An Efficient Method for Generating Capacity Reliability Evaluation Including the Effect of Planned Outages

The treatment of units on planned outage is an important consideration in generating system reliability studies. A single generation system model and load model cannot be used since the units on planned outage vary throughout the year. Some authors have considered planned outages by adding capacity on maintenance to load and then using a single generation system model consisting of all the units. This approach is, however, approximate and gives pessimistic calculated risk level. The realistic method of incorporating planned outages is to divide the year into intervals (generally of one week duration) over which the units on planned maintenance remain unchanged. The generation system and load models are then developed for each interval and convolved to yield interval indices which can be aggregated to produce annual indices. In further discussion this approach is referred to as the conventional method. This paper describes a more efficient method of incorporating planned outages. The proposed method consists of the following steps: 1. Build a load model for each week in an increment of Z MW. 2. From the load model of each week deconvolve the units on planned outage during that week. 3. Combine the weekly load models obtained in step 2 into the annual load model, by multiplying the weekly load models by 1/52 and then adding. The resulting model is the composite load model. 4. Now convolve all the generating units with the composite model obtained in step 3 to obtain the reliability indices.