Non-Destructive Testing for Winding Insulation Diagnosis Using Inter-Turn Transient Voltage Signature Analysis

Nadia Radja,M’Hemed Rachek,Soraya Nait Larbi

doi:10.3390/machines6020021

Nadia Radja, M’Hemed Rachek + Show 1 more

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https://doi.org/10.3390/machines6020021

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Journal: Machines	Publication Date: May 10, 2018
Citations: 3	License type: CC BY 4.0

Affiliation: Mouloud Mammeri University of Tizi-Ouzou

Abstract

The paper proposes a novel approach to assess the integrity of Electrical Insulation Systems (EIS) by evaluating the response of the Transient Voltage Signature Analysis (VSA) to voltage source inverters correlated with changes in the Insulation Capacitance (IC). The involved model structures are derived from the in-situ estimation of high-frequency electromagnetic RLMC lumped network parameters. Different physical phenomena such as inductive and capacitive effects, as well as skin and proximity effects are combined. To account for these phenomena, we use an approach based on equivalent multi-transmission line electric circuits with distributed parameters (R: resistances, L, M: self and mutual inductances, and C: capacitances) which are frequency-dependent. Using the finite element method, firstly the turn-to-ground and turn-to-turn capacitance parameters are performed by solving an electrostatic model with a floating electric potential approach, and secondly, the resistance and self/mutual inductances are computed from the strongly coupled magneto-harmonic and total current density equations, including the conduction and displacement eddy current densities. The sensitivity of the capacitances is measured according to insulation thickness, and the dielectric properties are adopted to test the degradation order scenarios of the EIS and comparing their time and frequency domains of transient voltage waveform behavior with respect to healthy assessed insulation systems.

Highlights

IntroductionElectrical Insulation System (EIS) materials may be subject to different aging mechanisms or insulation failure resulting from stresses induced by a variety of factors, including thermal (additional heating, thermal overload), electrical (high-energy transient voltages, partial discharges), ambient stress (contamination, accumulated moisture, high humidity, aggressive chemicals), mechanical (moving/vibrations of coils), and voltage spikes, caused by the voltage source of the converters [1,2,3]
The Electrical Insulation System (EIS) materials are the heart of electrical equipment.During operation, EIS materials may be subject to different aging mechanisms or insulation failure resulting from stresses induced by a variety of factors, including thermal, electrical, ambient stress, mechanical, and voltage spikes, caused by the voltage source of the converters [1,2,3].The high frequency switching of semiconductor devices results in repetitive and uneven voltage transients, an increased high frequency harmonic content, highly-distorted waveform magnitudes, and over voltages because of resonance
The stateconsequently, of health of thethe insulation be of assessed by identifying andthe tracking changes in high-frequency developed in order to investigate the impact the turn-to-ground capacitance; RLMC-circuit,model the second part of this paper describes the of insulated‐winding and high‐frequency the turn-to-turnRLMC‐circuit capacitance changes on the transient voltage distribution model developed in order to investigate thebehavior impact following of the various defects

Summary

Introduction

EIS materials may be subject to different aging mechanisms or insulation failure resulting from stresses induced by a variety of factors, including thermal (additional heating, thermal overload), electrical (high-energy transient voltages, partial discharges), ambient stress (contamination, accumulated moisture, high humidity, aggressive chemicals), mechanical (moving/vibrations of coils), and voltage spikes, caused by the voltage source of the converters [1,2,3]. The high frequency switching of semiconductor devices results in repetitive and uneven voltage transients, an increased high frequency harmonic content, highly-distorted waveform magnitudes, and over voltages because of resonance. Each of these factors play an important role in degradation of insulation reliability and cause localized supplementary electrical and thermal stresses on EIS, and increased dielectric and Joule losses as well as an increased operating temperature. Increased electric stress is the main cause of accelerated degradation of insulation dielectric properties, which drastically impacts the lifetime of insulation [4,5,6,7].

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