Study on the Transient Distribution Characteristics of Step Voltage in Prefabricated Substations Under Lightning Strike Conditions

Prefabricated substations, due to their enclosed compartments and metal casing structures, exhibit significantly different transient step voltage distribution patterns under lightning impulse compared with conventional civil construction substation buildings, posing a greater threat to the safety of personnel within the station. This study takes the transformer prefabricated compartment of a 110 kV operational prefabricated substation in China as the research object and constructs an electromagnetic model of the primary system, including the main grounding grid, prefabricated compartment body, and compartment grounding leads, based on the method of moments. The study systematically investigates the step voltage distribution characteristics inside the compartment and on the ground surface under three lightning strike conditions: compartment corner, edge, and surface, and conducts an in-depth analysis of the optimization effects of changes in the compartment spatial layout and the number of grounding points on the step voltage. The results show that under the same lightning strike conditions, there are significant differences in the step voltage distribution patterns inside and outside the compartment; changing the lightning strike location will significantly affect the step voltage distribution patterns inside and outside the compartment; adjusting the compartment's spatial position and the number of grounding points can effectively optimize the step voltage inside and outside the compartment. It is expected that the results of this study will provide data support for the lightning protection design of the primary system of prefabricated substations and are of great significance for improving the safety performance of such substations.