双馈风场进线对220 kV母线采样值差动保护的影响

Influence of double fed wind field incoming line on sampled value differential protection of 220 kV bus

由于采样值差动保护具有计算速度快、易考虑CT饱和等优点而被普遍应用于当前的母线保护装置中。然而暂态特性不同于传统火电机组的双馈风电机组大量接入电力系统,这会给现有的继电保护带来严重的挑战。以双馈风电场远距离接入220 kV电压等级变电站母线为例,在RTDS仿真平台上研究双馈风场进线对母线采样值差动保护的影响。结果表明,在母线区内故障时风场侧支路提供的短路电流存在弱馈、高谐波及频率偏移等特点。与此同时,计及CT饱和、双馈机组本身的无功优化控制策略等因素影响,使得该短路电流的复杂性更加突显,进而造成传统母线釆样值差动保护动作有延迟。为此,提出了一种自适应变数据窗的釆样值差动保护判据,并通过RTDS仿真平台验证了该方法行之有效。

Because the sampled value differential protection has the advantages of fast calculation speed and easy consideration of CT saturation,it is widely used in current busbar protection devices.However,when doubly fed induction generators,which have different transient characteristics from traditional thermal power units,are widely connected into power systems,it will bring serious challenges to the existing relay protection.Taking the doubly-fed wind farm connected to the busar of 220 kV substation as an example,the influence of doubly fed wind field incoming line on busbar sampled value differential protection is studied on the RTDS simulation platform.It is found that the short-circuit current provided by the wind side branch has the characteristics of weak feed,high harmonic and frequency offset when the fault occurs in the busbar area.At the same time,taking into account the CT saturation,doubly-fed unit itself reactive power optimization control strategy and other factors,it makes the complexity of the short-circuit current more prominent and results in the traditional busbar sampled value differential protection action being delayed.For this reason,a criterion for sampled value differential protection of adaptive variable data window is proposed,and the method is validated by RTDS simulation platform.