Electrostatic Hazard in High Power Transformers : Analyze of ten years of the Capacitive Sensor

摘要

In high power transformer, oil flowing on pressboard surface is suspected to be responsible of electrostatic hazards and failures. Different methods of risk assessment have been proposed to understand and prevent it: ministatic tester in the Westinghouse protocol, ministatic tester in the spinning disk measurement, monitoring of tangent delta and dissolved gases measurement… At P' institute of Poitiers an original sensor was developed used for quantification of the electric charge generated and of accumulated charge for an oil flow onto the surface of a transformer pressboard insulated from ground. Operational for 10 years, this bench has been used to study over a hundred couples of oil/pressboard, pairs of new oil and pressboard, pairs of aged oil and pressboard, pairs of suspicious oil and pressboards... The paper presents a comparative analysis of these 10 years of experience. This analysis provides, among other results, a critical electrostatic hazards assessment in transformers and an attempt of discrimination tentative of a suspected transformer.