Low-cost under-frequency relay for distributed load shedding

An under-frequency load shedding relay utilizing a single-chip microcomputer is described. The device may be used to shed off-peak load, thus replacing expensive emergency power reserve over the corresponding periods. The econonomic analysis shows that the device is cost effective when controling loads with an installed capacity greater than about 20 kw. The savings which accrue from the proposed approach increase with the installed capacity of the controlled load.