Provisions on the order of transformer power-off and power-on operations and classification of transformer working conditions

1.1 Transformer power outage operation sequence

The order of stopping and supplying power to the main transformer is: when power is off, the load side is stopped first, and then the power supply side; when power is supplied, the power supply side is supplied first, and then the load side.

The reason is:

a. When there are multiple power sources, shut down the power in the above order to prevent the transformer from reverse charging. If the power supply side is shut down first, a fault may cause the protection

The protection device may malfunction or refuse to operate, prolonging the fault clearing time and expanding the scope of power outage.

b. Power is supplied step by step from the power supply side, so that if a fault occurs, it is easy to check according to the power supply range.

c. When the bus voltage transformer on the load side is equipped with a low-frequency load reduction device and is not equipped with a current blocking device, the power supply side is shut down first when a power outage occurs.

Feedback from large synchronous motors can cause the low-frequency load reduction device to malfunction.

1.2 Classification of transformer working status

The working status of the transformer after operation is divided into four states, namely, operating state, hot standby state, cold standby state and maintenance state.

Operating status: The circuit breaker and disconnector of the transformer are in the operating working state of the closed position;

Hot standby state: the transformer only disconnects the circuit breaker and the isolating switch is still in the closed position and in a non-operating working state;

Cold standby state: the transformer circuit breaker and disconnector are in the non-operating working state in the open position;

Maintenance status: All circuit breakers and isolating switches of the transformer have been disconnected, the ground wire has been installed, the signboard has been hung, and the temporary

The non-operating state of safety technical measures such as barriers.