This paper illustrates of switching impulse over voltage due to changing of the load condition to the existing 220 KV transmission lines as well as substation system. The study of performed by computer based method using ATP simulations. The details of the system modeling represented for various equipments designs and selection of the power system. These phenomenons are effects on the shunt reactor and loads on or off over condition will investigate. This analysis of the overvoltage occurrences under the transients small optimal determining from the overvoltage withstand in the equipments and continuous supply as well as less disturbance of the power system[1].