Transformer leakage is a common problem in transformer faults, especially for some transformers that have been in operation for a long time. Mild cases can contaminate the appearance of equipment and affect its appearance, while severe cases can threaten the safe operation of equipment and even human life. Transformer leakage includes air entering and leaving (excluding air that normally enters through a dehumidifier) and oil leakage.
Reasons for leakage of transformersThere are two main reasons for leakage: on the one hand, it is hidden in the design and manufacturing process of transformers; On the other hand, it is caused by improper installation and maintenance of transformers. The main leakage areas of transformers often occur in radiator interfaces, flat disc valve caps, bushings, porcelain bottles, welds, sand holes, flanges, and other parts.
1. Air in and out
Entering and exiting the air is an invisible form of leakage. For example, the inlet and outlet air of the casing head, the diaphragm of the oil storage tank, the glass of the safety airway, the weld sand hole, and the steel sand inclusion are all invisible. For many years, the main malignant accidents in the power system have mostly been winding burn accidents and serious damage to the transformer body due to low voltage outlet short circuits.
2. Classification of leaked oil
The oil leakage of transformers can be divided into two types: internal leakage and external leakage, and external leakage can be further divided into two types: weld seam leakage and sealing surface leakage.
1) Internal leakage: Internal leakage
It is common for the oil in the oil filled bushing and the oil in the oil chamber of the on load tap changer to leak into the transformer body.
2) External leakage: External leakage is divided into two types: weld leakage and sealing surface leakage:
Weld seam leakage: Weld seam leakage is caused by sand holes in the welding area of the steel plate.
Sealing surface leakage: The situation of sealing surface leakage is quite complex, and specific problems need to be analyzed on a case by case basis. Preventing leakage on the sealing surface should be an important task during the overhaul or installation of transformers.
Fault analysis and solution1. Oil leakage at the welding point
Mainly due to poor welding quality, including virtual welding, desoldering, pinholes, sand holes and other defects in the weld seam. When the transformer leaves the factory, it is covered with welding flux and paint, which exposes hidden dangers after operation. In addition, electromagnetic vibration can cause welding cracking and leakage. For those that have already experienced leakage, first identify the leakage point and do not miss it. For areas with severe leakage, metal tools such as flat shovels or pointed punches can be used to rivet the leakage point, control the leakage amount, and clean the treated surface. Polymer composite materials are often used for curing, which can achieve long-term treatment of leakage after curing.
2. Seal leakage
The reason for poor sealing is that the seal between the box edge and the box cover is usually sealed with oil resistant rubber rods or rubber pads. If the joint is not handled properly, it can cause oil leakage faults. Some are tied with plastic tape, while others directly press the two ends together. Due to rolling during installation, the joint cannot be firmly pressed, which does not have a sealing effect and still leaks oil. Fushilan material can be used for bonding to form a cohesive joint, greatly controlling oil leakage; If the operation is convenient, the metal shell can also be bonded at the same time to achieve the purpose of leakage control.
3. Oil leakage at the flange connection
The flange surface is uneven, the fastening bolts are loose, and the installation process is incorrect, resulting in poor bolt tightening and oil leakage. First tighten the loose bolts, then seal the flange and address any potential leaks in the bolts to achieve complete remediation. Tightening loose bolts must be strictly carried out according to the operating process.
4. Oil leakage from cast iron parts
The main reason for oil leakage is due to sand holes and cracks in cast iron parts. Drilling anti crack holes is the best method to eliminate stress and avoid extension for crack leakage. During treatment, lead wire can be inserted into the leak point or riveted with a hammer according to the condition of the crack. Then clean the leakage point with acetone and seal it with material. Casting sand holes can be directly sealed with materials.
5. Oil leakage from bolt or pipe threads
When leaving the factory, the processing is rough and the sealing is poor. After a period of sealing, the transformer will experience oil leakage faults. Using polymer materials to seal bolts for the purpose of controlling leakage. Another method is to unscrew the bolt (nut), apply Fushilan release agent on the surface, and then tighten it after applying the material on the surface. After curing, the treatment goal can be achieved.
6. Oil leakage from radiator
The heat dissipation pipes of a radiator are usually flattened with slotted steel pipes and stamped to produce oil leakage in the bent and welded parts of the pipes. This is because when stamping the heat dissipation pipes, the outer wall of the pipe is under tension and the inner wall is under pressure, resulting in residual stress. Close the upper and lower flat valves (butterfly valves) of the radiator to isolate the oil in the radiator from the oil in the box, reducing pressure and leakage. After determining the leakage location, appropriate surface treatment should be carried out, and then seal treatment should be carried out using Fukushi Blue material.
7. Leakage of oil from porcelain bottles and glass oil labels
Usually caused by improper installation or seal failure. Polymer composite materials can effectively bond materials such as metals, ceramics, and glass, thereby achieving fundamental treatment of oil leakage.
2025-02-11 
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