The Best Way To Judge A Transformer Fault Intuitively

The method of judging if a transformer has a fault can be divided into two categories: intuitive judgment and analysis judgment. Intuitive judgments can be made about the transformer fault based on the aspects of sound, smell, color, and temperature.

1.Check by Sound

The alternating current passing through the transformer winding generates a periodic alternating magnetic flux in the iron core, causing the steel sheet to magnetize. An average “humming” sound is produced by the electromagnetic force between the wires of the winding and the magnetic force between the seams of the core. The sound is abnormal if it is uneven or other.

1. Higher than usual sound. If it is large and uniform, there may be overvoltage on the power grid or a transformer overload. When large power equipment is involved (such as large motors), the load changes greatly. Check the voltage and circuit table to determine the fault’s nature. Next, change the power grid operation mode and reduce the transformer’s load or stop the transformer’s operation depending on the situation.
2. It is possible that the transformer core is faulty if the sound is loud and noisy. For example, when the clamp or the screw for pressing the iron core is loose, the instrument’s indication is generally normal, and the color, temperature, and oil level of the insulating oil do not change much. It is then necessary to stop the transformer’s operation.
3. There may be a partial discharge on the surface of the transformer or bushing when there is a “squeak” sound. In bad weather or at night, corona glow or small blue and purple sparks can still be seen on the casing. At this point, the dirt on the casing surface should be removed, and silicone oil or silicone grease should be applied. Place your ear close to the oil tank of the transformer, and you will hear the “squeak” or “crack” sound inside the transformer due to local or poor electrical contact. The sound varies with distance from the fault location. You might hear a “crackling” sound when standing in front of the transformer if there is poor grounding or ungrounded metal parts. The transformer must be stopped at this point, and the distance between the iron core and each live part must be checked.
4. As a result of the vibration of the iron core, we think that some parts of the transformer are in mechanical contact when there is a continuous and regular impact or friction sound in the sound. Increase the spacing or strengthen the fixing if it occurs at the oil pipe or wire on the outer wall of the fuel tank.
5. There may be a serious fault in the winding causing the nearby parts to become severely heated if you hear the sound of boiling water. Poor tap changer contact and severe overheating of local points are likely to cause this sound. Transformer operation should be stopped immediately for maintenance at this time.
6. There may be a breakdown in the insulation of the transformer body when there is a large and uneven popping sound in the sound. During this time, the transformer should also be stopped immediately for maintenance.

2.Check by Smell and Color

It will smell and look different when the transformer fails internally and various components overheat.

1. Porcelain sleeve terminal tightening part is loose, and the surface has become overheated and oxidized, resulting in discoloration and abnormal odor.
2. Porcelain sleeve terminal tightening part is loose, and the surface has become overheated and oxidized, resulting in discoloration and abnormal odor.
3. The porcelain casing produces corona, which emits a strange odor, and the cooling fan and oil pump emit a burning scent when burned.
4. In addition to excessive moisture absorption, damaged gaskets, and too much water entering the oil chamber, the hygrometer discolors.

3.Check by Temperature

1. For transformers in operation, check that each terminal of the bushing is tightly connected to the busbar or cable and there are no signs of heating.
2. When the temperature on the thermometer exceeds the allowable limit specified in the operating standards temperature, it may be due to overload, abnormal ambient temperatures, malfunction of cooling fan and oil pump, not opening the radiator valve, insufficient oil due to leakage, damage to the thermometer, or internal failure of the transformer.

It should be noted that the above-mentioned judgments on transformer accidents made on the basis of sound, vibration, smell, discoloration, and temperature, must be used only as a preliminary intuitive judgment on the spot of the accident. It is important to understand that an internal fault of a transformer is not just an intuitive reflection of a single aspect, but rather it is an indicator of multiple factors and sometimes even appears to be false.

Measurement and comprehensive analysis are therefore vital for determining the cause of failure, defining the nature of the accident, and proposing a more complete and reasonable treatment.