Environmental Engineering Reference
In-Depth Information
Power production plus fault (DLC 2.1 to 2.3)
Every fault in the control and safety systems or an internal fault in the electrical system
that is relevant for the load on the offshore wind turbine structure must be taken into
account during power production. In doing so, it may be assumed that faults not
dependent on each other do not occur simultaneously.
Average wind speeds and the corresponding significant wave heights should be used for
DLC 2.1 and 2.2 (as for DLC 1.3 to 1.13).
Irregular sea states should be assumed for DLC 2.3 (as for DLC 1.1 and 1.2).
Start-up (DLC 3.1 to 3.3)
This design situation embraces all events that lead to loads on the offshore wind turbine
structure during the transition from standstill or idling to power production. The
average wind speeds and the corresponding significant wave heights should be assumed
for this (as for DLC 1.3 to 1.13).
Normal shutdown (DLC 4.1 and 4.2)
This design situation embraces all events that lead to loads on the offshore wind turbine
structure during the transition from power production to standby mode (standstill or
idling). The average wind speeds and the corresponding significant wave heights
should be assumed for this (as for DLC 1.3 to 1.13).
Emergency shutdown (DLC 5.1)
Average wind speeds and the corresponding significant wave heights should be assumed
for the case of the manual activation of the emergency-stop switch (as for DLC 1.3 to 1.13).
Parked (standstill or idling, DLC 6.1 to 6.7)
In this situation the rotor of an offshore wind turbine is in standby mode. According to
Table 4.4, either the steady or the turbulent wind model should be used for this design
situation (see Section 2.3.2). When applying the turbulent wind model, a dynamic
simulation should be carried out in combination with a stochastic sea state model.
However, when applying the steady wind model in combination with a deterministic
design wave, a quasi-static structural analysis should be carried out with appropriate
corrections for the dynamic response.
The turbulent wind model together with irregular sea states should be used for DLC
6.1a and 6.2a. The significant 50-year wave (H ¼ H s50 ) and the average 50-year wind
speed (V hub ¼ V ref ) should be used here. The average values of H s50 and V ref are to be
adapted to the duration of the simulation (see Table 2.9).
The steadyextremewindmodel incombinationwith the reduceddesignwave shouldbeused
forDLC6.1b and 6.2b. The extreme 50-yearwind speed, themax. 3 s gust (V hub ¼ V e,50 )and
the reduced 50-year wave height (H ¼ H red,50 ) 6) should be used here, see [11] 4.3.3.2 (15):
0 : 14
V e ; 50 ð z Þ¼ 1
:
25 V ref ð z
=
z hub Þ
H red ; 50
¼ 1
:
32 H s ; 50 H B
6) Note: The frequency of occurrence of H red is 3% in deep water.
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