Evaluating the reliability of electrical auxiliary systems in multi-unit generating stations

A method of evaluating the reliability of the electrical auxiliary system of a multi-unit station with interconnected or interconnectable unit and station supplies is described. The electrical auxiliary system may be represented in full, comprising transformers, cables, busbars, circuit breakers, normally-closed and normally-open interconnectors, parallel connections, standby generators, separate drives, etc. The method utilises the previously developed `cutset¿¿ technique for analysing electrical systems, and may be used to show to what extent the availability of the generating station is affected by the possible failures in the auxiliary system. Attention is drawn to the important role of the interconnectors and normally-open breakers, in overcoming the effect of long component repair times, and to the significant improvement of the auxiliary system reliability provided by standby gas turbine and diesel generators