SF_6断路器弧触头的关合侵蚀特性

Contact Erosion Characteristics in Making Process of SF_6 Circuit Breakers

SF6断路器关合操作时产生的关合涌流对弧触头会造成严重的侵蚀。为了研究弧触头在关合情况下的侵蚀特性,设计了模拟的SF6断路器灭弧室,对CuW80弧触头进行了关合侵蚀实验。实验记录了每次的燃弧时间和电流峰值,并计算了100次实验后的质量损失率。每20次关合实验后,拍摄触头表面照片,测量弧触头的接触电阻和工频耐压。最后分析了SF6断路器弧触头的关合侵蚀特性并探讨了侵蚀机理。认为在关合实验中弧触头的侵蚀来源有两个:一个是关合前预击穿电弧的烧蚀,一个是烧蚀后弧触头变软后的机械磨损,并且机械磨损的量占有相当的比例不可忽略。在电流峰值18 kA,燃弧时间<2 ms,机构速度7 m/s的情况下,机械磨损过程中的质量损失率大于1.0 mg/C,这也是关合情况下触头质量损失更大的主要原因。

For a SF6 circuit breaker in closing operation, closing surge can cause serious erosion to its arcing contacts. Inorder to study the characteristics of this erosion, we designed a simulative interrupter of SF6 circuit breaker to conducterosion experiments of CuW80 arcing contacts under closing condition. The arcing duration and current peaks of everytest were measured, and the mass loss ratio of the contact after 100 times of operations was calculated. Moreover, afterevery 20 operations, we photographed surfaces of the arcing contact and measured its electrical properties including con-tact resistance and power-frequency withstanding voltage. The characteristics and mechanism of erosion of arcing contactin SF6 circuit breaker in closing process were then analyzed. It is found that two major sources can induce the arcing con-tact erosion, namely, the pre-breakdown arc before closing and the mechanical wear of arc heated contact due to friction,and the wear caused by mechanical friction occupies a relatively large proportion and can＇t be ignored. Under the condi-tions that the mechanism velocity is 7 m/s, current peak is 18 kA, and arcing duration is less than 2ms, the mechanicalwear mass loss rate is greater than 1.0 mg/C.This is the main reason why an arcing contact wears faster during closingthan during opening.