Working grounding is to ground the neutral point of the transformer. Its main function is to stabilize the system potential, that is, to reduce the risk of overvoltage in the low-voltage system due to one phase grounding, high and low voltage short circuit, etc., and to prevent insulation breakdown.
Protective grounding refers to connecting the metal part of an electrical device that is not energized under normal circumstances to a grounding device to prevent this part from suddenly becoming energized in the event of a fault and causing harm to the human body.