Abstract: Frequent Switching of arc furnace in steel company causes a great effect on the insulation of arc furnace transformer winding which in turn may causes a shutdown of production for long periods of time. Therefore, it is necessary to study and analyze the causes of these outages and design an adequate protective device. In this paper the transient overvoltage resulted from vacuum circuit breaker switching arc furnaces of El-Delta for metal and steel company connected to the Egyptian distribution network is presented and discussed. The resulted overvoltage at the circuit breaker contacts can be as high as 3.0 p.u. While at the transformer terminals, the overvoltage reaches a high value, which can be as high as 2.44 p.u. A Fast Fourier Transform (FFT) analysis is used to analyze the overvoltage transients to determine the critical frequencies which must eliminated by the protective devices.