China's power transformers are mostly baoding oil-immersed transformers, oil leakage has occurred from time to time over the years, severe leakage not only decreased the service life of the transformer, affect the safety of the system, safe operation, but also on the social and user economic benefits of a severe impact. In recent years, in the overhaul process of the main transformer and transformer of various power plants, it is found that the causes of oil leakage in transformers are as follows:
Failure of rubber seals and cracking of welds
There are many welding spots and long welding seams in transformer, while oil-immersed transformer is a combination of welding and connecting based on steel welded shell.
The total solder joints of a 31500kVA transformer are more than 70, and the total length of welding seams is about 20m, so there are many leakage methods. The cause of direct leakage is rubber seal failure and weld crack, porosity, slag inclusion and so on.
Sealant aging, cracking, deformation
Transformer leakage occurs in connection, and more than 95 % is caused by sealant. The quality of the sealant depends primarily on its oil resistance function, oil resistance function is poor, the aging speed is fast, especially at high temperature, the aging speed is faster, it is very simple to lead to the aging of seals, cracking, decay, deformation, so that failure, forming transformer oil leakage.
Transformer production quality
In the production process of transformer, many welding spots, long welding seam, difficult welding, welding data, welding (classification characteristics of welding skill equipment) standards, skills, skills and so on will affect the welding quality, forming air holes, sand holes, virtual welding, de-welding appearance so as to make transformer oil leakage.
The plate butterfly valve is of poor quality
Another transformer is often a leakage of the location in the plate butterfly valve, the earlier production of the transformer, the use of the usual plate butterfly valve interface than rough, thin, single seal, is a screening commodity, very simple lead to transformer oil leakage.
Improper installation
The flange joint is uneven, and the sealing gasket cannot bear the force evenly. Non-uniform force on bolts near seal gasket is formed artificially. Flange joint deformation dislocation, so that the sealing pad on one side of the force is too large, the side of the force is too small, the side of the sealing pad on the other side of the force is too small because of the lack of compression on the simple leakage. The representation occurs in the connection of gas relay and radiator and the body; There is also a point is the gasket device, the contraction of the lack or too large, the lack of contraction, the transformer running temperature increased oil thinning, forming transformer oil seepage, the contraction of large, severe gasket deformation, aging speed up the service life shortened.
Mail wrong
During the process of mailing and construction delivery, the parts will be knocked against and improperly hoisted and transported, resulting in the parts being bumped and deformed, welds opening and cracks, etc., leading to leakage.
Type of oil leakage from transformers
2.1 air leakage
It's an invisible leakage. For example, the leakage of air in and out of the casing head, the gap of oil storage tank, the glass of the safety airway and the weld hole. Moisture and oxygen in the air will slowly through the leakage of the site infiltration into the body, the transformer internal and external seal is damaged, forming insulation moisture and oil accelerated aging and other questions.
2. 2 oil leakage
2. 2. 1 internal leakage.
The oil in the bushing or the oil in the load regulating tap switch chamber leaks to the transformer body.
2. 2. 2 external leakage.
Weld leakage and seal leakage, this is the most prone to make is the most common leakage phenomenon.
Prevention of oil leakage from transformers
3. 1. Select seals with outstanding raw materials
Transformer maintenance and disposal of leakage, should choose high temperature resistance, oil resistance excellent sealing. The most commonly used sealing data of domestic transformer profession is nitrile butadiene rubber, its oil resistance function depends primarily on the content of acrylonitrile in nitrile butadiene rubber, the higher the content of acrylonitrile, the better the oil resistance function, the greater the hardness, the more difficult to be deformed. In general, NBR with a hardness of 70 -- 80 shall be selected. Judge seal oil resistant function, usually do should seal aging experiment and the compatibility with transformer oil, immerse the 168 h in 120 ℃ of hot oil, and then measure the weight, volume and the change rate of hardness, select its small deformation, fit into standard packing.
3. 2 select high quality butterfly valve
Butterfly valve select ZF80 type vacuum bias butterfly valve. Compared with the usual butterfly valve, the vacuum pain butterfly valve has made great progress in mechanical strength, surface finish, and this product has one of the biggest advantages, that is, the selection of double-layer seal with the transformer flange joint, so as to eliminate the problem of oil leakage at the transformer joint.
3. 3 use electric welding to plug the leakage
As for the air holes and sand holes left by the casting of transformers, and the virtual welding, unwelding and cracks in the welding seams and welding spots, electric welding can be used to plug the leakage.
Before plugging welding should find the leakage point, leakage point smaller can be used directly by welding leakage point dead; The larger leakage point should be filled with asbestos rope or metal filler, and then in the vicinity of the surfacing welding, then choose small electrode high current rapid arc welding.
3. 4 standard seal replacement skills
About the different types and different capacity of transformer, whether to choose the flange connection is still threaded connection, replace the seal is necessary before to remove the dust on the surface of the connecting and rust, will seal clean after cleaning in the seal double-sided coated with sealant (usually choose 609 polymer sealant liquid), sealing glue dry for a period of time after solvent evaporation, flange, screw fastening cohesion.
3. 5 improve the skill level of the device, and root out leakage caused by improper device methods
If the flange interface is uneven or out of shape, check the interface first. If the dislocation is severe, the flange can be cut off for rewelding. It is necessary to ensure that the interface is parallel. When the device is installed, it is advisable for the sealing gasket to compress about 1/3 of its thickness.
3. 6 quick sealing and sealing rubber rod
This method is used for transformer small leakage, drip leakage situation, the transformer radiator wall is thin, and is not suitable for the use of welding plugging leakage disposal leakage point can adopt this method to plug. It is necessary to completely remove the oil, paint and oxide on the plugging part to reveal the nature of the metal. Then according to the proportion of good plugging glue, leakage parts for plugging, until the leakage stop.
4 summarizes
With the development of the power industry, how to improve the function of power equipment, to ensure the safe operation of the power system, is the urgent need to deal with the question of power production, therefore, whether the transformer oil leakage can be timely, complete disposal, also gradually become an important indicator to measure the power industry to develop skills. In recent years, we through to the main transformer and the plant transformer leakage oil question disposition, unceasing improvement, the summary prevention method, the transformer leakage oil rate greatly reduced, has provided the guarantee for the transformer safe operation, has obtained the economic benefit for the company, the society and the user.
Baoding zhongyi electric material manufacturing co., LTD. Is a professional transformer manufacturer in baoding transformer factory. It has professional production equipment, lifting equipment, tooling and testing equipment.
Main products: baoding dry type transformer, baoding box type transformer, baoding oil immersed transformer, baoding high and low voltage complete sets of equipment, etc. I companies to follow "detail decides success or failure, honesty molded the future" of the enterprise purpose, adhere to "quality measuring market, seek development by innovation, to management for efficiency" business philosophy, to make my company's products are widely used in power plant, chemical, construction, mining, metallurgy, rail transportation and other industries, to meet the needs of various users, my company rely on superior product quality, thoughtful service, won the trust of our customers.
