Voltage stability analysis on the NGC system

Abstract

The reactive power requirements on the National Grid Company (NGC) system have risen as a result of increased power flows and the shorter timescale on which power stations are commissioned and withdrawn from service. Power transfers across internal system boundaries are found in some cases to be determined by voltage limits and the need to avoid voltage collapse, rather than thermal capability of the transmission plant. Analytical techniques for voltage stability analyses have been under investigation with the ultimate objective of providing better tools for operational planning and operation. This paper describes the development of a method for voltage stability analysis using improved sensitivity techniques to rapidly calculate the transfer limit of any defined boundary. This is extended to include the modelling of synchronous compensators and static var compensators (SVCs), as well as on-load tap changers. Extensive testings of the algorithm are carried out on the NGC test systems.