What are the causes of dry-type transformers burning out during operation?

1 Fault Phenomenon

I am engaged in front - line fault maintenance work, and recently encountered problems with dry - type transformers. Dry - type transformers have a simple structure, are convenient for transportation, and easy for maintenance. They are widely used in power distribution places with relatively high environmental protection requirements. Because of their good fire - resistance, they can be installed in load - center areas to reduce voltage loss and power loss.

The property management company I work for manages 11 residential communities, with a total of 56 transformers, with a voltage level of 6000/400V. Among them, there are 38 dry - type transformers, model SCB9, with a capacity of 160 - 630kVA, all installed in box - type closed high - voltage switch cabinets. The power distribution stations in these communities have been put into operation for less than 2 years, and 5 dry - type transformers in operation have been burned one after another, which has seriously affected the lives of residents. I deeply feel the great responsibility and must thoroughly investigate the reasons.

2 Cause Analysis

As a front - line maintenance worker, my colleagues and I inspected, tested, analyzed the burned dry - type transformers. During the 5 accidents, the weather was good, there was no water accumulation or moisture in the cable trench at the bottom of the transformer, and there was no over - voltage in the system before and after the accidents. Checking the recent high - voltage test reports, the insulation was good, and the DC resistance difference met the standards.

To find out the reasons, the company invited relevant experts for consultation. I participated in the on - site investigation and found that the heat dissipation air ducts of the burned dry - type transformers were blocked. After dissection, it was seen that the insulation of the residual coils was brittle and uniformly cracked, indicating that the coils had been operating at high temperatures for a long time.

It was learned that the accidents all occurred between July and September, with hot weather and peak electricity load. The dry - type transformers had been operating at full load in the closed cabinets for a long time. Further inspection revealed that the heat dissipation air ducts were blocked by the slot plates of the control cables, causing the temperature of the transformers to continue to rise. Moreover, the only temperature alarm device was installed in the transformer room, unable to timely transmit over - temperature alarms.

Long - term high - temperature operation reduces the insulation resistance. Especially, the high - voltage coils have a high voltage level, and the decrease in insulation strength is prone to discharge, increasing the leakage current between the high - voltage layers, turns, and to the ground of the transformer, increasing the active power loss and the temperature continuously, forming a vicious cycle. Eventually, the insulating material loses its insulating performance, and inter - layer and inter - turn short - circuit insulation breakdown and burning occur . This is the main reason for the burning of dry - type transformers, and I also truly felt the impact of these factors on the equipment during on - site maintenance.

3 Treatment Measures
3.1 Cabinet Transformation and Device Installation

I participated in the transformation of the dry - type transformer cabinets by the company. We slotted the iron plates, set up air ducts around the transformer cabinets, and installed remote temperature alarm and high - temperature trip protection devices. This can monitor and respond to temperature abnormalities more timely, ensuring the operation of the equipment, and it is a specific measure I implemented in maintenance practice.

3.2 Cooling Fan Installation

For dry - type transformers of 400kVA and above, I assisted in installing cooling fans, which can automatically start and stop according to the set temperature, eliminating potential defects of operating transformers in advance and avoiding sudden accidents. In daily maintenance, I also pay attention to the operating status of these fans.

3.3 Remote Monitoring of Power Distribution Rooms

For the power distribution room of the 630kVA transformer, through remote information transmission, monitoring, and online monitoring of the operating temperature, insulation and other parameters of the transformer, as a front - line worker, I can timely grasp the operating health status of high - voltage equipment, ensuring the reliable operation of dry - type transformers, and it is also convenient for me to refer to these monitoring data during maintenance.

4 Preventive Measures
4.1 Daily Inspection Requirements

The company requires us operation and maintenance managers to conduct a patrol inspection of the high - voltage equipment in the power distribution room once a day, especially the operating status of dry - type transformers. I perform this task seriously every day, and report problems in a timely manner to ensure the safe operation of the equipment. This is an important part of my daily work.

4.2 Temperature Detection Specifications

An infrared thermometer is used to measure the temperature of the conductive connection parts of high - voltage equipment. The company stipulates that detection should be carried out once a week in spring, autumn and winter, and once a day in summer. I strictly operate according to this frequency to ensure that temperature abnormalities can be detected in a timely manner.

4.3 Comprehensive Inspection of Power Distribution Stations

For the power distribution stations without accidents, I participated in the comprehensive inspection and test, set up corresponding heat dissipation devices for dry - type transformers, ensuring good ventilation, eliminating potential equipment hazards, and taking measures for weak insulation points. I have accumulated experience in actual operations and also seen good results.

5 Conclusion

Because the armored switch cabinet has a small volume, compact structure, and poor heat dissipation effect, and the transformer is installed in a closed cabinet, a suitable cooling method must be adopted according to the capacity to avoid sudden accidents of dry - type transformers caused by unreasonable design.

It should be particularly noted that ordinary dry - type transformers must undergo a temperature rise test when put into operation in the cabinet, to understand the maximum temperature of long - term operation in advance, and eliminate potential hazards left to the power grid due to non - standard detection and construction.

After the implementation of preventive measures, no similar accidents have occurred to the operating dry - type transformers, effectively improving the reliability, and providing a guarantee for the safe operation of the power grid. As a front - line maintenance worker, I am more confident in dealing with the maintenance of such equipment.