These are the most frequently asked questions on the protection of wind turbines:
Q: Which class of LPS should be used for wind turbines?
A: The IEC 61400-24 standard requires that, unless otherwise shown by risk analysis, wind turbines should always be protected according to class of LPS I.
Q: Which are the relevant standards for protecting wind turbines against lightning strikes?
A: IEC 61400-24, the standards of the IEC 62305 series, the guidelines by the Germanischer Lloyd on the certification of wind turbines of 2010 and DNVGL-ST-0076 “Design of electrical installations for wind turbines“ of 2015.
Q: Which lightning protection measures must be taken in wind turbines?
A: The complete lightning protection system consists of an external lightning protection system and surge protection. The external lightning protection system is implemented by air-termination systems and down conductors which dissipate the lightning current to earth via defined paths. To ensure surge protection, it is advisable to use surge arresters (SPDs) at all dangerous places.
Q: Which types of surge arresters are there?
A: Surge arresters are classified into type 1, 2 or 3 arresters.
The arresters have different discharge capacities and voltage protection levels, that is the maximum voltage in case of a discharge process.
Q: How do I know which type of arrester to use?
A: It is decisive to know from which lightning protection zone (LPZ) the protected line enters the wind turbine. If a part of the incoming line is located in LPZ 0A, a direct lightning strike to the line is to be expected. In this case, a type 1 arrester is required (e.g. transformer connection, unprotected sensors of the nacelle). In addition, a type 1 arrester installed at the transformer connection establishes equipotential bonding in case of a direct lightning strike to the wind turbine.
If lines from LPZ 0B or higher enter the wind turbine, only surges are to be expected and therefore it is advisable to use type 2 arresters.
Q: Which further distinctions are there for surge arresters?
A: We do not only distinguish between different types, but also between Red/Line and Yellow/Line arresters.
Red/Line arresters can be used for the power supply systems, Yellow/Line arresters for the signal and communication lines of a wind turbine.
Q: Do surge arresters have to be monitored?
A: Both the IEC 61400-24 standard and the certification guideline by the GL recommend to permanently monitor surge arresters.
Red/Line arresters can be monitored via the integrated remote signalling contact (floating changeover contact). This contact signals that the protection module is disconnected due to overload.
Yellow/Line arresters of the Blitzductor XT series can be integrated in the condition monitoring system via DRC modules. This system shows in advance that a module has to be replaced.
Q: Does an arrester have to be replaced after each discharge process?
A: No, DEHN surge arresters can discharge lightning currents several times. This has also been proven in various laboratory tests whose results are backed by our long-standing field experience.
Q: What does a lightning protection concept for a wind turbine have to include?
A: A lightning protection concept must define the individual lightning protection zones as per IEC 61400-24 and the necessary protection measures. The protection measures include the integral parts of the lightning protection system, namely external lightning protection, surge protection and the earth-termination system.
Q: Which components have to be integrated in the equipotential bonding?
A: All metal components of a wind turbine must be integrated in the equipotential bonding. This also applies to concrete-embedded components of the reinforcement. Accessible components such as ladders must be connected to the equipotential bonding at intervals of 20 m to prevent dangerous potential differences in case of a lightning strike.