Void discharge behaviours as a function of cavity size and voltage waveform under very low‐frequency excitation

Hong Viet Phuong Nguyen,Bao Toan Phung

doi:10.1049/hve.2017.0174

Abstract

Measurement of partial discharge (PD) is a vital method to assess the health of the electrical insulation in high-voltage power equipment. As diagnostic testing at very low frequency (VLF) is increasingly being used, it is important to investigate PD behaviours under such a low-frequency voltage excitation. This study presents the PD characteristics at VLF excitation under different applied voltage waveforms, including sinusoidal and trapezoid-based waves. Also, the effects of cavity size on PD behaviours at VLF are investigated. Experiments were performed to measure PDs in a cylindrical void bounded by solid insulation. The results show that discharge activities at VLF, in general, exhibit lower magnitude and repetition rate when compared with power frequency. Also revealed is the strong dependency of discharge parameters on the rate of voltage rise. Physical mechanisms to explain discharge behaviours are given.

Highlights

Diagnostic tests play an essential role in examining the health of high-voltage power equipment, in particular for those which have been in service for a considerable period of time
Insulation materials are subjected to long-term exposure of internal partial discharge (PD) activities which are commonly considered as the main cause of deterioration
PD testing at very low frequency (VLF), generally at 0.1 Hz, is commonly employed

Summary

Introduction

Diagnostic tests play an essential role in examining the health of high-voltage power equipment, in particular for those which have been in service for a considerable period of time. Their insulation materials are gradually degraded over time as they are continuously suffered from a combination of electrical, thermal, mechanical, and environmental stresses. PD testing at very low frequency (VLF), generally at 0.1 Hz, is commonly employed It does not require much reactive power to energise the test object to the required high voltage. The test supply is small, compact, and convenient for field testing of high capacitance items such as high-voltage cables

Results

Discussion

Conclusion