Wind power plays an important role in the global energy transition. According to the Global Wind Energy Council (GWEC), 117 GW of new wind power capacity was connected to the grid worldwide in 2024. As wind turbines increase in capacity and wind farms expand into different environments, transformer reliability, efficiency and design have become increasingly important.
A suitable wind power transformer must meet electrical requirements while addressing load variations, cooling, mechanical strength and environmental conditions.
1. Why Does Wind Power Generation Need Step-Up Transformers?
Wind turbine generators commonly produce electricity at voltages such as 690 V, although actual voltage depends on the turbine design. This is generally lower than the medium-voltage collection system used in wind farms, which may operate at 33 kV, 35 kV or 66 kV, depending on the project.
A wind turb
Before requesting a quotation, purchasers should confirm:
Rated capacity and primary/secondary voltages
System frequency, vector group and impedance
Harmonic spectrum and expected loading profile
Cooling method and permissible temperature rise
Installation location and available space
Ambient temperature, humidity and corrosion conditions
Insulation level and protection requirements
Applicable standards and testing requirements
Providing these details at the quotation stage helps the manufacturer evaluate the application and propose a suitable transformer configuration.
ine step-up transformer raises the generator output voltage to the required collection-system level. Higher voltage reduces current for a given power level, helping reduce cable losses during transmission.
Depending on the turbine configuration, the transformer may be installed inside the nacelle, at the bottom of the tower or in a separate transformer station.
2. Dry-Type vs. Oil-Immersed Transformers: Which Is Better?
Both dry-type and oil-immersed transformers can be used in wind power applications. Selection depends on rated capacity, voltage level, installation location, cooling requirements, fire safety, environmental conditions and project budget.
| Comparison | Dry-Type Transformer | Oil-Immersed Transformer |
| Maintenance | No insulating oil to monitor; maintenance depends on the design and operating environment | Requires appropriate insulating-liquid inspection and maintenance |
| Safety and environmental protection | Eliminates insulating-oil leakage risk | Requires suitable oil containment and fire protection where applicable |
| Size and cost | May require more space and have a higher initial cost in some configurations | Can offer compact configurations and competitive costs, depending on design |
| Key considerations | Fire safety, ventilation and installation space | Cooling, oil management and maintenance access |
Dry-type transformers may suit installations where avoiding oil leakage and reducing liquid-related fire risks are priorities. Cast resin and vacuum pressure impregnated (VPI) designs can be considered according to project requirements.
Oil-immersed transformers provide effective cooling and may be suitable where capacity, thermal performance and installation arrangements favor a liquid-immersed design. Neither type is universally better. The final choice should follow the project's technical specifications and site conditions.
3. Do Wind Turbine Transformers Need to Consider Harmonics?
Yes. Power electronic converters used in wind turbines can introduce harmonic currents and voltages. These harmonics may increase winding and stray losses, causing additional heating and potentially affecting insulation life.
During design, the manufacturer should evaluate the expected harmonic spectrum, additional losses and thermal performance. Purchasers should provide relevant harmonic data during the quotation stage whenever available.
The transformer should be designed for the specified operating conditions and applicable standards. Evaluating harmonic effects helps the manufacturer determine appropriate design and cooling requirements.
4. Other Key Factors in Wind Turbine Transformer Design
In addition to harmonics, several electrical, mechanical and environmental factors influence wind turbine transformer performance.
Load Fluctuations and Mechanical Strength
Wind turbine output varies with wind conditions and turbine control, resulting in changes in transformer loading. Design should consider the expected load profile and any specified overload requirements. Winding support and mechanical strength must be appropriate for the expected operating stresses.
Cooling and Temperature Rise
Transformers installed inside nacelles or towers may face restricted airflow and limited space. Cooling design should account for transformer losses, ambient temperature, ventilation and available space to maintain the specified temperature limits.
Vibration Resistance
Transformers installed in nacelles or towers may be exposed to mechanical vibration. Mounting arrangements, structural components, electrical connections and winding support should be evaluated for the expected vibration conditions.
Environmental Adaptability
Onshore wind farms may experience dust, temperature variations and challenging outdoor conditions. Offshore projects may face high humidity and salt-laden air, increasing corrosion risks. Enclosure protection, corrosion-resistant measures and insulation systems should be selected according to the installation environment.
Insulation and Overvoltage Protection
Switching operations and other system events can create electrical transients. Insulation coordination, surge protection and grounding arrangements should be considered as part of the overall wind turbine electrical design.
5. Nacelle Installation vs. Tower-Base Installation
The installation location affects cable length, structural loading, cooling, maintenance and overall project cost.
| Comparison | Nacelle Installation | Tower-Base Installation |
| Cable length and losses | Can shorten the low-voltage cable route | Longer low-voltage cables may increase costs and losses |
| Structural loading | Adds weight to the nacelle and requires suitable structural support | Avoids placing transformer weight on the nacelle |
| Maintenance | Access may require work at height | Generally easier to access for inspection and maintenance |
| Space and cooling | Limited space and airflow require careful design | Usually provides more installation space and ventilation |
| Protection | Requires attention to lightning exposure, grounding and overvoltage protection | Protection must suit the location and electrical system |
| Overall cost | May reduce cabling but increase structural, lifting and maintenance costs | May simplify maintenance but increase cable-related costs |
Nacelle installation can shorten low-voltage cables, but structural loading, lifting requirements and maintenance challenges must also be evaluated. Tower-base installation generally offers easier access and more space, although longer cables may increase material costs and electrical losses.
The preferred arrangement depends on turbine design, transformer capacity, structural limits, maintenance strategy and total project cost.
6. Applicable Standards and Project Specifications
IEC/IEEE 60076-16:2018 covers dry-type and liquid-immersed transformers for wind turbine step-up applications with a highest voltage for equipment up to and including 72.5 kV. It addresses transformers connecting wind turbine generators to the wind farm collection system or an adjacent distribution network, but does not cover transformers connecting multiple wind turbines to a distribution or transmission network.
Project specifications should define rated power, voltage ratio, frequency, vector group, impedance, insulation level, harmonic conditions, cooling method, installation environment and required tests. The purchaser and manufacturer should confirm applicable standards and editions, together with inspection and testing requirements, before manufacturing.
7. How to Select a Suitable Wind Power Transformer
Before requesting a quotation, purchasers should confirm:
Rated capacity and primary/secondary voltages
System frequency, vector group and impedance
Harmonic spectrum and expected loading profile
Cooling method and permissible temperature rise
Installation location and available space
Ambient temperature, humidity and corrosion conditions
Insulation level and protection requirements
Applicable standards and testing requirements
Providing these details at the quotation stage helps the manufacturer evaluate the application and propose a suitable transformer configuration.
Conclusion
Wind turbine transformers connect wind generators to the electrical collection system. Their design involves more than voltage conversion: harmonics, load fluctuations, cooling, vibration, insulation and environmental conditions all influence transformer selection.
Whether a project requires a dry-type or oil-immersed transformer, nacelle or tower-base installation, the solution should be determined by the turbine configuration and project requirements.
TAL Transformer provides dry-type and oil-immersed transformer solutions for power distribution applications. Customers can share their wind power project specifications to discuss suitable configurations based on voltage, capacity, installation conditions and applicable standards.
