Supply to arc furnaces: measurement and prediction of supply-voltage fluctuation

Abstract
In the electric-arc furnace, arc motion and other factors cause a large irregular fluctuation of current. This fluctuating load results in a fluctuation of the supply voltage, which can cause annoying flicker in lamps connected to the system. The best short-term measure of the flicker severity of this voltage fluctuation is the r.m.s. value of the envelope with which the fluctuation modulates the supply-voltage wave. An instrument which indicates and records this r.m.s. voltage is described. To assess the long-term severity of the voltage fluctuation (whose amplitude varies widely during a complete furnace-operating cycle), a probabilistic method has been developed, based on a quantity called the gauge-point voltage fluctuation. Methods of estimating this quantity during the design stage of supplies to arc-furnace installations are described, including supplies to multifurnace installations. The limits for gauge-point voltage fluctuation in use in Great Britain are specified and the reasons for their choice discussed. Some comparison is made with earlier investigations in Great Britain and abroad.

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