SF_6-CF_4混合气体电弧开断特性的实验研究

Experimental Study on Arc Interruption Characteristics of SF_6 and Its Mixtures With CF_4

基于建立的可拆式高压气体断路器,研究了SF_6-CF_4气体的电弧开断特性。采用数字延时脉冲发生器控制断路器操作机构和晶闸管等的动作时序,利用屏蔽网包裹信号线以降低电磁干扰,借助毕托管和管内阻尼颗粒实现压力传感器的绝缘和隔热并抑制管内压力波的振荡。利用硅压阻式传感器和零区测量设备分别测量了电弧开断过程中喷口喉部气压及零区电压电流的变化。分析了短路电流和气体配比等对灭弧室中喷口喉部气压变化和电弧零区行为等的影响。将Mayr电弧模型应用于弧后行为的预测,通过改变恢复电压上升率(rate of rise of recovery voltage,RRRV)和零前电流斜率(di/dt)来分析SF_6-CF_4电弧的零区特性。结果表明,在SF_6中添加CF_4后,测量点气压增量及临界恢复电压上升率趋于下降。计算得到SF_6和50%SF_6-50%CF_4的临界弧后电流分别为0.74A和0.96A。50%SF_6-50%CF_4中临界恢复电压上升率为SF_6的77%,临界恢复电压上升率和测量点气压增量之间呈现出一定的相关性。

The arc interruption characteristics of SF6-CF4 were investigated based on a detachable gas circuit breaker （GCB） model. The digital delay generator was used to control the operating mechanism of CB and thyristor etc. The shielding net was used to attenuate the electromagnetic interference. Heat isolation, electrical insulation, and suppression of pressure wave in the tube were realized through a pitot tube filled with damping particles. Gas pressure, arc current and voltage around current zero were measured by the silicon piezoresistive pressure transducer and the current-zero measurement system, respectively. The influence of short-circuit current and ratio of mixtures on the pressure variations at nozzle throat and current-zero behaviours were analyzed. Mayr dynamic arc equation was used to predict the post-arc behaviors of SF6-CF4 arcs by varying rising rate of recovery voltage （RRRV） and current steepness at zero-crossing （di/dt）. It is found that the gas pressure increment and critical RRRV tends to get weak as CF4 is added to SF6. Critical post-arc current of SF6 and 50%SF6-50%CF4 are 0.74A and 0.96A, respectively. Critical RRRV of 50%SF6-50%CF4 are about 77% of that of SF6, revealing a certain correlation between the critical RRRV and the pressure increment.