抑制高压直流换流站附近变压器中性线直流电流措施的研究

Method for Blocking Direct Current in Substation Transformer Neutrals

为了减小由于直流电流经换流变压器中性线的侵入而对交流系统产生的不利影响,笔者提出了一种抑制高压直流输电系统换流站附近交流变电站内变压器中性线直流电流的措施。对换流站附近变电站站内变压器发生直流偏磁现象的原因、机理及其危害进行了分析研究。在分析了同内外学者研究现状的基础上,提出了一种在换流变压器中性线串接小电容器并设置其旁路电路的新措施来抑制直流电流侵入的措施,并从对系统继电保护方面的影响进行了分析。仿真试验分析结果证明了该装置的有效性,表明了这是一种可靠有效地抑制变压器中性线直流电流的方法。

The substation AC transformer near a high voltage DC converter station is often intruded by DC in its neutrals. This paper proposes a method to block this DC in order to reduce its negative effect. In this paper, the reasons why DC magnetic bias exists in AC power transformer are analyzed, and the DC magnetic bias principle and its hazard to transformer are also discussed. Furthermore, a new DC blocking method is developed, in which a main capacitor with a bypass circuit is connected in series with transformer neutral to block the fault current. The influence of the method on blocking DC in neutral and relay protection are analyzed. The simulation test verifies its validity for neutral grounded transformer.