Co-Ordination of Static Var Compensators With Long Distance Radial Transmission System for Damping Improvement

The capability of static var compensators to use supplementary signals for damping improvement has been studied. Damping is shown to be a function of the transmission system loading and a function of the static var compensator The study offers insights as to how static var compensators should be coordinated with respect to the transmission system. The technology under study is based on thyristor controlled reactor with switched capacitors. This paper is concerned with the capability of the static var controller to provide damping in radial long distance transmission lines. It is well known that the lack of positive damping sets a limit to the power transferable across a transmission line By use of supplementary feedback signals, the static var compensator can be made to enhance the system damping. This paper seeks to answer the following questions: 1) For a given design of the supplementary signal feedback, are there any operating regions in which negative damping is encountered? 2) What is the effect of an individual static var compensator in providing damping for a transmission system with multiple compensation systems? 3) What is the analytical model of a static var compensator which uses the thyristor controlled reactor technology? 4) How should the elements of the static var compensator be designed in conjunction with the transmission system when the objective is to improve damping? These questions are answered in the context of a radical line with equally spaced SVC stations as modelled in Fig. 1.