Measurement of Spark Discharge Inception Voltage Using CIGRE Method-II Type Metal-Air Gap-Metal Electrode System

A minute air gap may become a weak electrical point in an insulation system. A successive partial discharge (PD) in the minute air gap occurs under a low-voltage application. The spark discharge inception voltage under AC voltage (AC-SDIV) was measured by using the CIGRE-Method-II (CM-II) type metal-gap-metal (MGM) electrode system to understand the essential discharge characteristics under low atmospheric pressure. The AC-SDIV in the region of the product of air pressure and void distance (pd product) of 0.3 Pa· m and more almost agrees with the Paschen voltage. The AC-SDIV in the region of the pd product of less than 0.3 Pa· m decreases as the pd product decreases. The tunneling emission of the electron from the electrode due to the high Paschen field may occur.

I. Introduction

Further miniaturization and higher output power of electric power equipment have been desired [1]. There is concern about the generation of partial discharge (PD), which cause insulation degradation and dielectric breakdown due to the high electric field in the miniature air gap of the insulating system [2]. Discharge phenomena are affected by environmental factors, and it is important to understand discharge characteristics in various environments [3]. This study aims to investigate the spark discharge (SD) characteristics under wide range pd product ( gap distance). The SD inception voltage under the ac ramp voltage application (AC-SDIV) in the region of about 0.1 ~12.5 hPam is measured using CIGRE Method-II (CM- II) type metal- air gap - metal (MGM) electrode system[4].