Probabilistic Transfer Capability Assessment in a Deregulated Environment

A methodology for available (simultaneous) transfer capability (ATC) analysis based on a probabilistic approach is presented. It is postulated that the system is operated by an ISO. The traditional concept of “area” is extended to include a utility, an individual IPP, a large customer, etc. All areas are divided into three groups: (a) study area or area under the ISO control, (b) transfer participating areas, and (c) external areas which have no direct transactions or they have fixed transactions with the study area. A performance index based contingency selection procedure is applied within the study and transfer participating areas to rank those contingencies that will affect simultaneous transfer capability. The contingency ranking order is utilized by a variation of the Wind Chime diagram to selected contingencies that are then evaluated by an optimal power flow algorithm. Subsequently, the probability distribution of simultaneous transfer capability is computed based on the electric load, circuit and unit outage Markov models. The 24x3 bus IEEE RTS is utilized to evaluate the proposed method. The performance of the proposed method is also demonstrated on an actual large scale system (2182 bus, 8 area system).