66KV Oil-Immersed Transformer

Your Leading 66KV Oil-Immersed Transformer Supplier

 

Trust In Grid Co., Ltd. is a professional transformer manufacturer, specializing in the design and production of power transformer, high-voltage switchgear, power distribution equipment, energy storage systems (ESS), magnetic wire, bushing and machining parts. Our power transformers are available in 500KV, 330KV, 220KV, and 110KV models, and are widely used in power utilities, renewable energy systems (solar and wind), industrial facilities, data centers, transportation infrastructure, and OEM applications.

 

 
 
Why Choose Us?

 

Production Capacity

With 6 factories covering 240,000 m², over 2,000 employees, and 200+ engineers, we support large-scale projects and long-term global supply with more than 30 years of export experience.

Advanced Equipment

We operate a complete set of in-house production equipment, including cutting, winding, CNC machining, vacuum drying, and testing systems, with over 450 machines ensuring stable quality and efficient output.

Quality Control

All products are manufactured and tested in compliance with IEC, IEEE, ANSI, CSA, UL/cUL, CE, and ISO 9001:2015 standards, ensuring reliable performance and smooth international approval.

OEM & ODM Capability

Our engineering team provides OEM/ODM support, including customized design and technical optimization, delivering tailored solutions for utility, industrial, and renewable energy projects.

 

Specifications of 66KV Oil-Immersed Transformer

 

Parameter

Specification

Rated Voltage

66kV (HV) / 6.6–33kV (LV)

Rated Capacity

10 MVA – 100 MVA

Frequency

50Hz / 60Hz

Phase

Three-phase

Cooling Method

ONAN / ONAF

Insulation Medium

Mineral oil

Insulation System

Oil-paper insulation

Temperature Rise

Winding ≤65°C, Oil ≤55°C

Tap Changer

Off-circuit or OLTC

Vector Group

Dyn11 / YNd1

Impedance

Typically 8% – 12%

Core Material

CRGO silicon steel

Installation

Outdoor / Substation use

Standards

IEC 60076 / IEEE / ANSI

 

Advantages of 66KV Oil-Immersed Transformer
 

Superior Cooling Efficiency
Insulating oil offers excellent thermal conductivity and heat capacity, enabling the transformer to stay cool during high loads. According to ABB, oil-filled units often outperform dry-type transformers when it comes to sustained overloads.

 

High Power and Voltage Capacity
Oil-filled transformers can easily handle ratings above 5000 kVA, reaching into hundreds of MVA, making them ideal forgrid guide-scale and industrial use.

 

Long Lifespan
Thanks to efficient cooling and sealed designs, these units can operate for 25–40 years when properly maintained.

 

Cost-Effectiveness
Despite periodic maintenance, oil-filled transformers typically offer lower lifetime costs due to better efficiency and durability.

 

Excellent Overload Tolerance
The oil's thermal mass enables oil-immersed transformers to handle temporary spikes in demand more effectively than dry types.

 

35kV Oil-Immersed NLTC Power Transformer for New Energy Applications

 

Structure of 66KV Oil-Immersed Transformer

An oil immersed transformer consists of a core, windings, tank, radiators, and insulating oil.

 

Core: Built from CRGO steel to minimize hysteresis and eddy current losses.
 

Windings: Made of electrolytic copper with layered insulation for high dielectric strength.
 

Tank: Sealed steel enclosure filled with mineral or ester oil for thermal and electrical insulation.
 

Radiators: Finned structures that increase surface area to improve cooling efficiency.

 

Difference Between 66KV Oil-Immersed Transformers and Dry-Type Transformers

Performance and Efficiency

When comparing oil immersed5 and dry-type transformers, performance and efficiency are critical factors. Oil immersed transformers use mineral oil for cooling, which significantly enhances their thermal performance. This allows them to handle higher loads and maintain optimal efficiency levels even under strenuous conditions. Conversely, dry-type transformers rely on air cooling, which can limit their efficiency in high-demand scenarios.

Safety and Environmental Impact

Safety considerations are paramount in transformer design. Dry-type transformers have an edge in safety due to the absence of flammable liquids. They are less prone to fire hazards and are ideal for indoor use, including in schools and hospitals. In contrast, oil immersed transformers require diligent maintenance to manage potential oil leaks and associated environmental risks.

Cost Considerations

While the initial purchase price of oil immersed transformers may be lower, long-term cost implications can vary based on maintenance and operational efficiency. These transformers typically have lower operational costs due to their efficient cooling systems. However, the need for periodic oil analysis and potential environmental compliance costs can offset these savings. Dry-type transformers, though potentially more expensive upfront, might offer cost savings in environments where minimal maintenance is beneficial.

 

 

Manufacturing Process

Core Lamination Process
The transformer core is manufactured using high-grade CRGO silicon steel to minimize core loss and improve efficiency.

 

Winding Process (Copper / Aluminum)
Windings are produced using high-conductivity copper or aluminum, depending on project requirements.

 

Vacuum Drying & Oil Filling
This process ensures optimal insulation performance and long-term reliability.

 

Testing & Quality Control
Each transformer undergoes strict testing procedures in accordance with international standards.

 

Final Assembly & Packaging
Final assembly ensures mechanical integrity and readiness for transportation and installation.

66kV Oil-Immersed NLTC Power Transformer

 

Customization Options
 

Voltage: Optional

Capacity: Optional

Impedance: Optional

Cooling: Optional

OLTC: Optional

MOQ: Customizable

 

Payment Terms

T.T with 30% downpayment, 70%before shipment.

Paypal or West Union also accept.

 

Our Service Highlights

 

 

Pre-Sales Consultation & Design Support
Early technical engagement to define requirements and deliver optimized solutions.

 

During Sales & Project Execution
Transparent project management with controlled production, quality tracking, and on-time delivery.

 

Warranty Advantage
Minimum 2-year warranty on all products, ensuring reliable and risk-free operation.

 

After-Sales Support
24/7 technical support with fast response, spare parts availability, and training services.

 

Long-Term Partnership
Lifelong technical support and upgrade guidance for sustained performance.

 

Packaging & Shipping

 

Packaging details:
Shockproof foam/moisture-proof film, professional export cartons/wooden crates/pallets.
Final assembly ensures mechanical integrity and readiness for transportation and installation. 

 

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Certificates

 

 

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FAQ

 

Q: What is a 66kV oil-immersed transformer mainly used for?

A: It is used in medium-high voltage networks to step down power from transmission systems to regional or industrial distribution levels.
Oil-immersed units offer better cooling performance and higher capacity, making them suitable for heavy-duty applications.

Q: What cooling options are available for 66kV transformers?

A: Common options include ONAN for natural cooling and ONAF for higher load conditions with forced air.

Q: Can the transformer be customized for different voltage ratios?

A: Yes, voltage levels and tap ranges can be designed based on grid requirements and project specifications.

Q: How is temperature controlled during operation?

A: The transformer uses oil circulation and radiators to dissipate heat and maintain safe operating temperatures.

Q: What maintenance is required for oil-immersed transformers?

A: Routine oil testing, insulation checks, and cooling system inspections are typically required.

Q: Is it suitable for outdoor installation?

A: Yes, most 66kV transformers are designed for outdoor substations with weather-resistant structures.

Q: How long is the expected service life?

A: With proper maintenance, a 66kV transformer can operate reliably for 25–40 years.

 

We're well-known as one of the leading 66kv oil-immersed transformer manufacturers and suppliers in China, also support customized service. Please feel free to buy high quality 66kv oil-immersed transformer made in China here from our factory. Contact us for more details.

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