Structure and Design Features

Core

●Made of Cold-Rolled Grain-Oriented Silicon Steel Sheets (CRGO)

●Full oblique joints, multi-step stacking

●Low no-load loss, low noise design

Windings

●High-conductivity oxygen-free copper conductors

●HV winding: continuous or multi-layer cylindrical type, with axial oil ducts

●LV winding: foil or spiral type, high mechanical strength

●Inter-turn and ground insulation designed per international insulation coordination standards

Tank and Conservator (Oil Pillow)

●Rigid box-type or bell-type tank, high-strength welded structure

●Independent conservator mounted above the tank, connected via an inclined pipe

●Conservator equipped with capsule-type / diaphragm-type / metal bellows sealing elements, coordinated with breather for oil-gas isolation

●Configure magnetic oil level gauge or pointer-type oil level gauge, medium and large capacity transformers are equipped with an oil temperature indicator as standard, which can achieve over-temperature alarm and trip protection.

●Medium and large capacity transformers are equipped with gas relay (Buchholz Relay) installed between main tank and conservator

●External plate-type radiators on tank, with fans if necessary (ONAF)

●Equipped with pressure release valve, grounding terminals, etc.

Insulating Oil

●High-quality mineral insulating oil compliant with international standards

●Environmentally friendly insulating liquids optional: natural ester (vegetable oil) or silicone oil

Performance Advantages

●Adequate Volume Compensation: Independent conservator accommodates thermal expansion/contraction of large oil volumes, preventing excessive tank stress

●Comprehensive Protection System: Gas relay, pressure release valve, temperature and oil level monitoring all included

●Excellent Maintainability: Supports tank lifting inspection, oil filtration, oil sampling analysis, and oil replenishment

●Long Service Life: Oil-gas isolation design slows oil aging, design life ≥25 years

●Strong Short-Circuit Withstand Capability: Rigid tank + reinforced winding structure, compliant with international standards

Typical Applications

●Urban and rural grid substations

●Industrial parks, mines, petrochemical bases

●High-rise buildings, commercial center distribution

●Solar, wind power, and energy storage station step-up

●Ports, airports, rail transit power supply

Oil-Immersed Distribution Transformer FAQ

Q1: What routine maintenance does an oil-immersed transformer require?

A: Temperature Measurement & Cooling: Monitor top oil temperature (typically ≤85°C), ensure fans and oil pumps operate normally, and keep cooling channels unblocked.

Oil Level & Leak Prevention: Regularly inspect oil level and perform oil sampling tests (e.g., dielectric strength, moisture content). Verify oil level matches ambient temperature with no false readings. Focus on valves, flanges, and other critical points to prevent oil leakage.

Visual Inspection & Sound: Listen for uniform internal sound; check for abnormal vibration or discharge noise. Inspect bushings for cracks and discharge marks; check joints for overheating.

Accessories & Protection: Check that breather silica gel has not discolored or degraded; confirm no gas accumulation in the gas relay; ensure the explosion-proof tube or pressure release valve is intact.

Environment & Testing: Keep the site clean, ensure the oil containment pit is free of standing water, and maintain complete fire-fighting facilities. Perform preventive tests and oil sampling analysis at prescribed intervals.

Q2: Are there more environmentally friendly alternatives to mineral insulating oil?

A: Yes. In addition to traditional mineral oil, we offer environmentally friendly transformers using biodegradable natural or synthetic ester liquids as insulating media. These ester liquids are non-toxic, naturally biodegradable, and offer higher flash points (excellent fire resistance), making them ideal for locations with strict environmental and fire safety requirements (e.g., indoor substations, areas near forests).

Q3: What are the differences between various connection groups?

A: If your transformer supplies power to a single factory or residential area and does not need to operate in parallel with other transformers, different connection groups (such as the common Dyn11 and Yyn0) can both be used, though their actual performance differs significantly.

If you are expanding capacity or replacing a unit and the new transformer needs to operate in parallel with existing ones, you must carefully check the nameplate of the existing transformer. The connection group designation of the new transformer must be exactly the same as the existing one — never rely solely on capacity and voltage ratings!

Q4: How should the load rate of medium-to-large capacity transformers be set?

A: Medium-to-large capacity transformers must consider not only current load demands but also the Total Cost of Ownership (TCO) over the entire lifecycle. The recommended long-term operating load rate is 70%–85%. A load rate that is too low results in “oversized operation” with significant no-load loss waste; a load rate exceeding 85% for extended periods will accelerate insulation aging and shorten equipment life. In dual-transformer configurations, when one unit is out of service, the other can rely on forced cooling measures for short-term overload (typically not exceeding 30%) to ensure power supply continuity.

Q5: What should be considered when selecting transformers for special environments?

A: High Pollution or Coastal Salt Spray Environment: Oil-immersed transformers inherently possess strong environmental adaptability. For coastal areas or heavy industrial zones, we can provide superior salt spray and corrosion protection through special processes such as thickened anti-corrosion coatings and stainless steel accessories, ensuring long-term stable operation even in harsh environments.

High Temperature Environment: Sustained high temperatures reduce heat dissipation efficiency and accelerate the aging of insulating oil and paper. Therefore, in high-temperature regions, we typically recommend appropriately reducing the load rate (derating) or installing additional forced-air cooling systems.

Low Temperature Environment: Extreme cold causes insulating oil viscosity to increase sharply, severely impeding internal oil circulation and heat dissipation, and may cause rubber seals to become brittle and leak. For such environments, we select specialty transformer oils with extremely low pour points (e.g., -45°C or -50°C grades).

High Altitude Environment: High-altitude areas have thin air and low atmospheric pressure, presenting dual challenges: (1) significantly reduced air convection cooling capacity, leading to increased temperature rise; (2) reduced air insulation strength (breakdown voltage), making external insulation discharge more likely. Therefore, transformers for high-altitude use must have increased external insulation distances (e.g., extended bushing creepage distance) per standards, and typically require increased heat dissipation surface area or derating design to compensate for reduced cooling efficiency.

High Humidity Environment: Excessive humidity can cause surface condensation on transformers, reducing external insulation performance and potentially leading to flashover. We address this by reinforcing the creepage distance design of external insulation components such as bushings and ensuring the sealing system is absolutely reliable to prevent moisture ingress.

Dusty/Sandy Environment: Dust and sand can easily clog the gaps in radiators or corrugated tanks, affecting heat dissipation, and conductive dust may cause external short circuits. For such environments, we optimize the heat dissipation structure design (e.g., increasing fin spacing) and adopt fully sealed protection to prevent dust ingress.

Q6: What information is needed to obtain a quotation for a distribution transformer?

A: To obtain a quick and accurate quotation, please provide the following core parameters first:

1. Transformer type: Oil-immersed / Dry-type transformer
2. Rated capacity (kVA)
3. Primary and secondary voltage levels(e.g., 33kV / 0.4kV)
4. Rated frequency: 50Hz or 60Hz
5. Number of phases: Single-phase or Three-phase
6. Winding material: Copper or Aluminum windings supported, each with distinct advantages in cost and performance
7. Connection group symbol & impedance voltage (%): (Must be provided if parallel operation is required)

In addition, our transformers support customization. You may provide the following supplementary information based on actual needs:

1. Tap changer type: Conventional off-circuit tap changer, or optional on-load tap changer (OLTC)
2. Loss standards: Any specific loss standards or energy efficiency class requirements?
3. Installation environment: Altitude, extreme temperatures, etc.
4. Other requirements: Execution standards, special protection levels, instrument accessories, etc.

If you are looking for reliable power support for your project, please contact the Kima Electric team.

• Direct Factory & Manufacturer: We are a professional China Three-phase oil-immersed Power transformer manufacturer (available in 6.3kV,10kV,11kV, 13.2kV,15kV,20kV,22kV,33kV, and other voltages). Our factory is equipped with advanced production facilities and accepts OEM/ODM orders.
• Reliable Supplier: We serve as a trusted international supplier for global buyers looking to source high-efficiency and low-loss Three-phase oil-immersed Power transformers from China.
• International Standards & Global Reach: Our transformers are rigorously tested to comply with IEC 60076 and other international standards. We export to diverse markets across Southeast Asia, Africa, and the Middle East, adapting to various local grid environments.

Competitive Quotation: Contact us today to discuss your project requirements, get a customized solution, and receive a free wholesale quote.

Convenient Inquiry Process

●You may contact us via our website, email, or other channels, or download and fill out the “Inquiry Application Form” from our official website.

●You may also directly provide your existing technical documents, drawings, etc., as the basis for requirement assessment. We will provide a quotation as soon as possible.

Production & Quality Control

●Before formal production, we will provide detailed technical proposals including specifications, structural drawings, etc., for your review and confirmation.

●We strictly implement the ISO quality management system, comprehensively monitoring raw materials, production processes, and finished product inspection to ensure every customized product delivers stable and reliable quality.

Delivery & After-Sales Service

●Packaged in specialized wooden crates compliant with international standards, lined with high-performance moisture-proof materials to ensure absolute safety and dryness during long-distance transportation.

●Detailed user manuals, maintenance manuals, and related documentation are provided with the shipment.

●Remote or on-site installation guidance and commissioning services are available upon request.

●Comprehensive after-sales support including technical consultation, fault diagnosis, and spare parts supply to ensure long-term stable operation of the product.