The voltage regulation of the transformer is realized by switching the transformer tap through the rotary transformer switch, thereby changing the transformation ratio of the transformer. There are two switching methods: non-energized switch, called non-excited voltage regulation. The voltage adjustment range is usually within + 5%. The other is on-load switching, called on-load voltage regulation. The voltage adjustment range can reach + 30%. For transformers of 100kV and below, transformers with at least one-stage voltage should use on-load voltage regulation. In summary, the main transformer of this substation uses on-load voltage regulation.