Abstract: After the widespread application of low resistance grounding transformer system in 10 kV distribution network system, it was found during operation that if the zero sequence current transformer is wrongly connected and the built-in parameters of the device are not properly adjusted, it will cause hidden dangers of protection misoperation. This article analyzes the hidden dangers in the low rent grounding system of substation grounding transformers, summarizes the hidden danger investigation and rectification ideas of low resistance grounding transformer systems, and formulates hidden danger investigation plans from the aspects of circuit, device parameters, and protection functions. Accumulated technical experience for acceptance and inspection of low resistance grounding systems in substations.