Research On Fault Location Technology Of Distribution System With The Neutral Point Grounded Via The Arc Suppression Coil

With the rapid development of China’s social economy and technology,people’s demand for a better life is growing,and the requirements for power quality are getting higher and higher.It is crucial to improve the reliability of power supply for users.The distribution network undertakes the important task of distributing electric energy to users.The efficient and accurate troubleshooting of distribution system faults is one of the keys to improving the reliability of users’ power supply.China’s distribution network grid is mostly radiation type.The research on distribution network faults in our country and abroad mainly focuses on fault line selection and fault section location.There are few researches on fault location and it has not been put into practical use.Impedance method and traveling wave method are widely used in transmission network fault location,and the difficulties of distribution network fault location are:1.The network of lines is complicated,there are many terminal equipments,and the equipment investment of GPS is relatively large;2.The distribution network line is short,so it is difficult to improve the accuracy of location;3.There are many types of lines,the parameters are not accurate and the impedance method has certain difficulty.At present,China’s 10-35kV neutral point medium-voltage distribution network are grounded through arc suppression coil,they mostly use the solution of arc-suppression coil parallel with small resistance.after the permanent single-phase ground fault occurs,put the small parallel resistance being connected and this motion makes the fault current increase,and the protection device can operate reliably to disconnect the faulty line.Therefore,the research on the fault location technology of single-phase ground fault on the basis of it has great development prospects and necessity.To this end,this paper is based on the current situation of the neutral point arc suppression coil parallel with small resistance operation of the distribution network to carry out accurate positioning of fault points,precise positioning of complex lines and research and development of engineering positioning devices:1.The method of fault location using the disturbance signal generated by the parallel small resistor is studied.When the neutral point is connected by the arc suppression coil in parallel with the small resistance grounding mode,when the single-phase ground fault occurs in the distribution network,the parallel small resistance is input,and the current traveling wave will be generated and reflected after reaching the fault point.The amplitude of the reflected current traveling wave is larger.The characteristics are obvious.The transmission characteristics of the current traveling wave on the line after inputting the parallel small resistance and the single-ended fault location strategy using the traveling mode zero-mode component and the areal-mode component for fault location are analyzed.2.According to the characteristics of the distribution network,the solution of faults occurring in complex lines is studied,and the comprehensive ranging technology using multiple detection device information is studied.Complex lines consist of two cases:(1)overhead line-cable hybrid lines,and(2)solutions with single-phase supply lines at the end of the circuit.For the situation(1),the adaptability of the ranging strategy when the fault occurs in the multi-segment overhead line-cable hybrid line is analyzed.According to the situation(2),the transmission mechanism of the traveling wave when the fault occurs in the three-phase line and the single-phase line is analyzed separately,and the ranging strategy is adjusted.Finally,the least squares method is used to fuse the short and short information in the distribution network,and the bad data is eliminated while improving the ranging accuracy.The simulation using ATP/EMTP software proves the accuracy and practicability of the proposed fault location method.3.Based on the actual project,considering the configuration of the existing equipment in the distribution network,a single-phase ground fault accurate positioning device for hybrid distribution network based on parallel small resistance injection disturbance signal was developed,which is carried out for the needs of the device in practical application.The development of hardware and software ensures the rapid positioning of the fault zone of the single-phase ground fault of the distribution network and the precise location of the fault point,assists in the transformation and construction of the power grid,and serves the economic and social development.