Assessment of GB transmission system 400 kV south-east loop reactive compensation requirements

The south east corner of the Great Britain transmission system, spanning the coastal region from Kent to Southampton, presents National Grid Electricity Transmission with a number of challenging, and evolving, issues - mainly in regard to thermal capacity and voltage control in transient, dynamic and steady state conditions. This paper presents an investigation conducted to define the location, amount and appropriate technology of added reactive compensation plant to enhance the voltage stability of the South East Coast network. Using a detailed system model developed in DIgSILENT PowerFactory, a number of load flow, contingency, Q-V analysis and dynamic simulation studies are undertaken to identify the network reinforcement requirements. Specifically, a multi Q-V analysis technique is applied to quantify the effect of injecting reactive power simultaneously at several busbars, which allows a better understanding of the potential for interaction between existing and new reactive power compensation, and demonstrates the need for their coordination.