A Relation of the Parameters of Grounding Device with the Level of Over-voltage when a Surge Arrester Triggered

It is known that high-frequency rapidly damped oscillations occur at the front of the voltage pulse remaining after the operation of the nonlinear surge arrester (SPD). The amplitude of these oscillations is determined by the circuit properties in which the SPD stands, and it can significantly exceed the level of the remaining voltage at the SPD, negatively affecting the internal insulation of the high-voltage equipment elements. The parameters of these high-frequency oscillations are determined by the grounding device (GD) parameters in which the SPD is connected. Due to the results analysis of the numerical simulation of the current flow processes in the GD, it is shown that the GD impedance is complex, and the transient resistance of the GD can be used to describe the GD reaction to pulsed action. A distinctive feature of the transient resistance is their high sensitivity to load parameters in the high-frequency interval of the action (at the pulse front) and the steady-state value of the GD resistance after 10–20 microseconds, determined in stationary modes. The maximum values of high-frequency overvoltages are determined by the maximum values of a transient resistance. The numerical simulation results of the lightning current spreading process in a 3D formulation for various GD configurations showed that there is an optimal parameters ratio depending on the time constant of the soil (the product of dielectric constant and conductivity), at which minimum amplitudes of high-frequency oscillations are observed.