Transformers are very expensive equipment not only in purchase but also in repair. The only way to avoid breakdowns is to have proper transformer maintenance through periodic tests and routine inspections. These checks go a long way in providing warning signs of an impending service problem. Corrective measures can then be taken at a far less expensive juncture. Interpretation of maintenance data from a transformer is critical to identifying problems before they develop into extensive damage. The transformer’s long life and reliability depend on any transformer repair service accorded to the transformer in its life-span. It is particularly important to pay attention to information about the possible need of soon replacement.
Paying Attention to Variations in Sound Level
A transformer produces sound as it delivers its functions. The level of audibility of a transformer mainly depends on the ratio of applied voltage to the number of active turns. It could also be dependent on the degree of distortion on the load current. In lay man’s terms, a noticeable sound level change could imply the input or output voltage are faulty. This is because changes in voltage influence the sound level greatly. With every increase in voltage level, there is an equal increment in sound.
After verifying that the measured voltage is within the rating of the nameplate for the settings of the transformer’s tap, there should be enough grounds to take service action. In the case that the measured voltage is higher than the tap voltage by 5% or more, your transformer might be over-excited. To correct this, the transformer needs to be de-energized and a new tap selected and tested to be within 5% of the measured voltage.
There are a few more reasons that change the sound level. These include shots in the main winding. Carry out tests on each keeping a good record of the data. Some problems are only visible after analysis of data, so it is important to practice good data recording practices.
Evaluation of Tank Heating
A good indicator of overheating in a transformer is hot spots on the surface of tanks of liquid-filled transformers. If the hot-spots are so severe that they discolor or blister the paint on the tanks, there might be shorted or open lead connections. Changes in current paths might result from such temperatures leading to induced currents on the wall of the tank. This could pose a great danger especially to electrical technicians who are inexperienced. Transformers that have heat problems should be de-energized as soon as possible. Changes in the impedance measurements are particularly critical as they may show changes in the internal connections.
It is also important to take an oil sample from the liquid-filled transformers for gas-in-oil analysis. If the extreme temperatures persist and/or the gas -in-oil analysis indicates a consistent rise in combustible gas in the oil, an internal inspection should be done. The internal inspection should be able to clear up on which internal connections are faulty. If a connection is identified as defective, repair organization may be able to repair the transformer.