交直流混线电压互感器烧损剖析

Analysis of potential transformer burnout caused by AC and DC lines interconnection

针对交直流混线时电压互感器烧损,对10kV系统正常运行电压互感器三相阻抗不平衡时电压、过渡电阻接地系统电压以及过渡电阻接地又电压互感器三相阻抗不平衡时电压进行了研究,并结合10kV交流系统与1kV直流系统混线实例,分析了电压互感器烧损的具体过程;指出窜入交流系统的高压直流,促使电压互感器铁芯磁路迅速饱和导致阻抗的三相不平衡是造成电压互感器烧损的关键原因,及时有效地处理单相接地故障可以避免事故扩大,设计时在交直流线路交叉处采取有效的措施是避免出现混线事故的根本方法。

The interconnection of AC and DC lines causes the burnout of PT（Potential Transformer）. Voltages of normal operating PT in 10 kV system under three conditions are studied：with unbalanced three-phase impedance ,grounding with transition resistance and both. The process of PT burnout is analyzed in detail when 10 kV AC system interconnects 1 kV DC system. The high voltage DC flowing into AC system makes the PT iron core quickly saturated ,causing the unbalance of three -phase impedances and the burnout of PT. To remove the single-phase grounding fault effectively and in-time may stop the fault spreading,and to avoid the interconnection of AC and DC lines in design is fundamental measures.