配电网中性点经小电阻接地方式下的小电阻选取

Grounding Resistance under the Neutral-Point Grounding with the Low Resistor in Distribution Network

在以电缆供电为主的城市配电网中普遍采用中性点经小电阻接地方式,以解决接地电流过大的问题。其中小电阻阻值合理选择的关键在于准确计算接地电容电流。采用精确建模方法计及了线路的实际路径和T接开闭所的影响,在考虑接地过渡电阻的条件下,对10 kV配电网单相接地短路进行仿真,结果表明,根据中性点的耐压水平和保护灵敏度,该变电站的中性点接地方式适宜采用阻值为10Ω的接地电阻。

In the urban distribution network dominated by cable power supply,the method of the neutral point grounding through small resistance is widely adopted to solve the problem of excessive grounding current. The key to the rational selection of the small resistance value lies in accurately calculating the grounding capacitor current. The exact modeling method is used to take into account the actual path of the line and the influence of the T-connection opening and closing. With consideration of the grounding transition resistance and based on the resistance of the neutral point,the single-phase grounding short circuit of a 10kV distribution network is simulated. The simulation result shows that according to the withstand voltage level and the protection sensitivity of the neutral point,it is suitable for the neutral point of the substation to adopt 10 Ω of resistance.