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The Backbone of Power Delivery: Reliable, High-Efficiency Liquid-Filled Transformers

Oil-immersed distribution transformers are the most widely used and trusted solution for stepping down medium voltage power to the low voltage levels required for local consumption. With their time-tested design, these liquid-filled transformers offer superior cooling and insulation, ensuring unparalleled reliability and longevity even in the harshest environments.

At Energy Transformer, we engineer our oil-immersed distribution transformers for exceptional efficiency, durability, and safety. Our solutions are designed to power everything from rural communities to dense urban networks, meeting the diverse demands of utilities, industrial facilities, and commercial projects.

Ready to enhance your distribution network with proven, high-performance transformers? Request a Quote or Talk to an Engineer today to discuss your project needs.

What Are Oil-Immersed Distribution Transformers?

An oil-immersed distribution transformer is a static electrical device where the core and coils are submerged in an insulating liquid, typically mineral oil. This oil serves two critical functions: it acts as a superior electrical insulator and efficiently dissipates heat generated during operation. These transformers are the final link in the power grid, converting electricity from primary distribution lines (e.g., 11kV, 33kV) to the lower voltages (e.g., 400V, 480V) used by end-users.

They are the preferred choice for:

• Overhead Networks: Pole-mounted transformers in residential and rural areas.

• Underground Systems: Pad-mounted transformers in urban subdivisions and commercial centers.

• Industrial Sites: Ground-mounted units providing power to factories and workshops.

Voltage & Capacity Ranges

At Energy Transformer, we design and manufacture oil-immersed distribution transformers to handle a wide range of voltage and power requirements, ensuring we can support any local grid architecture.

• Primary Voltage: 10kV, 11kV, 13.8kV, 20kV, 22kV, 33kV, and 35kV. We also offer solutions for higher voltages on request.

• Secondary Voltage: 400V, 415V, 480V, 600V, 690V, and other custom-specified voltages to meet diverse global standards.

• Capacity (kVA): Our offerings range from small units of 15 kVA to large units exceeding 5000 kVA (5 MVA).

Our team can customize parameters such as vector groups, impedance, and insulation fluid type to perfectly match the specific needs of your distribution network.

Our Product Portfolio: Types & Mounting Options

We provide a variety of oil-immersed distribution transformers, each optimized for different applications and operational environments.

Conservator Type Transformers

These transformers feature an oil conservator tank mounted above the main tank. The conservator allows the oil to expand and contract with temperature changes, preventing the main tank from being exposed to air and moisture. A breathing device, such as a silica gel breather, is used to absorb moisture from the air entering the conservator.

Sealed Type Transformers

Also known as hermetically sealed transformers, these units do not have a conservator tank. The main tank is completely filled with oil and is sealed, preventing any contact with the atmosphere. This design eliminates moisture ingress and oxidation, making them virtually maintenance-free and extending their operational life.

Pole-Mounted Transformers

Specifically designed for installation on utility poles, these pole-mounted transformers are an economical and efficient solution for rural areas and residential neighborhoods with overhead power lines. Their compact design and robust construction ensure reliable performance in outdoor conditions.

Pad-Mounted Transformers

Designed for use with underground electrical systems, pad-mounted transformers are enclosed in a secure, tamper-proof steel cabinet. These transformers are a common sight in urban subdivisions, commercial areas, and industrial parks, providing a safe and aesthetically pleasing solution.

Technical Features and Customization

Our transformers are built with advanced features and customization options to maximize performance, safety, and longevity.

• Cooling Systems: Our standard cooling configuration for oil-immersed units is ONAN (Oil Natural Air Natural), where heat is dissipated through natural convection of the oil and air. We also offer ONAF and OFAF for larger units requiring forced cooling.

• Tap Changers: Transformers can be equipped with a De-Energized Tap Changer (DETC) to adjust voltage levels offline, ensuring optimal voltage supply to the network.

• Efficiency and Losses: We design our transformers to meet or exceed international standards like IEC 60076 and IEEE C57, with a focus on minimizing no-load and load losses to reduce lifetime operating costs.

• Accessories: Standard accessories for oil-immersed transformers include an oil level indicator, pressure relief device, and temperature gauge, with optional Buchholz relay for enhanced safety and monitoring.

Common Oil-Immersed Distribution Transformer Specifications

Capacity (kVA)	Primary Voltage (kV)	Secondary Voltage (V)	Cooling Type	Impedance (%)	Weight (kg)
50	11	415/240	ONAN	4	350
100	22	400/230	ONAN	4.5	550
500	33	480/277	ONAN/ONAF	5.5	1800
1000	13.8	600	ONAF	6	2500
2500	35	400/230	ONAF	7	4500

Note: The specifications above are for illustrative purposes. We provide fully customizable solutions based on your specific project needs.

Applications & Use Cases

Our oil-immersed distribution transformers are integral to local power delivery, serving a diverse range of customers and projects.

• Residential Areas: Ensuring a steady and safe power supply for homes and neighborhoods.

• Commercial Buildings: Providing reliable electricity for shopping centers, office parks, and residential complexes.

• Industrial Facilities: Supplying power for small-to-medium-scale manufacturing, factories, and workshops.

• Utility Projects: Essential components for municipal and private power companies to expand and maintain their distribution networks.

Why Choose Energy Transformer?

• Global Certifications: Our products are compliant with major international standards, including ANSI, IEC, IEEE, and GOST, and can be provided with certifications like CE and UL.

• Factory-Direct Manufacturing: As a leading oil-immersed transformer manufacturer, we control the entire process from design to delivery, ensuring quality and competitive pricing.

• Robust Quality Assurance: Every transformer undergoes rigorous testing, including routine and type tests, to guarantee reliability. We welcome third-party inspections from agencies like SGS and Bureau Veritas.

• Proven Track Record: With years of experience exporting transformers to markets in North America, Europe, Africa, and the Middle East, we have the expertise to handle global logistics and compliance.

FAQs about Oil-Immersed Distribution Transformers

Q: What is the lifespan of an oil-immersed transformer? A: With proper maintenance and operation, a high-quality oil-immersed transformer can have a lifespan of 30 to 40 years or more. Using a sealed-type design can extend this by eliminating exposure to external contaminants.

Q: What kind of maintenance is required for oil-immersed transformers? A: For conservator-type transformers, maintenance includes periodic checks of the oil level, oil quality testing, and replacement of the silica gel in the breather. Sealed-type units require minimal maintenance, typically only routine inspections.

Q: Are there eco-friendly alternatives to mineral oil? A: Yes, we offer the option of using biodegradable ester fluids (e.g., natural esters) as an alternative to mineral oil. These fluids are non-toxic and have a higher flash point, making them safer and more environmentally friendly.

Q: What is the difference between a sealed type and a conservator type transformer? A: A conservator type transformer has a separate tank to manage the oil's expansion and contraction, which requires a breather to allow for air exchange. This design needs more maintenance. A sealed type transformer is completely sealed, with no contact with the atmosphere. It uses the elasticity of the tank walls or a gas cushion to handle oil volume changes, resulting in less maintenance and a longer life for the oil.

Q: Can these transformers be used in areas with high pollution or salt spray? A: Yes. Oil-immersed transformers are highly durable and are commonly used in polluted or coastal environments. Their robust steel tank and high-quality paint system provide excellent protection against corrosion. We can also provide special coatings and materials for extreme conditions.

Q: What information is needed to get a quote for a distribution transformer? A: To get a fast and accurate quote, please provide the following key details:

• Capacity (kVA)

• Primary and Secondary Voltage Levels

• Vector Group

• Frequency (50Hz or 60Hz)

• Number of Phases (Single or Three Phase)

• Tap Changer type (if required)

• Any specific standards or accessory requirements

Ready to Power Your Community?

Whether you are expanding a distribution network or simply upgrading existing equipment, our team of engineers at Energy Transformer is ready to provide expert advice and a custom-engineered solution.

Contact us today to get a fast quote and take the first step toward a more reliable and efficient power system.