智能配电网建设中的继电保护问题 讲座二 配电网故障分析计算问题及其发展

Relay Protection Issues in Construction of Smart Distribution Network Lecture 2 Analysis and Calculation Methods of Faults in Distribution Networks and their Developments

传统短路电流的计算方法已难以适应分布式电源接入后配电网短路电流的计算。介绍了配电网短路电流的近似计算公式。分析配电网故障时分布式电源(DER)短路电流输出的特点,给出了用于短路电流输出计算的DER等效电路。指出传统短路故障计算机算法用于配电网存在的问题,介绍了一种高效率的基于端口补偿原理的配电网短路故障计算方法。利用模变换法推导出小电流接地故障暂态分析等效电路,更正了目前普遍使用的等效电路的错误。

Abstract：The conventional short-circuit calculation method has been found difficult to be applied to the distribution networks embedded with large amount of distributed electric resources（DERs）. Approximate fault current calculation formulae for radial distribution networks are presented. The DER＇s contribution to fault currents of distribution networks is analyzed, and fault current calculation equivalent circuits of DERs are given. The problems of conventional computer methods for short-circuit calculation of distribution networks are described. An efficient computer method for short-circuit calculation of distribution networks based on compensation principle is introduced. An equivalent circuit for transient analysis of single phase fault in noneffectivelly earthed network is derived using modal transformation,and the mistake of conventional equivalent circuit is corrected.