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Technical description of the Z72 wind turbine

The turbine consists of various large components or building blocks mounted together at site and resulting in a wind turbine system. These building blocks are explained below.

The generator The generator is a multi-pole permanent magnet generator and is directly mounted to the hub. The magnets take care of the rotor excitation so no external field excitation is needed. This implies that the generator losses reduce by 25% compared to a wound rotor with external field excitation. The stator, equipped with cooling fans, is located on the outside and is cooled by the outside air. The stator windings are vacuum impregnated and have a 7 kV insulation value commonly used in medium voltage generators. In the inside of the generator dried and, if necessary, filtered air is circulated. This air assures an equal temperature distribution in the generator and, as little leakage occurs through the seals, over-pressures the generator. Thus dust and salt particles cannot enter the generator. This generator has been designed and will be delivered by ABB Finland. The weight of the generator is 49 ton and measurements are 3.9m x 2.0m.

The main bearing The main bearing is a specially designed two row cylindrical roller bearing of large diameter. The inner nonrotating ring is mounted to the generator stator. The outer rotating ring is mounted between the hub and generator rotor. The bearing takes axial and radial loads as well as bending moments. The bearing is provided with a fully automatic lubrications system monitored by the turbine controller.

The nacelle The nacelle is a compact nodular cast iron construction which houses the yaw mechanism, a service hoist and a switch board. Both generator and tower are flanged to the nacelle. The geometry of the casting assures an ideal transfer of loads to the tower and has resulted in a simple design. The weight of the nacelle assembly is 19 ton and the measures 3.3m x 2.9m x 3.3m. The nacelle is delivered with a standard red silhouette top light.

The hub The rigid rotor hub is a nodular cast iron structure mounted onto the main bearing. Blades are connected to the hub using a four point pre-stressed ball bearing. It is sufficiently large to provide a comfortable working environment for two service technicians during maintenance of the pitch system, pitch bearings and blade root from inside the structure. Entrance to the hub is achieved through the inner main bearing ring. The weight of the assembled hub is 19 ton and the measurement is 3.8m x 3.8m x 3.7m Vital electronics in the hub are protected against lightning.

The blades The three rotor blades are constructed from a glass/epoxy mixture by using vacuum injection technics. The aerodynamic profiles have been chosen on basis of their good efficiency and their very low sensitivity to dirt. The weight of each blade is 4,600 kg. The length of the blades is 34.0 metres against an outer blade root diameter of 1,9 metres. The biggest cord is 3.1 metres high. All blades have an integral lightning protection system mounted in each of the blades. These blades are manufactured by Norwegian blade manufacturer Umoe and is based on the so called APX70-mould. Though, the design also allows blades from other blade manufacturers. The tower The nacelle is placed on a tubular steel tower, fully protected against corrosion. The tower allows access to the nacelle via a secured hinged access door at its base. The tower is fitted with an internal ladder, rest platforms and lighting. The complete tower exists out of three or four sections, which are bolted together on site. As a standard, the tower is connected to the earth through an earth circuit around the foundation. Depending on soil conditions the earth system will be modified to the local conditions.

The converter The Z72 uses a variable speed system with a permanent magnet excited synchronous generator giving a high efficiency and high quality power. The generator power with variable frequency is rectified and converted to a constant frequency (AC-DC-AC conversion) and fed into the grid (see single line diagram). A full size converter is used to optimise the quality of the frequency and voltage in order to minimise harmonic currents based upon the ABB ACS 1000 medium voltage converter series. The converter controls the power as a function of the rotational speed of the turbine and keeps it constant at nominal power. The rotational speed of the turbine is pitch controlled to keep it within the specified range. Converter and pitch control act as a "master-slave" system. The reactive power is controllable but standard set to zero (cos=1). The UPS system gives the wind turbine the capability to remain in operation in case of a grid voltage dips of 200 msec. For grid operators these features are important advantages.

Single line diagram

Abbreviations INU ARU MCB Aux power UPS

: : : : :

Power converter generator side Power converter grid side Main circuit breaker Auxiliary power supply for nacelle and rotor sub-systems and UPS Uninterruptible power supply (optional)

The control system The hardware of the Z72 control system is built up in modules. The control and safety functions are done in the same area or space where the needed measurements and control or safety actions are performed. The control PLC's are mutually connected by means of an optical glass fibre communication line. The communication is performed by means of a network protocol. The functions of the PLC's are stated below.

1. · · · · · · · · · · · · ·

The PLC in the rotor Monitoring of rotor hardware Interfacing with second or (emergency) protection system Periodic execution test second protection system Blade pitch control Manual blade pitch control Measurement of blade angles Check of synchronisation of blade angles Measurement of rotor speed Control of generator dryer Control of pitch bearing grease system Rotor PLC alarm Rotor PLC trip Field bus communication with nacelle

2. · · · · · · · · · · · · · ·

The PLC in the nacelle Monitoring of nacelle hardware Yaw control Wind speed and direction (2x) measurement Main bearing temperature monitoring and alarm/trip Generator stator temperature monitoring and alarm/trip Determination on/off generator dryer Cable twist monitoring and alarm/trip Tower top acceleration monitoring and alarm/trip Control of air dryer Control of grease pumps of main and yaw bearing Monitoring status parking brake Monitoring status security pin Nacelle PLC trip Nacelle PLC alarm

3. The PLC in the AC-DC-AC converter · · · · · Control of generator stator electric characteristics (AC voltage, current cos() and power) Communication to nacelle PLC (data transfer; fault alarm, ready message) Grid connection and disconnection Monitoring of PLC hardware Interfacing with converter

· · · · ·

Management System Field bus communication with nacelle KWh and kVar monitoring Tower base PLC alarm Tower base PLC trip

There is distinguished between an" alarm", which is a warning message and a "trip", which stops the turbine. The special installation hoist To optimise installation activities a special hoist has been designed in cooperation with Mammoet. The hoist has been designed to facilitate the installation of the turbine in remote areas or complex terrain and to avoid high crane cost for mounting the generator and the rotor assembly. The Z72 is characterised by a heavy generator and light nacelle. The typical configuration of the turbine offers the possibility to mount a hoist on top of the nacelle. With this hoist the generator, but also the assembled hub with blades, will be mounted without a heavy and expensive mobile crane. For a hub height of 65 m a 400 tonnes main mobile crane is needed to mount the tower and nacelle. In addition an extra tail crane of approximately 160 tonnes is needed. This capacity is determined by the weight of the upper tower section and nacelle and the lifting height. The hoist itself has a weight of 7 tonnes and a lifting capacity of 60 tonnes. It can be used on any height and is fixed on top of the nacelle by means of a pivot. No bolted connections are used but only a locking pin has to be applied. The hoist is balanced by means of a fixing on the foundation. By means of a hydraulic cylinder on ground level the hoist can only be hinged vertically. This implies that a load can be moved horizontally, essential for easy mounting. The diesel driven winch is located on ground level and is housed in a 40 ft. container that is fixed on the foundation. Therefore, no power from the grid is required. The hoist is containerised in a second 40 ft. container.

Technical specification Rotor Type Position Diameter Swept area Rotor speed Power regulation Rotor tilt angle Blade set Type Blade length Tip chord Root chord Aerodynamic profile Coning Material Surface gloss Surface colour Manufacturer Inverter system Type Control Cooling Grid coupling Generator Type Nominal power Voltage Field excitation Protection Cooling Insulation class Manufacturer

3-Bladed Horizontal axis Up wind 70,65 meter 3920 m² Variable Nominal 23 rpm Pitch control 5°

Synchronous 2000 kW 4000 Volt Permanent magnets IP 54 Air F ABB AMG2500UU60

LM-34-P3 / UM70 34 meter 0,97 meter 3,05 meter NACA 634 ­ 632 xx/DU-FFA 1,3 ° Glass fibre reinforced epoxy Semi-matt 5-15 ISO 2813 Light grey RAL 7035 LM, Umoe or others

Service brake Type Maintenance brake Position At hub flange Callipers Hydraulic 5 pieces Yaw system Type Yaw bearing Yaw drive Yaw brake Tower Type Hub height Surface colour Surface gloss

Active 4 point ball bearing Triple electric motors Passive friction brake

Voltage source inverter Micro processor Water / air cooled AC-DC-AC

Tapered tubular tower 65 & 80 meter Light grey RAL 7035 Semi-matt 5-15 ISO 2813

Transmission system Type Direct drive Couplings Flange connections only Controller

Safety system Type Independent pitching blades Activation Redundant electrical mechanical Masses Rotor

Type Remote monitoring Manufacturer

PLC LWMS Harakosan Europe BV

36 ton (with LM blades) 33 ton (with Umoe blades) Generator 49 ton Nacelle 19 ton Tower 65 meter 100 ton Tower 80 meter 150 ton

Load supporting data Hub Nodular cast iron Main bearing Single cylindrical roller bearing Generator carrier Nodular cast iron GGG.40.3 Nacelle Nodular cast iron GGG.40.3

Operational data Cut in wind speed Cut in wind speed after cut out Cut out wind speed Cut out wind speed Nominal power Designed for wind class Power factor Power quality Power quality standard Power peak

3 m/s 20 m/s (10 minute average) 25 m/s (10 minute average) 35 m/s (2 second average) 13 m/s (momentaniously) IB according to IEC 61400-1 Controllable between 0.92 and 1.00 THD <3% IEEE 519 P < 1.03

Temperature On operation On standby

- 20 °C - + 40 °C - 30 °C - + 50 °C

Wind and site information Maximum 2 s gust 70 m/s Maximum average 10 m/s wind speed Maximum z° 0.25 Maximum flow inclination (terrain 8° slope)

Electrical specification

Generator Type Apparent power Line voltage Phase current Excitation Nominal rotor speed Protection Number of phases Power at 4000 V and nominal Power factor at 25% load Power factor at 50% load Power factor at 75% load Power factor at 100% load Power factor standard Power factor optional Harmonic current distortion Power peak Flicker Inrush current at start up Controlled power up Controlled power down DP/dt control Multiple pole synchronous 2080 kVA 4000 Volt 436 A By permanent magnets 23 rpm IP 54 3 grid conditions 1.00 (standard) 1.00 (standard) 1.00 (standard) 1.00 (standard) Controllable between 0.92 and 1.00 leading or lagging Controllable in a range to be agreed upon with the customer THD < 3% P < 1.03 C=4 No inrush (0 A) 30 s approximately 12 s approximately other values optional Optional

Drive train efficiency at nominal grid conditions Efficiency at 25% load 93,0% Efficiency at 50% load 94,5% Efficiency at 75% load 94,0% Efficiency at 100% load 93,0% Cooling Generator cooling Back to back cooling Converter protection Circuit breaker Surge arrestors Winding protection Insulation class Analogue temperature

Outside cooling by wind Air / water

ABB 10 kA

F 4 x PT -100

Earthing requirements Earth resistance Depth electrodes Ring electrodes Foundation reinforcement Medium voltage connection Transformer rated apparent power (dependent on desired cos (phi) ) Rated frequency Rated voltage primary Taps Metering Rated voltage secondary Losses at nominal power Protection of LV side transformer MV main circuit breaker

According to IEC Minimal 2 x 50 mm2 / Maximum resistance 2,5 Ohm Minimum 1 x 50 mm2 Must be connected to earth electrodes

2100 kVA

50 Hz or 60 Hz Maximum 50.000 V. (dependent on local grid) -7,5, -5, -2.5, 0, +2.5, +5, +7.5% on HV - Inquire for other possibilities. To be installed independent from turbine 4000 V 1,5% LV surge arrestors. To be supplied with the transformer. Capable of protecting the transformer, SCC of turbine is minimal, see below.

Short circuit current contribution of turbine 1 max To be measured Dl / dt max To be measured Rated voltage 4000 V Rated current @ cos (phi) = 1 To be measured Grid requirements Low voltage Minimum frequency Maximum frequency Maximum harmonic voltage distortion on point of common coupling (POCC), without turbine. Power consumption from grid At stand by At stand by ­ yawing During cut in active pitch & yawing

4000 Vac, +10% -- -10% 96% of nominal 102% of nominal Other limits optional According to IEC 61000-3-6 and VDEW

1,5 kW 9 kW Maximum 30 kW



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