What tests should be conducted before putting a transformer into use if it has been out of service for one month or has been idle or out of service for more than six months?
1. After the transformer is shut down for one month, the insulation resistance should be measured before resuming power transmission. Only after passing the test can it be put into operation.
2. Transformers that have been idle or suspended for more than 6 months should undergo insulation resistance and insulation oil withstand voltage tests before being put into operation.
3. The special service life of drainage and irrigation transformers in dry and cold areas can be appropriately extended, but not exceeding 8 months.
What regulations must be followed for the operation and shutdown of transformers?
(1) Newly commissioned transformers must undergo 5 impulse tests at rated voltage and 3 tests after maintenance.
(2) When the transformer is put into operation, first place it in the cooler. The cooler runs for a period of time (about 15 minutes) and stops when the oil temperature no longer rises. When stopping operation, first stop the transformer.
(3) In a neutral point direct grounding system of 110kV and above, the neutral point must be grounded before the transformer is put into operation or stopped. After the operation is completed, determine whether to disconnect according to regulations and requirements. The arc suppression coil connected to the neutral point of the transformer should be pulled out first before being put into operation. Do not connect the neutral points of two transformers to the neutral bus of the arc suppression coil at the same time.
(4) During power outage operation, first stop the load side switch, and then stop the power side switch (from low to high when multiple power sources are stopped); First pull the transformer side knife switch, then pull the busbar side knife switch. The situation is exactly the opposite during power operation.
(5) After the standby transformer is put into operation, it should be determined that the load has been loaded based on the actual location of the equipment and the indication of the electricity meter, in order to cut off the power supply of the operating transformer. Although the transformers on the diagonal and 3/2 connections have been disconnected, the heavy gas and differential protection of the transformers can still cause the switch on the closed side to trip. According to the actual situation and on-site regulations, switch the gas protection to the signal position or withdraw the gas.
(6) Long term parallel operation of transformers within the station is not allowed. Low voltage knife switches can be used to cut off the circulating current on the low voltage side, while high-voltage knife switches can be used to cut off transformers in no-load stations.
