Transformer is one of the key electrical equipment in power distribution station, because oil-immersed transformer has good dielectric strength, strong heat transfer performance and low engineering cost, it can solve the heat dissipation problem of heat pipe in large space of transformer and the problem of high working voltage insulation layer and is widely used use. However, the oil leakage problem, which is common in the operation of oil-immersed transformers, seriously endangers the safe operation of the transformer.
Transformer oil leakage will pose a serious threat to the safe operation of the transformer. First, if the transformer has long-term oil leakage or a lot of oil leakage, there will be insufficient aviation hydraulic oil. When the aviation hydraulic oil level in operation is reduced too much, it will cause the malfunction of CBM maintenance. When the transformer oil is less and more serious, the internal winding will be exposed, which will cause the insulation layer to be destroyed, and even cause a thermal breakdown safety accident, which will cause the transformer to stop and endanger the reliable supply of power engineering; the second is the transformer oil leakage, which is very easy to cause Moisture enters, causing moisture to return inside the transformer; third, the location of the transformer leaking oil is very easy to adhere to dust, causing large-scale adhesion of oil stains on the surface, which greatly harms the appearance of the brand image and makes maintenance difficult; fourth is the leakage of aviation hydraulic oil Waste water resources and environmental pollution. Therefore, the problem of transformer oil leakage must cause great attention of transformer maintenance staff.
Analysis of the Causes of Transformer Oil Leakage
There are many reasons for transformer oil leakage, which are often related to the quality of parts manufacturing, software environment, installation quality, and operation period. To summarize the oil leakage of transformers in recent years, the key is the following multiple aspects.
1. Embrittlement of the gasket
Transformer oil leakage mostly occurs at the junction of automobile fuel tanks and parts, and about 90% of the leakage is caused by the embrittlement of the sealing gasket. The key to the quality of the sealant is its wear resistance. If the wear resistance is weak, the embrittlement rate is rapid. Especially at high temperatures, the embrittlement rate is rapid, and the temperature during transformer operation reaches about 70 ℃. It is very easy to cause embrittlement, deformation, and even ineffectiveness of hydraulic seals, resulting in oil leakage of the transformer.
2. Hard working environment
Most of the transformers are operated outdoors, operating in a difficult environment, and the temperature difference is large. The average outdoor temperature in summer reaches 42°C, and in winter it reaches 15°C below zero. In addition to the heat generated by the transformer itself, the long-term thermal expansion and contraction cause the gasket to lose ductility and cause oil leakage.
3. Poor welding quality
Oil-immersed transformers should be based on the thick steel plate electric welding welding shell as the basic assembly of various electric welding welding and connection. In the production and manufacturing, the automobile fuel tank has many spot welding, long welding, electric welding welding is difficult, welding materials, welding methods, electric welding The technical strength of the welding staff is harmful to the welding quality of electric welding. For example, each 31500 kVA transformer has a total of more than 70 spot welds, and shortcomings such as welding vents, sand holes, false welding, and poor contact have caused transformer oil leakage.
4. Mechanical processing technology
The machining process and procedure flow do not meet the requirements, the tightening is too loose or too tight during the assembly line, the gasket is not cleaned or uneven, the flanges of the spare parts are uneven, and the human factors cause the foot around the gasket during installation The bolts are not symmetrically supported; the flange connection head deforms and shifts, and this situation mostly occurs at the coal-bed methane automobile relay and the radiator and itself. There are also large transformer waterproof bushings due to poor installation quality and support at the junction of the waterproof bushings, which is very easy to cause oil leakage at the waterproof bushing.
5. Harm to the technical strength of maintenance workers
Nowadays, the first-line team of enterprise maintenance has a relatively serious situation of staff fragmentation. Due to the limitation of staff and mechanical equipment, most transformer repairs rely on outsourcing teams. The outsourcing staff has a weak sense of responsibility. They did not strictly implement the technical specifications during the maintenance, and did not search for leaks carefully. After the maintenance, the leakage was not detected or the negative pressure time was insufficient, resulting in shortcomings after the maintenance.
6. Destroyed by external force
When the transformer is being transported and hoisted, the parts and accessories are impacted, the radiator and other hoses are distorted by external force, or other components are injured and deformed, the welding port is open, and the crack appears. After the transformer is invested in operation, the temperature rises. The working pressure increases, causing oil leakage.
How to deal with transformer oil leakage
Before dealing with oil leakage, careful analysis must be made to find out the cause of the leakage and the exact leakage point. For the existing oil stains, first use a small flat spatula, steel wire brush to clean up, then clean with perchloroethylene, acetone, alcohol and other cleaning agents, rinse with clean water, and finally wipe with a clean cloth repeatedly to find the exact location of the leak .
1. Use welding to control transformer oil leakage
When oil leakage is found in the upper part of the transformer oil tank, only a small amount of oil can be discharged for welding; when leakage is found in the lower part of the oil tank, due to excessive waste of oil draining from the lifting core and limited by site conditions, welding with oil can be used. Repair welding with oil should be carried out when the oil leakage is not significant. Otherwise, the vacuum drain method should be used to cause the negative pressure to be welded. The vacuum degree of the negative pressure should not be too high. The internal and external pressures should be equal to avoid inhaling molten iron. When repairing welding, the oil stains on the welding part should be removed, it is best to rinse with alkaline water and then wipe dry; pay attention to prevent penetration and fire during the welding process, and the welding part must be below the oil surface; Continued, rapid spot welding, the arcing time should be controlled within 10s～20s, and continuous welding for a long time is absolutely not allowed. When repairing the pores with serious oil leakage, you can use iron wire to block or riveting before welding; when welding near the sealing rubber gasket or other vulnerable parts, cooling and protective measures should be taken.
2. On-site fast bonding method to plug transformer oil leakage
Soleil carbon nano polymer material is a cold welding bonding technology, which has the advantages of strong bonding force, strong weather resistance, and comprehensive mechanical properties such as elastic deformation of metal. It can realize online control of transformer oil leakage under safety.