EXIGENCIAS DEL BANCO CENTRAL DE CHILE EN MATERIAS DE SEGURIDAD

Loads as described in Sections 4.3.2.1 to 4.3.2.4 shall be taken into account for each design load case. Where relevant, the following influences shall also be taken into account:

4.3.4.1 General influences

− wind field perturbations due to the wind turbine itself (wake-induced velocities, tower shadow, tower upwind effect etc.)

− the influence of three-dimensional flow on the blade aerodynamic characteristics (e.g. three- dimensional stall and aerodynamic tip loss) − dynamic stall effects of the airflow for the pro-

files used

− unsteady aerodynamic effects − aeroelastic effects

− aerodynamic asymmetries, which can arise through production or assembly tolerances of the rotor blades. A verified tolerance shall be ob- served. If this is not (or not yet) known, a devia- tion of the blade angle of attack of ±0.3° (i.e. for a three-bladed rotor: blade 1 at 0°, blade 2 at – 0.3°, blade 3 at +0.3°) shall be assumed.

− structural dynamics and the coupling of vibra- tional modes: The elasticity of the blades, elastic- ity of the drive train and generator (drive train dynamics) as well as the tower bending shall be considered. The elastic mounting of the machin- ery, vibration dampers, the torsional stiffness of the tower and the influence of the foundation shall also be included, if their influence cannot be neglected.

− eccentricity: For at least the blades, the hub and all relevant components of the drive train, the ac- tual mass eccentricity according to the manufac- turer’s specifications shall be taken into account. − dynamic response when parked (standstill or

idling) and application of the EWM (see Sections 4.3.3.6 to 4.3.3.8) with steady wind model by a gust reaction factor to the tower loads (see Sec- tion 6.6.5.3)

− Additionally, in the case of horizontal-axis tur- bines with active yaw control, operation of the yaw system during the entire service life shall be considered if the yaw speed exceeds 15/R in °/s or the yaw acceleration exceeds 450/R2 _{in °/s}2

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4.3.4.2 Operational influences

(1) Static and load-dependent bearing friction moments (especially blade pitch bearing, yaw bear- ing) shall be considered.

(2) The behaviour of the control and safety sys- tems of the wind turbine shall be taken into account in the load case definitions and during all load simula- tions performed.

(3) In case the control system provides active features for load reduction, it has to be ensured that they are in operation over the whole lifetime of the wind turbine. Possible malfunctions of these features shall be detected and consequences considered, see Section 2.1.3. The influence of the malfunctions of the control system features, including corrective ac- tions, shall be considered in load analysis as load case DLC 2.1; see Section 4.3.3.2, para 3. In case any errors are detected with delay, this delay shall also be considered in the extreme and fatigue load analysis. 4.3.4.3 Operation within the resonance

range of the tower

If the operation of the wind turbine is approved within the resonance range of the tower with a tolerance of ±5 % of the tower’s natural frequency (Section 6.6.5.1), suitable vibration monitoring systems shall be provided (Section 2.3.2.8). With the evaluation (Section 4.B.3) of the load calculation, suitable threshold values for permissible vibrations shall be defined and taken into account.

4.3.5 Partial safety factors for loads

4.3.5.1 Partial safety factors for the loads in the analysis of the serviceability limit state (SLS)

(1) For the analysis of the serviceability limit state, see Section 1.3.2.2.2, a partial safety factor for loads of γF = 1.0 shall be used for all load components.

(2) It shall be verified that no deflections endan- gering the safety of the wind turbine occur under the design conditions listed in Table 4.3.1 and, if applica- ble, Table 4.3.2. One of the most important considera- tions is that no contact can be permitted to occur between the blades and the tower. The maximum elastic deflection in the most unfavourable direction shall be determined for the load cases listed in Table 4.3.1 and, if applicable, Table 4.3.2.

(3) In consultation with GL, methods of statistical extreme value analysis (e.g. [4.9] to [4.13]) may also be used for the blade deflection. An extrapolation time of 50 years shall be applied.

(4) Observance of the permissible clearance be- tween blade and tower shall be verified in accordance with Section 6.2.4.1, para 7.

4.3.5.2 Partial safety factors for the loads in the analysis of the ultimate limit state (ULS)

4.3.5.2.1 Partial safety factors for ultimate loads in the analysis of the ultimate strength

(1) Ultimate loads shall be used for the analysis of the ultimate strength, loss of stability and loss of equilibrium; see Section 4.3.3, para 11. If the loads of different causes can be determined independently of each other, the partial safety factors for the loads shall have the minimum values given in Table 4.3.3. (2) In many cases, especially when unsteady loads lead to dynamic effects, the load components cannot be determined independently of each other. In these cases, the highest partial safety factor of the corre- sponding design situation in Table 4.3.3 shall be ap- plied for the partial safety factors for the loads γF (see

also Section 1.3.3).

4.3.5.2.2 Partial safety factor for the loads in the analysis of the fatigue strength

The partial safety factor for the loads shall amount to γF = 1.0 for all design situations.

4.3.5.3 Special partial safety factors

Smaller partial safety factors for loads may be used after consultation with GL, if the loads were deter- mined from measurements, or from analyses verified by measurements, with a higher level of confidence than is normally the case. The values of all partial safety factors shall be given in the design documenta- tion.

4.3.5.4 Partial safety factor for the loads during earthquakes

The safety factor for the loads during earthquakes is γF = 1.0.

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Table 4.3.3 Partial safety factors for loads γF

Unfavourable loads Favourable _loads

Type of design situation (see Tables 4.3.1 and 4.3.2) Source of loading N Normal and extreme A Abnormal T Transport and erection All design situations Aerodynamic 1.35 1.1 1.5 0.9 Operational 1.35 1.1 1.5 0.9 Gravity 1.1/1.35* 1.1 1.25 0.9

Other inertial forces 1.25 1.1 1.3 0.9

Heat influence 1.35 – – –

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