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