Introduction to the IEC standard. Peter Hauge Madsen Risø DTU

Transcription

1 Introduction to the IEC standard Peter Hauge Madsen Risø DTU

2 IEC or ISO? (Electric component, machine or building or a wind turbine) Wind turbine generator system ~ Wind turbine structure 2

3 The wind turbine a complex system service crane transformer Nacelle generator gearbox Power curve Risø DTU Technology

4 IEC TC88: IEC standards series IEC Design requirements IEC Small wind turbines IEC Design requirements for offshore wind turbines IEC Gears for wind turbines IEC (5) Wind Turbine Rotor Blades IEC , Acoustic noise measurement techniques IEC Power performance measurements IEC Measurement of mechanical loads IEC Declaration of sound power level and tonality IEC Measurement of power quality characteristics IEC Conformity Testing and Certification of wind turbines IEC TR Full scale structural blade testing IEC TR Lightning protection IEC (1-6) Communication IEC TS Availability IEC Electrical simulation models for wind power generation IEC : Transformers for wind turbines applications Slide 4

5 IEC : 2005 Wind Turbines Design Requirements Principles specifies essential design requirements to ensure the engineering integrity of wind turbines. Its purpose is to provide an appropriate level of protection against damage from all hazards during the planned lifetime Content External conditions (e.g. wind) Wind turbine classes Structural design (e.g. load cases and methods) Control and protection system (what to consider) Mechanical system (e.g. yaw, brakes) Electrical system (e.g. lightning) Site assessment Assembly, installation, erection Commisioning, operation, maintenance

6 IEC : 2005 Wind Turbines Design Requirements - Amendment Power production plus occurrence of fault or loss of electrical network connection (DLC ) Partial safety factor for consequence of failure and component classes Ultimate strength analysis Partial safety factor for load (gravity foundations) Critical deflection analysis Blade (tip) deflection Gearbox Yaw system Assessment of the topographical complexity of a site Asssessment of wake effects from neighbouring wind turbines Assessment of structural integrity by reference to wind data Annex (Informative) Wake and wind farm turbulence. Annex (Informative) Statistical extrapolation of loads for ultimate strength analysis. Annex (Informative) Contemporaneous loads. 6

7 Wind turbine classes Wind turbine classes are defined in and intended to cover most possible sites Wind turbine class I II III S V ref (m/s) 50 42, A I ref (-) 0,16 B I ref (-) 0,14 C I ref (-) 0,12 Values specified by the designer Turbulence intensity 0,5 0,4 0,3 0,2 0,1 Class A Class B Class C V ave = 02, V ref ( z hub) V(z) = V hub z/ ; α = 0,2 α V hub m/s

8 Wind in IEC Rayleigh distributed wind speed: Power law wind profile: α = 0,2 ( ) P ( V ) = 1 exp π V / 2V V R hub hub ave ave V(z) =V = 02, V hub ref ( z/ ) α z hub 2 Extreme wind speed model: Steady: V ( z), V z e50 = 14 ref z hub V ( z) = 08, V ( z) e1 Turbulent: e50 V () ( z 50 z = Vref ) z hub V ( z) = 08, V ( z) 1 50 σ1 = 0, 11V hub 011, 011, 8

9 Turbulence Mann and Kaimal Model σ (,75V + b) ; 5,6 m/ s 1 = Iref 0 hub b = lateral component σ 2 0, 7σ 1 upward component σ 3 0, 5σ 1 0,7 z z 60 m Λ 1 = 42m z 60 m Inertial subrange 2 S ( f) = 005, σ ( Λ / V ) f hub S ( f) = S ( f) = S1( f) 3 σ1 hub ref ( hub ) 2 Var σ1 Vhub = ( Iref ( 14m/s, )) E V = I 075, V + c ; c = 38m/s, 9

10 Measurements 10 IEC MT01 meeting 14-

11 Extreme turbulence model Based on 50-year return period and lognormal TI: Normalized turbulence: σ1 I ref 1.44m / s Vave Vhub σ1 = c Iref 0072, ; c =. c 4 c 10 2 m/s 11

12 Gust models Extreme operating gust (EOG) 36 EOG Wind speed in hub height Time t s Extreme direction change (EDC) Extreme coherent gust with direction change (ECD) Extreme wind shear (EWS) 12

13 IEC Design Load cases Turbine operation normal power production start up and shut down control failure or network failure parked or idling state yaw error Wind conditions Extreme wind Wind distribution Turbulence Wind shear Dynamic events Load type Fatigue loads Ultimate load

14 The design load effect Approach 1 Approach 2 Characteristic load Characteristic load Dynamic and/or non-linear analysis Multiply by load factor Characteristic load effect Design load Multiply by load factor Dynamic and/or non-linear analysis Design load effect Design load effect γ f F k 1 1 γ γ n m f k 14

15 Partial Safety Factors for Loads (ultimate) Normal (N) Unfavourable loads Type of design situation (see Table 2) Abnormal (A) Transport and erection (T) Favourable* loads All design situations 1,35* 1,1 1,5 0,9 * For design load case DLC 1.1, given that loads are determined using statistical load extrapolation at prescribed wind speeds between V in and V out, the partial load factor for normal design situations shall be γ f =1,25. If for normal design situations the characteristic value of the load response F gravity due to gravity can be calculated for the design situation in question, and gravity is an unfavourable load, the partial load factor for combined loading from gravity and other sources may have the value 2 γ = 11, + ϕς f 0, 15 for DLC1.1 ϕ = 025, otherwise Fgravity 1 ; Fgravity ς = Fk 0; Fgravity > F F k k * Pretension and gravity loads that significantly relieve the total load response are considered favourable loads. In the case of both favourable and unfavourable loads, the limit state function becomes ( ) γ S γ F, γ F R( f ) n f,unfav k,unfav f,fav k,fav d 15

16 Partial Safety Factors (ultimate) Partial safety factors for consequences of failure: Component class 1: γ n =0,9 Component class 2: γ n =1,0 Component class 3: γ n =1,3 For non fail-safe mechanical /structural components with non-ductile behaviour γ m shall be not less than: General partial safety factor for materials, γ m : γ m 11, applied to characteristic material properties of 95 % survival probability, p, with 95 % confidence limit 1,2 for global buckling of curved shells such as tubular towers and blades, and 1,3 for rupture from exceeding tensile or compression strength. MINIMUM REQUIREMENTS!! 16

17 Partial Safety Factors (fatigue) Miner's rule For loads and all normal and abnormal design situations γ f =1,0 Partial safety factors for consequences of failure: Component class 1: γ n =1,0 Component class 2: γ n =1,15 Component class 3: γ n =1,3. MINIMUM REQUIREMENTS!! For materials: γ m 1,5 provided that the SN curve is based on 50 % survival probability and COV<15 %. Welded and structural steel: γ m = 1,1 with the 97,7 % survival probability is used as basis for the SN curves. Fibre composites: γ m = 1,2 with 95 % survival probability with a confidence level of 95 % shall be used as a basis for the SN-curve 17

18 Assessment of a wind turbine for sitespecific conditions Two approaches: a demonstration that all these conditions are no more severe than those assumed for the design of the wind turbine; a demonstration of the structural integrity for conditions, each equal to or more severe than those at the site. Site conditions: Topographical complexity; Wind conditions; Air density; Earthquake; Electrical network conditions; Soil conditions. 18

19 IEC site assessment rules Checklist Extreme winds Shear of vertical wind profile Flow inclination Background turbulence Wake turbulence Wind-speed distribution 19

20 12MW project Høvsøre cup/lidar to 300 m Lines show logarithmic wind profile. Symbols show data. Notice good correspondance only at <40 m height. Lines show mixing-length profile using boundary layer height. Symbols show data. Notice good correspondance at all heights in the boundary layer. Colours: atmospheric stability - vu very unstable, n neutral, vs very stab

21 Measured turbulence intensity I Mean wind speed Turbulence intensity measurements at Horns Rev, h=62m, No. of 10min values

22 Assessment of the topographical complexity of a site To obtain the slope of the terrain, planes are defined that fit the terrain within specific distances and sector amplitudes for all wind direction sectors around the wind turbine and pass through the tower base. The slope, used in Table 4, denotes the slopes of the different mean lines of sectors passing through the tower bases and contained in the fitted planes Distance range from wind turbine < 5 zhub < 10 zhub < 20 zhub Sector amplitude 360º 30º 30º Max slope of fitted plane Maximum terrain variation < 0,3 zhub < 10 o < 0,6 zhub < 1,2 zhub C CT = 1 + ( ˆ σ / ˆ σ ) + ( ˆ σ / ˆ σ ) ,375 C CT = 1+0,15 i c The resolution of surface grids must not exceed the smallest of 1.5 zhub and 100 m. A complexity index i c is defined, such that i c = 0 when less than 5 % of the energy comes from complex sectors, and i c = 1 when more than 15 % of the energy comes from complex sectors. In between i c varies linearly. 22

23 Thank you for your attention 13 Janu Slide 23 Det Norske