ANALYSIS OF DIELECTRIC PROPERTIES OF DISTRIBUTION TRANSFORMER OIL INSULATION: A CASE STUDY OF JERICHO (NIGERIA) DISTRIBUTION NETWORK

摘要

The insulating liquids used in liquid-immersed transformers not only provide insulation, but serve to transfer heat from the windingsto the surrounding. The liquid must be kept free of contaminants and moisture, just as the air insulation of dry-type transformers.This paper therefore focused on the analysis of the dielectric properties of distribution transformer oil insulation using a case studyof installed distribution transformers at Jericho distribution network, Ibadan, Nigeria. Thirty samples were taken from differentinstalled distribution transformers at Jericho distribution network. A conventional dielectric test system (Baur DTA 100 E oil tester)was used to measure the breakdown voltage of these oil samples. A transformer insulating oil passes dielectric test if the measuredbreakdown voltage is not less than 25kV for 11/0.415kV distribution system or 45kV for 33/0.415kV distribution system inaccordance with the guideline from the American Society of testing Materials (ASTM). It was observed that fifteen test samples oftransformer insulating oil passed dielectric test while with remaining fifteen samples did not meet up the required standard. Thisimplies that those samples that failed the test would not be able to provide the insulation to the transformer winding which can leadto excessive heat, and consequently might caused explosion or fire outbreak in the transformer.