The reasons for oil leakage in transformers are as follows:

1.1 Rubber seal failure and weld cracking

Transformers have many welding points and long welding seams, while oil-immersed transformers are a collection of various welding and connections based on steel plate welded shells.

A 31500kVA transformer has a total of more than 70 welding joints, and the total length of the welding seam is about 20m, so there may be many leakage channels. The cause of direct leakage is the failure of rubber seals, cracks in the welds, pores, slag inclusions, etc.

1.2 Aging, cracking and deformation of sealant

Transformer leakage mostly occurs at the connection, and more than 95% is mainly caused by the sealant. The quality of the sealant mainly depends on its oil resistance. The poorer oil resistance has a faster aging rate. Especially at high temperatures, the aging rate is faster, which can easily cause seal aging and cracking. Deterioration, deformation, and even failure, causing oil leakage of the transformer.

1.3 The manufacturing quality of the transformer

In the transformer manufacturing process, many welding spots in the fuel tank, long welding seams, difficult welding, welding materials, welding (classification characteristics of welding process equipment) specifications, processes, technology, etc. will affect the welding quality, resulting in pores, sand holes, virtual welding, and desoldering This phenomenon causes the transformer to leak oil.

1.4 The quality of the plate butterfly valve is not good

Another part of the transformer that often leaks is at the plate butterfly valve. The connection surface of the ordinary plate butterfly valve used in the earlier production transformer is relatively rough, thin, and single-layer sealed. It is an obsolete product and is very easy to cause transformer oil leakage.

1.5 Improper installation method

The flange connection is not flat, the gasket can not be uniformly stressed during installation, and the bolts around the gasket are artificially caused to be unevenly stressed, and the flange joints are deformed and misaligned. The sealing gasket on the side with less force is likely to cause leakage due to insufficient compression.