Assessment of Spare Breaker Requirements for High Voltage Transmission Stations

This paper describes a probabilistic method based on a total risk index (probability times consequences) for assessing the number of spare breakers required for a group of similar high voltage breakers used in switching and transformer stations. The proposed method uses a Markov model for assessing the probability of failures and a bulk power system reliability program for evaluating failure consequences. The method considers a number of factors such as the group size, unit failure rate, unit repair time, transmission station layout, and other power system parameters that may impact the number of spare breakers. A cost/benefit analysis approach is used in determining the required number of spare breakers. The number of spare units is determined when the total cost (sum of spare unit costs, system operating costs and system outage costs due to breaker failures) is minimum. An example is given to illustrate the proposed method of assessment.