The stability and power flow limits of an electrified railway system with voltage controlled SVCs

This paper investigates the limit of acceptable capacitive output of SVCs used to provide compensation in an electrified railway system. When working beyond this limit, any increase of reactive power compensation will no longer help to support the system voltage, but will reduce it. The phenomenon is similar to that of voltage collapse experienced in some heavily loaded transmission systems. A method is established to calculate the maximum compensation for such a railway system. Finally a realistic system is used to illustrate the negative effect of excessive compensation under heavy load conditions