Matching site and power system requirements design of the two Pelham SVCs

This paper describes the design and layout for the two SVCs installed in the Pelham substation, north of London. Both SVCs of equal size and design have a nominal rating of -75 MVAr to 150 MVAr and are connected to the National Grid 400 kV system. The specified system requirements on operating range, harmonic performance and loss considerations led to an SVC configuration which contains one thyristor switched capacitor (TSC) branch, one thyristor switched reactor (TCR) branch for continuous reactive power control and a single tuned filter branch for harmonic limitation. The system voltage of the SVC secondary side was optimised to 14 kV based on thyristor equipment capabilities. The paper shows the voltage and current stresses of the thyristor valves taking into account system faults for the TCR branch and misfiring effects for the TSC branch. The approach to filter design considering the harmonic performance requirements is described. The Pelham SVCs commenced commercial operation in summer 1992