Modelling multistate problems in sequential simulation of power system reliability studies

The paper presents a new approach for taking into account multistate units and common-mode outages in sequential Monte Carlo simulation. Although the state space transition diagrams for multistate units and common-mode outages are well established, they can only be utilised in random or nonsequential simulation, and not in sequential simulation. Using an equivalent or derating-adjusted forced outage rate for generating units instead of a multistate model can lead to pessimistic results. Usually, the common-mode failure rate is small compared with independent failure rates, but such failures may have severe consequences on the power system performance. Many utilities are, therefore, now using multistate and common-mode representations for composite power system adequacy analysis. The conventional sequential simulation is capable of evaluating composite generation-transmission systems without these failure modes. The effectiveness of the technique is demonstrated using several small examples. Also, the adequacy of the RBTS and the IEEE-RTS is evaluated, and the results are compared with those given by an analytical technique. These again demonstrate the applicability and effectiveness of the approach