Research On The Suppression Measures Dealing With Abnormal Fusing Of High Voltage Fuse For Potential Transformer In 35kV Distribution Networks

35kV power grid plays the role of backbone in distribution network of Daqing Oilfield so that its safety and reliability have vital importance. In recent years,35kV PT high-voltage fuses fuse frequently and abnormally, which seriously affects the safe and reliable operation of the system. It is noticed that this kind of problem is universal in distribution network of oilfield. Hence, it is of great importance to study the problem and put forward corresponding suppression measures to improve the reliability of 35kV distribution network.According to the problem that PT high-voltage fuses are frequently fused in the 35kV distribution network of Daqing Oilfield, this paper makes a statistical analysis on the fault data from different aspects for the sake of searching for the regularity of the problem. It is how the ferroresonance and transient current generated from the discharge of line-to-ground capacitance as the instantaneous ground fault disappears affect PT high-voltage fuses that are preliminarily analyzed from the aspect of system. The fusing characteristics of PT high-voltage fuses are influenced by materials of fuse elements, processing technology, time-current characteristics and so on. The fusing current of PT high voltage fuses has a±20% dispersity. When in operation, the melts may be affected by corona discharge because of their thinness.Based on EMTP/ATP, the typical Dengfeng substation of Daqing Oilfield is chosen to make a model. All kinds of transient current traveled across the PT high-voltage fuses are analyzed under the conditions of both neutral earthing via arc extinguishing coil and neutral earthing via arc extinguishing coil paralleled with resistance. The simulation results show that instantaneous grounding fault and transient currents generated by system operations will cause certain shock to the PT high-voltage fuses although the fuse will not fuse directly under those conditions. Compared with neutral earthing via arc extinguishing coil, neutral earthing via arc extinguishing coil paralleled with resistance can significantly decrease the shock that generated by system transient currents to PT high-voltage fuses.The test platform of corona discharge acted on melts in PT high-voltage fuses has been set up to analyze the impacts of corona discharge on melts with the help of a partial discharge detector and an ultraviolet imager. The test results reveal that the fuse melt has no significant corona discharge on the normal operating voltage.Finally, based on the statistical analysis of faults, simulation calculations and experimental results, suppression measures fit for the 35 kV distribution network of Daqing Oilfield are proposed. On one hand, the main measure is to increase the rated current of PT high-voltage fuses from 0.5A to 2A. On the other hand, choose neutral earthing via arc extinguishing coil paralleled with resistance instead of earthing via arc extinguishing coil as the auxiliary measure. By analyzing the effects of the two measures on system protection and PT protection, it's feasible to adapt the two measures in engineering application.The Power Supply Company of Daqing Oilfield selects thirteen 35kV substations as pilots considering the suppression measures mentioned above that increase the rated current of PT high-voltage fuses from 0.5A to 2A. Throughout nearly one year's field operation experiences, there're no reports on the fusing of PT high-voltage fuses, which shows that the proposed measures are highly effective and provide power industry with a new technical scheme to solve this kind of problem.