This study depicts the electric field distributions inside a typical 500/220 kV open distribution substation under during different working conditions, Hot-Stick and Bar-Hand positions. The electric field is investigated for different workers heights of 1m, 1.5m and 1.8m above ground for (Hot-Stick position) and at height levels of 8m, 11m, 14m and 17m above ground as positions for live line maintenance under 220 kV Busbars, 500 kV Busbars, 220 kV Incoming and Outgoing feeders and 500 kV Incoming and Outgoing feeders respectively. The simulation results are compared with field values measured inside this typical substation and compared to international guidelines for personnel exposure to electric field.