低电阻接地方式的研究及应用

随着国家建设城市化的趋势,大部分大中型城市受城区场地、美化和环保等因素的要求,10kV架空线路不断下地,电缆线路的比重逐年上升。新建10kV城市配电网大量采用以电力电缆为主、架空线路为辅的电网结构,使对地电容电流大大增加。经消弧线圈接地具有以下问题:第一,经济性差:随着电容电流的不断加大,需要更多的消弧线圈以提供更多的补偿容量;第二,技术不可靠:消弧线圈太多导致对分接头的及时调整有困难,而且若电容电流计算值或测量值不准确,接地时易出现谐振过电压。所以10kV配电网改用中性点经低电阻接地的方式运行。文章通过对消弧线圈接地方式和低电阻接地方式对比研究,结合北京市朝阳区多个110kV变电站低电阻接地改造工程,提出城市配电网低电阻接地运行方式的正确性,并对低电阻的阻值和接地变压器容量的计算进行说明。

With the trend of urbanization of national construction, the proportion of cable lines in most large and medium-sizedcities is increasing year by year because of the demand of urban site, beautification and environmental protection and so on. A largenumber of new 10kV urban distribution networks use the power cable as the main structure supplemented by overhead lines, whichgreatly increases the earth capacitive current. The grounding of arc-suppression coil has the following problems： first, poor economy：with the increase of capacitance current, more arc-suppression coil is needed to provide more compensation capacity; Second, thetechnology is unreliable： too many arc-suppression coils lead to difficulties in adjusting the tap in time, and if the capacitance current calculation value or measurement value is not accurate, the resonance overvoltage is easy to occur when grounding. So 10kVdistribution network is operated by neutral point grounding with low resistance. Based on the comparative study of arc suppressioncoil grounding mode and low resistance grounding mode, combined with the low resistance grounding reconstruction project of 110kVsubstations in Chaoyang District, Beijing. The correctness of low resistance earthing operation mode in urban distribution network isput forward, and the calculation of low resistance resistance and earthing transformer capacity is explained.