Abstract: Abstract: As one of the most common faults in substations, DC system grounding has a great impact on the stability of power system. Therefore, as a substation operator, only by being familiar with its principle and the principle of daily DC system fault handling can we better ensure the stable and reliable operation of the power system power supply, so this paper takes a 110kV substation DC system grounding event as an example to provide reference for the daily work of substation operators.