Investigating the Impact of Ground-Return Parameters on Transitional Voltages at Switching-Off Unloaded Power Transmission Lines

The electrical parameters calculations of the overhead transmission lines are very important to the areas concerned to electromagnetic compatibility and transitional processes in power systems. Therefore, accurate calculations of these parameters were performed in this research, taking into account the ground-return parameters (Carson correction factors). The return parameters of the homogenous ground (one-layered ground) the overhead transmission line passes over were taken into consideration via using the actual value of the ground resistivity. In this research, the effect of ground-return parameters on transitional voltages at switching-off an unloaded transmission line using SF6 circuit-breaker was recorded and clarified. As a result, when the ground-return parameters are taken into account, the overall transmission line inductance increases. This has an obvious impact on the rate of rise of recovery voltage for the SF6 circuit-breaker inter-contact space, that consequently affects the transitional voltages during switching-off process.