What are the forms of 3 phase transformer leakage?
Oil leakage in three-phase transformers poses significant risks to operational safety, equipment longevity, and grid reliability—often leading to unplanned downtime, costly repairs, and even fire hazards if left unaddressed. Beyond immediate operational disruptions, leaks can contaminate the surrounding environment and compromise the transformer’s insulating properties, escalating into catastrophic failures over time.
Two primary categories of factors contribute to such leakage issues: inherent flaws during the design and manufacturing stages (e.g., subpar material selection, inadequate quality control) and external factors tied to installation and maintenance (e.g., improper handling, neglect of routine inspections). Understanding the most vulnerable components and common leakage mechanisms is critical for proactive mitigation.
Vulnerable Components for Leakage
Three-phase transformers feature multiple high-risk areas where oil leakage is likely to occur, particularly at joints, connections, and components subjected to thermal stress or mechanical vibration. Key trouble spots include:
- Radiator connection points
- Flat butterfly valve caps
- Bushing assemblies
- Insulating porcelain components
- Welded seams and joints
- Casting sand holes
- Flange connections
These areas are prone to leakage due to their exposure to temperature fluctuations, operational vibration, and wear over the transformer’s service life. Poor manufacturing tolerances or improper installation can further exacerbate vulnerabilities.
Weld-Related Oil Leakage
Welding defects are a leading cause of transformer oil leakage, often stemming from inadequate fabrication processes. Common issues include incomplete fusion (cold welding), weld separation, pinholes, and gas bubbles trapped during welding. These flaws are frequently masked by welding flux residues or factory-applied paint, remaining dormant until the transformer is put into operation.
Operational electromagnetic vibration exacerbates the problem by creating cyclic stress on welded joints, causing microcracks to expand over time. For transformers adhering to industry standards (e.g., AWS D1.1 for structural welding), non-destructive testing (NDT) such as ultrasonic or radiographic inspections during manufacturing can identify hidden weld defects before deployment.
Seal Failure-Induced Leakage
Seal degradation or improper sealing is another major contributor to oil leakage, typically affecting the tank edge, tank cover, and other mating surfaces. These areas rely on oil-resistant rubber gaskets or adhesive strips to maintain a tight seal. Leakage occurs when:
- Sealant materials are incompatible with transformer oil or degrade under high temperatures.
- Joint surfaces are not properly cleaned or aligned before assembly, leaving gaps.
- Uneven compression during installation (e.g., from improper bolting) prevents full contact between sealing surfaces.
Using high-quality, temperature-resistant seals (rated for the transformer’s operating range) and following manufacturer-specified torque values during assembly can significantly reduce this risk.
Flange Connection Leakage
Flange joints—critical for connecting major components—are susceptible to leakage due to surface irregularities, loose fasteners, or incorrect installation techniques. Even minor deviations in flange flatness (beyond the recommended tolerance of 0.1mm) can create pathways for oil to escape.
Common mistakes include over-tightening or under-tightening bolts (leading to uneven pressure distribution) and reusing worn washers. Proper installation requires cleaning flange surfaces to remove debris, using calibrated torque wrenches to ensure uniform bolt tension, and inspecting gaskets for wear or damage before assembly.
Casting Defect-Related Leakage
Iron castings (e.g., tank components, valve bodies) often suffer from inherent flaws such as sand holes and microcracks, which develop during the casting process. These defects arise from improper mold design, inconsistent cooling rates, or contamination of raw materials.
While surface sand holes may be sealed temporarily during manufacturing, operational stress (e.g., thermal expansion, vibration) can widen these pores, allowing oil to seep through. Adhering to casting standards like GB/T 1348-2019 (for ductile iron castings) and conducting pressure testing on cast components can help detect such defects early.
Threaded Bolt and Pipe Leakage
Leakage at threaded connections (e.g., bolts, pipe fittings) is typically caused by poor machining precision or inadequate sealing. Roughly finished threads create uneven contact surfaces, while low-quality sealants or improper thread wrapping (e.g., insufficient PTFE tape) fail to form a reliable barrier.
Over time, thermal cycling and vibration can loosen threaded fasteners, further compromising the seal. Using precision-machined components, applying compatible thread sealants, and conducting periodic re-torquing during maintenance can mitigate this issue.
Radiator Oil Leakage
Transformer radiators—vital for heat dissipation—are often constructed by flattening and stamping seamed steel pipes. Leakage commonly occurs at pipe bends and welded joints, primarily due to residual stress from the stamping process. During fabrication, the pipe’s outer wall is stretched while the inner wall is compressed, creating internal stress that persists post-manufacturing.
Operational thermal cycling (heating and cooling) exacerbates this stress, leading to fatigue cracks in high-tension areas. Using seamless steel pipes for radiators or implementing stress-relief heat treatment after stamping can reduce leakage risk. Regular pressure testing of radiators also helps identify weak points before failure.
Insulator and Glass Component Leakage
Insulating porcelain components and glass oil-level indicators are prone to leakage due to improper installation or seal deterioration. Mishandling during installation (e.g., excessive torque when mounting insulators) can crack the porcelain or damage internal seals. Additionally, prolonged exposure to harsh environmental conditions (e.g., humidity, chemical pollutants) degrades sealants, creating gaps for oil leakage.
Proper installation involves using torque-limiting tools to avoid over-tightening and selecting weather-resistant seals for outdoor transformers. Routine inspections should include checking for cracks, discoloration, or seal swelling in these components.
By addressing these root causes and implementing proactive maintenance practices—such as regular NDT inspections, proper seal replacement, and adherence to manufacturing standards—transformer operators can significantly reduce oil leakage risks, ensuring long-term reliability and safety. For manufacturers like Lihe Transformer, prioritizing quality control during design and fabrication is foundational to minimizing leakage-related issues in end-user applications.