The operating voltage of the power transformer should generally not be higher than 105% of the operating tap voltage, and should not exceed the maximum operating voltage of the system. For special usage conditions, it is allowed to operate at no more than 110% of the rated voltage.

　　The oil temperature of the top layer of the oil-immersed transformer should not exceed the operation regulations or the manufacturer's regulations. For transformers with forced oil circulation and water cooling, the oil temperature of the top layer should not exceed 700°C.

　　The instrument indication of the transformer put into operation should be monitored frequently to grasp the operation status of the transformer in time. If defects or abnormalities are found, measures should be taken to eliminate them in time. If it cannot be eliminated at that time, surveillance must be strengthened. Prevent the expansion of accidents and determine countermeasures as soon as possible.

　　1. Water supply mode of transformer cooling water system

　　The cooling water is generally taken from the technical water supply pipe of the unit when the transformer is in load operation, and the cooling water is generally taken from the public water supply main pipe of the power station during no-load operation, and is pressurized by the no-load cooling water pump to supply water to the transformer.

　　2. Drainage method of transformer cooling water system

　　Under normal circumstances, the cooling water of the transformer under no-load and load conditions is discharged to the draft pipe of the unit through the main drainage pipe of the technical water supply system of the unit. There is a connecting valve between the drain pipes of each transformer. The connecting valve is normally closed. When the draft pipe of the unit is required to be emptied and the transformer is still in narrow-load operation, the connecting valve between the transformer and the adjacent transformer can be opened to discharge the no-load cooling water to the draft pipe of other units.