特高压换流站直流分压器二次侧过电压保护

特高压换流站遭受雷击时,将造成接地网暂态地电位升高。雷击引发的接地网暂态电位升高具有电压幅值高、频率范围宽等特征,其产生的瞬态电位能通过传导的方式耦合至直流分压器二次侧导致过电压保护器件动作。如果分压器二次侧过电压保护器件动作后不能及时恢复将引发继保装置误动作。阐述了直流分压器暂态响应特性,搭建了直流分压器模拟试验电路,开展了直流分压器二次侧放电管的动作恢复特性试验,并通过EMTP软件进行了仿真研究。结果表明目前换流站直流分压器二次回路放电管动作后不能迅速恢复工作状态而导致双极闭锁,而放电管串联压敏电阻方案对限制直流分压器同极性过电压侵扰并使分压器回路快速恢复至正常工作状态具有一定作用,实测与仿真研究结果可为特高压换流站内直流分压器二次系统的过电压防护设计提供参考。

Study on Surge Protection of DC Divider Secondary Side in UHV Converter Station

When UHV converter station is struck by lightning, the transient ground potential of grounding grid will increase. The transient potential rise of grounding grid caused by lightning stroke is characterized by high voltage amplitude and wide frequency range, and its generated transient potential can be coupled to the secondary side of DC divider by conduction, causing action of overvoltage protection device. If the overvoltage protection device in divider secondary side cannot be recovered in time after action, it will cause maloperation of the relay protection device. In this paper, the transient response characteristics of DC divider are described, a simulation test circuit of DC divider is set up, the action recovery characteristic test of DC divider secondary discharge tube is performed, and simulation research is carried out with EMTP software. Results show that the discharge tube in DC divider secondary circuit in converter station cannot quickly restore its normal working state after action, leading to bipolar block. However, the series varistor scheme of discharge tube has certain effect on limiting the interference of DC divider with the same polarity overvoltage and making the DC divider restore to normal working condition quickly. The measured and simulated results can provide reference for design of overvoltage protection of DC divider secondary system in UHV converter station.