A Holistic Fuzzy Measure for Load Priority in Under Frequency Load Shedding Schemes

Electrical Power Systems should be designed in order to minimize the effects of system disturbances and to enable decision-making based on different configurations and relevant priority analysis. Automatic Under Frequency Load Shedding is a known effective solution to the problem of contingencies in the electrical power grid and it is the last resource to mitigate the damage caused by severe and unexpected contingencies. However, to the best of our knowledge, the load priority configuration, which have been presented so far in load shedding process do not take into account some important aspects, such as social, economic or political importance of the connected loads, as well as how negative is the impact on the public image of power utilities when disconnecting specific load branches. This paper aims to provide a general priority holistic function which can be applied to different load shedding schemes, independent of the adopted philosophy and operating principles. The proposed ranking is developed using a Fuzzy system for load priority classification that takes several aspects into consideration. To illustrate the method, an electrical power system was simulated, comparing a traditional load shedding scheme with two different sets of load priorities and evaluated by the proposed metric.