Two new methods to assess short-term transmission reliability

In this paper we present the short-term reliability assessment problem as a risk management problem where the uncertainty involved is related with transmission outages and the consequences are measured by the deficit experimented by loads. Two new methods are formulated and implemented in an academic test system. First, we formulate the short-term reliability related risks associated with the possibility of transmission failures which are measured through the probability of several scenarios in consideration and the respective consequences experimented by some market participants, in this paper the load curtailment. Second we develop a new market-based method to allocate reserve considering explicity reliability requirements submitted by the demand. In this new method the energy price after the occurrence of contingency (redispatch) is calculated after the fact, due to this issue the method is called ex-post. Third, we formulate another market-based method to allocate reserve considering the reliability requirement submitted by the demand in an explicit way. In this case the energy price calculated before the occurrence of contingency (redispatch) does not change, independent of the system condition, therefore the method is called ex-ante. Finally, we compare both new methods in an academic test system where we conclude that both methods allocate reserve fulfilling prespecified reliability requirements. The difference in allocation results in a difference in costs but not in reliability level. Moreover, the tradeoff is in between the economic signal given by stability of the energy price in presence of contingencies and cost necessary to have different amount of reserve.