配电网单相接地期间电压互感器直流偏磁机理及抑制措施分析

为解决单相接地期间中性点不接地配电网电压互感器直流偏磁，导致励磁电流畸变过电流，谐波、振动、损耗和发热增加等，造成电压互感器故障、一次侧熔断器频繁熔断和危害配电系统的问题。通过瞬时对称分量法求解了故障期间电压互感器励磁电流表达式，分析了电压互感器直流偏磁的产生机理，提出了一种考虑灭弧的直流偏磁抑制措施，基于PSCAD/EMTDC仿真软件搭建了中性点不接地配电网，针对单相接地引起电压互感器直流偏磁的影响因素及抑制措施的有效性进行仿真。结果表明，铁心饱和、故障相角是影响电压互感器直流偏磁的重要因素，所提措施能够有效抑制直流偏磁过电流的发生。

Simulation of DC Bias Mechanism and Suppression Measures of Potential Transformer Caused by Single-phase Grounding

In order to solve the problems of DC bias of potential transformers in distribution networks without grounding at neutral points during single-phase grounding, resulting in distortion of excitation current overcurrent, increased harmonics, vibrations, losses and heat generation, etc., resulting in potential transformer failures, frequent fuses of primary-side fuses and hazards to the distribution system. The excitation current expression of the potential transformer during the fault period is solved by the instantaneous symmetrical component method, the generation mechanism of the DC bias of the potential transformer is analyzed, and a DC bias suppression measure considering arc extinguishing is proposed. Based on PSCAD/EMTDC simulation software, the neutral point ungrounded distribution network is built, and the influence factors of the DC bias of the potential transformer caused by the single-phase grounding and the effectiveness of the suppression measures are simulated. The results show that core saturation and fault phase angle are important factors affecting the DC bias of the potential transformer, and the proposed measures can effectively suppress the occurrence of DC bias overcurrent.