Research On Prevent Technologies Of Sudden Damage To Large Power Transformers

For the sudden damage of the grid hub-transformer, this research accounts for the main reasons of the transformer accidents in this year, and points out the winding turn-to-turn insulation is the crucial reason. Based on the analysis of the process from turn-to-turn insulation defects to the transformation burning accidents, and combining the existing research about the transformer turn-to-turn insulation problems, this research indicates that the situation of increasing partial discharge signals appears in the early period of the transformer damage, followed by the abnormal changes of the current. The judgment criterion of the transformer winding turn-to-turn fault is to monitor the partial discharge signals as priority, and the fault current as complement.The partial discharge signal detection techniques adopted in this research includes UHF, AE and HFCT. To combine the three methods, it could sensitively find out the discharge signals and ensure the discharge signals effectively, accurately and without operational mistakes. Meanwhile, to calculate transformer impedance on the basis of detecting partial discharge signals, it could bring about the varying pattern of the transformer current when turn-to-turn short circuit happens, which becomes a theoretical basis to judge and prevent turn-to-turn fault of the transformer. Finally, this method is applied to a66KV oil-immersed transformer. By adding taps and presetting electrode, the live line transformer after adjusting the electrode can simulate the real operation of turn-to-turn discharge condition. Using the UHF-AE-HFCT detection method and the analysis of winding turn-to-turn fault current, the discharge signals and the fault current signals could be detected at the same time when the turn-to-turn discharge fault happens. Served as the judgment criterion of the transformer winding turn-to-turn insulation fault, it could prevent the accidents of the sudden damage of transformers effectively.