Impact of substation configuration on protection system failure propagation and its effect on reliability of supply

Relatively fewer studies exist in literature on including the complex effects of transmission protection system related failure dependencies in the reliability prediction models. Usage of extensive Markov models has been usually advocated to capture the impact of protection system reliability on power system reliability. A new analytical method which makes use of approximate methods of system reliability evaluation has been recently proposed by us, which circumvents the need for Markov models. It is a unique minimal cutset-based approach for single circuit meshed transmission systems, where several basic and load/energy oriented reliability indices are obtained. The objective of this paper is to extend the procedure to examine the impact of substation configurations on protection system failure dependency propagation and its effect on bulk load point reliability indices. Preliminary investigations show a marked impact of employing a station configuration with simplified bus representation, especially in multi circuit meshed transmission systems, on the resulting reliability indices. The results of the proposed methodology are demonstrated on a suitably modified four bus illustrative test system, for cases with and without the consideration of protection system failures for a realistic station configuration.