Normal operation of transformer
①Rated operating mode. The transformer can operate according to the nameplate specifications under specified cooling conditions. The allowable temperature during operation of the oil-immersed transformer should be checked based on the upper oil temperature. The upper oil temperature should comply with the manufacturer's regulations, but the maximum temperature should not exceed 95°C. In order to prevent the transformer oil from deteriorating too quickly, the upper oil temperature should not frequently exceed 85°C.
The external voltage of the transformer should generally not exceed 105% of the rated value. At this time, the secondary side of the transformer can carry rated current. In individual cases, after testing or with the consent of the manufacturer, the applied voltage can be 110% of the rated voltage.
② Overload is allowed. Transformers can operate under normal overload or accident overload conditions. Normal overload can be used frequently, and its allowable value is determined based on the load curve of the transformer, cooling conditions, and the load carried by the transformer before overload. Accident overloading may only be used in accident situations (transformers that are still operational).
The allowable value of accident overload should comply with the manufacturer's regulations; if there are no manufacturer's regulations, the self-cooling oil-immersed transformer can be operated according to the requirements in the table.
(a) Abnormal phenomena during operation. If any abnormal phenomena are found during operation of the transformer (such as oil leakage, insufficient oil level in the oil pillow, abnormal heating, abnormal sound, etc.), efforts should be made to eliminate them. If any of the following conditions occurs, repairs should be stopped immediately.
① The internal sound is loud, very uneven, and there are popping sounds.
②Under normal cooling conditions, the temperature is abnormal and continues to rise.
③Inject oil into the oil pillow or spray into the explosion-proof pipe.
④ Oil leakage causes the oil level to drop below the limit on the oil level indicator.
⑤ The oil color changes too much and carbon appears in the oil.
⑥ The casing is severely damaged and discharged.
(b) Unallowable overload, abnormal temperature rise and oil level. If the overload of the transformer exceeds the allowable value, the load of the transformer should be adjusted in time. When the transformer oil temperature rises beyond the allowable limit, the cause should be identified and measures should be taken to reduce it. Therefore, the following work must be performed.
① Check the load of the transformer and the temperature of the cooling medium, and check with the temperature that should be achieved under this load and cooling temperature.
② Check the temperature gauge.
③ Check the mechanical cooling device of the transformer or the ventilation condition of the transformer room.
If it is found that the oil temperature is more than 10°C higher than usual under the same load and cooling temperature, or the oil temperature continues to rise while the load remains unchanged, and the cooling device, transformer room ventilation and thermometer are all normal, it may be an internal fault of the transformer (such as Fire in the iron core, short circuit between coil layers, etc.), stop repairs immediately.
If the oil in the transformer has solidified, the transformer is allowed to be put into operation with load, but attention must be paid to whether the upper oil temperature and oil circulation are normal.
When it is found that the oil level of the transformer is significantly lower than the oil level that the oil temperature should be at that time, oil should be added immediately. If the oil level drops rapidly due to a large amount of oil leakage, it is forbidden to change the gas relay to only act on the signal, but measures must be taken quickly to plug the leakage and refuel immediately.
