Lightning Protection
Protection from the effects of direct and nearby strikes
The lightning protection of our wind turbines aims to protect from the effects of direct and nearby strikes. Even though protection from lightning can not be wholly assured, our lightning protection system has shown very good performance in wind turbine applications all over the world.
The overall design basis refers to the international standard IEC 1024-1 and the Danish Standard DS 453.
The components of our wind turbines are protected in various ways:
- Blades
The blades are protected with a dedicated protection system that has been laboratory-tested to currents of 200 kA without showing any signs of damage other than superficial weld marks from the strike itself. Each blade has a lightning rod fitted close to the tip. The rod projects slightly above the blade surface on both sides. A flexible steel wire located inside the blade provides the conduction path from the rod to the rotor hub which in turn is used as a conductor to the main shaft. Electrical and hydraulic equipment located inside the hub is completely protected by the Faraday cage of the hub itself.
- Nacelle
The canopy is fabricated in 5-mm steel plate, acting as a Faraday cage for the nacelle. The meteorological instruments at the rear of the canopy are protected by a separate lightning rod projecting well above the instruments. All main components are efficiently grounded, and metal oxide arrestors in the controller provide transient protection from effects of nearby strikes.
- Controller
Metal oxide arrestors protect the turbine controller. The arrestors are installed with mechanical overload protection to prevent explosion in case of a direct lightning strike. The controller is fitted with three arrestors, one for each phase, all connected to the local grounding system. All metal parts, such as DIN rails, cabinet doors, and components are efficiently grounded.
- Tower
The steel tower acts as a conductor from the nacelle and controller to the earth. Earth connection is provided through several Cu leads.
- Grounding
We recommend grounding to a resistance of less than 10 Ohms, using two depth electrodes and a ring earth surrounding the foundation.