What are the requirements for commissioning and decommissioning of dry type transformers?

(1) Dry type transformers newly put into operation must be subjected to 5 impulse tests at rated voltage, and 3 impulse tests after overhaul.

(2) When the dry type transformer is put into operation, put the cooler first, the cooler will run for a period of time (about 15min), and then stop when the oil temperature no longer rises. When shutting down, stop the dry-type transformer first.

(3) In the 110kV and above neutral point direct grounding system, when the dry-type transformer is put into operation or out of operation, the neutral point must be grounded before operation, and then decide whether to disconnect it according to regulations and requirements. The arc suppression coil connected to the neutral point of the dry-type transformer should be withdrawn first and then put into operation. Do not connect the neutral points of two dry type transformers to the neutral bus of one arc suppression coil at the same time.

(4) During power failure operation, first stop the switch on the load side, and then stop the switch on the power supply side (from low to high when there are multiple power supplies); first pull the dry-type transformer side switch, and then pull the bus side switch. The opposite is true for power supply operation.

(5) After the standby dry type transformer is put into operation, it should be confirmed that the load has been brought on according to the actual position of the equipment and the indication of the meter, so that the running dry-type transformer can be powered off. For dry-type transformers with diagonal and 3/2 connections, although the dry-type transformer has been powered off, the heavy gas and differential protection actions of the dry-type transformer can still cause the switch on the closing side to trip. The gas protection should be changed to the signal position or the gas should be withdrawn according to the actual situation and on-site regulations.

(6) Station dry-type transformers are not allowed to be paralleled for a long time. The low-voltage side circulating current can be cut with the low-voltage knife switch, and the dry type transformer used in the no-load station can be cut with the high-voltage knife switch.