A 35–69 kV power transformer is a critical component in today’s medium-high voltage transmission and distribution networks. Designed for high reliability, low losses, and long-term operation, this transformer range is widely used in utility substations, industrial facilities, renewable-energy plants, and grid expansion projects. With capacities up to 60 MVA, it provides a robust and flexible solution for demanding electrical systems.

What Is a 35–69 kV Power Transformer?

A 35–69 kV power transformer is typically used for step-up or step-down voltage transformation between transmission and distribution networks. These transformers are engineered with advanced insulation systems, low-loss cores, and heavy-duty windings to ensure stable performance under continuous and fluctuating loads.

Common Design Features

• Oil-immersed construction

• ONAN/ONAF/OFAF cooling

• High-efficiency silicon-steel or amorphous metal core

• Copper or aluminum windings

• Standards: IEC 60076 / IEEE / ANSI / GB

This voltage class is regarded for excellent energy efficiency, mechanical strength, and long service life.

Applications of 35–69 kV Power Transformers

1. Utility and Distribution Substations

Used for medium-high voltage conversion in regional power grids, ensuring stable distribution to residential and commercial zones.

2. Heavy Industrial Loads

Suitable for steel mills, cement plants, mining operations, chemical factories, and other facilities requiring continuous high-reliability power.

3. Renewable Energy Integration

Used as step-up transformers in:

• Wind farms

• Solar PV plants

• Hybrid energy stations
  These transformers boost generated power to 35–69 kV for long-distance transmission.

4. Transportation and Infrastructure

Ideal for airports, rail transit systems, ports, data centers, hospitals, and large commercial complexes.

5. Grid Expansion and Substation Upgrades

Upgrading aged substations to improve capacity, reduce losses, and increase grid stability.

Technical Specifications (Typical Data Sheet)

The following is a professionally structured parameter table widely used in product catalogues:

Note: Parameters can be fully customized according to project needs.

Key Advantages of the 35–69 kV Power Transformer

✔ High Energy Efficiency

Low no-load and load losses reduce overall operating costs and meet modern energy-saving standards.

✔ Strong Short-Circuit Strength

High-quality copper windings and reinforced mechanical structure ensure excellent resilience during grid faults.

✔ Superior Thermal & Insulation Performance

Designed for harsh conditions including high altitude, humidity, coastal environments, and elevated temperatures.

✔ Long Service Life

Premium insulation system and optimized magnetic design ensure 25–30 years of stable operation.

✔ Custom-Engineered Solutions

Voltage, capacity, winding material, cooling, bushings, terminals, enclosure, and installation arrangements can all be custom-designed.

How to Select the Right 35–69 kV Transformer

When choosing a medium-high voltage transformer, consider:

1. Rated load & overload profile

2. Grid voltage fluctuation & regulation needs (OLTC/DETC)

3. Cooling requirements (ONAN vs. ONAF)

4. Energy efficiency level

5. Environmental conditions

6. Installation layout & size limitations

Professional manufacturers can provide optimized solutions based on project parameters.

The 35–69 kV power transformer is a highly reliable, high-efficiency solution for modern transmission and distribution applications. With capacity options up to 60 MVA, this voltage class is widely used across utilities, industries, renewable energy systems, and infrastructure projects. A well-designed transformer ensures reduced energy losses, enhanced stability, and long-term operational safety.