Environmental Engineering Reference
In-Depth Information
2
Actions on wind turbines
2.1 Permanent actions
In addition to the typical dead loads of the plant (rotor and nacelle) and the structure
(tower and foundation), there are also other loads that are classed as permanent actions:
for example the loads of items fitted inside the tower (cables, intermediate platforms,
etc.), and those due to further electrical equipment, for example transformers,
ventilation systems.
And when it comes to offshore wind turbines there are yet further dead loads to be
considered such as external platforms, boat moorings or cathodic corrosion protection.
For the dynamic analysis in particular, the masses of the individual items and
components must be known and taken into account accurately in the design.
2.2 Turbine operation (rotor and nacelle)
The actions due to the operation of the turbine are determined by means of numerical
simulations (see also Section 4.9.1). In addition to various wind load models, with
the superposition of wave action effects where applicable, such simulations must also
take into account particular operating situations, for example starting and stopping
procedures.
The load case combinations to be investigated are laid down in the relevant codes
and guidelines, for example the DIBt guideline for onshore wind turbines [9], see
Section 4.5.3, and DIN EN 61400-3 for offshore wind turbines [10]. Load combinations
are also defined in the guidelines published by a number of certification bodies, for
example the GL Guideline [11], see Section 4.6.4.
Note:TheGL Guideline for offshore wind turbines [11] is based on Rules and
Guidelines, IV Industrial Services - 1 Guideline for the Certification of Wind
Turbines dating from 2003/04, which in July 2010 was republished in a revised
edition.
2.3
Wind loads
2.3.1 Wind loads for onshore wind turbines
According to DIN 1055-4 [12], the environmental conditions in Germany (including
the German Bight) can be divided into four wind zones (Figure 2.1).
The reference values (v
ref
;q
ref
) in the table are valid for
- averaging over a period of 10min,
- a 0.02 probability of being exceeded in one year,
- a height of 10m above ground level,
- flat, open terrain, which corresponds to terrain category II in DIN 1055-4
annex B.
