Increasing hub heights have resulted in a high number of wind turbines now being equipped with concrete or hybrid towers. These towers are comprised of a concrete base and a tubular steel tower on the top. When it comes to lightning protection, DEHN Africa advises that it is essential to implement a single, common earth-termination system for all wind turbine purposes, as lightning current must be dispersed in order to prevent the wind turbine from being destroyed in the event of a lightning strike.
The earth-termination system should discharge high lightning currents to the ground, distributing them without exposing humans and animals to electric shock, whilst averting dangerous thermal or electrodynamic effects.
The main functions of earth-termination systems for wind turbines include:
- Protective earthing with the task of connecting electrical equipment to the ground and protecting persons and material assets in the event of electrical fault;
- Functional earthing, to ensure safe and hassle-free operation of electrical and electronic equipment; and
- Lightning protection earthing to safely conduct the lightning current from the down conductors to the ground.
- The design of earth-termination systems according to IEC 61936-1 should fulfil the following four requirements:
- Mechanical strength and corrosion resistance.
- The handling of calculated maximum fault current from a thermal point of view, especially when the transformer is located in the nacelle.
- Avoid damage to objects and equipment.
- Protection of people from voltage and earth-termination systems occurring in the case of maximum earth fault current and lightning strikes.
Tubular steel towers fulfil these requirements due to their cross-section and completely metallic body (Faraday cage). However, should the reinforced concrete towers be made of pre-fabricated concrete elements, they must consist of an integrated earth-termination system.
Furthermore, foundations made with reinforced concrete are used as earth electrodes as they have a low earth resistance and provide an excellent basis for equipotential bonding and foundation. Earth electrodes make both technical and economical sense, hence they should be designed and installed as per DIN 18014.
The market leader DEHN, a globally active family-owned electrotechnical company with more than 1600 employees worldwide, offers innovative products and solutions as well as comprehensive services in the field of surge protection, lightning protection and safety equipment. DEHN focuses on the protection of system and building technology, the transportation, telecommunication and process sector, photovoltaic systems, wind turbines, etc. The company's continuous growth is based on more than 100 years of tradition and experience as well as highest quality standards and consistent customer and market orientation throughout the world.
