The electric arc furnace（EAF）uses the heat caused by the arc light between electrodes to melt the metal. Especially at the instant of arc ignition

the current varies abruptly with severe fluctuation. The highest fluctuation closes to short circuit

whilst the lowest fluctuation just like open circuit. Frequent variation of the current would cause voltage drop on the network impedance

result in the fluctuation of network voltage and lead to deterioration of power quality.In this paper

the influence of voltage fluctuation at instant of arc ignition on existing SVC reactive power compensation system of certain substation is analyzed

its shortcoming is pointed out and reasonable modification program is given on the basis of comparison of simulation result.Finally

very satisfactory result is obtained.