Research On The Partial Discharge Effecting Factors In Transformer Inter-turn Insulation

A particular form of partial discharge(PD), which happens on the inter-turn windings of transformer, is not fully studied by people. The incentives of PD on the inter-turn windings of transformer have not been identified; Therefore it is necessary to study incentives of this kind of PD, how to affect the inter-turn insulation system, lead to transformer accident in normal condition.A transformer inter-turn winding discharge model was constructed in this paper, sulfur corrosion, metal particles and insulation paper moisture, insulation paper rupture due to overvoltage were considered, a complete set of transformer inter-turn discharge model was established. And the PD has been measured under these four different conditions, and compared with the normal conditions of the real transformer, and find out how to affect inter-turn insulation and cause transformer accidents.The research has been shown that the electrical model PD is26kV under normal conditions, but has decreased sharply under sulfur corrosion with the ageing time, the minimum PD is only5kV, which is less than1/5that of the normal conditions. The metal particles has great effect on the PD of the inter-turn winding, the PD reaches7kV. When the insulation paper moisture content reaches5.7%, the PD is about5kV; the PD caused by insulation paper rupture due to winding deformation is about8kV. The inter-turn voltage is no more than4kV under normal conditions in a220kV transformer. It points out that it is possible to cause inter-turn winding insulation breakdown under normal condition in low voltage by corrosive sulfur, metal particles, insulation paper moisture and insulation paper rupture, which are main reasons to lead to transformer accidents.