Degradation diagnosis of electrical insulation performance of 6.6 kV class epoxy resin insulator contaminated with iron powder and moisture

摘要

This study deals with partial discharge (PD) characteristics of epoxy (EP) insulator contaminated with iron powder and moisture placed in a bus duct. PD occurring inside the bus duct would produce a transient earth voltage (TEV) as a product of surface current flowing on the outer wall and impedance of the material. In addition, it deals with development examination of an insulation diagnosis technology using TEV sensors attached on the outside wall of the bus duct. PD characteristics of EP insulator are investigated under high voltage AC (HVAC) and different contamination conditions with iron powder and moisture. Experimental results revealed that PD occurs only when EP insulator is contaminated by both iron powder and moisture at the same time. Also, it was found that PDIV decreases when the relative humidity in the surrounding increases. Furthermore, it was found that signal intensity detected with TEV sensor placed at a given position on the bus duct model increases when insulation resistance of contaminated EP insulator decreases. It was confirmed that one of degradation diagnosis method is effective by examining the signal intensity TEV sensor up to dielectric breakdown.