A Comparative Study of System versus Load Point Indices for Bulk Power Systems

Adequacy evaluation of a bulk power system normally includes the outages of generating units, transmission lines and transformers. An outage event may affect a wide area of the system or it may affect a small group of buses or perhaps a single bus. This depends upon the components under outage, their relative importance and location in the network configuration, the corrective action taken and the load curtailment philosophy, etc. The calculated indices resulting from the outage contingencies considered should indicate those areas in the system which are less adequate and are prone to disturbances. Overall system indices do not adequately convey this information and therefore it is appropriate to also emphasize individual load point indices. Relatively little attention has been paid to the examination of the individual bus indices and the tendency among analysts working in this area is to concentrate on the system indices [1]. The two sets of indices, individual load point indices and the system indices respond quite differently to variations in the system load and to the depth that outage contingencies are evaluated. This paper illustrates the variation in the bus and system indices using the IEEE Reliability Test System (RTS).