大机组降压运行对分区电网短路电流的影响

Short-circuit current analysis under the generator voltage-class-reduction scheme in district grids

大机组降压运行是一种缓解区域电网输变电容量与负荷发展不平衡现象有效且经济的手段。然而,大机组降压运行在减小原电压层面电网系统短路阻抗的同时会增大拟接入电压层面电网母线的短路电流,使得低压侧短路电流超过断路器遮断容量,严重影响电网的安全运行。提出大机组降压运行短路电流变化分析方法及计算模型,研究短路电流变化与降压机组参数之间的数学关系,并应用于湖南省大机组降压运行方案选择中。仿真与工程应用表明,所提出的短路电流变化分析方法能准确且直观地反映大机组降压中短路电流的变化情况,为电网安全稳定经济运行提供保障。

Generator voltage-class-reduction scheme is a kind of efficient and economical approach to solve the imbalance between the increasing local-demand and generator capacity.Whereas,the generator voltage-class-reduction scheme will decrease the short-circuit impedance on the original network side(high-voltage side),in the meanwhile,the short-circuit current in the quasi-accessed networks side(low-voltage side)will be increased,making the short-circuit current exceed the interrupting capacity of the circuit breaker in low-voltage side and affecting the safe operation of the power grid seriously.This paper mainly proposes a novel method of calculating the short-circuit current and a mathematical model in the generator voltage-class-reduction scheme to research the relationship between the variation of short-circuit and the parameters of the generator.The method has been applied to select the generator voltage-class-reduction schemes in Hunan power grids.According to the results of the simulation and application,the method of short-circuit current analysis in this paper can accurately and directly reflect the changing of the short-circuit current in generator voltage-class-reduction schemes,which provides a guarantee for the power grid running with safety and stability.