Daily Maintenance and Care of Oil-Immersed Transformers

Oil-Immersed Transformers feature good heat dissipation, low loss, large capacity, and low price. Most transformers currently operating on the power grid are oil-immersed transformers. Although dry-type transformers have advantages over oil-immersed transformers, oil-immersed transformers have their own unique merits as long as they are properly maintained and cared for.

During operation, transformers may experience the following faults:

1、Transformer oil leakage, oil level too high or too low, oil temperature too high.

2、Abnormal instrument indications.

3、Excessive internal noise from the transformer.

4、Cracks or severe damage on the transformer bushing.

5、Continuous gas relay alarm.

So, how can these problems be identified in the daily operation and maintenance of oil-immersed transformers? Below are some inspection standards for the daily operation and maintenance of oil-immersed transformers.

1、Check whether the transformer oil temperature exceeds the allowable range. The service life of the transformer has a certain relationship with temperature. As the temperature rises, the oxidation rate of the oil increases, and the oil ages faster. When checking the temperature of the transformer oil, do not only pay attention to the indication on the transformer's thermometer; the ambient temperature should also be measured. Since each transformer has different load sizes, cooling conditions, and seasons, the operation of a transformer cannot be judged solely based on whether the top oil temperature exceeds the allowable value. Therefore, when inspecting the transformer, the ambient temperature, load conditions, and oil surface height should also be recorded. Compare these with previous values for analysis and judgment to determine whether the transformer is normal.

2、A normal operating power transformer produces a uniform humming sound. This is the result of vibration caused by the force generated in the silicon steel sheets of the core due to the alternating magnetic flux in the core. Overvoltage and overcurrent causing louder sounds than usual, loosened individual parts, and discharge sounds caused by external weather conditions can all cause abnormal noises in the transformer. The causes of abnormal noises are numerous and complex, requiring us to continuously accumulate experience in practice to determine the reasons for these noises.

3、Oil seepage can cause the oil level to drop, misleading our judgment of transformer faults. Check that the transformer cover screws are complete and without oil seepage; the radiator tubes of the transformer body are intact, clean, and without oil seepage; the oil drain valve is tightly closed and without oil seepage.

4、Check that the glass and rubber of the explosion-proof tube are undamaged. The explosion-proof tube can release high-pressure gases and oil generated during a fault, reducing and relieving the pressure on the tank.

5、Check the color of the silica gel in the breather. The silica gel serves to remove moisture from the inhaled air. The silica gel is normally blue-white when effective. When the silica gel turns light yellow or other colors, it indicates that the silica gel has failed and needs replacement.

There are many more inspection standards. In summary, when checking the operating condition of the transformer, remember to turn off the lights to check whether various connections and instrument indications are normal, listen for any abnormal sounds from the equipment, and smell for any special odors. This can help identify many abnormal points, facilitating the maintenance of the transformer.