For grounding of the transformer main body, the grounding type is determined by the operating voltage of the transformer (the higher of primary and secondary voltage).
　(1) Class A grounding is required when the operating voltage is high voltage.
　(2) When the operating voltage exceeds 300 V, Class C grounding is required.
　(3) When the operating voltage is 300 V or less, Class D grounding is required.

2023.8.7：FAQ What are the 3 key points of transformer grounding?