Why can't the transformer run under overload?

What is overload operation?

Overload operation means that the actual operating current or power of the electrical equipment exceeds its design or specified rating. This condition may cause overheating, insulation aging, performance degradation, or even damage to the device.

The causes of overload may include:

Excessive load: The load attached to the device exceeds its design capacity, resulting in current or power exceeding the rated value.

Equipment aging: As equipment is used for longer periods of time, its performance may gradually deteriorate, making it more prone to overload under the same load.

Environmental factors：Such as high ambient temperature and poor heat dissipation, which may also cause the device to be overloaded.

dry-type-transformer

Why can't the transformer run under overload?

‌The main reasons why a transformer cannot run under overload include the following:

‌Temperature rise and insulation aging: When the operating current of the transformer exceeds the rated current, the load loss increases sharply, resulting in the transformer temperature rise. Temperature plays a decisive role in insulation aging. Studies have shown that the life of insulating parts and materials will be reduced by 50% for every 8℃ increase in operating temperature. Long-term overload operation will make the transformer temperature is too high. And in serious cases, it will cause the transformer to burn ‌.

‌Loss increase: The transformer is generally designed according to the rated capacity, and the operating balance point is about 67%. When the transformer load exceeds the rated capacity, the copper loss will increase in a square relationship, resulting in increased loss‌.

‌Output voltage reduction: When the output current of the transformer reaches the short-circuit current, the voltage will drop to zero, which will affect the normal operation of the transformer and the quality of power supply ‌.

‌Reduced service life: The service life of the transformer will be reduced. Because the winding of the transformer is mainly made of insulating material, too high temperature will accelerate the aging of the insulating material and shorten the service life of the transformer ‌.

‌Overload type: Overload is divided into normal overload and accident overload. The former is caused by the increase in user electricity consumption, and the latter is caused by emergencies such as power system failures. No matter what kind of overload, it may cause the transformer winding to overheat. Overheating the winding for a long time may cause the coil to burn ‌.

Solutions for overload operation

Reasonable load allocation: Optimize the production process, ensure the orderly use of electrical equipment, reduce the simultaneous utilization rate, so as to avoid the overload operation of the transformer.

Voltage adjustment: By adjusting the output voltage of the transformer, the current can be reduced and the load rate of the transformer can be reduced. However, it should be noted that the adjustment of voltage should be carried out within the allowable range to avoid adverse effects on the power grid and other equipment.

Improve the power factor: High load rate will lead to insufficient reactive power compensation capacity, so it is necessary to regularly replace power capacitors with capacity attenuation, and install reactive power compensation devices in place at large inductive loads to improve the power factor. This can not only improve the active power output capacity of the transformer, but also reduce the operating current and power loss.

Cooling measures: Transformers are cooled by installing air conditioning or adding forced exhaust measures. Cooling the transformer reduces losses, increases efficiency, and protects the transformer from high temperature damage.