Introduction

The primary function of an electric power system is to provide electrical energy to its customers as economically as possible and with an acceptable degree of continuity and quality. Modern society has come to expect that the supply of electrical energy will be continuously available on demand. This is not possible due to random failures of equipment and the system, which are generally outside the control of power system personnel. Electricity supply generally involves a very complex and highly integrated system. Failures in any part of it can cause interruptions which range from inconveniencing a small number of local residents, to major and widespread catastrophic disruptions of supply. The economic impact of these outages is not restricted to loss of revenue by the utility or loss of energy utilization by the customer but include indirect costs imposed on society and the environment due to the outage. In the case of the 1977 New York blackout, the total costs of the blackouts were suggested to be as high as $350 million, which 84% was attributed to indirect costs.(1)