Review of Partial Discharge Activity Considering Very-Low Frequency and Damped Applied Voltage

Xiaolei Wang,Respicius Clemence Kiiza,Mohamad Ghaffarian Niasar

doi:10.3390/en14020440

Abstract

When detecting the presence of partial discharge (PD) activity in the insulation system in high-voltage equipment, the excitation voltages at variable frequency have been widely used instead of power-frequency (50/60 Hz) sinusoidal voltage in order to reduce the charging power. This work reviews the relevant research on PD activity at very low frequency (VLF) method, including sinusoidal or cosine-rectangular voltage shape, and damped AC (DAC) method. Based on the research history and development status, some major PD characteristics, such as PD inception voltage (PDIV), PD amplitude, PD charge, PD phase-resolved pattern, and several hot issues, such as surface charge decay and statistical time lag, have been discussed. Moreover, the advantages, disadvantages, and applied conditions of two reviewed methods has been summarized. Finally, the prospects have been made on the main development trends of this research field in the future.

Highlights

Partial discharge activity has been normally recognized as a symptom of degradation and overstress in high-voltage electrical insulation system
Most of the results show that PD inception voltage (PDIV) increases with the decrease of test frequency, for instance, corona discharge in air studied by Zhou et al [35], partial discharge (PD) activity in discshaped cavities in polycarbonate insulation given in [32] and PD in XLPE cables with and without artificial internal defects in [72]
damped AC (DAC) testing method is based on single voltage excitation, and the following PD characteristics can be obtained from the PD activity at DAC voltage: (a) maximum PD amplitude; (b) phase-related PD pattern; (c) PD changes as a function of the decaying voltage; and (d) PD extinction voltage (PDEV) [87]

Summary

Introduction

Partial discharge activity has been normally recognized as a symptom of degradation and overstress in high-voltage electrical insulation system. In the case that the results are not similar, the information of frequencydependence of PD behavior can be obtained In this case, the benefit of this method is that the local conditions at defects within or on the insulation, such as electric field distribution, surface charge accumulation and decay process, change with the varying frequency, leading to the changing of PD behavior. The developed method for reducing the capacitive charging power is to detect the presence of PD activity with very low frequency (VLF) method, like stressing the test object at 0.1 Hz, or by using damped AC method in the range of 20–1000 Hz [5,6], which has been increasingly popular for the PD detection of high-voltage power cables [2]. It has been well accepted for the insulation system of shielded power cables and AC electric machineries [17,18]

PD Measurement

Capacitive Equivalent Circuit Model

Niemeyer’s Model

Frequency-Dependence of PD Characteristics

VLF Cosine Rectangular Voltage

PD Measurements

PD Characteristics at DAC Voltage

Comparisons of VLF and DAC Methods

The applications of DAC

Conclusions