Characteristics and on-site treatment of dominant faults of large transformers
The visible fault refers to the fault whose characteristics and manifestations are more intuitive and obvious. Here, combined with the actual situation on the site, the causes and characteristics of the dominant faults of large transformers are described and analyzed. And the common on-site treatment methods are introduced, which are some relatively simple methods.
I. Appearance anomaly and fault type:
When anomalies and faults occur in the operation of transformers, they're often accompanied by corresponding appearance characteristics. Through these simple external phenomena, some defects can be found and qualitative analysis of anomalies and faults is carried out, and further analysis or treatment schemes are proposed. It can be analyzed and processed from the following aspects:
1, explosion-proof cylinder or pressure release valve film is damaged.
When the transformer does not breathe well, the air above the transformer oil pillow diaphragm will expand sharply when the temperature rises, and the pressure will increase. If the film is damaged, it will be accompanied by a large amount of transformer oil.
The main reasons and measures are as follows:
1) The respirator is blocked due to silica gel or oil seal injection and foreign matter in the pipeline.
The silicone should account for 2/3 of the respirator, and 1/3 of the oil seal can be filled with oil. You can check the pipeline by filling nitrogen.
2) During installation and maintenance, the bolts fastening the film are too tight or the flange is uneven, external damage, or personnel accidentally touch.
Replace the damaged film.
3) internal short circuit failure, produces a lot of gas.
The gas sample can be taken from the gas relay first. If the ignition can burn, it is necessary to take the oil sample for chromatographic analysis and electrical inspection to determine the nature of the fault. The cause of the fault is not identified, and the transformer cannot be put into operation before eliminating the defect.
4) The oil pillow of the diaphragm structure is injected improperly during maintenance or installation, and the gas on the oil pillow is not discharged according to the regulations.
Power failure fill the oil pillow with transformer oil, and then put the transformer oil to the appropriate oil level.
5) The capsule structure of the oil pillow due to low oil level, the capsule blocked the oil pillow and the transformer body of the pipeline connection.
Install a support capsule at the joint of the pipe to plug the joint directly.
2. Casing flashover discharge.
The flashover discharge of the bushing will make it heat up and age, which will cause a short circuit accident at the transformer outlet.
The main reasons and measures are:
1) The surface is dirty, in rainy and humid weather, due to the improvement of the electrical conductivity of the dirt and discharge.
It is necessary to clean the transformer bushing with a power outage and apply RTV long-acting coating to improve its anti-pollution flasticity.
2) There are defects during installation, maintenance, or manufacturing.
During the test, dielectric loss and other insulation indicators exceed the standard, or porcelain parts are incomplete, need to replace the casing.
3) In the design, the external creepage distance is selected to be small, and the transformer is operated in an area with high pollution levels.
Replace the casing with a large creepage distance or take anti-pollution flashover measures such as adding silicone rubber to increase the creepage skirt.
4) Internal overvoltage and atmospheric overvoltage appear in the system.
Test and check the casing and transformer, all qualified before they can be put into operation.
5) The casing surface is attached to a ceramic skirt with a debris short joint.
Live with insulation rod can be picked out.
6) Rain or snow weather or ice, stop running.
3, Leakage of oil.
Almost every transformer has a problem, that is all sealing points, even the iron plate, have leakage of oil due to trachoma.
Leakage of oil generally will not lead to the immediate shutdown of the transformer, but if the oil leakage is not dealt with in time, it will seriously endanger the safe operation of the transformer.
Because of the numerous transformer sealing parts and various forms, the symbols of leaking oil are different.
The main reasons and measures are as follows:
1) the aging and cracking of the sealant pad is generally caused by poor quality of the rubber pad or delayed replacement.
It needs to be replaced in time after maintenance.
2) The sealing point is not tightened in place, and the oil-free part will accelerate the aging of the rubber pad, and the air will enter the transformer body.
Whenever found, always tighten.
3) The valve is of poor manufacturing quality and is not strictly closed.
Drain and replace the valve.
4) trachoma or poor welding quality.
Oil welding can be carried out, but fire prevention measures must be taken, and iron plate trachoma can also be covered with a certain area of iron plate on the surface to deal with.
5) Oil leakage from the oil pump.
Some parts of the negative pressure in its operation do not leak oil, once stopped will leak, this situation will often bring air into the transformer, causing gas signaling and even action trips.
It is difficult to find, and it is necessary to stop the inspection and treatment of each oil pump.
6) The rubber pad is stressed and deformed, the sealing structure is unreasonable, and the manufacturing and installation process is poor, which will also lead to leakage of oil.
It should be handled according to specific reasons.
