PD Pulse Discrimination of Different Conducting Particles in Transformer Oil Under Uniform Field

Abstract

Integrity of insulation is the key measure to ensure the healthy condition of the transformer. In transformers, transformer oil play very vital role, both as insulation and as a coolant. Particles such as cellulose fibre from paper or pressboard, copper from winding leads or connecting bus bars and iron from mechanical assembling parts of core or body of transformer are commonly present in oil as during the transformer manufacturing processes, or due to electromagnetic vibration, mechanical wear, and tear. Even if the transformer presence a conducting particle can degrade the insulation performance greatly. The conducting particle present in transformer oil may result in very high localised electric field stress in the insulation system and it may lead to Partial Discharge (PD) or breakdown in the insulation. PD Characteristics of irregular shaped copper and iron particles in transformer oil with uniform field were studied. Phase Resolved PD (PRPD) pattern, PD characteristics such as magnitude, number, discharge power, rise and duration time were analysed. The experimental results were compared to discriminate the PD characteristics caused by copper and iron particles in transformer oil. The observed PRPD pattern were comparatively similar regardless of applied electric fields and particle type. The experiential PD characteristics is observed to be predominant for iron particles due to its lesser density and superior charge carrier density when compared to copper particles.