Scheme to improve transient response of industrial systems

This paper is based on recent electrical system studies carried out on an Imperial Chemical Industries (ICI) plant located in Scotland, which derives its power supplies from both in-house generators and grid interconnection. The objective was to examine methods of improving the transient response of the industrial system under various external and internal fault conditions, with a view to improving the security of supplies to important drives and auxiliaries. High levels of plant security and enhanced synchronous-generator stabffity are normally associated with multiple-grid and in-house distribution feeders, with corresponding low values of impedance between the supply sources and motor drives. However, this paper examines all aspects of system behaviour during fault conditions and concludes that, in this instance, an improvement to overall transient performance is achieved by increasing grid feeder reactance immediately after fault inception. In the case of external faults developing on the interconnected grid, computer-aided studies show the advantage of rapidly switching out one of the grid transformer feeders. Similarly, in the event of selected internal faults occurring, study results show the improvement achieved by rapidly opening normally closed ring mains, thereby doubling the effective ring feeder reactance.