(1) Temperature test: Whether the transformer is operating normally depends on the temperature level. The regulations stipulate that the upper oil temperature shall not exceed 85C (i.e. a temperature rise of 55C). Generally, transformers are equipped with dedicated temperature measuring devices.

(2) Load measurement: In order to improve the utilization rate of transformers and reduce energy loss, it is necessary to measure the actual power supply capacity that transformers can bear during operation. The 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 regulations require 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, insulation resistance measurement must be carried out to prevent insulation aging and accidents. When measuring, efforts should be made to stop the operation of the transformer. The insulation resistance value of the transformer should be measured using a megohmmeter, and the measured resistance should not be less than 70% of the previously measured value. When using a megohmmeter, the low-voltage coil can be rated at 500 volts.