一起交直流混联系统事故原因分析及整改措施

Analysis on Cause of An Accident in AC/DC Hybrid System and Rectification Measures

对南方电网系统一起500 kV断路器爆炸引起电网系统连锁反应的事故进行分析,指出500 kV砚都站发生的断路器爆炸造成高肇、天广、楚穗3回直流换相失败,并造成广州换流站极2阀冷系统停运,肇庆换流站与500 kV砚都站电气距离非常近,受到故障的影响最大,高肇直流电压发生剧烈波动,出现大量谐波分量,直接导致双极直流线路低电压保护27 du/dt动作,高肇直流双极再启动成功后,由于肇庆换流站阀冷系统问题导致极2闭锁,同时对其存在的风险进行深入剖析,最后提出有效的整改措施,防止类似事件的再次发生。

The cascading failure in China South Power Grid caused by an explosion accident of 500 kV circuit breaker is analyzed, and it is pointed out that the explosion accident of 500 kV circuit breaker occurred in Yandu substation simultaneously led to the commutation failures of three EHV/UHV DC transmission lines, i.e., the ±500 kV DC transmission line from Gaopo to Zhaoqing, the ±500 kV HVDC transmission line from Tianshengqiao to Guangzhou and the ±800 kV DC transmission line from Chuxiong to Suidong, and further the accident led to the forced outage of valve cooling system for Pole II of Guangzhou converter station. Because Zhaoqing converter station is electrically close to 500 kV Yandu substation, thus Zhaoqing converter station is subjected to the most severe affection, and the DC voltage of ＋500 kV DC transmission line from Gaopo to Zha0qing drastically fluctuated and a lot of harmonic components appeared and directly made the bipolar DC line under-voltage protection （27du/dt） acted. After the success bipolar re-starting of±500 kV DC transmission line from Gaopo to Zhaoqing,： the still existed forced outage of valve cooling system for pole II led to the pole II re-blocked. The author analyzes the spread of the accident as well as the related hidden danger, and proposes effective rectification measures to prevent the reoccurrence of similar cascading failures.