并联电容器组中性线电流不平衡保护的分析研究

Study on Neutral-line Unbalance Current Protection in Shunt Capacitor Bank

采用双星形中性点不接地的并联电容器组,利用中性线不平衡电流信号容易实现微机保护。针对电容器组的电容元件击穿情况,根据电容器容量发生变化量,计算分析了中性线不平衡电流的变化规律。建立了电容元件击穿后仿真模型,并计算验证了理论分析。探讨了中性线电流不平衡保护的保护范围和整定值选取,为电容器组有效保护、快速动作提供保证。

Shunt capacitor bank at a 10 kV bus is the general compensation equipment using in the transmission and distribution of AC power grid. The shunt capacitor bank is widely used in a power substation with frarned structure. The unbalance current of the neutral-line can be applied to protect the shunt capacitor with the double-star connection. According to the capacitor-unit breakdown condition, it was deduced the changing rule of the neutral-line unbalance current using the varied-capacitance of the capacitor bank. It was certified the correction of the academic analysis using the numerical model of one serial capacitor-unit breakdown. To provide the effective and quick protection of the shunt capacitor bank, the protection range and setting value of the neutral-line unbalance current were given.