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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Advanced drive trains technologies' taking place on Tuesday, 11 March 2014 at 16:30-18:00. The meet-the-authors will take place in the poster area.

Giovanni Nappi DNV GL Renewables Certification, Denmark
Giovanni Nappi (1) F P Niels Lerke (1)
(1) DNV GL Renewables Certification, Hellerup, Denmark

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Giovanni Nappi is Senior Engineer at DNV GL Renewables Certification.
In 2007, after attaining a M.Sc. cum laude in Mechanical Engineering from the University of Perugia, Italy, he started his career as Design Engineer at Siemens Wind Power, responsible for designing a wide range of mechanical and structural components for WTG Hubs and Nacelles.
Since 2010 he has been at DNV, where he is still exerting his role as leading expert in connection with Type Certification of Wind Turbine components, including independent 3rd party evaluation of design, manufacturing and testing.


Introduction of the new gearbox design standard for wind turbine generators: a gap analysis between IEC 61400-4 and ISO 81400-4


The IEC 61400-4 standard was published on December 2012, thereby becoming a mandatory precondition for Type Certification of Wind Turbine Generators (WTGs) according to the IEC 61400-22 scheme. This long-awaited standard cancels and replaces the controversial ISO 81400-4, published in 2005 and applicable only to WTGs with rated power under 2 MW.

Even though several gearbox suppliers for long time have delivered products already meeting or in some cases even surpassing the new requirements of IEC 61400-4, some of these are expected to raise the bar with regards to minimum certification deliverables for design, testing, monitoring and maintenance of gearboxes.


By means of a gap analysis the present paper intends to outline the aspects of IEC 61400-4 being enforced that were previously not part of ISO 81400-4.
Furthermore, it means to provide an overview on the certification requirements that need to be fulfilled by WTG and gearbox suppliers in order to certify gearboxes and thus deliver the next generation of drive trains to the global market.

Main body of abstract

The gap analysis focuses in particular on items such as: drivetrain specific wind turbine loads, new testing requirements for validation of gearbox designs, improved design requirements for bearings as well as expanded description of design requirements for gearbox structural elements and finally considerations of lubrication system and condition monitoring systems.

Among the most notable testing requirements which are enforced by the new standard, one which is expected to impact significantly WTG manufacturers and gearbox suppliers is the clause on robustness tests and field tests. All the same, some lack of clarity in the requirements is identified especially with regards to robustness tests, which is possibly going to create some confusion and misunderstandings in the industry.

The investigation deals then with the impact that the new standard will have on documentation and certification requirements. Clearly, the enforcement of new clauses might result also in higher efforts requested to the industry in order to prove compliance with these requirements to certification bodies.
However, the clearer definition of criteria might have a positive impact also in this area and allow more efficient process for a gearbox supplier to certify its product according IEC 61400 regulations.

Finally, the delicate topic of how to integrate consistently a Component Certificate for a gearbox within the Type Certificate of a WTG is addressed and general guidelines for a successful integration are given.


The recently published IEC 61400-4 brings a number of novelty elements into design and validation of WTG gearboxes. Some of these impact stakeholders, at least in terms of certification efforts, if not in terms of knowledge and test equipment.
It may even request additional investments, considering that a winning drivetrain concept for WTGs is not in sight yet and rated power is still expected to grow.

However, a better definition of the game rules has also a positive impact. In particular it allows a more efficient process for design and validation of gearboxes, delivering a trusted and internationally recognized product.

Learning objectives
Delegates attending to this presentation can expect to learn:

1. What new design/validation/certification requirements for WTG gearboxes are being enforced with the publishing of the IEC 61400-4 standard.
2. How to address some of these new provisions from a certification point of view.
3. Ultimately, how to deliver a trusted and solid solution while managing the risks connected with innovation.