Bus-based reliability indices and associated costs in the bulk power system

This paper presents a methodology to evaluate the reliability and to calculate interruption costs at the load bus level in the bulk power system (Hierarchical Level II). The method is based on a nonsequential Monte Carlo simulation combined with a linear optimization model in which the load at every bus is represented by two components, a firm and a nonfirm (curtailable) portion. Expected values of not served energy (EENS), not served demand (EPNS) and loss of load probability (LOLP) are computed for the whole system (global indices) as well as for each load bus. The paper includes a sensitivity analysis taking into consideration variations of the indices due to factors such as interruption costs and load shedding policies. In a number of countries the evaluation of bus-based reliability indices has become a key component in the negotiation of supply contracts in the open access environment. The same indices are useful to assess the reliability of the supply at the delivery point to both distribution utilities and large industrial customers.