Etminan - Sunderland Polytechnic England
Kitchin - Sunderland Polytechnic England

The light flicker problem 1 has been researched in many countries and different flicker measurement procedures and threshold limits have been developed. Flicker sources may have periodic or stochastic voltage fluctuation, with a frequency of up to about 25 Hz, of duration lasting from several seconds up to minutes or even hours. The principal aim of flicker measurement 2 is to express the acceptability of a given flicker level in terms of an agreed standard which ideally should be internationally recognized. Measurement techniques which are capable of evaluating flicker level in both uncompensated and ompensated load conditions, can be used to express improvement made by the introduction of compensation. Early flicker measuring instruments were mainly based on analogue electronics, 2 whereas recent developments, such as the UIE/IEC flicker meter , employ computer programs for signal filtering and calculation of flicker severity. In places where analytical calculation proves difficult or impossible due to the highly random characteristics of the electric load, statistical calculation can be employed. The UIE flicker meter was developed as a result of the UIE Disturbances Study Committee efforts, in order to establish an internationally agreed functional and design specification for a flicker measuring apparatus. The aim of the flicker meter is to simulate response of lamp-eye-brain chain, and to carry out an on line statistical calculation of flicker level and present the evaluated results. The inclusion of the latter part is not mandatory in the flicker meter, since the statistical calculation can be done off-line using a proper storage medium. However its inclusion is recommended to make the meter more efficient and complete. In the case of an electric arc furnace, voltage fluctuation waveform, giving rise to flicker at the point of common coupling (PPC), has erratic and random characteristics and cannot be defined in terms of an analytical equation. Statistical evaluation techniques are used in the UIE flicker meter to express the flicker level present in the system. Flicker meter results of two simulated Thyristor Switched Capacitor (TSC) compensators for a periodically varying load, and a randomly varying load, have been obtained and presented. Relative merits of the two simulated load models haze been compared as a measurement of electric arc furnace (EAF) performance with compensator systems. Simulation details of the systems discussed in this paper are given in reference 3.