抑制主变压器中性点入地直流电流的几种措施

Several Measures for Suppressing Direct Current in Neutral Point of Main Transformer

针对高压直流输电系统以大地回流方式运行时,有较大直流电流流过交流电网中部分中性点接地的变压器,对变压器正常运行造成影响,甚至损坏变压器的问题,分析了变压器中性点直流电流产生的原因,总结了抑制变压器中性点直流电流的几种措施,并对目前较为成熟的两种抑制直流措施(在主变压器中性点装电容隔直装置或反向直流注入装置)的工作原理及设备情况进行了介绍,比较了二者的优缺点,运行实践证明,两种抑制直流措施均能正确投入及有效抑制直流电流,使流经主变压器中性点的直流电流降至允许范围内,可确保主变压器的安全运行。

While high voltage direct current transmission（HVDC）system is operating in the mode of ground return,there is a larger direct current flowing through some neutral grounded transformers in AC power grid,which impacts the normal operation of transformers or even damages them.Therefore,the paper analyzes the causation of the direct current in transformer neutral point,summarizes several measures to suppress it,describes the working principle and equipment situation of two comparatively ripe DC suppressing methods （i. e. installing capacitive DC blocking device or reverse DC injection device at the neutral point of main transformer）, and compares the advantages and disadvantages of the two methods. It is verified in operation that both the two DC suppressing methods can work correctly and efficiently, confine the direct current flowing through main transformer neutral point to allowable limits, and ensure the safe operation of main transformer.