Partial discharge characteristics over different levels of humidity and plasma exposures in a PMMA bounded void

Abstract

The issue of high voltage equipment tropicalization is critical particularly when high voltage equipment designed for temperate application are imported to areas in the tropics. It raises the question whether the insulation used in these equipments can performance under the impact of high relative humidity level and the intense midst noon sun rays. This paper presents the study of dielectric material performance under the impact of relative humidity and plasma exposures to simulate the material aging in service by studying the discharge characteristics of PMMA which was used as the basis of study. The discharge characteristics in cylindrical void bounded by dielectric of polymethylmethacrylate (PMMA) which were exposed to different levels of relative humidity (RH) and plasmas intensity were investigated. The insulation material under test was subjected to AC excitation. The partial discharge (PD) signatures produced were measured with the aid of a CIGRE Method II (CM II) electrode system. It was found that when the void cavity was humidified from 33% up to 98%(extreme level), the PD inception voltage decreased about 15%. For negative AC cycles, the following discharges occur with larger number of pulses, however, with small number of magnitudes. PD seems easily to occur with larger number of pulses as the surface of specimen was degraded by plasma (especially under humid environment).So it is recommended that high voltage equipments imported from temperate countries must performance in the tropics adverse environmental conditions.