Use of load shedding scheme to increase the capacity limit on the single largest generator

Abstract

This paper examines the stability of the Sri Lankan power system with the emergence of the large coal power plants. Such coal power plants are being introduced to Sri Lanka with the aim of bringing down electricity costs. Sri Lanka at present, has a maximum peak demand of around 2100 MW with an off peak demand of being a low of nearly 900 MW during the early hours of the morning. It is in such a backdrop that a large coal power plant of 300MW has been introduced to Sri Lanka intended to run as base load. Due to reasons of current practice, the capacity limit of the single largest generator is set at 20% of the instantaneous system demand. Thus underutilization of the coal power plant would occur during the off peak hours. This paper looks into ways of increasing the 20% limit up to an amount such that the coal power plant could be used to full capacity even during off peak hours. The 220 kV and part of the 132 kV transmission system of Sri Lankan power system has been modeled on PSCAD software, taking into account the various parameters of power stations and transmission lines. With the use of the software, contingency situations have been analysed and the load shedding scheme currently being used by the CEB is revised such that the limit placed on the single largest generator could be increased to 25% of the current demand.