Insulation assessment of high voltage oil impregnated paper bushing and resin impregnated paper bushing

Abstract

Transformer diagnostic testing is perform to reveal the condition of the transformer. Early detection of problems can minimize the repairs involved and mitigate catastrophic failures. CIGRE findings show that bushings are common reason for power transformer failures. There are few research development conducted over the years to improvise construction of condenser bushings. One of the first technologies was the Resin Bonded Paper (RBP), but not manufactured anymore due to many technical & environmental reason. Secondly and the most widely used is Oil Impregnated Paper (OIP) technology apparently because of its low primary cost. In the circumstances? whenever there is problem with the insulation or internal degradation, it can accumulate high internal pressure inside bushing which can cause explosion of OIP bushing. That why migration from Oil Type to Dry Type Bushing Technology chosen to reduce risk of explosion /caught in fire during bushing failures .The new safer alternative considered is the Resin Impregnated Paper (RIP) technology which offer better technical performance over OIP bushings. This study presents comparison on insulation assessment of both types of bushing through power factor measurement and dielectric frequency response (DFR) analysis that contributing to assessment of failure characteristics of OIP and RIP bushings. Field testing was implemented to capture data for comparison purpose focusing on selection power transformer in grid division installation. The measurement of bushing insulator capacitances and measurement of the dissipation factor is to determine bushing health condition while DFR measurements as a supporting diagnostic tool for bushing condition assessment on paper inside the bushing. Commonly, both OIP & RIP constructions are that they are subject to very high mechanical, electrical and thermal stresses during operation. With result of this study, it may become possible to identify failure characteristic of insulating material between Oil Impregnated Paper Bushings (OIP) and Resin Impregnated Paper Bushings (RIP) and explain that moisture content in oil and paper has significantly contributed to the degradation of bushing. This methodology can be utilize for effective way to monitor moisture content at site and as a tool to decide condition of insulation bushing.