饱和铁心型超导限流器压敏电阻的实验

Experimental of Over-voltage Suppression in a HTS Three-phase Saturated Core Fault Current Limiter by a ZnO Varistor

压敏电阻可抑制超导限流器断直流时产生的高压,同时加速直流励磁能量的释放以促使限流器交流侧快速退饱和,进入感性限流状态。为验证其保护和能量吸收作用,用NI采集卡、Labview以及其他电流电压传感器和可控的IGBT器件设计和制造了检测控制系统。对不同压敏电压等级的压敏电阻进行断直流的放电实验以验证其抑制电压的保护作用。结果表明:断直流时储存能量的释放是超导限流器产生高压的原因;励磁储能一定且压敏电阻通流量一定的条件下,压敏电压越大断直流产生的电压也越大,同时电流断开时间越小则能量释放时间越小。所得结果为设计更大容量的超导限流器,选择不同压敏电阻的压敏电压和通流量等级提供了实验和计算参考。

A HTS three-phase Superconducting Fault Current Limiter （SCFCL） with Saturated Core and a ZnO varistor （Metal Oxide Varistor）were investigated to determine the effects of the ZnO varistor as an over-voltage suppressor and energy dissipation for the SCFCL, which aids to speed up transition from saturated to normal of the AC coils and result in the more effective current limitation. The sample machine of SCFCL with the real-time data acquisition and control system based on Labview, NI board, current transducers , voltage transducers and IGBT etc were designed and fabricated. To determine the over-voltage suppressing and energy dissipation effect of varistor, some varistors with same current level and different varistor voltage were connected to DC superconducting coil in parallel for experiment of turning off DC excitation by IGBT. Also a relationship among energy, varistor voltage, time of DC current descend and the reason of production of high voltage was presented. The experimental results shows that the high voltage comes from the dissipation of DC excitation energy; and when the DC excitation energy and the current level of varistor keep constant, higher the varistor voltage is, higher the produced voltage is, at the same time, less the time of DC current descend is, it also means that less the time of DC excitation energy dissipation is. The results help to design and fabricate superconducting fault current limiter with high current level and select different ZnO varistor with different varistor voltage and current level.