Michael Graham - Wind Energy Handbook

12 Chapter 11Figure 11.1 Large electric power system.Figure 11.2 Typical UK distribution transformer and earthing arrangements.Figure 11.3 Voltage control of a distribution circuit.Figure 11.4 Alternative locations of a transformer in a wind turbine.Figure 11.5 Protection circuitry of a wind turbine.Figure 11.6 Transformer and switchgear of 1.5 MW wind turbine.Figure 11.7 Unprotected GRP wind turbine blade damaged by a positive lightni...Figure 11.8 Blade lightning protection for a large wind turbine.Figure 11.9 Electrical power collection system of a wind farm.Figure 11.10 Schematic of a wind farm earthing system.Figure 11.11 Simplified typical protection scheme for a small wind farm conn...Figure 11.12 Typical shape of continuous and short‐time operating regions.Figure 11.13 Reactive power/power characteristics required in Great Britain....Figure 11.14 Reactive power/power characteristics required in two continenta...Figure 11.15 Commonly used reactive power compensators.Figure 11.16 Frequency response.Figure 11.17 Delta control of real power.Figure 11.18 Typical fault ride through characteristic.Figure 11.19 Additional control loops to provide synthetic inertia to a vari...Figure 11.20 Illustration of generation adequacy.Figure 11.21 Generation merit order, showing the effect of increasing wind g...Figure 11.22 Flows of information in a wind power forecasting tool.Figure 11.23 Origin of power quality issues. (a) Disturbances originating in...Figure 11.24 Influence of frequency on the human perception of sinusoidal vo...Figure 11.25 Principle of flicker measurement (IEC 61400‐4‐15 2008b).Figure 11.26 Use of a fictitious grid to establish voltage variations for va...Figure 11.27 Harmonic equivalent circuit of a VSC based wind turbine generat...Figure A11.1 Fixed‐speed wind turbine on a radial circuit.Figure A11.2 Example of calculation of voltage rise on a redial circuit (all...

13 Chapter 12Figure 12.1 Offshore wind farm capacity. (a) Offshore wind farm capacity wor...Figure 12.2 Lillgrund wind farm layout. Lillgrund Pilot Project (2009a).Figure 12.3 Lillgrund wind farm: variation in array efficiency with wind dir...Figure 12.4 Variation of turbulence intensity with wind speed – onshore and ...Figure 12.5 Pierson–Moskowitz (PM) and JONSWAP spectra for H s= 3 m and T p=...Figure 12.6 Simulated water surface elevation time history based on JONSWAP ...Figure 12.7 Data from wind‐wave scatter diagram for site NL‐1.Figure 12.8 Joint probability density of two uncorrelated normally distribut...Figure 12.9 Circle of radius β in U 1. U 2space, representing environmental co...Figure 12.10 Fifty year significant wave height against mean wind speed envi...Figure 12.11 Regular wave theory selection diagram: log scales (Barltrop et ...Figure 12.12 Parameter definitions and coordinates for regular, periodic, tw...Figure 12.13 Velocity potential contours for Airy wave theory.Figure 12.14 Horizontal particle velocity at the wave crest: Airy theory as ...Figure 12.15 Streamlines for Airy wave theory with the frame of reference fi...Figure 12.16 Streamlines for Airy wave theory with frame of reference moving...Figure 12.17 Streamlines for Dean stream function wave theory with moving fr...Figure 12.18 Horizontal particle velocity profiles below wave crest and trou...Figure 12.19 Dependence of steady flow drag coefficient on relative roughnes...Figure 12.20 Variation of wake amplification factor, ψ = C D/ C DS, with K...Figure 12.21 Variation of inertia coefficient, C M, with Keulegan–Carpenter n...Figure 12.22 Variation of C D, C M, C D/ C M, and the ratio of maximum drag force...Figure 12.23 Variation of wave loading on a 4 m dia vertical cylinder over a...Figure 12.24 Variation of wave loading on a 4 m dia vertical cylinder over a...Figure 12.25 Effect of large cylinder diameter on inertia coefficient, based...Figure 12.26 Wave breaking at vertical cylinder.Figure 12.27 Time histories of impulsive force on cylinder according to diff...Figure 12.28 Development of water pile-up as wavefront advances around cylin...Figure 12.29 Time history of force per unit length on cylinder due to breaki...Figure 12.30 JONSWAP spectrum autocorrelation function and its time derivati...Figure 12.31 Simulated water surface time history and desired constraints at...Figure 12.32 Example of a simulated water surface elevation time history con...Figure 12.33 Variation of cost of energy with turbine diameter based on INNW...Figure 12.34 Wind turbine sub‐assembly failure rates and downtime per failur...Figure 12.35 Indicative arrangement of monopile and transition piece with in...Figure 12.36 Response of 0.76 m diameter pile embedded to a depth of 7.6 m i...Figure 12.37 Degradation of clay secant shear modulus with increasing shear ...Figure 12.38 Comparison of measured and predicted ground‐level load‐displace...Figure 12.39 (a) PISA 1‐D pile model showing the soil reaction components ac...Figure 12.40 Form of non‐dimensionalised load‐displacement curves.Figure 12.41 Non‐dimensionalised ultimate lateral load per unit depth versus...Figure 12.42 Large displacement response of an 8.75 m diameter pile embedded...Figure 12.43 Pile rotation versus applied moment during initial loading and ...Figure 12.44 Variation of dimensionless functions T band T cwith M max /M rand...Figure 12.45 Variation of extreme and fatigue moments over height of support...Figure 12.46 Support structure natural frequency exclusion zones for a 5 MW ...Figure 12.47 Variation of support structure weight with mean water depth....Figure 12.48 Example support structure for 5 MW turbine.Figure 12.49 Comparison of quasi‐static and resonant transfer functions for ...Figure 12.50 Effect of diffraction on the transfer function for quasi‐static...Figure 12.51 Variation of aerodynamic damping with wind speed for fixed‐spee...Figure 12.52 Spectra of water surface elevation and resonant mudline bending...Figure 12.53 Mudline moment spectrum approximation.Figure 12.54 Schematic for simplified calculation of fatigue damage.Figure 12.55 Reinforced concrete gravity base design used at Lillgrund wind ...Figure 12.56 Gravity bases for Lillgrund under construction on barge at quay...Figure 12.57 Lowering of gravity base by floating crane during installation ...Figure 12.58 Prestressed concrete gravity base design used at Thornton Bank ...Figure 12.59 Elevation on Blyth gravity base foundation in cross‐section.Figure 12.60 Gravity base foundations for Blyth offshore wind farm under con...Figure 12.61 Four legged jacket structure to support REpower 5 MW turbine at...Figure 12.62 Transition section configured to provide direct load paths from...Figure 12.63 Anchorage of jacket leg to pile using concentric jacket stab‐in...Figure 12.64 Installation of tower, nacelle, and rotor assembly by floating ...Figure 12.65 Theoretical variation of 5 MW turbine monopile support structur...Figure 12.66 Tripile structure after installation. The pile tops, which spor...Figure 12.67 Comparison of design S ‐ N curves for transverse butt welds witho...Figure 12.68 Double‐sided butt weld with 30° bevel angles.Figure 12.69 Comparison of butt weld fatigue strength reduction factors due ...Figure 12.70 Cumulative failure probability for a weld designed using a DFF ...Figure 12.71 Types of floating offshore wind structures: (a) spar buoy, (b) ...Figure 12.72 Ratios of extreme turbine loads on different floating platforms...Figure 12.73 Spar buoy nomenclature.Figure 12.74 Variation of spar length, steel spar weight, ballast weight, an...Figure 12.75 Possible arrangements of three and four column semi‐submersible...Figure 12.76 Variation of column spacing, draft, notional column steel weigh...Figure 12.77 Variation of column spacing, draft, natural pitching period and...Figure 12.78 Spar buoy mooring system layout.Figure 12.79 Variation of mooring loads, stiffnesses, and inclination with s...Figure 12.80 Artist's impression of Hywind Scotland wind farm.Figure 12.81 Two Hywind spar buoys loaded onto a vessel prior to flotation....Figure 12.82 Pitch motion of all five turbines during operation in a mean wi...Figure 12.83 WindFloat Atlantic platform during load‐out from quayside to se...Figure 12.84 Floatgen in situ.Figure 12.85 Options for transmission from offshore wind farms.Figure 12.86 Typical UK Round 2 offshore wind farm power collection and tran...Figure 12.87 Per‐phase approximate equivalent circuit of 1 km of 132 kV cabl...Figure 12.88 Typical offshore wind farm ac connection.Figure 12.89 Impedance of the network of Figure 12.88 seen from 132 kV busba...Figure 12.90 Voltage propagating through a wind turbine power collection rad...Figure 12.91 VSC HVdc transmission from an offshore wind farm.Figure 12.92 MMC using half bridges.