Numerical Analysis of Transient in Secondary Cable above a Grounding Grid under a Lightning Strike

When a lightning strikes a substation, transient disturbance will affect the secondary cable on the grounding grid through the uneven ground potential distribution and the mutual inductance between the cable and the ground grid. In this paper, a numerical method to calculate the transient disturbance in the secondary cable is presented. Based on the method of moments, a circuit model of grounding grid is developed taking into consideration the mutual inductance between the secondary cable and the ground conductor, while a transmission line 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. Simulation results show that the mutual inductance between the double end grounded cable and the grounding conductors greatly affects the transient disturbance in secondary cable. While the uneven potential distribution mainly affects that by forming a potential difference between both ends of the cable and the ground grid.