Impact of equipment availability on composite system reliability

The reliability of supply in a bulk electricity system is directly related to the availability of the generation and transmission facilities. In a conventional vertically integrated system these facilities are usually owned and operated by a single company. In the new deregulated utility environment, these facilities could be owned and operated by a number of independent organizations. In this case, the overall system reliability is the responsibility of an independent system operator (ISO). Composite system reliability evaluation involves the analysis of the combined generation and transmission system in regard to its ability to serve the system load. The load point reliabilities are a function of the capacities and availabilities of the generation and transmission facilities and the system topology. In Canada, availability data on generation and transmission facilities are collected by individual electric power utilities and disseminated by the Canadian Electrical Association. Accurate and consistent collection of data is an important function in a modern power system and a vital component in a probabilistic approach to system development and growth. This paper examines the effect of equipment availability on the load point and system reliability of two test systems using a Monte Carlo simulation approach. The paper shows that the availabilities of specific generation and transmission facilities have major impacts on the load point and system reliabilities. These impacts are not uniform throughout the system and are highly dependent on the overall system topology and the operational philosophy of the system.