Transformer detection requires the transformer to be shut down. Generally there are the following steps
1. After the transformer is stopped, first perform the transformer once or twice and hang the ground wire.
2. Secondly, clean the surface of the transformer and check whether the connection of the circuit is loose, and then check whether the oil level of the transformer is lower than the normal oil level. If these are not normal, you need to deal with it and refuel
3. Transformer testing, such as the insulation resistance straight group and the discrimination ratio between high and low voltage, etc., these data need to be measured
Finally, if it is good, you can go online.