free website for high voltage solutions

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Reading Recommendation: Impedance-Based Method for Nondestructive Damage Identification

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.

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

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

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

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.

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

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

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.

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.

Find more application guide from CR MAGNETICS
http://www.crmagnetics.com/newprod/applist.asp

Free software for unit converter as isslustrated in the above graph.
From CR MAGNETICS, INC.
http://www.crmagnetics.com/newprod/freesoftware.asp

It is quite useful for beginnners and engineers.

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.