort,” explained Rick Hartlein, NEETRAC’s director. “Electric utilities must do a number of things to keep lightning from damaging the power delivery system, which can cause power outages or damage to equipment plugged into electrical outlets in homes and businesses.”
Thunderstorms can produce more than 100 million volts – compared to the 120 volts in household wall outlets and 240 volts that power large home appliances. To deal with those added millions of volts, utilities rely on a complex array of lightning arrestors, static lines and grounding systems.
Lightning arrestors, for instance, contain special materials that under normal conditions do not permit the flow of electrical current. But when they sense a sudden surge of electricity from a lightning strike, they change properties in a few microseconds, becoming conductors rather than insulators. When strategically placed on the electric grid, the arrestors carry the lightning surges away to the ground – after which the arrestors return to their role as insulators.
Without the arrestors, lightning could arc across the insulators that support power lines, causing interruptions and damaging other equipment. In severe cases, the damage could cause line circuit breakers to trip, resulting in power outages to businesses, hospitals and whole communities.
At NEETRAC’s facilities near Atlanta’s Hartsfield-Jackson International Airport, Hartlein and his research team evaluate the arrestors and help utilities choose the right locations for them.
“Lightning arrestors are not inexpensive devices and they must be maintained once they are put on the system,” Hartlein said. “You want to distribute them on the system frequently enough to protect it, but not so frequently that you are wasting money.”
After multiple lightning strikes and years out in the elements, lightning arrestors themselves can fail, creating a momentary short-circuit on the power grid. If that happens, a device built into the arrestors senses the problem and fires a tiny explosive charge that physically disconnects the faulty arrestor from the distribution system. NEETRAC has developed specialized laboratory testing procedures to evaluate the performance of these devices. Helping the industry develop better equipment requires an understanding of lightning and how it works. For instance, though it’s generally not visible to the human eye, most lightning strikes in the Southeast are made up of between three and five separate pulses between 30 and 120 milliseconds apart, each one containing potentially damaging electrical energy.
In the Southeast, 90 percent of lightning has a negative charge. But positively-charged lightning also occurs, most often in the winter. Positive lightning ionizes the atmosphere more efficiently than negative lightning and can therefore travel longer distances.
“Positive lightning can travel 10 miles from the storm before striking an object on the ground, so the storm clouds may not even be visible when the lightning strikes,” said Ray Hill, a research technologist with NEETRAC. “This is the source of what people call a ‘bolt from the blue.’ Because it tends to be a single pulse, positive lightning can be more dangerous since all of the energy is in a single stroke – and people aren’t expecting it.”
Though NEETRAC’s lightning impulse generator can create explosive results, most testing at the center’s facilities is less dramatic. For instance, salt fog chambers simulate long-term exposure in moist and corrosive environments to study how utility system components will withstand years of exposure to the elements. Strong ultraviolet lights and high temperatures test the ability of rubber seals to withstand summertime heat and strong sunlight while keeping moisture away from sensitive components. Computer simulations developed by Sakis Meliopoulos, a member of the Georgia Tech electric power faculty, help determine the most efficient way to ground the electric grid, which provides the only effective way to control damaging current. “The utility companies do a lot to keep lightning from damaging their systems, which helps keep the lights on,” Hill added. “When it comes down to that last bit of lightning protection for the service that comes into a home, consumers should consider additional surge protection, particularly for electronic equipment. But nothing is absolute – all you can really do with lightning protection is to get the odds in your favor.”
Writer: John Toon
From Research News & Publications Office
Georgia Institute of Technology
Studies Benefit Utilities, Manufacturers and ConsumersAtlanta (February 4, 2009) —Firing bolts of lightning at expensive electrical equipment is all in a day’s work at NEETRAC – the National Electric Energy Testing Research and Applications Center. The goal for the lightning research and other testing done by the center is to improve reliability for the nation’s electric energy transmission and distribution system.
The 2.2 million-volt impulse generator needed to produce artificial lightning is just one part of the test gear used to evaluate utility industry equipment that ranges from wooden poles and aluminum transmission lines to transformers and switches. Part of Georgia Tech’s School of Electrical and Computer Engineering, the center is supported by 32 equipment manufacturers and utility companies that provide nearly 60 percent of the electricity used in the United States.
A major part of the work is ensuring reliability during the lightning storms that threaten utilities and their customers.
“Lightning is electricity of the wrong sort,” explained Rick Hartlein, NEETRAC’s director. “Electric utilities must do a number of things to keep lightning from damaging the power delivery system, which can cause power outages or damage to equipment plugged into electrical outlets in homes and businesses.”
Thunderstorms can produce more than 100 million volts – compared to the 120 volts in household wall outlets and 240 volts that power large home appliances. To deal with those added millions of volts, utilities rely on a complex array of lightning arrestors, static lines and grounding systems.
Lightning arrestors, for instance, contain special materials that under normal conditions do not permit the flow of electrical current. But when they sense a sudden surge of electricity from a lightning strike, they change properties in a few microseconds, becoming conductors rather than insulators. When strategically placed on the electric grid, the arrestors carry the lightning surges away to the ground – after which the arrestors return to their role as insulators.
Without the arrestors, lightning could arc across the insulators that support power lines, causing interruptions and damaging other equipment. In severe cases, the damage could cause line circuit breakers to trip, resulting in power outages to businesses, hospitals and whole communities.
At NEETRAC’s facilities near Atlanta’s Hartsfield-Jackson International Airport, Hartlein and his research team evaluate the arrestors and help utilities choose the right locations for them.
“Lightning arrestors are not inexpensive devices and they must be maintained once they are put on the system,” Hartlein said. “You want to distribute them on the system frequently enough to protect it, but not so frequently that you are wasting money.”
After multiple lightning strikes and years out in the elements, lightning arrestors themselves can fail, creating a momentary short-circuit on the power grid. If that happens, a device built into the arrestors senses the problem and fires a tiny explosive charge that physically disconnects the faulty arrestor from the distribution system. NEETRAC has developed specialized laboratory testing procedures to evaluate the performance of these devices. Helping the industry develop better equipment requires an understanding of lightning and how it works. For instance, though it’s generally not visible to the human eye, most lightning strikes in the Southeast are made up of between three and five separate pulses between 30 and 120 milliseconds apart, each one containing potentially damaging electrical energy.
In the Southeast, 90 percent of lightning has a negative charge. But positively-charged lightning also occurs, most often in the winter. Positive lightning ionizes the atmosphere more efficiently than negative lightning and can therefore travel longer distances.
“Positive lightning can travel 10 miles from the storm before striking an object on the ground, so the storm clouds may not even be visible when the lightning strikes,” said Ray Hill, a research technologist with NEETRAC. “This is the source of what people call a ‘bolt from the blue.’ Because it tends to be a single pulse, positive lightning can be more dangerous since all of the energy is in a single stroke – and people aren’t expecting it.”
Though NEETRAC’s lightning impulse generator can create explosive results, most testing at the center’s facilities is less dramatic. For instance, salt fog chambers simulate long-term exposure in moist and corrosive environments to study how utility system components will withstand years of exposure to the elements. Strong ultraviolet lights and high temperatures test the ability of rubber seals to withstand summertime heat and strong sunlight while keeping moisture away from sensitive components. Computer simulations developed by Sakis Meliopoulos, a member of the Georgia Tech electric power faculty, help determine the most efficient way to ground the electric grid, which provides the only effective way to control damaging current. “The utility companies do a lot to keep lightning from damaging their systems, which helps keep the lights on,” Hill added. “When it comes down to that last bit of lightning protection for the service that comes into a home, consumers should consider additional surge protection, particularly for electronic equipment. But nothing is absolute – all you can really do with lightning protection is to get the odds in your favor.”
Writer: John Toon
From Research News & Publications Office
Georgia Institute of Technology
The idea of using artificial neural network in measurement system with hot probe for testing parameters of heat-insulating materials
Stanislaw Chudzika,
a.Institute of Electronics and Control Systems, Czestochowa University of Technology, al. Armii Krajowej 17, 42-200 Czestochowa, Poland
Received 30 April 2007;
revised 17 November 2008;
accepted 29 December 2008.
Available online 14 January 2009.
Abstract
The article presents a mathematical model of a measurement system with hot probe for testing thermal parameters of heat-insulating materials. Currently in situ measurement of thermal conductivity is widely done by the line heat source (LHS) method. The basic problem with this method is the number and type of the assumptions needed. In this study, another method was proposed to measure the thermal parameters by using an artificial neural network. The model of a nonstationary heat flow process in the sample of material with hot probe and auxiliary thermometer is based on a two-dimensional heat-conduction model. For solving a system of partial differential equations that describe the model, the finite element method (FEM) was applied. The measurement system uses an artificial neural network (ANN) to estimate the coefficients of inverse heat conduction problem for solid. The network determines the value of effective thermal conductivity and effective thermal diffusivity on the basis of temperature responses of hot probe and auxiliary thermometer. In developing of the ANN model, several configurations were evaluated. The optimal ANN model was capable of predicting the thermal conductivity values with a relative error <1%. The influence of measurands errors on identified values of the thermal parameters was analysed. Learning process and simulation analyses were conducted in the Matlab environment. It is possible to implement the architecture of a trained neural network with a simple microcontroller embedded system.
Keywords: Neural networks; Thermal conductivity; Thermal diffusivity; Inverse heat conduction problem
Article Outline
1. Introduction
2. The idea of measurement system with hot probe
3. Mathematic model and results of the simulation of a nonstationary heat flow process in the sample
4. The application of artificial neural networks for thermal parameters identification
5. Results of simulations
6. Conclusion
Acknowledgements
References
Taken from Sciencedirect.
a.Institute of Electronics and Control Systems, Czestochowa University of Technology, al. Armii Krajowej 17, 42-200 Czestochowa, Poland
Received 30 April 2007;
revised 17 November 2008;
accepted 29 December 2008.
Available online 14 January 2009.
Abstract
The article presents a mathematical model of a measurement system with hot probe for testing thermal parameters of heat-insulating materials. Currently in situ measurement of thermal conductivity is widely done by the line heat source (LHS) method. The basic problem with this method is the number and type of the assumptions needed. In this study, another method was proposed to measure the thermal parameters by using an artificial neural network. The model of a nonstationary heat flow process in the sample of material with hot probe and auxiliary thermometer is based on a two-dimensional heat-conduction model. For solving a system of partial differential equations that describe the model, the finite element method (FEM) was applied. The measurement system uses an artificial neural network (ANN) to estimate the coefficients of inverse heat conduction problem for solid. The network determines the value of effective thermal conductivity and effective thermal diffusivity on the basis of temperature responses of hot probe and auxiliary thermometer. In developing of the ANN model, several configurations were evaluated. The optimal ANN model was capable of predicting the thermal conductivity values with a relative error <1%. The influence of measurands errors on identified values of the thermal parameters was analysed. Learning process and simulation analyses were conducted in the Matlab environment. It is possible to implement the architecture of a trained neural network with a simple microcontroller embedded system.
Keywords: Neural networks; Thermal conductivity; Thermal diffusivity; Inverse heat conduction problem
Article Outline
1. Introduction
2. The idea of measurement system with hot probe
3. Mathematic model and results of the simulation of a nonstationary heat flow process in the sample
4. The application of artificial neural networks for thermal parameters identification
5. Results of simulations
6. Conclusion
Acknowledgements
References
Taken from Sciencedirect.
On-line detecting of transformer winding deformation based on parameter identification of leakage inductance
Transformers are required to demonstrate the ability to withstand short circuit currents. Over currents caused by short circuit can give rise to windings deformation. In this paper, a novel method is proposed to monitor the state of transformer windings, which is achieved through on-line detecting the leakage inductance of the windings. Specifically, the mathematical model is established for on-line identifying the leakage inductance of the windings by applying least square algorithm (LSA) to the equivalent circuit equations. The effect of measurement and model inaccuracy on the identification error is analyzed, and the corrected model is also given to decrease these adverse effect on the results. Finally, dynamic test is carried out to verify our method. The test results clearly show that our method is very accurate even under the fluctuation of load or power factor. Therefore, our method can be effectively used to on-line detect the windings deformation.
作 者：
Hao Zhiguo Zhang Baohui Li Peng
作者单位：
School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China
刊 名：
西安交通大学学报（英文版）
英文刊名：
ACADEMIC JOURNAL OF XI'AN
作 者：
Hao Zhiguo Zhang Baohui Li Peng
作者单位：
School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China
刊 名：
西安交通大学学报（英文版）
英文刊名：
ACADEMIC JOURNAL OF XI'AN
Tuesday, April 7, 2009
Which Renewable Technologies are Profitable Investments?
Investing in Renewable Technologies: Wind, Solar, Geotherm, Hydro, Biomass
Eventually renewable energies will dominate the world's energy supply system. There is no real alternative. Mankind cannot indefinitely continue to base its life on the consumption of finite energy resources. Today, the world's energy supply is largely based on fossil fuels and nuclear power. These sources of energy will not last forever and have proven to be contributors to our environmental problems. The environmental impacts of energy use are not new but they are increasingly well known; they range from deforestation to local and global pollution. In less than three centuries since the industrial revolution, mankind has already burned roughly half of the fossil fuels that accumulated under the earth's surface over hundreds of millions of years. Nuclear power is also based on a limited resource (uranium) and the use of nuclear power creates such incalculable risks that nuclear power plants cannot be insured. Renewable sources of energy are an essential part of an overall strategy of sustainable development. They help reduce dependence of energy imports, thereby ensuring a sustainable supply. Furthermore renewable energy sources can help improve the competitiveness of industries over the long run and have a positive impact on regional development and employment. Renewable energy technologies are suitable for off-grid services, serving those in remote areas of the world without requiring expensive and complicated grid infrastructure. In his 2007 State of the Union address, President George W. Bush outlined plans to ease the United States out of its foreign oil dependence through the use of renewable energy resources, and reduce gas usage by a full 20% in ten years through alternative fuels. “Extending hope and opportunity depends on a stable supply of energy that keeps America's economy running and America's environment clean. For too long our nation has been dependent on foreign oil, and this dependence leaves us more vulnerable to hostile regimes and to terrorists who could cause huge disruptions of oil shipments and raise the price of oil, and do great harm to our economy. It's in our vital interest to diversify America's energy supply -- the way forward is through technology. We must continue changing the way America generates electric power by even greater use of clean coal technology, solar and wind energy, and clean, safe nuclear power. To reach this goal, we must increase the supply of alternative fuels by setting a mandatory fuel standards to require 35 billion gallons of renewable and alternative fuels in 2017 - and that is nearly five times the current target.” His speech emphasized the many benefits of developing and investing in renewable energy technologies. This report on Investing in Renewable Technologies expands further on this speech and offers an in-depth analysis of all the renewable energies available today, from biofuels to geothermal. The report explores the benefits of each energy source, the growth drivers, challenges and barriers, economics of that energy, and much more. A complete analysis of all the renewable energies in use today, along with a section devoted to country analysis is also provided in the report.
GET YOUR COPY NOW: Download PDF
Eventually renewable energies will dominate the world's energy supply system. There is no real alternative. Mankind cannot indefinitely continue to base its life on the consumption of finite energy resources. Today, the world's energy supply is largely based on fossil fuels and nuclear power. These sources of energy will not last forever and have proven to be contributors to our environmental problems. The environmental impacts of energy use are not new but they are increasingly well known; they range from deforestation to local and global pollution. In less than three centuries since the industrial revolution, mankind has already burned roughly half of the fossil fuels that accumulated under the earth's surface over hundreds of millions of years. Nuclear power is also based on a limited resource (uranium) and the use of nuclear power creates such incalculable risks that nuclear power plants cannot be insured. Renewable sources of energy are an essential part of an overall strategy of sustainable development. They help reduce dependence of energy imports, thereby ensuring a sustainable supply. Furthermore renewable energy sources can help improve the competitiveness of industries over the long run and have a positive impact on regional development and employment. Renewable energy technologies are suitable for off-grid services, serving those in remote areas of the world without requiring expensive and complicated grid infrastructure. In his 2007 State of the Union address, President George W. Bush outlined plans to ease the United States out of its foreign oil dependence through the use of renewable energy resources, and reduce gas usage by a full 20% in ten years through alternative fuels. “Extending hope and opportunity depends on a stable supply of energy that keeps America's economy running and America's environment clean. For too long our nation has been dependent on foreign oil, and this dependence leaves us more vulnerable to hostile regimes and to terrorists who could cause huge disruptions of oil shipments and raise the price of oil, and do great harm to our economy. It's in our vital interest to diversify America's energy supply -- the way forward is through technology. We must continue changing the way America generates electric power by even greater use of clean coal technology, solar and wind energy, and clean, safe nuclear power. To reach this goal, we must increase the supply of alternative fuels by setting a mandatory fuel standards to require 35 billion gallons of renewable and alternative fuels in 2017 - and that is nearly five times the current target.” His speech emphasized the many benefits of developing and investing in renewable energy technologies. This report on Investing in Renewable Technologies expands further on this speech and offers an in-depth analysis of all the renewable energies available today, from biofuels to geothermal. The report explores the benefits of each energy source, the growth drivers, challenges and barriers, economics of that energy, and much more. A complete analysis of all the renewable energies in use today, along with a section devoted to country analysis is also provided in the report.
GET YOUR COPY NOW: Download PDF
Do Biofuels Really Reduce Greenhouse Gas Emissions?
Biofuel is any fuel that is derived from biomass - recently living organisms or their metabolic byproducts, such as manure from cows. It is a renewable energy source, unlike other natural resources such as petroleum, coal, and nuclear fuels. Agricultural products specifically grown for use as biofuels include corn and soybeans, primarily in the United States; as well as flaxseed and rapeseed, primarily in Europe; sugar cane in Brazil and palm oil in South-East Asia. Biodegradable outputs from industry, agriculture, forestry, and households can also be used to produce bioenergy; examples include straw, timber, manure, rice husks, sewage, biodegradable waste, and food leftovers. These feedstocks are converted into biogas through anaerobic digestion. Biomass used as fuel often consists of underutilized types, like chaff and animal waste. The idea of using biofuels from renewable sources is attractive as biofuels could help reduce greenhouse gas emissions and our dependency on fossil fuels. However, a new study, which looked at the full life cycle of biofuels, shows that, depending on the type and source of biofuel, the benefits and environmental impacts can vary considerably. The results highlight differences that could help inform policymakers considering tax-breaks for renewable fuels. Biofuels are currently the most important form of renewable energy in road transportation, but the debate over their environmental impact is ongoing. Some argue that when cultivation, including deforestation and soil acidification, is taken into account, biofuels consume more energy than they produce. Today, biofuels provide about 1% of global transport fuel. Already, they are causing serious harm to the climate, to communities, food sovereignty and food security and to biodiversity. Most biofuels are agrofuels – made from crops and trees grown specifically for that purpose, such as sugar cane, palm oil, soya, jatropha or maize. Agrofuel expansion means more intensive agriculture and thus more agro-chemicals (including synthetic fertilizers). It also means more destruction of natural ecosystems, which play a vital role in regulating the climate, and the displacement of millions of small farmers, pastoralists and indigenous peoples. This report takes a look at whether biofuels are causing global warming or not. The report analyzes the greenhouse gas emissions from biofuels, and what the impact of this will be on the global energy market.
From www.energybusinessreport.com.
From www.energybusinessreport.com.
Fossil Fuels + Solar Energy = The Future of Electricity Generation
Dave Ugolini and Dr. Justin Zachary, Bechtel Power Corp., and Hyung Joon Park, Bechtel Enterprises
Renewable energy, though still accounting for a comparatively small portion of overall supply, generates a larger portion of the world’s electricity each year. Combining many of the available solar energy conversion technologies with conventional fossil-fueled technologies could reduce fuel costs while simultaneously helping utilities that are struggling to meet their renewable portfolio goals.Renewable energy technologies face two near-term deployment hurdles when compared to traditional forms of power generation. First, their initial capital cost typically is much higher on a dollars per installed kilowatt basis, and that first cost is only partially compensated for by lower operation and maintenance (O&M) and fuel costs. This is especially true when today’s higher project costs are compared to those of conventionally fueled projects installed a decade or more ago.
The other important issue is dispatchability. There are few renewable options available to a dispatcher on a still, overcast day when the public demands electricity. Fast-acting gas turbines will have the advantage over renewable energy supplies when instantaneous matching of supply with demand is required — at least until some form of energy storage mitigates the intermittent nature of renewable energy sources. However, progress to commercialize large-scale energy storage technologies has been evolutionary, rather than revolutionary, and many technical and cost issues are yet to be resolved.
So why not take the best of both power generation technologies and integrate renewable power sources, such as concentrating solar thermal power (CSP), with existing or new combined cycles or conventional steam plants? The resulting hybrid plant will increase power or reduce fossil fuel consumption (justifying the high capital costs), mitigate the intermittent nature of most renewable technologies, remain dispatchable, and help many utilities with large fossil plant investments meet their renewable energy mandates.
The Best of Both Worlds
Conventional gas-fired combined-cycle plants represent perhaps 40% of the installed power generation resources in the U.S., yet they produce much less than half of the electricity sold. These plants uniformly have very high thermal efficiency and the smallest carbon footprint of any fossil-fueled generation technology, but the steeply rising cost of natural gas has pushed these plants into unfamiliar territory, where they operate as cycling rather than baseload plants. In other words, a typical combined-cycle plant is suitable for including in an integrated solar combined cycle (ISCC) configuration, where the solar energy portion of the plant can provide additional power at peak demand. We explore the solar power options for conventional steam plants later in this article.
The conversion of a combined-cycle plant to an ISCC begins with adding an additional source of heat, such as solar energy, to reduce natural gas consumption and thereby improve overall plant efficiency.
There are other advantages of an ISCC, even when compared with standalone CSP-inspired plant designs. (See POWER, December 2007 for a review of the Nevada Solar One CSP plant.) For example, the ISCC uses existing components (such as steam generators, steam turbine, and condensing system) that reduce the installation cost of a typical CSP system. Also, the potential for generation is increased because the steam turbine would be already synchronized to the grid when the solar energy contribution is added, thus avoiding lost generation during start-up. Another key advantage is gained during rising ambient temperatures, when gas turbine performance steadily drops. Operation of the solar energy portion of the ISCC compensates for that loss in efficiency and electricity production and improves the plant’s part-load performance.
Combining solar energy with conventional coal-fired plants is also possible in regions with reasonably good solar conditions. For these plants, where the steam pressures and temperatures are higher than for ISCC, the type of solar conversion technology used (Fresnel, parabolic trough, or tower) will dictate how solar is integrated into the plant.
Finally, don’t discount the possibility of hybridizing conventional plants with other, even multiple, forms of renewable energy such as biomass and wind. Our discussion of ISCC illustrates a single development path electric utilities could follow to efficiently and inexpensively bring multiple forms of renewable energy online in short order. Many other options are available, depending on the design of existing plants and their location particulars.
Taken from Powermag. to view the full page here.
Renewable energy, though still accounting for a comparatively small portion of overall supply, generates a larger portion of the world’s electricity each year. Combining many of the available solar energy conversion technologies with conventional fossil-fueled technologies could reduce fuel costs while simultaneously helping utilities that are struggling to meet their renewable portfolio goals.Renewable energy technologies face two near-term deployment hurdles when compared to traditional forms of power generation. First, their initial capital cost typically is much higher on a dollars per installed kilowatt basis, and that first cost is only partially compensated for by lower operation and maintenance (O&M) and fuel costs. This is especially true when today’s higher project costs are compared to those of conventionally fueled projects installed a decade or more ago.
The other important issue is dispatchability. There are few renewable options available to a dispatcher on a still, overcast day when the public demands electricity. Fast-acting gas turbines will have the advantage over renewable energy supplies when instantaneous matching of supply with demand is required — at least until some form of energy storage mitigates the intermittent nature of renewable energy sources. However, progress to commercialize large-scale energy storage technologies has been evolutionary, rather than revolutionary, and many technical and cost issues are yet to be resolved.
So why not take the best of both power generation technologies and integrate renewable power sources, such as concentrating solar thermal power (CSP), with existing or new combined cycles or conventional steam plants? The resulting hybrid plant will increase power or reduce fossil fuel consumption (justifying the high capital costs), mitigate the intermittent nature of most renewable technologies, remain dispatchable, and help many utilities with large fossil plant investments meet their renewable energy mandates.
The Best of Both Worlds
Conventional gas-fired combined-cycle plants represent perhaps 40% of the installed power generation resources in the U.S., yet they produce much less than half of the electricity sold. These plants uniformly have very high thermal efficiency and the smallest carbon footprint of any fossil-fueled generation technology, but the steeply rising cost of natural gas has pushed these plants into unfamiliar territory, where they operate as cycling rather than baseload plants. In other words, a typical combined-cycle plant is suitable for including in an integrated solar combined cycle (ISCC) configuration, where the solar energy portion of the plant can provide additional power at peak demand. We explore the solar power options for conventional steam plants later in this article.
The conversion of a combined-cycle plant to an ISCC begins with adding an additional source of heat, such as solar energy, to reduce natural gas consumption and thereby improve overall plant efficiency.
There are other advantages of an ISCC, even when compared with standalone CSP-inspired plant designs. (See POWER, December 2007 for a review of the Nevada Solar One CSP plant.) For example, the ISCC uses existing components (such as steam generators, steam turbine, and condensing system) that reduce the installation cost of a typical CSP system. Also, the potential for generation is increased because the steam turbine would be already synchronized to the grid when the solar energy contribution is added, thus avoiding lost generation during start-up. Another key advantage is gained during rising ambient temperatures, when gas turbine performance steadily drops. Operation of the solar energy portion of the ISCC compensates for that loss in efficiency and electricity production and improves the plant’s part-load performance.
Combining solar energy with conventional coal-fired plants is also possible in regions with reasonably good solar conditions. For these plants, where the steam pressures and temperatures are higher than for ISCC, the type of solar conversion technology used (Fresnel, parabolic trough, or tower) will dictate how solar is integrated into the plant.
Finally, don’t discount the possibility of hybridizing conventional plants with other, even multiple, forms of renewable energy such as biomass and wind. Our discussion of ISCC illustrates a single development path electric utilities could follow to efficiently and inexpensively bring multiple forms of renewable energy online in short order. Many other options are available, depending on the design of existing plants and their location particulars.
Taken from Powermag. to view the full page here.
Subscribe to:
Comments (Atom)
Posts
