RELIABILITY EVALUATION IN SUBSTATION, SWITCHING STATION AND DISTRIBUTION SYSTEMS
Grover, Mohinder Singh
The reliability performance of transmission and distribution systems can be evaluated in quantitative terms by the application of probability methods. This thesis develops a simple and sequential approach for the reliability analysis of practical systems. A cut set approach is utilized to form series-parallel representations of complex system configurations. A consistent set of equations is used in conjunction with the cut set approach to evaluate the outage frequency and duration indices at different load points in the system. The failures of individual power system components may have quite different effects on the total system. In this thesis, component failures are model-led with regard to their system effects. This method of modelling provides a more accurate representation of component and system behaviour. Reliability analysis of practical systems often requires complex and time consuming computations. A digital computer program has been developed to minimize the labour involved. The program output provides a concise and orderly description of the various combinations of events within the system that could result in an interruption. System reliability can be improved by the judicious selection of maintenance policies. This thesis illustrates that maintenance policies cannot be determined solely by qualitative considerations. Reliability benefits associated with a component co-ordinated maintenance policy are quantitatively evaluated. The cut set approach is extended to the evaluation of frequency and duration of overloads utilizing two additional indices of interrupted load and energy to estimate the overload severity. The application of supply interruption costs in the evaluation of economically justified investment is illustrated in this thesis. The savings in the costs of supply interruptions obtained by the use of spare transformers, standby units, additional facilities etc. can then be compared utilizing these techniques, with the investment in these facilities.