PHOENIX CONTACT | Customer Magazine UPDATE 3/11

Tracking Down Lightning Lightning Protection for On- and Offshore Wind Power Systems Prof. Dr.-Ing. Klaus Scheibe from the Kiel University of Applied Sciences performs ground- breaking research in the field of lightning. He is particularly interested in devising measures to protect industrial objects, such as wind turbines, against lightning strikes. He kindly found the time for an interview with the UPDATE editors. UPDATE: Professor Scheibe, what kind of damage occurs when lightning strikes in wind turbines? Professor Scheibe: If lightning protection measures have been properly carried out – that is, in accordance with valid lightning protection standards and the principles for installing surge voltage protection components and those for electromagnetic compatibility – no damage to any of the facility’s components is to be expected, provided regular maintenance is performed. However, if this is not the case, wind turbines can get damaged when lightning strikes.This includes damage to rotor blades, other mechanical system components, or also electrical and electronic system components. UPDATE: Are offshore facilities subjected to a greater risk from lightning strikes? Professor Scheibe: Yes, because repairing and recommissioning system components of offshore wind turbines is much more difficult and time consuming than for land- based systems. Also, large or heavy system components and the required cranes may need to be transported to the offshore facility by boat.This contributes to significantly increasing downtimes of such facilities compared to onshore systems. In addition, modern offshore wind turbines generate about 5 to 6 MW power, again increasing the energy loss in the event of a downtime. UPDATE: How important is lightning monitoring for operators of wind turbines? Professor Scheibe: Monitoring is an essential operating safety element – and this also includes the effects of lightning.What makes it even more important is the fact that expected current loads resulting from lightning strikes, comprising parameters such as lightning current amplitude, rate of change of the surge current, load and specific energy, are difficult to assess. While surge voltage protection devices meet the demanding provisions of DIN EN 61643-11, in the field they are subjected to extreme loads. For this reason, monitoring is very important in this area as well.What would greatly simplify things for the operator is if they were able to perform remote monitoring, for instance, using a wireless network. UPDATE: What is your recommendation to operators of wind turbines in order to maximize the safety and uptime of their systems? Professor Scheibe: Wind turbine operators should involve manufacturers of lightning and surge voltage protection systems at a very early planning stage, and they must ensure that the system is implemented in compliance with EMC constraints. Proper coordination of the protective measures includes following the manufacturer’s installation instructions to the dot, in particular as concerns ground conductors. On top of this, the specific spatial conditions of a wind turbine need to be taken into consideration. In this context, the capacitive and inductive interference into the low-voltage power supply, signal lines and data lines that can occur when lightning strikes is of particular importance. UPDATE:Thank you very much for this interview. Prof. Dr.-Ing. Klaus Scheibe, Department of Computer Science and Electrical Engineering, Kiel University of Applied Sciences. “Monitoring is an essential element of operating safety.” Interview 03UPDATE 3|11