Analysis of Transient in Secondary Cable Due to a Direct Lightning Strike on Grounding Grid

When a substation suffers from a lightning strike, beside the interference from the space, there are two main ways in which the transient disturbance affects the secondary cable through the grounding system: the uneven potential distribution and the mutual inductance between the secondary cable and the ground conductor. In this article, a circuit model of grounding grid is developed taking into consideration the mutual inductance between the secondary cable and the ground conductor. While a circuit model of the secondary cable is established with the consideration of uneven ground potential distribution and the mutual inductance between the secondary cable and the ground conductor. Then, the two models are unified to calculate the transient disturbance in the secondary cable due to a lightning strike on the grounding grid. The feasibility of the method is verified through experiments. Then, the effect of the ground potential difference of the grounding grid and its mutual induction with the cable is analyzed. The results show that both the mutual inductance between the cable and the grid and the uneven ground potential distribution greatly affect the transient disturbance in secondary cable.