电阻型高温超导限流器暂态电阻特性分析

Analysis of Transient Resistance Characteristics for Resistive Type High Temperature Superconducting Fault Current Limiter

高温超导故障限流器(SFCL)因集自触发、限流、损耗较小等优点已成为解决目前电网短路故障问题的有效设备,为电力系统中电能的传输质量和稳定性提供了有效保障。该文通过对YBCO超导材料电、热性能的分析,建立电阻型超导限流单元瞬态电阻与其通过的电流和所在环境温度变化规律的数学模型。应用电力系统电磁暂态仿真软件PSCAD/EMTDC进行线路建模和短路故障运行状态模拟,并联合采用Matlab构建等效数学模型。通过数值暂态联合仿真分析,获得单相短路故障情况下与三相短路故障情况下超导故障限流器的限流比率及超导限流单元的电阻和温度变化特征。并对超导带材进行冲击电流试验,验证其电阻变化规律。计算和分析结果表明,在不同强度的短路电流冲击下,高温超导故障限流器产生的瞬态电阻受短路电流幅值和变化率影响较大。阻值变化的速率随短路电流变化速率的增大而增大,因此对于不同程度短路电流需采取不同的限流保护策略。该研究对超导限流器距离保护的研究提供了时间维度的参考,对掌握各种复杂拓扑类型高温超导限流器限流特性具有参考意义。

Providing an effective guarantee for power transmission quality and stability in power system,high temperature superconducting fault current limiter(SFCL)is an effective device to solve the problem of short circuit fault in power girds,due to the superior properties of self-triggered,high current limiting ability and low normal operation loss.In this paper,a mathematical model for the dependence of transient resistance of resistive type superconducting current limiting unit(SCLU)on its transport current and ambient temperature is built,by analyzing the electrical and thermal properties of YBCO superconductor.In order to investigate the law of the current limiting ability of SFCL with suffering fault current in the power grid,PSCAD/EMTDC and Matlab have been combined to simulate this behavior.PSCAD/EMTDC is used for line modeling and short circuit fault operation simulation and Matlab is used to build the superconducting equivalent mathematic model.According to the analysis of numerical transient simulation,current-limiting ratio in high temperature SFCL,resistance variation characteristic in SCLU and temperature variation characteristic in SCLU are obtained,under the condition of single-phase shortcircuit fault and three-phase short-circuit fault,respectively.Moreover,for verifying the law of resistance variation,the superconducting tape is subjected to the impact current test.Calculation and analysis results show that,transient resistance of high temperature SFCL is greatly influenced by short-circuit current amplitude and its rate of change,when facing with different intensity of short-circuit impact current.Considering the growth of rate of change in current will accelerate the variation of resistance of superconducting material,for different short current in circuit,the current-limiting process and protective strategy of high temperature SFCL should be different.The work in this paper contributes references to distance protection of high temperature SFCL on time dimension,which is of significant reference for mastering the current limiting characteristics of high temperature SFCL with various complex topologies.