The Role of Space Charge on Corona Inception Threshold Conditions in Rod-Plane Air Gaps at DC/AC Combined Voltages

Xuyuan He,Zichen He,Yunbo Zhou,Luxing Zhao,Xingming Bian,Boyang Shen,Jie Zhu

doi:10.1109/access.2021.3111025

Abstract

This work investigates the corona inception voltage and the motion of space charge near a rod-plane electrode under combined DC-AC voltages. For a high AC component, the corona inception voltage of the equivalent negative corona exceeds that of the equivalent positive corona. For a small AC component, the corona inception voltage of the equivalent positive corona exceeds that of the equivalent negative corona. The corona inception voltage decreases with increasing AC component. The charge-motion model based on hydrodynamics is used to analyze the charge motion for different AC/DC voltage ratios. The charge remaining for equivalent negative coronas exceeds that for equivalent positive coronas with high AC components. In addition, the charge remaining for equivalent positive coronas exceeds that of equivalent negative coronas with small AC components. As the AC component decreases, the remaining space charge increases. The results show that space charge tends to “block” corona inception. The more space charge remains, the higher the corona inception voltage is. Therefore, the variation in space charge and the corona inception threshold conditions under combined DC-AC voltage differ from those under only DC or AC voltage.

Highlights

Nowadays, with the expansion of the transmission grid in China, the lack of space for new power transmission lines is becoming a serious problem
When the electric field on the electrode is above the corona inception, corona discharge will occur
Qi and Zhou studied the partial discharge (PD) and found the inception voltage of PD increases as the DC component increasing because of the reverse electric field generated by charge [32], [43]

Summary

INTRODUCTION

With the expansion of the transmission grid in China, the lack of space for new power transmission lines is becoming a serious problem. Previous studies show that in the transmission line model, the AC voltage has negligible effect on the charge generated by the DC conductor [2] It is questionable whether this conclusion applies to short-gap model such as rod-plane model. Qi and Zhou studied the partial discharge (PD) and found the inception voltage of PD increases as the DC component increasing because of the reverse electric field generated by charge [32], [43]. EXPERIMENTAL SETUP An experiment on the corona inception voltage of rod-plane electrode at combined DC-AC voltage was carried out. He et al.: Role of Space Charge on Corona Inception Threshold Conditions in Rod-Plane Air Gaps TABLE 1.

EXPERIMENTAL RESULTS

CORONA INCEPTION CRITERION

Findings

CONCLUSION