Heavy 66kV/69kV High Voltage Transformer 10MVA to 80MVA Grid-Connected Utility Transformer

Heavy 66kV/69kV High Voltage Transformer (10–80 MVA) –Features

The 66kV/69kV oil-immersed high voltage transformer is purpose-built for medium-scale substation deployment, renewable energy integration, and industrial grid reinforcement. With rated power ranging from 10 MVA to 80 MVA, this three-phase transformer serves as a critical link between generation and distribution networks across various voltage tiers.

Engineered with a Y-connected or Delta-connected high voltage winding, the unit offers customizable secondary voltages such as 13.2 kV, 12.47 kV, 11 kV, or 4.16 kV, meeting diverse regional and utility specifications. The magnetic core is made of high-grade cold-rolled grain-oriented silicon steel, reducing no-load losses, while the precision-wound copper conductors ensure low load loss and high thermal endurance.

The transformer is housed in a sealed, welded steel tank with corrugated fins or radiator banks, filled with thermally stable mineral or biodegradable ester oil, enabling excellent insulation and heat dissipation. High-voltage bushings, pressure relief valves, gas relays, and thermometer ports are standard, while advanced add-ons like on-load tap changers (OLTC), digital monitoring systems, and smart IoT modules can be optionally integrated.

Each unit is subjected to routine and type tests, including full-load and lightning impulse testing, ensuring reliability under demanding grid conditions. The design complies with IEC, ANSI, IEEE, CSA, UL, and GOST standards, supporting safe operation, long lifecycle, and low maintenance.

Energy Transformer offers OEM branding, private-label services, and flexible production runs for global clients. These transformers are extensively exported to North America (USA, Canada, Mexico) and South America (Brazil, Argentina, Chile, Colombia, Peru, Ecuador), serving utilities, EPC contractors, solar and wind projects, and regional distribution authorities.

Heavy 66kV/69kV High Voltage Transformer (10–80 MVA) Technical Specs

No.	Item	Specification	Remark
1	Power Rating	10 MVA to 80 MVA	Flexible to meet project requirements
2	Primary Voltage	66 kV / 69 kV (Delta or Wye connection)	Medium voltage input for utility grids
3	Secondary Voltage	4.16 kV, 11 kV, 12.47 kV, 13.8 kV (customizable)	Multiple voltages for different grids
4	Phase	Three-phase	Compatible with 50Hz or 60Hz frequency
5	Cooling Type	ONAN or ONAF (Oil Natural Air Natural / Forced Air)	Efficient oil-immersed cooling
6	Core Material	Grain-oriented silicon steel	Low core loss and noise
7	Insulation Medium	Mineral oil	Excellent dielectric strength
8	Temperature Rise	Max 65掳C (ONAN), up to 75掳C (ONAF)	Industry standard safety compliance
9	Enclosure	Corrosion-resistant steel tank	Suitable for harsh outdoor environments
10	Standards Compliance	IEC 60076, ANSI C57.12, IEEE, UL, CSA	Global safety and quality standards
11	Certifications	CE, UL, GOST, CSA	Recognized international quality marks
12	Connection Options	Delta-Wye, Wye-Delta, Delta-Delta, Wye-Wye	Flexible grid connection configurations
13	Applications	Utility substations, renewable energy, industrial sites	Critical power transmission and distribution
14	Protection Features	Overload protection, temperature sensors, Buchholz relay	Enhanced safety and reliability
15	Dimensions & Weight	Customized based on capacity	Optimized for transport and installation
16	Operational Efficiency	Low loss design, high energy efficiency	Energy-saving and eco-friendly
17	Ambient Temperature Range	-25掳C to +45掳C	Suitable for diverse climates in Americas
18	Total Losses (at Rated Load)	1.0% to 1.4%	Minimizes operational energy loss
19	No-Load Loss	0.15% to 0.4%	Reduces standby power consumption
20	Load Loss	0.7% to 1.0%	Optimized for load conditions
21	Impedance Voltage	5.0% to 7.0%	Stable voltage regulation
22	Short-Circuit Withstand Capacity	25 kA to 50 kA	Meets grid fault tolerance standards
23	Insulation Class	Class A (up to 105掳C)	Suitable for long-term operation
24	Winding Material	Copper or Aluminum	Copper preferred for conductivity
25	Tap Changer Type	On-load tap changer (OLTC) or off-load tap changer	Flexible voltage regulation
26	Bushing Type	Porcelain or composite bushings	Weather-resistant and durable
27	Cooling Oil Volume	300 to 1200 liters	Sized to transformer capacity
28	Design Life	25 to 35 years	Reliable long-term operation
29	Noise Level	55 to 65 dB	Low noise design for urban use
30	Warranty	1 to 3 years	Flexible warranty options
31	Delivery Time	45 to 75 days	Fast delivery for standard orders
32	Lead Time for Custom Orders	90 to 120 days	On-time delivery for customized solutions
33	Surge Arrestor	Optional integrated surge arrester	Protects against voltage spikes
34	Buchholz Relay	Standard for oil transformers	Early fault detection
35	Pressure Relief Device	Equipped with pressure relief valve	Safety under excess pressure
36	Online Monitoring	Optional IoT-enabled monitoring	Real-time condition tracking
37	Environmental Compliance	RoHS, REACH compliant	Meets global environmental standards
38	Oil Type Options	Mineral oil or biodegradable ester-based oil	Eco-friendly insulation options
39	Shipping & Packaging	Heavy-duty packaging for export	Ensures safe transport worldwide
40	Market Focus	North America (USA, Canada, Mexico), South America (Brazil, Chile, Argentina)	Widely supplied to major American markets

✅ 66kV/69kV Heavy-Duty High Voltage Step-Down Oil-Immersed Transformer Overview

A 66kV or 69kV oil-immersed step-down transformer is a critical component in regional power transmission networks, used to reduce high voltage to medium or distribution-level voltages such as 33kV, 13.8kV, or 11kV. These heavy-duty, grid-connected utility transformers are built for continuous three-phase operation, featuring high-grade copper or aluminum windings, robust insulation, and sealed oil tanks. ENERGY TRANSFORMER designs each unit to meet grid standards with ONAN/ONAF cooling and on-load tap changers (OLTC) for stable voltage regulation. Certified to IEC, ANSI, CSA, CE, GOST, and other global utility codes.

✅ 66kV/69kV Step-Down Transformer MVA Ratings (10 MVA to 80 MVA)

ENERGY TRANSFORMER manufactures 66/69kV power transformers in a variety of standard and custom MVA ratings, including 10 MVA, 16 MVA, 25 MVA, 40 MVA, 63 MVA, and 80 MVA. These units are ideal for urban substations, wind farms, hydroelectric plants, and industrial parks. Every model is tested for short-circuit withstand, lightning impulse, and temperature rise according to IEC 60076. Low-loss design and overload protection features ensure long service life and high operational efficiency.

✅ How to Calculate MVA for 66/69kV Grid-Connected Power Transformers

Use the formula: MVA = (√3 × Voltage × Current) ÷ 1,000,000. For instance, at 69kV and 420A, the transformer rating is ~50 MVA. Accurate MVA calculation ensures compatibility with circuit breakers, protection relays, and feeder capacity. ENERGY TRANSFORMER offers engineering support for system capacity sizing, fault current analysis, and transformer coordination in grid planning.

✅ What Is a 66kV or 69kV Step-Down High Voltage Utility Transformer?

These high voltage substation transformers step down electricity from transmission voltage to distribution level, serving as a key node in subtransmission grids and industrial substations. Designed for heavy load conditions, they use star-delta or star-star vector groups, OLTC voltage regulation, and smart monitoring options. Applications include smart grids, wind energy transmission, mining operations, and chemical plants. ENERGY TRANSFORMER ensures rugged design, seismic compliance, and long-term operation in extreme climates.

✅ 66/69kV Oil-Filled Transformer Dimensions and Space Requirements

Typical size varies by rating. A 40 MVA transformer may be 5.5–6.5 m long, 3–4 m wide, and 3.5–4.5 m high. Higher ratings like 63 MVA or 80 MVA require larger foundations and more installation space. We provide detailed 2D/3D drawings, base plates, and clearance layouts for accurate civil work planning. Compact modular designs with detachable radiators or skid-mount options are available for tight substations or containerized deployment.

✅ 66/69kV Transformer Weight and Transportation Planning

Weight depends on power rating and design. A 25 MVA unit may weigh 40–50 tons (net), while an 80 MVA transformer may exceed 90 tons. Total shipping weight (including oil and crates) can go over 120 tons. ENERGY TRANSFORMER supplies all lifting and hoisting data with lifting lugs, center-of-gravity markings, and reinforced crates, ensuring safe delivery via road, rail, or ocean freight.

✅ 66kV/69kV Transformer Price and Cost Considerations

Price depends on MVA rating, insulation class, core material (grain-oriented silicon steel), winding type (Cu/Al), and accessories such as OLTC, surge arresters, or digital monitoring. For example, a 40 MVA transformer may cost between $250,000–$450,000 USD, depending on options. ENERGY TRANSFORMER controls cost by producing core, tank, and windings in-house, and offers EXW, FOB, or CIF pricing for global delivery.

✅ Full Load Current for 66/69kV Oil Transformers

Use I = MVA / (√3 × kV). A 25 MVA transformer at 66kV has a current rating of ~219A. ENERGY TRANSFORMER includes rated current for HV/LV sides in all drawings and nameplates, and supports proper selection of bushings, CT/PT ratios, relay coordination, and cable sizing. Optional current monitoring sensors available.

✅ Installation Requirements for 66kV/69kV Power Transformers

Installation includes a civil foundation, oil containment bund, earthing system, fire separation, and HV fencing. ENERGY TRANSFORMER provides foundation drawings, installation guides, and on-site support upon request. We also offer dry-air injection, vacuum oil filling, and test commissioning services.

✅ Transformer Tank, Conservator System, and Protection Cabinet Features

Our oil tanks are hermetically sealed steel structures with corrosion-resistant coatings, welded joints, and pressure-tested assemblies. Conservator tanks manage oil expansion and include nitrogen-sealed or silica-gel breathers. Protection box includes Buchholz relay, OLTC drive, fan controls, and digital display. Safety devices: pressure relief valve, oil level indicator, sudden pressure alarm, gas relay.

✅ Vector Groups and Voltage Class Configurations for 66/69kV Units

Standard voltage classes: 69/13.8kV, 66/11kV, 66/33kV, 69/34.5kV, etc. Vector groups: YNd11, Dyn11, YNyn0, chosen based on grounding system and fault current management. ENERGY TRANSFORMER supports custom vector groups for synchronization with local grids. All units marked with vector data, polarity, and wiring diagrams on nameplate and documents.

✅ Copper vs Aluminum Windings in 66kV/69kV High Voltage Transformers

Copper is preferred for lower losses, higher mechanical strength, and longer lifespan. Aluminum is an economic alternative for budget-sensitive applications. ENERGY TRANSFORMER provides both, with high-reliability layer or disc winding structures, oil-duct cooling, and inter-turn insulation tested to IEC and ANSI standards.

✅ Efficiency and Losses in 66/69kV Transformers

Typical efficiency > 99.5% at full load. A 25 MVA unit may have ≤25 kW no-load loss and ≤140 kW load loss. ENERGY TRANSFORMER uses low-loss CRGO steel, precision winding techniques, and optimized cooling for minimal losses. Loss data is provided on test report and nameplate. Optional IoT monitoring systems track real-time losses and alert operators to deviations.

✅ Global Certifications for 66/69kV Power Transformers

All units are certified to IEC 60076, ANSI C57, CSA C88, GOST 11677, with optional CE, SASO, UL, and other project-based standards. Routine, type, and special tests are conducted per order. Factory Acceptance Tests (FAT) available onsite or via remote video. Third-party inspections by SGS, BV, or customer-specified agents welcome.

✅ Nameplate Data for 66/69kV Transformers

Includes: manufacturer name, model code, rated voltage, rated MVA, frequency, cooling type, insulation class, vector group, weight, oil volume, loss values, standards, serial number, and year. ENERGY TRANSFORMER provides QR code-linked digital datasheets, and dual-language (EN/RU or EN/ES) nameplates upon request.

✅ 66kV/69kV Grid Transformers for Sale Worldwide

ENERGY TRANSFORMER supplies grid-connected 66kV/69kV step-down transformers to over 40+ countries, including Saudi Arabia, Vietnam, Kazakhstan, Chile, Nigeria, the USA, Canada, Mexico, Argentina, Colombia, and Brazil. Fast lead time, full export documents, and turnkey delivery (FOB/CIF/DDP available). Contact us for custom design support, datasheets, pricing, and project references.

66kV/69kV Grid-Connected Utility Transformer Factory Delivery, Packaging, and International Shipping Process (10MVA–80MVA)

Why Choose 66kV/69kV Grid-Connected High Voltage Transformer (10–80 MVA, Oil-Immersed)?

Energy Transformer’s 66kV/69kV oil-immersed transformer is engineered for stable voltage transformation in utility grids, industrial hubs, and renewable energy projects. With ratings from 10 MVA to 80 MVA, it offers reliable performance for substation and interconnection needs.

✅ Optimized for Grid Integration
Step-down design enables seamless power delivery from regional transmission to distribution or industrial consumption levels.

✅ Robust Design & Cooling
Heavy-duty construction and efficient ONAN/ONAF oil cooling ensure long-term durability and stable operation in demanding environments.

✅ Global Standards & Compliance
Manufactured to IEC, IEEE, GOST, and CE certifications—ensuring safety, reliability, and export readiness.

✅ Flexible Ratings & Configurations
Custom voltage ratios, vector groups (YNd1, Dyn11, etc.), and OLTC/DETC options available to match local grid needs.

✅ Fast Production & Worldwide Delivery
Standard lead time within 60–90 days. Shipped to over 40+ countries across North & South America, Asia, Africa, and the Middle East.

📩 Contact us today for custom pricing, datasheets, or technical support for your 66kV/69kV transformer projects. Factory-direct solutions—fast, reliable, and fully certified.