To ensure the proper development and continuous service life of wind turbines, the international standard IEC 61400 specifies technical requirements for the design of wind turbines. An independent certification body must confirm compliance with these standards. This also includes the comprehensive structural testing of rotor blades according to IEC 61400-23. This is one of the prerequisites for the approval and operation of new turbine types.

Over the past eleven months, the Nordex Group has subjected a rotor blade of the N175/6.X to these necessary mechanical tests on the accredited rotor blade test rig at the Fraunhofer Institute for Wind Energy Systems IWES in Bremerhaven. The measurements of the properties of the rotor blade of the latest turbine of the Delta4000 series, such as natural frequencies and damping parameters, as well as the electrical resistance values of the lightning protection system, aimed to validate the simulations in practice. The measurements were carried out on one of the first rotor blades, which was manufactured at the Nordex Research and Development Centre in Rostock. The mechanical tests, in which the rotor blade was subjected to static load cases and fatigue tests, corresponded to the previously simulated service life.

During the entire test period, the expected behaviour of the rotor blade was successfully confirmed: Critical parameters such as deflections, strains and natural frequencies were consistently within the permissible tolerances.

In addition, a 15-meter-long rotor blade tip of the N175/6.X with integrated anti-icing system was subjected to extensive lightning tests in accordance with IEC 61400-24. In Polytech’s accredited lightning laboratory in Denmark, high-voltage impact tests and high-current tests were successfully completed. The tests that have been passed once again confirm the robustness of the Nordex lightning protection system.

“It is crucial to test for lightning as close to real-life conditions as possible. We are pleased to service Nordex Group and a long list of customers from in and outside the wind industry with our accredited facilities, so we can make well-documented test results for certification or keeping momentum in their R&D projects,” Andreas Christensen, Manager of Polytech’s test center explains.

“At Nordex, we know the value of industry standards. These standards define the requirements for the design of wind turbines and also their compliance. This is becoming increasingly important as rotor blades today become longer and longer and rotate at higher altitudes. With the right material and design of the rotor blades, not only can the power of the wind be used optimally, but also the planned service life can be achieved, or the risk of lightning damage can be minimized. At Nordex, we also test more than is required by the IEC standard. Our goal is to achieve even higher product maturity. The results of the tests are therefore of great value to us as a manufacturer,” says Hendrik Klein, Head of Blade Materials, Design and Test at the Nordex Group.