Deterministic/probabilistic contingency evaluation in composite generation and transmission systems

Deterministic criteria and techniques have been developed and applied in power system planning and operation over many decades. Their essential weakness is that they cannot account for the stochastic nature of system behavior, of customer demands, or of component failures. The deterministic criterion usually applied in a composite system is designated as the (n-1) criterion. Application of the (n-1) criterion does not provide information on the actual impacts of the different contingencies on the load point and system reliability. Probability techniques are now highly developed, but they have been used mainly in the planning and operation of generating capacity. There is relatively little utilization in the planning and operation of composite generation and transmission systems. This paper examines the impacts of different single contingencies on the composite system reliability of two test systems using probability techniques. The approach presented provides valuable information for system planning. This information cannot be obtained using deterministic techniques.