新型混合式3～66kV自备电网中性点接地方式

New hybrid neutral point treatment for 3～66 kV auxiliary power network

介绍了新型混合式 3～ 6 6kV自备电网中性点接地方式。这种中性点接地方式加上了接地短路切除动作的选择保护 ,以及两组不同保护水平的交流无间隙金属氧化物避雷器。在电网正常运行时 ,中性点电阻器接地 ,限压水平约 2倍相电压 ;当线路电流保护拒动或母线短路时 ,电网变成中性点不接地或消弧线圈接地方式运行 ,限压水平为 2 9～ 3 0倍相电压。新型混合式 3～ 6 6kV自备电网中性点接地方式综合了自备电网中性点不接地(或消弧线圈接地 )和电阻器接地两种方式的优点 ,是国际上较优的电网中性点接地方式 ,也可应用于 6～ 10kV配电网中。

This paper describes a new hybrid neutral point treatment for 3～66 kV auxiliary power network, which integrates the selective protection for switching off earth short circuit and two sets of AC metal-oxide surge arresters without gaps at different protection level. The neutral resistor is earthed during normal operation of the network, with the voltage limiting level about twice as much as the phase voltage. In case of bus short circuit fault and the current protection's failure to operate, the isolated neutral mode or the arc-suppression-coil-earthed mode comes into effect, with the voltage limiting level 2.9～3 times as much as the phase voltage. The proposed neutral point treatment, combining the advantages of both the isolated (or the arc-suppression-coil-earthed) neutral system and the resistance-grounded system, is an internationally commendable neutral point treatment and applies also to 6～10 kV distribution grid.