Voltage reduction as a means of reducing distribution load

Most electric utilities have emergency procedures for reducing system load when their generation and outside purchases cannot meet the expected load and reserve requirement. One such procedure reduces voltage by means of transformer tap changes or voltage regulators at selected substations and circuits. This paper is not concerned with the means by which this is done but rather with the selection of circuits for voltage reduction. For some time, the rule of thumb in the industry has been that a 1% voltage change produces 1% total power change. At the present time there is considerable questioning of how much load reduction is actually gained by voltage reduction. In an attempt to clarify the behavior of different types of substations, a series of tests was performed at three different types of substations; residential, commercial and a combination of residential and commercial. These tests were performed in the afternoon and evening in the winter, spring and summer utilizing fast instrumentation developed by Karl Andrews and G. L. Park.²