Research On Causes And Solutions Of The Frequent Fusing Problem Of PT Fuse In Distribution Network

In recent years, PT high voltage fuse burning-off accident has occurred many times in the 10 k V system of Yunnan power grid, which seriously affected the safe and reliable operation of 10 k V system. 2012 years, in the 10 k V side of STL110 k V substation in Kunming, there were 45 times accidents of PT high voltage fuse burning-off. In other power supply bureau of Yunnan power grid, similar accidents has also occurred and the reasons need to be identified. In view of the problems and phenomenon of PT high voltage fuse frequent burning-off in Yunnan power grid, researching on the cause and solution to reduce the phenomenon of PT high voltage fuse burning off frequently is conducive to improve the reliability and economy of 10 kV power grid.This paper analyzed PT high voltage fuse burning-off accidents in the whole country, and found this problem is common in the distribution network in China. At the beginning of the substation’s establishment, the reasons for PT high voltage fuse burning-off may likely be Ferromagnetic resonance or capacitive current during single phase grounding recovering. However, with the development of power distribution network, the accidents caused by Ferro resonance will be less and less, and the accidents caused by single phase grounding recovery will be more and more. With the development of power electronic devices in the user side, the accidents caused by harmonic pollution problem may be gradually increasing.Through the statistics of the PT high voltage fuses burning-off events in STL substation, with the power quality waveform data provided by the substation, we can conclude that: there were 94.12% of PT high voltage fuse burning-off accidents happened on the first section bus of STL substation caused by single phase grounding recovery, and there were 50% of PT high voltage fuse burning-off accidents happened on the second section bus of STL substation caused by single phase grounding recovery, about 40% happened on the second section bus caused by harmonic pollution.According to the component parameters of the distribution network in Yunnan STL substation, through theoretical analysis and Simulation analysis by using PSCAD software, this paper verified: The effectiveness of zero sequence PT method for suppressing the low frequency oscillation current generated by the single phase grounding recovery on the first and second section bus, and the effectiveness of passive filter method for restraining the three harmonic pollution on the second section bus.This paper integrated the statistical analysis, the mechanism of the fuse and the simulation study, derived the following solutions in order to solve the problem of frequent burning-off of PT high voltage fuse in the 10 k V system of STL substation. For the problem on the first section bus, the problem can be solved by zero sequence PT at present, and in the long run the neutral point should be drawn and the neutral point should be grounded by the arc suppression coil. For the problem on the second section bus, temporarily a passive filter should be installed to filter the zero sequence harmonics in the system, and the same time the neutral point should be drawn and the neutral point should be grounded by the arc suppression coil, and then to find harmonic sources and treatment as soon as possible and standardize the customer’s high voltage equipment access network for realizing the long-term control of distribution network harmonic.