У вялікім ток system, in order to meet the requirements of relay protection sensitivity coordination, part of the main transformer needs to be заземлены, and the other part is not grounded.

If the neutral points of two main transformers in one station are not grounded at the same time, the main consideration is the coordination of zero-sequence ток and zero-sequence voltage protection.

A substation with multiple transformers running in parallel usually adopts a method in which the neutral point of some transformers is grounded, while the neutral point of the other part of the transformer is not grounded. In this way, the ground fault current level can be limited within a reasonable range, and at the same time, the size and step-by-step situation of the zero-sequence current of the entire power grid will not be affected by changes in the operation mode as far as possible, and the sensitivity of the zero-sequence current protection of the system will be improved.