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.







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




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
3-Bladed
Horizontal axis
Up wind
70,65 meter
3920 m²
Variable
Nominal 23 rpm
Pitch control
5°
Surface colour
Manufacturer
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
Inverter system
Type
Control
Cooling
Grid coupling
Voltage source inverter
Micro processor
Water / air cooled
AC-DC-AC
Transmission system
Type
Direct drive
Couplings
Flange connections only
PLC
LWMS
Harakosan Europe BV
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
Synchronous
2000 kW
4000 Volt
Permanent magnets
IP 54
Air
F
ABB AMG2500UU60
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
Tapered tubular tower
65 & 80 meter
Light grey RAL 7035
Semi-matt 5-15
ISO 2813
Safety system
Type
Independent pitching
blades
Activation
Redundant electrical mechanical
Masses
Rotor
Controller
Type
Remote monitoring
Manufacturer
Generator
Type
Nominal power
Voltage
Field excitation
Protection
Cooling
Insulation class
Manufacturer
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
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
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)
Temperature
On operation
On standby
- 20 °C - + 40 °C
- 30 °C - + 50 °C
Electrical specification
Generator
Type
Apparent power
Line voltage
Phase current
Excitation
Nominal rotor speed
Protection
Number of phases
Multiple pole synchronous
2080 kVA
4000 Volt
436 A
By permanent magnets
23 rpm
IP 54
3
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
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
Outside cooling by wind
Air / water
Converter protection
Circuit breaker
Surge arrestors
ABB
10 kA
Winding protection
Insulation class
Analogue temperature
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