To ensure the normal operation of the transformer, the following tests should be conducted regularly:

(1) Temperature testing：The operation status of the transformer is normal, and the temperature is very important. The regulations stipulate that the upper oil temperature shall not exceed 85C (i.e. temperature rise of 55C). Generally, transformers are equipped with dedicated temperature measurement devices.

(2) Load measurement：In order to improve the utilization rate of transformers and reduce the loss of electrical energy, it is necessary to determine the true power supply capacity that the transformer can bear during operation. Measurement work is usually carried out during the peak electricity consumption period of each season, using a clamp ammeter for direct measurement. The current value should be 70-80% of the rated current of the transformer. If it exceeds the limit, it indicates overload and should be adjusted immediately.

(3) Voltage measurement：The regulation requires that the voltage variation range should be within ± 5% of the rated voltage. If it exceeds this range, a tap should be used to adjust the voltage to reach the specified range. Generally, a voltmeter is used to measure the terminal voltage of the secondary coil and the terminal voltage of the terminal user.

(4) Insulation resistance measurement： In order to keep the transformer in normal operation, it is necessary to measure the insulation resistance to prevent insulation aging and accidents. When measuring, efforts should be made to stop the transformer from running. The insulation resistance value of the transformer should be measured using a shake table, and the measured resistance should not be lower than 70% of the previous measured value. When selecting a shake table, the low-voltage coil can use a voltage level of 500 volts.