Company of the Day - DEHN + Söhne: the "One-Stop-Shop" for Wind Turbine Protection

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With increasing global power consumption, wind energy is contributin a growing part to the energy mix. To expand wind power capacity, new wind farms are being installed, especially offshore. Lightning and surge protection for wind turbines is particularly hereby important: wind turbines are especially vulnerable to lightning strikes due to their complex design, height and exposed location. This particularly affects wind turbines with a height of more than 200 metres because the risk of lightning striking a wind turbine increases quadratically with its height.

For offshore wind turbines, high availability is paramount as yield losses resulting from downtime are high. For this reason, comprehensive lightning and surge protection measures are required. This is reflected both in the relevant standards and certificates for wind turbines*.

Rely on lightning and surge protection products from DEHN:

Dehn is a worldwide recognised expert in the field of wind energy. Its customers include international manufacturers and suppliers of wind turbines. Dehn develops customised protection concepts for wind turbines and additional equipment for the operation of wind turbines. In the DEHN test laboratory, sub-components can be tested up to a lightning impulse current of 400 kA (10/350 μs)**.

* Guideline for the Certification of Wind Turbines, Germanischer Lloyd Industrial Services GmbH, 2010
** pursuant to IEC 61400-24 Lightning Protection of Wind Turbines

Profit from DEHN's expertise in developing lightning protection zone concepts

Thanks to its long-standing experience in lightning protection and numerous tests on wind turbines, DEHN knows how to develop lightning protection systems for wind turbines. Its aim is to prevent lightning damage to rotor blades, bearings and gearboxes as well as downtime resulting from lightning currents and surges.

The lightning protection zone concept for wind turbines described in IEC 61400-24 is based on the IEC 62305 standard, which defines the selection and arrangement of lightning and surge protection measures*.

The IEC 61400-24 standard recommends to dimension the lightning protection system of a wind turbine according to class of LPS I** unless a risk analysis demonstrates that a lower class of LPS is sufficient for the individual components. The lightning protection system of a wind turbine consists of

• External lightning protection
• Internal lightning protection / surge protection
• Equipotential bonding and earthing

In order to plan protection measures, a wind turbine is subdivided into lightning protection zones (LPZs)**. The areas which are vulnerable to lightning strikes (LPZ 0A) are determined by means of the rolling sphere method.
LPZ 0** is the outer zone where the threat is due to the unattenuated lightning electromagnetic field and where the internal systems may be subjected to the full or partial lightning current.

LPZ 0 is subdivided into:
• LPZ 0a: Parts of the wind turbine which may be subjected to direct lightning strikes and the full lightning electromagnetic field.
• LPZ 0b: Parts of the wind turbine which are protected against direct lightning strikes, but where the full lightning electromagnetic field is present.

LPZ 1 and LPZ 2 are inner zones which are protected against direct lightning strikes. However, impulse currents must be limited by current distribution, isolating interfaces and surge protective devices at the zone boundaries.
* IEC 61400-24 Lightning Protection of Wind Turbines / IEC 62305 Protection against Lightning
** LPZ: Lightning Protection Zone

DEHN lightning and surge protection products in a wind turbine

Lightning / surge protection for power supply systems:
By implementing coordinated surge protection measures for power supply systems, the risk of a system stillstand due to lightning currents and surges can be avoided. This increases the availability of the wind turbine in the long term. Two example of Dehn products here are:
- DEHNbloc® Maxi: Coordinated single-pole type 1 lightning current arrester.
- DEHNguard®: Type 2 surge arrester with integrated “Life-time Indication” early warning system.

Lightning / surge protection for IT-Systems:
A consistent protection concept prevents damage to information and data systems. Condition monitoring is indispensable for the safe operation and availability of wind turbines. This is ensured by the LifeCheck® arrester monitoring system with RFID technology which also allows remote monitoring of arresters, for example via a wireless network. Two example of Dehn products here are:
- BLITZDUCTOR®: Modular and universal combined arrester / surge arrester* for data lines, bus systems, measured value transmission, temperature measuring devices, heating systems and weather sensors.
- LifeCheck® arrester monitoring via RFID technology

Components for the tower, foundation and equipotential bonding - An earth-termination system is required for safe operation of the electrical installations and equipment, as well as for the due functioning of the lightning protection system. This earth-termination system is connected to the equipotential bonding system via the main earthing busbar which is connected to equipment and surge protective devices.

External lightning protection for measurement equipment and signalling devices - Air-termination systems from DEHN protect wind measurement equipment and aircraft warning lights on the nacelle from direct lightning strikes.

Arc fault protection - The DEHNshort protection system provides active arcfault protection. Passive arc fault protection is realised with the DEHNcare® personal protective equipment

Wind turbines place special demands on lightning and surge protection measures which must be taken into account already at the design stage. The protection concept and correct dimensioning of surge protective devices are paramount for the safe operation of wind turbines. DEHN is the "one-stop-shop" for lightning and surge protection measures.

If you would like to know more about what w3.windfair.net can offer, please do not hesitate to contact Trevor Sievert at ts@windfair.net

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