Varelen Electric Co., Ltd

66 kV transformer for wind applications



The wind energy sector has seen tremendous growth and innovation over the past few decades. From modest beginnings in the 1990s, where wind turbines produced a mere 0.5 MW of power, today’s turbines are capable of generating over 10 MW. Despite these advancements, the voltage output of wind turbines remained at 33 kV for many years. However, a significant shift occurred in 2017 when an offshore wind farm in Denmark implemented 7 MW turbines connected to a 66 kV grid. This upgrade has led to enhanced efficiency and reduced losses in wind power generation. A critical component in this transformation is the development of new 66 kV wind transformers.

The Challenge for Wind Farms

Wind farms, both onshore and offshore, face several challenges in optimizing their operations. Initially, wind turbines produced relatively low power outputs, and the infrastructure was built to handle these levels. As turbine technology advanced, the power output increased significantly, but the voltage level remained at 33 kV, limiting efficiency and increasing losses. Offshore wind farms, in particular, face harsh environmental conditions, such as high winds, saltwater corrosion, and significant mechanical stresses. These factors necessitate the development of robust and efficient solutions to maintain and enhance wind farm performance.

Wind Farm Solutions

To address the evolving needs of wind farms, a new generation of transformers was required. Varelen design and manufacturing 5MVA Aand 10MVA fluid-immersed transformer designed for a 66 kV grid voltage, your OEM partners. This innovative design maximizes space efficiency and aligns with the Eco design directive. Additionally, the transformers feature a water cooling system to enhance the performance of medium-voltage equipment within the nacelle.

high voltage 66KV transformer

Special Technical Aspects

  1. Dimensions

    compact design , maintaining a minimal size and weight despite their 8MVA capacity. Weighing less than 20 tons, these transformers are both practical and efficient for modern wind turbine applications.

  2. Efficiency

    Efficiency is a crucial aspect of renewable energy generation. Upgrading to a 66 kV voltage level significantly enhances operational efficiency compared to the previous 33 kV standard. The WIND transformers are designed to meet the latest efficiency standards and comply with the Eco design directive, ensuring they provide optimal performance for the growing offshore wind market.

  3. Robustness and Reliability

    Offshore wind farms are exposed to severe environmental conditions, including high winds, saltwater, and mechanical stresses. Varelen's transformers are engineered to withstand these challenges, offering robust and reliable performance.  with decades of experience, have developed these high-tech transformers to endure the most demanding conditions, ensuring long-term reliability.

  4. High-Temperature Design

    Transformer are built to handle high temperatures according to IEC 60076 standards. They utilize water to fluid heat exchangers and high-temperature insulation materials. By using ester as an insulation fluid, these transformers can operate at higher temperatures than those using mineral oils. Ester’s biodegradability also enhances operational safety and environmental compatibility.

  5. Low Maintenance

    Maintenance of offshore equipment is both challenging and expensive. The WIND transformers are designed to require minimal maintenance, providing reliable operation for decades. This low-maintenance design is crucial for offshore wind turbine operators looking to minimize operational costs and ensure consistent performance.

The Benefits of 66 kV Wind Transformers

  1. Enhanced Efficiency

    The shift to a 66 kV voltage level reduces losses and enhances the overall efficiency of wind power generation. This improvement translates into more power being delivered from the turbines to the grid, optimizing the performance of wind farms.

  2. Compact and Lightweight Design

    The compact and lightweight design, This design not only saves space but also simplifies installation and maintenance processes.

  3. Environmental Friendliness

    Using ester (FR3 oil) as an insulation fluid provides several environmental benefits. Ester is biodegradable and can operate at higher temperatures than mineral oils, enhancing both safety and environmental compatibility. This makes the transformers more sustainable and reduces their environmental impact.

  4. Reliability in Harsh Conditions

    5mva oil immersed transformer use marine coating C5, The robust design of the transformers ensures reliable performance even in the harshest offshore environments. This reliability is crucial for maintaining consistent power generation and minimizing downtime due to equipment failures.

  5. Cost-Effective Maintenance

    The low maintenance requirements of the transformers make them a cost-effective choice for wind farm operators. By reducing the need for frequent maintenance, these transformers help to lower operational costs and improve the overall economic viability of wind power projects.


The introduction of 66 kV transformers has revolutionized wind power generation, offering significant improvements in efficiency, reliability, and sustainability. The high voltage WIND transformers, with their advanced design and robust performance, are at the forefront of this transformation. As the wind energy sector continues to grow, these transformers will play a crucial role in ensuring the efficient and reliable delivery of renewable energy. By addressing the challenges of modern wind farms and providing innovative solutions, 66 kV transformers are paving the way for a more sustainable and efficient future in wind power generation.

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