油浸式电力变压器故障分析-佛山市禅星特变压器有限

Fault Analysis of Oil-immersed Power Transformers

1. Oil Leakage at Welding Joints

The main cause is poor welding quality, such as insufficient welding, weld detachment, pinholes, and sand holes in weld seams. These defects are covered by welding flux and paint when the oil-immersed transformer leaves the factory and only become exposed during operation. In addition, electromagnetic vibration may crack the welds, leading to oil leakage.

For transformers with existing oil leakage, first locate all leakage points without omission. For severely leaking areas, use metal tools such as flat shovels or pointed punches to rivet the leakage points and control the oil leakage volume. Then clean the surface to be repaired thoroughly. At present, polymer composite materials are widely used for curing, which can achieve long-term leakage treatment after solidification.

2. Oil Leakage at Seals

The common cause is poor sealing performance. The seal between the tank flange and tank cover is usually realized with oil-resistant rubber rods or rubber gaskets. Improper handling of the joints will result in oil leakage faults. Some joints are bound with plastic tape, while others simply press the two ends together. Due to rolling during installation, the joints cannot be compressed tightly, failing to perform the sealing function and still causing oil leakage.

Fushilan materials can be used for bonding to integrate the joints, which can significantly control oil leakage. If operation permits, the metal shell can also be bonded simultaneously to achieve the purpose of leakage treatment.

3. Oil Leakage at Flange Connections

Uneven flange surfaces, loose fastening bolts, and incorrect installation processes can lead to poor bolt tightening, resulting in oil leakage. First, tighten the loose bolts strictly in accordance with the operating procedures, then perform sealing treatment on the flanges, and also handle the bolts that may leak, so as to achieve complete leakage treatment.

4. Oil Leakage at Bolt or Pipe Threads

Rough processing and poor sealing during factory production will cause oil leakage faults in oil-immersed transformers after a period of sealed operation. One solution is to use polymer materials to seal the bolts for leakage treatment. Another method is to unscrew the bolts (or nuts), apply Fushilan release agent on the surface, then coat the surface with sealing materials and retighten them. The leakage can be effectively treated after the materials are cured.

5. Oil Leakage at Cast Iron Components

The main cause of oil leakage is sand holes and cracks in cast iron parts. For leakage caused by cracks, drilling stop-hole is the best method to eliminate stress and prevent crack extension. During treatment, according to the crack conditions, drive lead wires into the leakage points or rivet them with a hammer. Then clean the leakage points with acetone and seal them with special materials. For casting sand holes, they can be directly sealed with the materials.

6. Oil Leakage at Radiators

Radiator cooling pipes are usually made by flattening and stamping seamless steel pipes. Oil leakage often occurs at the bent and welded parts of cooling pipes. This is because during the stamping process, the outer walls of the pipes are subject to tensile stress and the inner walls are subject to compressive stress, leaving residual stress in the pipes.

First, close the upper and lower plate valves (butterfly valves) of the radiator to isolate the oil in the radiator from that in the tank, so as to reduce pressure and oil leakage volume. After identifying the leakage location, conduct appropriate surface treatment, and then use Fushilan materials for sealing treatment.

7. Oil Leakage at Insulators and Glass Oil Gauges

This problem is usually caused by improper installation or seal failure. Polymer composite materials can well bond materials such as metal, ceramics, and glass, thus achieving a fundamental solution to oil leakage.