饱和铁心型超导限流器满足电网重合闸条件分析

Analysis on Conditions for Saturated Iron-Core Fault Current Limiter to Match With Reclosure of Circuit Breakers

饱和铁心型超导限流器(saturated iron-coresuperconducting fault current limiter,SI-SFCL)在限流过程中独特的非线性阻抗变化特性与电网继电保护的配合是一项关键技术,尤其是限流器在完成限流后需要快速恢复,以配合电网断路器重合闸的要求。限流器的恢复过程本质上是超导磁体的重新励磁,既要在尽量短的时间内完成超导磁体的充磁,又要尽量降低快速励磁时对励磁电压、电流的要求,降低直流励磁系统的设计难度,并提高设备运行的安全性和稳定性。基于对上述超导限流器重合闸要素的分析,得出结论:SI-SFCL在电网重合闸时,直流励磁不必完全恢复至额定工作值,只要能够确保在一定交流退磁作用下,铁心的最小磁化强度处于磁化曲线的拐点处即可。用PSIM进行仿真分析,校验了该判据的合理性。

It is a key technology for saturated iron-core superconducting fault current limiter （SI-SFCL） to make its distinctive nonlinear impedance change during the fault current limiting process matching with protective relaying of power grid, and especially after the current limitation the SI-SFCL should rapidly return to its normal state to satisfy the requirement for reclosure of circuit breakers. The essence of the process of recovering SI-SFCL is the re-excitation of superconducting magnet. There are two conditions to be satisfied： not only the duration for complete magnetizing ofsuperconducting magnet should be as short as possible, but also the requirements of fast excitation to excitation voltage and current should be lowered as possible to reduce technical difficulty in the design of DC excitation system, meanwhile both security and stability of SI-SFCL operation should be improved. Based on the analysis of above-mentioned conditions for SI-SFCL to match with reclosure of circuit breakers, the conclusions are as following： during the reclosure of circuit breakers it is not necessary to return the magnetizing of SI-SFCL to its normal state; it is permissible that under a certain AC demagnetizing effect the minimum intensity of magnetization of the iron-core locates at the inflection point of the magnetization curve. The reasonableness of the conclusions is verified by simulation based on PSIM.