Why Can't the Neutral Points be Grounded at the Same Time When Two Transformers are Running Side by Side?

In high current system, in order to meet the requirements of relay protection sensitivity coordination, one part of the main transformer is grounded, and the other part is ungrounded.

The neutral points of two main transformers in one station are not grounded at the same time, so the coordination of zero sequence current and zero sequence voltage protection is mainly considered.

In a substation with multiple transformers running in parallel, one part of the neutral points of the transformer is grounded and the other part is ungrounded. In this way, the level of ground fault current can be limited in a reasonable range, and the size and step of the entire grid zero-sequence current can not be affected by the change of operation mode, and the sensitivity of zero-sequence current protection of the system can be improved.