Fault type analysis of oil immersed transformer

Oil immersed transformer is different from other transformers in that it uses oil as its main feature. The technology department and after-sales department of our company have sorted out some common faults of oil immersed transformer and their solutions

Short circuit fault: there are two-phase short circuit and three-phase short circuit, which are mostly caused by hidden dangers left in the manufacturing process.

Grounding fault: one or several cores of oil immersed transformer break down to ground, and the insulation resistance is lower than 10k Ω Called low resistance grounding, higher than 10k Ω It is called low resistance grounding. It is mainly caused by oil immersed transformer corrosion, lead skin crack, insulation dry, joint technology and material.

Linear breaking fault: one or several cores of oil immersed transformer are completely or incompletely broken. Oil immersed transformer is affected by mechanical damage, terrain change or short circuit, which can cause disconnection.

Mixed fault: above two kinds of faults.

1、 To prevent overload operation of oil immersed transformer: if it is overloaded for a long time, it will cause coil heating and aging of insulation. When the oil immersed transformer is in operation, its coil and iron core produce copper loss and iron loss. These losses turn into heat energy, which makes the temperature of the iron core and coil of the oil immersed transformer rise. If the temperature exceeds the allowable value for a long time, the insulation will gradually lose its mechanical elasticity and aging.

2、 Check the exhalator, and refuel regularly in case of oil shortage. Monitoring the upper oil temperature in the operation of oil immersed transformer can not guarantee the safe operation of oil immersed transformer, but also must monitor the temperature difference between the upper oil temperature and the cooling air temperature rise. The difference between the temperature of oil immersed transformer and the ambient air temperature is called the temperature rise of oil immersed transformer

3、 Reasonable capacity in normal operation, the power load of oil immersed transformer should be about 75-90% of the rated capacity of oil immersed transformer.

4、 Overload overload is divided into normal overload and accident overload. Normal overload is caused by the increase of power consumption under normal power supply. It will increase the temperature of oil immersed transformer, accelerate the insulation aging and reduce the service life of oil immersed transformer. Therefore, overload operation is not allowed under normal circumstances. Under special circumstances, the oil immersed transformer can operate under overload for a short time, but it shall not exceed 30% of the rated load in winter and 15% of the rated load in summer. In addition, the overload capacity of the oil immersed transformer should be determined according to the temperature rise of the oil immersed transformer and the regulations of the manufacturer. When an accident occurs in the power system or user substation, in order to ensure the continuous power supply to the important equipment, the oil immersed transformer is allowed to operate under overload for a short time, that is, the accident overload. When the accident overload occurs, the coil temperature will exceed the allowable value, so the aging of the insulation is faster than the normal condition. But the chance of accident overload is less. In general, the oil immersed transformer is under load operation, so the short-term overload will damage the insulation of the oil immersed transformer. The time and multiple of accident overload shall be implemented according to the regulations of the manufacturer.