Impact of the Periodicity of Feeder Re-Allocation on the Efficiency of Under-Frequency Load Shedding

When a large generation-consumption unbalance occurs, under-frequency load shedding (UFLS) is the last resort to restore this balance by disconnecting loads from the electrical power system. In France, the UFLS is realized at the level of primary substations by allocating groups of MV feeders to under-frequency relays. Choosing and implementing this allocation requires substantial operator work, and is currently done once a year in France. In the near future, however, it may become both necessary and technically feasible to update the UFLS scheme more frequently; this is the investigated topic of this paper. Firstly, several re-allocation strategies are defined, whose periodicity ranges from months to hours. Then their applications are simulated on a large real-world dataset based on the actual consumption of individual MV feeders from an entire French region over two years. The performance of the various proposed strategies are compared and recommendations regarding the implementation of future UFLS re-allocation methods are provided.