Analysis of overhead ground wire sizes in distribution systems

This paper presents an approach to analyze the overhead ground wire (OHGW) sizes in distribution system focus on the i²t of line to ground fault current. For line to ground fault, the fault current and duration time when fault take place as well as the relay operating time have been concerned. The line type I, OHGW not connected to the neutral of substation power transformer, give the short circuit current magnitude which is less than the current from Line Type II, OHGW connected to the neutral of substation power transformer. So the line type I gives the smaller OHGW sizes than line type II. For the short circuit current not greater than 3 kA, the 25 mm² can be used for the distance of 3 km from substation and 35 mm² from that location should be used. For the short circuit current not greater than 7 kA, the 35 mm² should be used for distance of 500 m from the substation, 70 mm² between 500 m-3 km and the 35 mm² beyond that location should be used. For the short circuit current not greater than 12 kA, the 50 mm² should be used for 500 m from substation, 70 mm² should be used between 500 m-3 km and 35 mm² for line beyond that location should be used.