Page 218 - Fluid Power Engineering

W i nd T urbine Generator (WTG) Components 189

a finite element model (FEM). The structural dynamics of this system
is then simulated in the time domain by applying: (a) Wind loads as a
function of time, (b) using the equations of motion, and (c) properties
of materials to resist forces, moments, and torsion.

Turbine Certification
Certification of a utility-scale wind turbines has become a necessity.
It gives the buyers, financiers, and grid operators confidence that a
certified WTG has undergone design review, field testing, and other
processes to ensure that there is integrity to the claims of the manufac-
turer. Specifically, certification provides an independent verification
of manufacturer’s claims about Class of turbine (Class I, II, III; A, B,
C), power production curve, noise emission curve, structural integrity,
and safe operations.
There are four entities involved in certification:

Turbine manufacturer that wishes to obtain a “type certifica-

tion.” At the end of the certification process for a specific type
of turbine, a manufacturer will get a type certificate for the
turbine.
International Electrotechnical Commission (IEC), the interna-

tional standards organization. IEC defines and publishes the
standards for almost all aspects of a wind turbine.
Accredited Certification Agent. A turbine manufacturer con-

tracts with an accredited certification agent to certify a turbine.
There are several companies that certify utility scale turbines,
the leading companies of which are: DNV in cooperation with
Risoe, Germanischer Lloyd, TUV Nord, and others.
Accredited Design Evaluation and Testing Agent. A certification

agent does not perform all the design evaluations and it may
not perform testing. Specialized engineering companies in-
dependently evaluate designs and, if necessary, perform de-
tailed finite element method (FEM) analysis of specific com-
ponents. Specialized testing companies perform independent
testing of turbines and the results are submitted to the certifi-
cation agent.

Type certification process, according to IEC WT01, involves three
mandatory modules and one optional module: 10,11

Design Evaluation Conformity Statement. The intent of this

module is to evaluate the conformance of design and doc-
umentation with established standards (like IEC 61400-1).