Key Points of Transformer Daily Maintenance and Troubleshooting for Common Faults

In the power system, transformers are extremely crucial equipment, just like the "hub" of power transmission, ensuring that electrical energy can be smoothly converted between different voltage levels and delivered to various places. Given that transformers are prone to be affected by numerous factors during long-term operation, it is of great significance to conduct daily maintenance and promptly troubleshoot common faults to maintain their reliable operation. The following elaborates on the key points of transformer daily maintenance and the troubleshooting of common faults in detail.

Cleanliness: It is necessary to regularly check whether there is dust or oil accumulation on the surface of the transformer. Excessive dust will affect heat dissipation, and oil stains may indicate oil leakage or other hidden problems. Maintenance personnel can use clean rags to wipe the surface to clearly observe the condition of the equipment.

Connection Parts: Carefully check whether the connection terminals, busbar connections and other parts are loose and whether there are signs of overheating and discoloration. Loose connections will increase the contact resistance and cause heating, and in severe cases, may lead to electric arc and other accidents. Judgment can be made by observing oxidation and scorching conditions and using tools to test the tightness of the connections.

Integrity of the Enclosure: Check whether the enclosure of the transformer has cracks, deformations or damages. Damage to the enclosure will affect its protective performance, and oil leakage may occur in oil-immersed transformers, destroying the insulation and heat dissipation conditions.

Oil Temperature: Transformers generate heat during operation, and the oil temperature is an important indicator reflecting their operating status. Use the thermometer on the oil tank to record the oil temperature regularly and compare it with the normal range. Generally, the upper oil temperature of a normal oil-immersed transformer should not exceed 85 °C (varying according to different models and specifications). Abnormal increases in oil temperature may be caused by overload, poor heat dissipation or internal faults, and further investigation is required.

Oil Level: The level of the oil is very important. A too low oil level will affect insulation and heat dissipation, while a too high oil level may cause oil overflow. Check whether the oil level is within the normal range through the oil level indicator on the conservator, and pay attention to the normal fluctuations of the oil level with temperature changes. Analyze the reasons when abnormal changes occur.

During normal operation, transformers emit a uniform and continuous "buzzing" sound, which is generated by the vibration of the iron core caused by the alternating magnetic flux. Maintenance personnel should listen to the sound based on their experience. Abnormal sounds, such as louder sounds, noisy sounds or intermittent sounds, may indicate loose internal components, iron core faults or winding short circuits, and the transformer needs to be shut down for further inspection with professional instruments.

Regularly measure the insulation resistance of the transformer. Use an insulation resistance tester to measure the resistance values between each winding, between the winding and the iron core, and between the winding and the enclosure. The resistance should meet the factory standards. If it drops significantly, it may be caused by moisture absorption, insulation aging or local damage, and corresponding repair measures such as drying and replacing materials need to be taken.

For transformers equipped with a cooling system, check whether the cooling fans are operating normally, whether there are abnormal vibrations and noises, and whether the heat dissipation fins of the radiator are clean and blocked, to ensure that the cooling system can effectively take away heat and maintain the normal oil temperature.

First, check the load condition of the transformer to see if it is overloaded. Then check whether the cooling system is working properly, as overload and poor heat dissipation are common causes of overheating.
Use infrared thermal imaging instruments and other equipment to detect whether there are local overheating points in key parts such as the iron core and windings. If there are, it may be internal faults such as winding turn-to-turn short circuits or multiple grounding points of the iron core, and further disassembly and inspection and repair are required.

Carefully look for the oil leakage parts from the appearance. Oil leakage usually occurs at the welds of the oil tank, sealing gaskets and valve interfaces. Observe whether there are oil stains or drops. For slight oil leakage, a magnifying glass can be used for searching.
If the oil leakage is caused by aging or damage of the sealing gasket, replace it in time and ensure good sealing. For oil leakage at the welds of the oil tank, repair by welding according to the specific situation. During the maintenance, take good safety precautions and handle the transformer oil properly to avoid accidents and pollution.

When a short circuit is suspected, first measure the DC resistance of the windings and compare whether each phase is balanced. If the DC resistance of a certain phase is significantly smaller, there may be a turn-to-turn short circuit. Check the operation of the protection devices to analyze the location and severity of the fault.
Then use professional electrical testing equipment to comprehensively test the windings, determine the location of the short circuit, repair or replace the damaged windings, and conduct electrical performance tests after repair to ensure normal use.

Abnormal sounds indicate internal problems. Listen carefully to the characteristics of the sound again to determine the approximate location where the sound is generated. For example, if the abnormal sound comes from the iron core, it may be caused by loose clamping bolts or foreign objects between the silicon steel sheets. It is necessary to open the enclosure of the transformer to tighten and check and clean up the foreign objects.
If the abnormal sound comes from the winding part, it may involve problems such as loose windings or short circuits. Combine the short circuit fault troubleshooting methods and the inspection of the appearance and insulation of the windings to find the causes and solve them.

In conclusion, the daily maintenance and fault troubleshooting of transformers are highly professional and complex tasks. Maintenance personnel need to operate carefully in accordance with relevant regulations, discover and solve problems in a timely manner to ensure the long-term safe and stable operation of transformers and lay a solid foundation for the reliable power supply of the power system.