About JINSHANMEN TECHNOLOGY CO., LTD: The company mainly produces oil immersed power transformers, dry-type power transformers, oil immersed three-dimensional coiled power transformers, dry-type three-dimensional coiled power transformers, mining explosion-proof dry-type transformers, mining explosion-proof mobile substations, amorphous alloy power transformers, on load capacity regulating power transformers, locomotive dry-type transformers, as well as prefabricated substations, modular substations, wind energy box type substations, high and low voltage switchgear and other transmission and distribution equipment. With rich experience in transformer manufacturing and maintenance, we are committed to providing reliable solutions for transformer operation safety, including professional guidance on oil leakage handling of 250 kva power transformer and 250 kva 3 phase transformer.
I. Overview of Transformer Oil Leakage
Transformer oil leakage has long plagued the global transformer industry and power supply departments. Both small and medium-sized 250 kva power transformers and industrially commonly used 250 kva 3 phase transformers are likely to face this hidden danger. Oil leakage not only affects the standardized operation of power supply enterprises, but also seriously threatens power supply safety. In severe cases, it can cause transformers to withdraw from operation and trigger power outages, while resulting in environmental pollution and energy waste. Its harmfulness has attracted widespread attention in the industry.
According to the operation data of a certain power grid, among 779 35kV transformers, about 55% have varying degrees of oil leakage, with more than 1270 leakage points. Among them, more than 50% of the total leakage points are radiator interfaces, flat butterfly valve caps, and radiator plugs; 16% are bushing leakage; 12% are gas relay interface leakage and other parts. Especially in the long-term operation of 250 kva 3 phase transformers, these parts have higher leakage risks due to stress changes caused by load fluctuations.
II. Troubleshooting Methods for Transformer Oil Leakage
The causes of oil leakage in different parts are different, and the treatment methods need to be implemented targetedly. The following are the treatment schemes for common leakage points:
1. Oil Leakage at the Upper Part of Bushing
Main causes: Insufficient compression of the gasket, loose clamping of the connecting wire clamp, or damage to the gasket due to operation heating. For example, the oil leakage of the low-voltage bushing of No. 3 rectifier transformer in No. 4 chamber of No. 3 furnace electrostatic precipitator is due to this reason. This problem is also common in the bushing installation of 250 kva power transformers.
Troubleshooting: Replace the gasket, or tighten the compression nut of the conductive rod and the upper wire clamp to ensure uniform pressure on the sealing surface.
2. Oil Leakage at Sand Holes and Weld Seams
Main causes: Improper processes during casting and welding, inadequate leak testing, or material defects. Such leakage is likely to be left during the transformer production process, and is one of the main types of leakage in transformers of various capacities (including 250 kva 3 phase transformers).
Troubleshooting: If the sand hole is small and the oil leakage is small, live leak plugging can be adopted: clean the oil stain and paint at the leakage part, seal with ceramic steel, and the problem can be solved after curing; when dealing with weld seam leakage, first remove the paint and oxide layer with a hacksaw to expose the metal color, wipe it clean with alcohol, apply sealant, and complete the sealing after curing; if the surface of the leakage part is smooth, grinding is required to increase adhesion; for power outage welding repair, carbon dioxide gas shielded welding and automatic arc welding processes are recommended. After welding repair, strictly implement leak testing and leak detection standards.
3. Oil Leakage Caused by Gaskets
Main causes and troubleshooting methods:
(1) Uneven pressure: Bolts are not tightened, insufficient compression of gaskets, or excessive compression leading to loss of elasticity. Troubleshooting: Adjust the pressure of the compression bolts, and the compression amount of the nitrile rubber oil-resistant gasket is recommended to be 1/3 of the thickness.
(2) Problems with the sealing pressure surface: Presence of foreign objects, rough or skewed contact surfaces. Troubleshooting: Remove foreign objects and re-compress; rough surfaces need to be ground flat, or fill the concave parts with quick-acting leak plugging sealant; if the sealing surface is too small, replace the non-porous gasket with a porous compression gasket to increase the sealing contact area.
(3) Poor gasket quality: Select nitrile rubber gaskets produced by regular enterprises to ensure oil resistance and temperature resistance, which is the key to ensuring the sealing reliability of 250 kva power transformers.
(4) Unbalanced pressure of the rubber ring (flange): Continuous single-point operation when tightening bolts is likely to cause uneven stress. Troubleshooting: Adjust the pressure of each bolt evenly to ensure balanced stress at the rubber ring interface.
4. Oil Leakage at Air (Oil) Release Bolt Seals
Main causes: Unreasonable bolt design. When the pressure is too low, the gasket compression is insufficient; when the pressure is too high, the gasket exceeds the elastic limit, both of which will cause leakage.
Troubleshooting: Modify the bolt structure by turning a circular sealing groove with a depth of about 3mm in the bolt cap to limit the gasket in the groove, avoid outward expansion during extrusion, and maintain the good elasticity of the gasket.
III. Prevention Measures for Transformer Oil Leakage
1. Adopt New Sealing Materials and Improve Detection Methods
Traditional domestic nitrile rubber gaskets are difficult to meet the long-term operation needs of transformers due to formula and process limitations, and are prone to aging and cracking leading to leakage. Especially when the local temperature of the transformer exceeds the limit temperature of nitrile rubber, the risk of seal failure increases significantly. The selection of acrylic rubber with excellent high temperature resistance and oil resistance (which can work continuously in hot oil at 150℃ and has excellent aging resistance) has been applied in many enterprises in the industry and achieved good results. JINSHANMEN TECHNOLOGY uses such high-quality sealing materials in the production of 250 kva power transformers and other products.
2. Improve Cross-Section Shape of Seals
The angle at the corner of the tank edge seal is small, and the traditional circular rubber strip is prone to cracking and leakage. Replacing it with an "8"-shaped cross-section rubber strip can avoid cracking and form a double sealing structure to improve sealing reliability; at the same time, the sealing of air release plugs, oil sample valves and other parts is changed to O-ring sealing to further reduce the risk of leakage.
3. Improve Sealant Adhesives and Air Release Plug Structure
Adopt high-performance sealant adhesives; uniformly replace the air release plugs of transformers entering the factory for maintenance with vacuum butterfly valves, which adopt double-layer sealing at the interface with the transformer flange to effectively solve the interface leakage problem; improve the structure of the bushing air release plug, customize various specifications of air release plugs, and change the contact surface from flat to conical to improve sealing stability. This improvement has been applied in the production and maintenance of 250 kva 3 phase transformers of the company.
4. Implement Integral Accessory Trial Installation and Leak Detection
JINSHANMEN TECHNOLOGY has compiled and improved the "Assembly Process Requirements for Transformer Anti-Leakage", which stipulates that all transformer accessories must undergo integral assembly and leak testing. Through integral assembly, problems such as incorrect installation dimensions, poor sealing, and unreasonable structure must be solved in the factory, otherwise the product will not be allowed to leave the factory.
5. Strengthen Supervision and Strictly Control Quality
Clearly specify the quality requirements and compensation clauses for oil leakage in the transformer order technical agreement; strengthen the training of dispatched supervision personnel, strictly control each production process, especially conduct regular inspections after accessory pre-installation and leak testing, and require the manufacturer to rectify unreasonable problems in a timely manner to eliminate oil leakage from the source.
6. Standardize Hoisting and Transportation Operations
Strengthen the training of hoisting personnel on transformer knowledge, clarify the transportation speed to avoid acceleration impact during transportation; adopt multi-point support measures to reduce the pressure on the tank edge support surface and the risk of deformation; cooperate with design units to relax the size of the transformer load-bearing foundation in the construction of new substations and the reconstruction of old substations to avoid structural damage leading to leakage during installation.
7. Strengthen Component Quality Control
Strictly follow the ISO9000 standard, screen, evaluate and re-inspect the subcontractors of valves, radiators, on-load tap changers and other components, and strengthen the incoming physical quality inspection; select high-quality domestic components to comprehensively improve the quality of transformer components and provide guarantee for the long-term stable operation of products.