How to conduct no-load test operation of transformer? What are the steps?

How to conduct no-load test operation of transformer?

(1) Before putting the transformer into operation, it must be confirmed that the transformer meets the operating conditions.

(2) During trial operation, first place the tap changer in the middle gear position and conduct a no-load trial operation; then switch to other gears to observe whether the contact is good and whether the operation is reliable.

(3) When the transformer is put into operation for the first time, it can be switched on at full voltage. If conditions permit, the voltage should be gradually increased from zero. When closing due to impact, the transformer is generally put in from the high voltage side.

(4) After the transformer is energized for the first time, the operation time should not be less than 10 minutes in order to carefully monitor whether there are any abnormal noises inside the transformer (you can use a dry thin wooden stick or an insulating rod to touch the transformer shell with one end , put one end to your ear and listen carefully to see if the sound from the transformer is slight and even after power is supplied). If there are intermittent explosions or sudden violent sounds, the trial operation should be stopped immediately (cut off the power supply of the transformer).

(5) Regardless of whether the transformer is newly installed or overhauled, it should be closed with full voltage impact 5 times. There should be no abnormal phenomena. The excitation inrush current should not cause the relay protection device to malfunction to test the transformer. Whether the insulation performance, mechanical performance and relay protection of the winding are qualified.

(6) For transformers cooled by strong wind or strong oil circulation, the temperature rise under no-load should be checked. The specific method is: without turning on the cooling device, run the transformer without load for 12 to 24 hours, and record the ambient temperature and the oil temperature of the upper part of the transformer. When the oil temperature rises to 75°C, start 1 or 2 sets of coolers for heat dissipation, continue to measure the temperature and record the oil temperature until the oil temperature is stable.