变压器中性点串接电容抑制偏磁措施及其引起的过电压分析

Applying Series Capacitor to Restrain Power Transformer DC Biasing and the Caused Over-Voltage

串接电容已成为治理直流偏磁的一种有效的方法,文章对工作原理及其引起系统过电压情况进行了理论和仿真分析。首先对其抑制直流偏磁原理作了简单的分析;然后以云南电网典型变电站为例建立相应的模型对直流电流分布进行仿真分析,并与实际测量数据对比,验证了模型准确有效;接着通过在中性点串接不同电容来仿真偏磁直流在相关变电站的分布规律,为串接电容的选型提供了理论依据;最后着重对中性点串接电容后的系统过电压,特别是中性点过电压情况作了仿真计算,计算结果表明,串接电容法在一定程度上会影响主变中性点的过电压。因此,选择适当电容,需要综合考虑中性点过电压情况和偏磁直流的抑制效果。

Series capacitor has become an effective way of DC Bias governance. The theoretical and simulating analyses of the principles and the system caused over-voltage are made in this paper. Firstly, a simple analysis of the principle of DC Biasing is made; then an appropriate model is established with a typical substation in Yunnan Power Grid. The simulation analyses and actual measurement data comparisons verify the accuracy and effectivity of the proposed model. Then simulations of DC distribution in related substation are performed, followed by series different capacitor in the neutral point. It will provide a theoretical basis for the capacitor in series with the selection. Finally, the overvoltage, especially the neutral overvoltage is simulated and calculated in detail, the results of which show that the series capacitor method may affect the transformer neutral point over-voltage to a certain extent. Therefore, an appropriate capacitor selection need a serious consideration on the inhibitory effect of the neutral point of over-voltage and bias DC.