火花间隙对保护换流变压器中性点接地电容的研究

Study on Protection of Neutral Point Earthing Capacitance of Converter Transformer by Spark Gap

高压系统中直流偏磁对换流变压器和交直流输电产生巨大的危害,限流和隔直是抑制直流偏磁的主要方法,目前广泛采用的是通过中性点串联电容的方法,对电容的保护研究很少。本文利用PSCAD/EMTDC建立500 k V的高压直流输电电磁暂态仿真平台,在发生工频过电压时,对换流变压器中性点处串联电容的过电压,以及其2端保护装置火花间隙进行了仿真和分析,选择了最佳容抗值的电容器,并探究了火花间隙对中性点串联电容器的保护,结果表明:火花间隙对换流变压器中性点接地电容以及变压器中性点起到保护作用。

In high voltage system, a great harm is caused to the converter transformer and AC and DC power transmission by the DC biasing. The main method to suppress the biasing is current limiting and blocking.At present, the widely used method is series capacitance through the neutral point, but there is little research on the protection of the capacitor. In this paper, the electromagnetic transient simulation platform for 500 k V HVDC is set up by PSCAD/EMTDC, and in case of power frequency overvoltage, the overvoltage of the series capacitor at the neutral point of converter transformer, and also the spark gap of the protection device on both sides are simulated and analyzed, the capacitor with the most ideal capacitive reactance is selected, and the protection of spark gap to the neutral point series capacitor is also discussed. It is shown by the result that the spark gap has the protection function to the neutral point earthing capacitor of converter and the neutral point of transformer.