Chuqimen Substation Of Chongqing 10kV Power Network Neutral Grounding Modes Study

The problem about neutral-point-grounding mode is an all-around technical problem which associated with not only power system reliability, insulation coordination, electromagnetic interference,but assault safety。In China, the neutral grounding modes of the 10kV net involved of none grounding, grounding by arc suppressing coils, resistance grounding or reactance grounding in the past。With the development of civic power network, low resistance grounding mode was used to restrain the over voltage, particularly in Guangzhou ,Shanghai,Beijing ,and Zhuhai etc. It was reported that the over-voltage level of low resistance grounding mode is lower than that of arc suppressing coil mode, but the operation carried out the other way。At substations in Guangzhou and Shanghai it was found that the low resistance grounding mode is successful。But in some areas ,such as Zhuhai , substations grounding with low resistance revealed some problems,including power supply reliability rapidly dropping,transmitting line often tripping；and person safety being threatened。So interiorly the grounding mode selection of the 10kV network was disputed, which mainly focused on the fault form of 10kV net grounding, the apply area of suppressing arcing coil grounding mode, power supply reliability level of the two modes, person safety, communication interfere and the workload of maintenance.This paper studied on how to select the neutral grounding mode of 10kV net. Firstly it analyzed the grounding modes of 10kV net. Then with the demonstration of Chuqimen substation of Chongqing ,this paper built a numerical value equivalent model. Taking account of the transformation of the capacitor current or the variety of the grounding point resistance, it calculated the over-voltage level and the grounding-point short current value of the net with arc suppressing coil grounding mode or low resistance grounding mode. Therefore, the conclusion is valuable to engineering apply, and could be consulted for the selection of the neutral point grounding mode of the civic 10kV network. As to Chuqimen substation of Chongqing, it is suggested to remain arc suppressing coil mode in recent years.