What are the maintenance points of transformer operation?
Writer： Hengfeng you electric Time：2023-03-27 views：times
Key points of transformer maintenance
1. Allowable temperature
During the operation of the transformer, copper loss and iron loss will occur in its coil and core, and these losses will become heat energy, which will increase the temperature of the core and coil of the transformer. If the temperature exceeds the allowable value for a long time, the insulation will gradually lose mechanical elasticity and aging.
The temperature of each part of the transformer is different during operation. The temperature of the coil is the highest, followed by the temperature of the iron core. The temperature of the insulating oil is lower than the temperature of the coil and the iron core. The upper oil temperature of the transformer is higher than the lower oil temperature. The allowable temperature of the transformer during operation shall be checked according to the upper oil temperature. For class a insulation transformer, in normal operation, when the ambient air temperature is up to 400C, the ultimate working temperature of the transformer winding is 1050C. Since the temperature of the winding is 100C higher than the oil temperature, it is required that the upper oil temperature of the transformer shall not exceed 950c to prevent the deterioration of the oil quality. Under normal conditions, the upper oil temperature shall not exceed 850c to prevent the excessive oxidation of the insulating oil. For transformers with forced oil circulating water cooling and air cooling, the upper oil temperature should not always exceed 750C.
Only monitoring the upper oil temperature during the operation of the transformer can not guarantee the safe operation of the transformer. It is also necessary to monitor the temperature difference between the upper oil temperature and the cooling air, that is, the temperature rise. The difference between the transformer temperature and the ambient air temperature is called the temperature rise of the transformer. For class a insulated transformer, when the maximum ambient temperature is 400C, the national standard stipulates that the temperature rise of the winding is 650C, and the allowable temperature rise of the upper oil temperature is 550c. As long as the temperature rise of the transformer does not exceed the specified value, it can ensure the safe operation of the transformer within the specified service life under the rated load.
3. Reasonable capacity
During normal operation, the power load borne by the transformer shall be about 75-90% of the rated capacity of the transformer.
4. The maximum unbalanced current of low voltage of transformer shall not exceed 25% of the rated value; The allowable variation range of transformer power supply voltage is plus or minus 5% of rated voltage
If it exceeds this range, the tap changer shall be used to adjust the voltage to reach the specified range. (the adjustment shall be conducted with power cut off) the voltage is usually adjusted by changing the position of the tap tap of the primary winding. The device connecting and switching the tap position is called tap changer, which adjusts the transformation ratio by changing the number of turns of the high-voltage winding of the transformer. The low voltage has no effect on the transformer itself, only reduces some output, but has an impact on the electrical equipment; As the voltage increases, the magnetic flux increases, the core saturates, the core loss increases, and the transformer temperature increases.
5. Overload
Overload is divided into normal overload and accident overload. Normal overload is caused by the increase of user's power consumption under normal power supply. It will increase the temperature of the transformer, lead to accelerated aging of the insulation of the transformer, and reduce the service life. Therefore, overload operation is not allowed in general. Under special circumstances, the 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 transformer shall be determined according to the temperature rise of the transformer and the regulations of the manufacturer.
In case of an accident in the power system or the user's substation, in order to ensure the continuous power supply to important equipment, the transformer is allowed to operate under overload for a short time, that is, the accident overload. The accident overload will cause the coil temperature to exceed the allowable value, so the insulation will age faster than the normal condition. However, there is little chance of accidental overload. In general, the transformer operates under load, so short-term overload will damage the insulation of the transformer. The time and multiple of accident overload shall be implemented according to the regulations of the manufacturer.
For more information, please pay attention to Qingdao hengfengyou electric. Our factory focuses on the production and manufacturing of American box type substation, which has been sold to the American market in 2018.
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