WTG Transformers for Wind Farms: Key Specifications and Selection Guide

12-11 2025 | By:

Wind farms require highly reliable transformers to ensure stable power collection, efficient transmission, and long-term performance under harsh environmental conditions. This SEO-optimized guide explains the key types of Wind Turbine Generator WTG  transformers, their parameters, and how to select the right model for onshore and offshore applications.

1. Types of Wind Turbine Generators WTG Transformers

WTG transformers convert the generator’s low voltage—typically 0.4–0.69 kV—into medium or high voltage (10 kV / 20 kV / 35 kV) for grid transmission.
They are engineered to handle vibration, variable loads, temperature fluctuations, and long operational cycles.

Below is a comprehensive parameter comparison table covering all mainstream WTG transformer types.

WTG Transformer Types & Technical Parameters Table

2. Transformer Sizing and Selection in Wind Farms

Accurate transformer sizing is critical for efficient system operation. Consider the following:

✓ Load Calculation

Use demand factors to assess total turbine output and auxiliary loads.

✓ Capacity Matching

Example:
If total load = 291.4 kVA, the appropriate choice is 315 kVA transformer.

✓ Voltage Regulation

• NLTC (Off-circuit Tap-Changer) – lower cost

• OLTC (On-load Tap-Changer) – required for grids with large voltage fluctuations

✓ Environmental & Installation Constraints

Wind farm sites often face:

• Poor road access

• High humidity

• Salt-spray corrosion (offshore)

• Temperature extremes

✓ Cooling System Considerations

• Air-cooled is suitable for smaller dry-type units

• Oil-cooled (ONAF) supports larger capacities and better heat dissipation

3. WTG Step-Up Transformers: Function & Requirements

The step-up transformer is placed close to—or inside—the turbine to raise generator output voltage to grid connection levels.

Onshore Wind Turbines

• Often use oil-immersed transformers

• May integrate HV/LV switchgear forming a modular substation

Offshore Wind Turbines

Installed inside the nacelle or tower, requiring:

• Anti-corrosion coating

• Sealed enclosure

• Fire-safe insulation (dry-type)

• Zero maintenance

WTG step-up transformers must withstand:

• High vibration

• Rapid load fluctuations

• Long operation cycles

• Temperature rise from generator heat

4. Key Factors for Selecting Wind Farm Transformers

✔ Capacity & Electrical Matching

The transformer must align with:

• Turbine rated output

• Grid voltage level

• Power collection system layout

✔ Safety & Cost Performance

Consider:

• Losses

• Overload capability

• Cooling efficiency

• Fire resistance

✔ Environmental Adaptability

Offshore transformers must excel in:

• Salt-fog resistance

• Moisture protection

• Corrosion resistance

• Vibration damping

✔ Manufacturer Capability

Select suppliers able to provide:

• Certified designs (IEC / IEEE / GB/T)

• Custom wind-power engineering solutions

• Proven field experience

Optimized selection guarantees high efficiency, safety, and long operational life of the entire wind power system.

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