Why not adopt ungrounding (ungrounded method) in wind turbine blade lightning protection?

1. Lightning risk characteristics of wind turbines

• Wind turbines are installed in high places and isolated environments, making them highly vulnerable to lightning strikes. In particular, blades are the most frequently directly struck by lightning strikes, and blade damage caused by lightning strikes can result in generator shutdowns and enormous repair costs.

2. Necessity of safe discharge of lightning current

• When lightning strikes a blade, a strong current of tens to hundreds of kA flows instantaneously. If this current is not safely discharged to the ground, the blade and internal generator devices can be seriously damaged.

• The grounding system quickly disperses lightning current to the ground, preventing secondary damage such as device damage, fire, and electric shock.

3. Limitations of the non-grounded method

• The ungrounded (insulated) method is based on the concept of blocking or diverting the flow of lightning current, but is not suitable for facilities such as wind turbines that are in direct contact with the atmosphere, have large structures, and are directly exposed to lightning.

• In the case of ungrounded lightning current can randomly flow inside the blade or along the surface, which can cause serious secondary damage such as insulation breakdown, structural damage, fire, electronic device malfunction, and personal injury.

• In fact, wind turbine blades are designed with a receptor and a down-going conductor to ensure that lightning current flows safely through the blade to the nacelle, tower, and grounding system.

4. Standards and legal requirements

• International standards (IEC 61400-24, etc.) and domestic technical standards (KEC, Electrical Installation Technical Standards, etc.) stipulate that an effective grounding system must be established to protect wind turbines from lightning strikes.

• Since the grounding system must perform complex functions such as safely discharging lightning current, eliminating potential differences, and ensuring electrical equipotential, the ungrounded method does not meet the standards.

5. Conclusion

• The reason why wind turbine blades are not grounded is because if lightning current cannot be safely discharged, it can cause serious danger to both the equipment and people.

• Therefore, it is essential to apply a grounding system (lightning arrester and down conductor, ground electrode, etc.) to the blade to effectively discharge the lightning current to the ground.