As a key part of power system, dry-type transformer can achieve different voltages required by users through step-up or step-down. However, if the transformer fails, the consequences will cause huge losses to users. Therefore, in order to ensure the stability and prolong the service life of the dry-type transformer, regular maintenance is essential.
How to inspect and maintain 10kV transformer

In the power system of the unit, 10kV transformer is widely used. After a long time of operation, the performance and efficiency of 10kV transformer will change. Therefore, it is necessary to do a good job in the maintenance and repair of 10kV transformer In order to ensure the stability and safety of 10kV transformer operation, it is necessary to formulate a reasonable maintenance plan, determine the maintenance period and maintenance content, and strengthen daily maintenance, which can effectively extend the service life of 10kV transformer and prevent the occurrence of faults
1、 Strengthen regular inspection of 10kV power transformer
(1) Regularly check the cleanliness of porcelain bushing and insulator, timely clean the dust adhered on the surface, and remove the oxide film or rust of exposed conductor.
(2) During the operation of the transformer, vibration will occur and affect the fasteners. Therefore, it is necessary to cut off the power after the operation for a period of time to maintain the fasteners and ensure the fastening and reliability of the electrical connection.
(3) Check the tap changer regularly. And check the fastening, rotation flexibility and contact positioning of the contact.
(4) In the oil immersed transformer, check whether there is leakage, rust, dirt deposition and any mechanical damage that restricts the free flow of oil.
(5) Regularly check whether the insulating oil of the oil immersed power transformer is enough, and the operation of the fan of the dry-type power transformer and the display of the temperature controller are normal.
(6) The regular inspection of tap changer of voltage regulating transformer includes the inspection of insulating oil and the lifting core of switch. The inspection cycle can be carried out according to DL / t574-95. The insulating oil in the tap changer turns black after multiple switching, and the withstand voltage decreases. Generally, when the withstand voltage value decreases to 20kv-25kv, the new oil shall be replaced. The tap changer shall be inspected regularly according to the switching times or service time, mainly to check the wear of the quick mechanism and the contact, and the fatigue of the energy storage spring, the contact pressure spring and other components.
2、 Strengthen daily patrol inspection of 10kV power transformer
(1) Daily patrol shall be conducted at least once a day and night patrol shall be conducted at least once a week.
(2) The number of patrol inspection shall be increased in the following cases: within 72h after the first operation or maintenance and transformation; Sudden meteorological changes (such as thunderstorm, strong wind, heavy fog, heavy snow, hail, cold wave, etc.); High temperature season and peak power consumption period; When the transformer operates under overload.
(3) The daily patrol inspection of 10kV power transformer shall include the following contents: the oil temperature shall be normal, there shall be no oil leakage and oil leakage, and the oil level of the oil level gauge of the oil conservator shall be normal; The sound of power transformer shall be normal; The feel temperature of each part of the radiator shall be similar, and the cooling accessories shall work normally; The moisture absorber shall be intact and the adsorbent shall be dry; Lead joints, cables and buses shall be free of heat; The pressure relief device, safety air passage and explosion-proof membrane shall be intact; Tap position and power indication of tap changer shall be normal; There shall be no gas in the gas relay; All control boxes and secondary terminal boxes shall be tightly closed and free from moisture; The appearance of the dry-type transformer shall be free of dirt, the fan shall operate normally, and the temperature controller shall display normally; The transformer room shall be watertight, the doors, windows and lighting shall be in good condition, with good ventilation and normal temperature; The transformer shell and all parts shall be kept clean.
 

 

3、 Daily maintenance of 10kV power transformer
(1) Problems such as oil leakage, high or low oil level, abnormal temperature, abnormal sound and abnormal cooling system often occur in the operation of power transformer. Try to find out the causes, correct them and make records.
(2) When the load of the power transformer exceeds the allowable normal overload value, the load of the transformer shall be reduced as required to prevent safety accidents
(3) In case of the following phenomena, the power transformer shall be cut off immediately for maintenance: the internal sound of the power transformer is loud and there is discharge sound; Abnormal temperature and rising phenomenon; Fuel injection of oil conservator or safety airway; The oil level drops to the indication limit of the oil level gauge; The oil color changes too fast; The porcelain bottle is seriously damaged and discharged.
(4) When it is found that the oil temperature of the power transformer is high and the oil level corresponding to the oil temperature is significantly reduced, oil shall be added immediately. When refueling, the regulations shall be observed. If the oil level drops rapidly due to a large amount of oil leakage, the gas protection shall be changed to only act on the signal, and the measures to plug the oil leakage must be taken quickly, and refueling shall be carried out immediately. When the oil level of the transformer rises gradually due to the temperature rise, if the oil level at the highest temperature may be higher than the oil level indicator, the oil shall be drained to reduce the oil level to an appropriate level to avoid oil overflow.
(5) For routine maintenance of dry-type transformer, if power can be cut off, check whether the fasteners are loose and wipe the dust on them. Large and medium-sized maintenance mainly involves measuring insulation resistance, such as high and low voltage to ground resistance.
4、 Treatment of common problems of 10kV power transformer, treatment of oil tank sand hole or weld leakage
(1) The sand hole is small and the oil leakage is small, which can be plugged during operation. Clean the oil leakage part first, then block the oil leakage hole with soap, and apply LD-1 quick acting leakage sealing sealant.
(2) The oil leakage of the weld seam is small. First, clean the paint skin and oxide layer at the oil leakage part to expose the natural color of the box, then scrub it with alcohol and apply sealant. If the leakage part is smooth, it can be roughened on the surface to enhance the adhesion of the sealant.
(3) The oil leakage is large, and the transformer needs to be transported back to the manufacturer for treatment. It is recommended to use carbon dioxide shielded welding or automatic arc welding. After welding, pressure leakage test shall be conducted (generally, 15kpa above 315KVA and 20KPa below 250kVA), and paint shall be applied after it is solved.

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