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Operation & Maintenance Considerations Report







Completed By Clappercon Renewable Consultants











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Executive Summary


Clappercon have delivered a feasibility study and reported on the best selected system for the Glenorse
wind park. This
report follows this work as an introduction to the main practical cost base for any wind
park project. Understanding O&M, it costs, consequences and the importance of bespoke O&M contracts
is vital to the continued viability of the Glencorse project.


When

negotiating finance deals banks and investors will want to see a clearly defined O&M strategy that
will pass on financial losses via turb
ine downtime to a third party.
In this report the current O&M market is
discussed alongside O&M costs, the consequence
s of turbine downtime, turbine components and their
maintenance, the differences between offshore & onshore O&M (for future projects) and finally
recommendations are made for a strategy to adopt when entering O&M negotiations with Acciona, the
chosen turbi
ne manufacturer.

The report is deliberately lengthy so as to ensure Forth Valley Wind
Ventures will gain a full overview of all the O&M issues involved.





























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Table of Contents

1.0 O & M in 2011
................................
................................
................................
........

4

1.1

Past & Present Summary

................................
................................
................................
.......

4

1.2

Service Propositions


Industry Leader for Reference
................................
......

5

2.0

Costs & Downtime

................................
................................
.........................

6

2.1

Cost Iceberg
................................
................................
................................
................................
....

6

2.2

Costs Breakdown

................................
................................
................................
........................

7

2.3

Causes & Consequences of Downtime

................................
................................
........

8

2.4

Cost Expectations
................................
................................
................................
....................

11

3.0

The Main Component Trends & Maintenance

................................
......

12

3.1

Gearbox

................................
................................
................................
................................
..........

12

3.2

Generator

................................
................................
................................
................................
.......

14

3.3

Pitch & Yaw Control
................................
................................
................................
................

16

3.6

Wind SCADA
................................
................................
................................
................................

19

4.0

The Full Service

................................
................................
............................

22

5.0

Onshore v Offshore Comparison
................................
.............................

24

6.0

Recommendations

................................
................................
.......................

25

6.1

Final Conclusions

................................
................................
................................
....................

25

6.2

Pareto

................................
................................
................................
................................
...............

25



























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1.0 O & M

in

2011

1.1

Past & Present

Summary


The decades preceding the millennium wind turbine market w
itnessed a regressive reactive
approach to
wind turbine operations & maintenance as owners drove the turbine components to
failure

and reactively
repaired faults. Indeed
such an attitude to wind turbine O&M can still be seen today but in most cases
has been consigned to the past as modern profitability forecasting has highlighted the disastrous effect
on profits a poor O&M approach can have.
1


1.1.2

Current approaches to
wind turbine O&M have matured to complex data analysis where
consideration is given to the impact of component failure and subsequent turbine downtime as an
exponential part of the overall wind farm feasibility and cash growth.

However, a balance between
e
xpensive condition monitoring systems and reactive maintenance is still trying to be struck as it is
possible to save costs with a mixture of both practices.
2


1.
1.
3

A step away from
total
reactive maintenance has been deliberately taken towards
preventative
and predictive maintenance tha
t seeks to reduce O&M
costs
. T
hese forms of maintenance are
necessarily in their infancy as the large 1MW + turbine market has not given enough historical data to
make O&M for each turbine model an entirely predic
table venture.

Indeed with the current explosion in
the offshore turbine market O&M policy for offshore wind parks will become the single most significant
factor in determining the ongoing financial viability
of these massive 100 + turbine

wind parks.


1
.
1.
4

Wind park location

& wind speed are

also having an impact on modern O&M as
government

s

lift

moratoriums on certain habitats and new technological breakthroughs allow wind turbines to be
operated in ever extremer conditions.

O&
M policy for a turbine operating on a

medium wind

Scottish
moorland must be necessarily different to that for a turbine generating in the hot
fast wind
sandy plains of
California. Again the maintenance requirements for the same turbine in these two differe
nt environments
is

at a relatively infant stage as data analysis on the impact of climate on the various components that
make up an industr
ial wind turbine is only approximately a decade old.


1.
1.
5

Weather forecasting is a vital part of O&M as scheduling
annual & preventative maintenance
correctly can ensure as little downtime as possible when the wind is blowing; preferably all O&M should
take place on ‘low wind’ days but in practice this is not possible due to the nature of technician resource
and the un
predictability of the weather.
There can be no more frustrating site for a wind park manager
than an idle turbine on a windy day.





1

From ‘National Instruments


Wind Turbine Condition Monitoring’, www.zone.ni.com……, accessed
01/02/2011.

2

From ‘So what is involved in servicing a wind turbine’,
www.windpowermonthly.com/news/989447/So
-
involved
-
servicing
-
turbine/

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1.2

Service Propositions



Industry Leader for Reference


‘Typically, turbine manufacturers guarantee 95 percent turbine
availability over a 20 year operating
window’.
3

To deliver this promise the majority of turbine manufacturers offer their own service proposition
and provide initial five year warranties for the majority of parts/components. This allows them to build a
bra
nd reputation and also improve the product via direct feedback from their own maintenance teams.
Indeed Enercon’s EPK division is regarded as the industry standard and offers a popular 12 to 17 year
contract for wind park maintenance

and it is interesting
to see what it offers and the advantages this
delivers
4

-




ENERCON PartnerKonzept


facts and figures

Guaranteed technical availability

~ Up to 97 % per year at nearly all sites worldwide ~ Reimbursement of
output loss if guaranteed availability is not a
ttained ~ Steady yields provide planning and financing
security ~ Contract periods ranging from 10 to 15 years ~ EPK follow
-
up package available for operating
years 15


20 ~ No additional costs for spare parts or main components (with a standard machine
b
reakdown / downtime policy covering regular remaining risks) ~ No need to make financial provisions for
larger repairs ~ ENERCON’s additional insurance policy combined with a standard machine breakdown
and downtime insurance provides complete

protection
against unforeseeable events ~ Constant 24 / 7
SCADA (System Control and Data Acquisition) monitoring ~ Prompt reaction time due to a decentralized
service network ~ Calculable operating costs based on energy yield. Calculation formula
-

Fee = kWh
produced

°


price per kWh (SCADA system).

5


1.2.1

‘The customer pays a minimum fee depending on the respective wind turbine…..this means the
customer pays more in good wind years with good wind yield and less in bad wind years with less output
thus stabilizing a
nnual wind turbine profit.’

The EPK single contract for all maintenance is very attractive
and must be considered an asset with the knowledge that turbine downtime is the biggest single revenue
loser for a wind park owner.


1.2.3

Given the relative risks i
nvolved in
wind park ventures having the EPK service
guarantees
alongside
the wind yield charging structure mitigates the largest proportion of wind park risk


the wind
not blowing. Risk managers and financiers like risk reduction and built in c
ost reduction clauses. Only the
EPK meet these demands and
goes

even further offering long

extended service contracts that in some
cases may last as long as the wind park itself
.










3

From ‘Wind Turbine Availability Excellence


Using advanced control communications to decrease
downtime’, www.intel……

4

From ‘ How to find the right maintenance contract’, www.windpowerm
onthly.com/news/indepth/1009791

5

From ‘ENERCON wind energy conerters


PartnerKonzept (EPK),
http://www.enercon.de/p/downloads/Enercon_ EPK_uk.pdf
, accessed 01/03/2011.

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2.0

Costs & Downtime

2.1

Cost Iceberg


Figure 1
-

O&M costs iceberg
6


The costs iceberg

in figure 1

gives an excellent picture of the current problems facing wind turbine
maintenance analysis and shows how the intangibles costs currently
weigh down the tangible costs. T
his
is a scenario that a clever O&
M strategy should look to
reverse by collecting and analys
ing as much data
as possible as well a
s learning lessons each year then

applying a strategy that ensures those less
ons
result in a tangible saving:



Last year the snow fall in Glendevon was excepti
onal. Such was the level of snow we could not go out
and perform maintenance on any of the turbines as the vehicles we had could not clear the access roads
of snow drifts. This year we are prepared though and have a snow cat on standby’


This is a transcri
ption of a conversation with the manager of Green Knowes wind farm in early 2011. It is
a great example of an intangible cost arising and how a simple solution will prevent turbine downtime in
the future; this was a lesson well and truly learned.









6

From ‘Wind Turbi
ne Availability Excellence’, http:download.intel.com/embedded/energy/windturbine.pdf,
accessed 04/03/2011.

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2.2

Costs Breakdown


Figure 2


Ingredient of Operations & Maintenance
7


2.2.1

When analysing the cost of O&M to the wind park owner it is appropriate to not only calculate an
overall cost per kWh or MWh produced but also to establish where the costs are
arising from within the
overall system. From the pie charts in figure 2 it is immediately obvious that scheduled maintenance is
the biggest cost as a proportion across Germany, the UK and the USA. This result could be considered
surprising given recent em
phasis in the industry on battling unscheduled maintenance and the downtime
this delivers. It can only be assumed that the data for figure 2 was take
n

from the relatively early years in

the life of the analysed wind parks as the charts are consistent with
the high insurance & administration
costs of the initial years of operation.


2.2
.2

Comparing figure 2 with the bar chart in figure 3
(page 8)
the above argument becomes
consistent as once again high insurance costs and maintenance make up the bulk of the
cost total.
Repair begins to rise as initial warranty periods end and in the post 6 years old period repair &
maintenance make up the bulk of the cost unit.





7

From ‘Breaking down the cost of wind turbine maintenance’,
http://www.windpowermonthly.com/news/1010136/Wind
-
turbine
-
gearboxes
-
effort
-
improve
-
reliability/
,
accessed 09/04/2011.

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Figure 3


Age related costs
8


2.3

Causes &
Consequences of Downtime


2.3
.1

Having

briefly

summarised the
cost ingredients

importance is then given to what is causing
downtime and the consequences this has for electricity production (days out). Figure 4 clearly shows that
electrics are responsible for the largest number of failure incidents but

this translates to only 4.4% of days
out despite being responsible for 22.9% of the overall failure incidents. It is easy to understand why this is
the case as electrical faults can often be remedied remotely or if needed in person on site. On site
electr
ical repairs are generally quick and a experienced technician will solve the majority of problems in a
short period of time.



Figure 4


Failure analysis
9




8

From ‘Plant age and Development costs’,
http://windmonitor.iwes.fraunhofer.de/windwebdad/www_reisi_page_new.show_page?page_nr=240&lang=
en
, accessed 08/04/2011.

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2.3
.2

In comparison to the electric faults

gearbox failure does not happen as often but when it do
es
repair is lengthy and downtime is significant. Gearbox failure only represents 5.41% of failure incidents
but results in 18.63% of the days out per failure. The reasons for this are the complexity of the
mecha
nical repairs that are needed. I
n a worst c
ase scenario an overhaul or replacement of the gearbox
would require

crane removal, an activity that is hugely costly in terms of finance and downtime.



2.3
.3

Further evidence of failure rates and
causes

(days out)

is given in figure 5 on page 10
. Given
the data available
a cost for the consequences of this failure is required but it is an
entirely irrelevant
figure without exact model
data alongside data from a site

with similar climatic conditions to the site you
are building on.
An average per
turbine is £80,000 per annum but this does not take into account a
significant component failure like a
gear
box breakdown. Installing a new gearbox could cost well in
excess of £200,000 so a continuation fund is most definitely necessary as

well as an O&M
/ extended
warranty contract that compensates for the
losses

such an event would incur.

This information is useful
however in helping to dictate the overall O&M strategy for the wind park as it immediately indicates how
important preventative maintenance
is on the drive train, gear box, rotor blades and rotor hub as a failure
in any of these systems results in significant downtime as a proportion of the actual incident level
recorded for each system.







9

From ‘Breaking down the cost of wind turbine maintenance’,
http://www.windpowermonthly.com/news/1010136/Wind
-
turbine
-
gearboxes
-
effort
-
improve
-
reliability/
,
accessed 09/04/2011.

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10

Figure 5


Failure Analysis



10

From ‘ Reliability & Avail
ability of Wind Turbine Electrical & Electronic Components’, http://www.reliawind.eu/files/publications/pdf_13.pdf , accessed

20/04/2011.

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2.4

Cost Expectations


Forecasting future O&M costs
is a difficult task in 2011 due to the lack of available data for newer high MW
models that have only been installed in recent years and are not yet part of a concerted manufacturer led data
collation program. The graph in Figu
re 6

shows that a peak in O&M

costs will be delivered between years 18 &
22 of the project. This estimation is sensible and takes account of the aging equipment and its ongoing ability
to function.



Figure 6


Maintenance & Repair costs prediction
11


2.4.1

Wind turbines are designed

to survive a 25 year lifespan but this is largely dependent on the climatic
c
onditions at the wind park site

and the quality of the O&M strategy being carried out. It is sensible to believe
that a cleve
r

preventative maintenance strategy would lessen the
impact of age on the

machinery and help to
avoid an

absolute peak in O&M costs in the later years of a wind parks life.













11

From ‘Forecasting of Maintenance and Repair costs of Wind Energy Plants’,
www.powergenu.com/courses/4/PDF/1007PGU_FrctgofMantnce.pdf
, accessed 15/04/2011.

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3.0

The Main Component Trends & Maintenance

3.1

Gearbox


There are two main
generator
models on the market that offer a variety

of different power ratings. The
difference between the two models is significant and an understanding of the difference is essential to
understanding the different O&M challenges offer
ed by each model. Figure 7

is a direct drive turbine that has
no gear b
ox.
This model is
predominantly

used for offshore wind park’s as removing the gear

box delivers a
system that is more reliable,
maybe
l
ighter, smaller and
has less moving part
s

than the traditional
gear driven

wind turbine.

It should also be noted that complications with offshore O&M i.e. access
, assures that

removing
any potential gearbox reliability problems is a positive step.





Figur
e 7


Direct Drive system with annular

generator
12



12
From ‘ Control of Wind Turbines’,
https://netfiles.uiuc.edu/.../NPRE%20475%20
Wind
%20Power%20Systems/
Control
%20of%20
Wind
%20Turbines.p
df

, accessed 12/04/2011.

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Figure 8



Wind Turbine Component Assembly with gear box
13



13

From ‘ Wind Turbine Reliability’,
http://www.windpowermonthly.com/news/1010395/Wind
-
turbine
-
gearboxes
-
effort
-
improve
-
r
eliability/
, accessed 09/04/2011.

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3.
1.
1

Figure 8 show
s
the standard wind turbine system that has dominated the market to date but is now
being challenged by the direct drive model. The main reliability issue with these turbines has
been the gearbox
but the statistics show that wind turbine gearboxes are actually very reliable its just that when one does fail it is
a massive task to overhaul or replace this vital component.


3.
1.
2

Figure 9 shows the complexity of the gearbox and given

its size, housing and sheer number of
components it is easy to see why a failure is so troublesome. Some small repairs can be carried out
up tower
but
if housing removal is required to replace gears, bearings or the shaft then it becomes a significant job

involving crane hire and removal.




Figure 9


Wind turbine gearbox system block diagram
14


3.2

Generator


Modern wind turbine models make use of both
synchronous

and
asynchronous

generators to create the power
that drives the commerciality of the wind park site. All wind turbine generators operate in three phase state but
there is a choice when it comes to which generator to use that is driven by cost, weight and reliability.

The
majority of existing wind parks are running turbine’s that use the traditional

high speed geared system with
asynchronous

generators.
These generators require consistent servicing and monitoring by skilled technicians.
Given the time consuming nature of this servicing there has been a marked move away from high speed lots of
moving parts systems to direct drive wind turbines that make us
e new lightweight technologies to compensate
for the size of
a larger permanent magnet
synchronous

generator. The advantages of this system are


They are more stable and secure during normal operation and th
ey do not require an
additional DC supply for
th
e excitation circuit.





14

From ‘
Reliability Analysis and Prediction of Wind Turbine Gearboxes
’,
http://www.reliawind.eu/files/publications/pdf_34.pdf
, accessed 10/03/2011.


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The permanent magnet synchronous generators avoid the use of slip rings, hence it is simpler and
maintenance free.


Higher power coefficient and efficiency.


Synchronous generators are suitable for high capacities and asynchronous
generators, which consume more
reactive power, are suitable for smaller capacities.


Voltage regulation is possible in synchronous generators where it is not possible in induction types.


Condensers are not required for maintaining the power factor in sync
hronous generators, as it is required in
induction generators.


Because of high coercivity of high performance permanent magnet materials, such as neodymium, air
-
gap
depth is more tolerable, which puts lower structural constraints on frame and bearing
assemblies.

15


3.2.1

The above advantages have been recognised by industry in the

wind
turbine market and

intentions to
further develop the direct drive system have been demonstrated by major manufacturers including Siemens;




Siemens's plans hinge on a
new design that reduces the weight of the system's generator. In conventional
wind turbines, the gearbox increases the speed of the wind
-
driven rotor several hundred fold, which radically
reduces the size of the generator required. Direct
-
drive generators
operate at the same speed as the turbine's
blades and must therefore be much bigger
--
over four meters in diameter for Siemens's three
-
megawatt
turbine. Yet Siemens claims that the turbine's entire nacelle weighs just 73 metric tons
--
12 tons less than that
on its less powerful, gear
-
driven 2.3
-
megawatt turbines.

16

3.2.2

There is obviously less wear and tear in a direct drive generation scenario due to less moving parts at
lower speeds which will mean the maintenance schedule will be less rigorous than that o
f a geared system.
This is a big positive for the offshore market that has had a positive impact on the onshore market as the
advance towards more durable and lighter generator’s has reduced costs with the further bonus of added
reliability.













15

From ‘ Permanent magnet synchronous generators’,
http://en.wikipedia.org/wiki/Permanent_magnet_synchronous_generator
, accessed 28/04/2011.

16

From ‘Wind Turbine’s Shed Their

Gears’,
http://www.technologyreview.com/energy/25188/
, 24/04/2011.

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3.3

Pitch & Yaw

Control


The pitch control system is another major system tha
t has to be maintained. Below is

a simple diagram of a
pitch control system in action which illust
rates the moving parts involved.



Figure 10


Pitch Control System
17


3.3.1

Pitch
control is vital to ensuring the load on the overall system is kept at tolerable levels as well as
ensuring the blades keep turning at the most efficient speed for power generation in the prevailing weather
conditions.


3.3.2

Independent Pitch Control sy
stems are commonly used in modern wind turbines where the
independence refers to each blade being controllable in its own right with the blade housing at the hub
containing the pitch control system. Electromechanical or Hydraulic

pitch drives

are available

and therefore
require differi
ng forms of maintenance. R
edundancy is always built in to this vital system as if the blades
cannot be pitched correctly the situation becomes both dangerous and costly.

Examples of pitch control
systems are shown
in figure’s

11 and 12 on page 17
.




17

From ‘Pitch Control of Wind Turbine Generator by using New Mechanism’,
http://www.esrgroups.org/journal/jes/papers/6_1_7.pdf
, accessed 20/04/2011.


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Figure 11


Electromech
a
n
ical Pitch Control showing
actuators.



Figure 12


Hydraulic

Pitch Control showing
actuators.
18


3.3.4
The pitch control systems suffer from low failure rates due to redundancy and also the proven
technology involved that has been tested for decades for use in other industries. Hydraulic systems are proven
to be very reliable and so long as maintenance sche
dules are adhered to should prove
un
problematic
throughout the life of the turbine. Indeed the reliability of the pitch control system itself is
v
ital to overall turbine
health as it controls the main vibrational forces impacting the turbine by pivoting the blades regularly to create
minimum system
turbulence
.


3.3.5
The yaw control system pivots round the tower to ensure the hub and blades face t
he prevailing wind
direction which allows the pitch control to tilt the blades to p
roduce maximum available power:





18

From
-

‘Products & Solutions’,

http://www.boschrexroth.com/country_units/america/united_states/sub_websit
es/industries/wind_energy/win
d_components/wind_comp_rotor/wind_comp_rotor_pitch_hyd/index.jsp
, accessed 18/04/2011.

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Figure 13


Yaw Control System with highly sensitive gear drives.
19


3.3.6
Modern wind turbines use active yawing as a means to directly
control the position of

the turbine on the
tower

as this allows very precise computer controlled positioning to minimise power losses delivered by
subtle
movements in prevailing wind direction.


3.3.7
Yaw system maintenance is very standard and should no
t require any long lasting attention as the
system is designed to deal with the intensive static and dynamic loads that occur when the wind turbine is
functioning. Bearing wear should be monitored as a priority as replacing the yaw drive system would requi
re
dis
-
assembly of the turbine which would be very costly in terms of manpower and lost power generation
revenue.


3.3.8
An example of a modern yaw control system can be witnessed in Siemens updated Intelligent Yaw
Control System:



For yaw control,
Siemens offers highly efficient solutions based on the turbine controller (SIMATIC Microbox
PC with WinAC RTX F). They allow for adaptive wind tracking of the nacelle to ensure that it is optimally
positioned in the wind at all times. For this purpose, the

sensors signal the wind direction to the controller
which sets positioning drives in motion as necessary. Complex PC
-
based control algorithms reduce the
powerful forces acting on the rotor, the turbine, and the remaining structure when movements along the

vertical axis occur. This high
-
performance system combination ensures controlled start
-
up and prevents play in
the tower.

20


3.3.9
Using intelligent yaw control and an active pitch control system is essential to the long term health of
modern wind turbi
nes
. W
ith these systems being improved year on year wind power production will become
better controlled resulting in lighter, more reliable and less expensive components being used thus bringing
down the cost of
each MW of electricity produced infinitely.




19
From
-

‘Products & Solutions’,

http://www.boschrexroth.com/country_units/america/united_states/sub_websites/industries/wind_energy/win
d_components/wind_comp_rotor/wind_comp_rotor_pitch_hyd/index.jsp
, accessed 1
8/04/2011.

20

From ‘Intelligent Yaw Control’,
http://www.automation.siemens.com/mcms/topics/en/wind
-
automation/process/controls/
yaw
-
control/Pages/default.aspx
, accessed 20/04/2011.


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3.6

Wind
SCADA


3.6.1

In order to effectively mon
itor and manage wind turbine O&M SCADA IT systems are used to analyse
numerous data streams. The data is then presented
on user
-
friendly interface that allows engineers and
technicians to plan then perform
required maintenance / servicing in a timely manor.


3.6.2

The flow of a wind SCADA system is shown in the block diagram below that illustrates perfectly how
vital a connection the system is in delivering information from the turbines themselves
to the eng
ineer’s
performing required tasks.



Figure 14



Enercon Wind SCADA
21

3.6.3

Further explanation of the information a wind SCADA system delivers is given in the excellent
expl
anation from Siemens Wind Power:


Status Views

A detailed view of a specific
turbine will typically present the following data:




21

From ‘ Enercon Wind’,
http://www.astroman.com.pl/index.php?mod=magazine&a=read&id=900
, accessed
20/04/2011.

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Wind turbine data:

Wind speed, active and reactive power, yaw angle, etc. and command,
operational and fault status



Electrical and mechanical data:

3 phases and current voltage, power factor, frequency, r
otational
speeds (generator and rotor RPM), temperatures of gear oil, generator, nacelle, etc.



Statistical data:

Total and subtotal turbine statistics such as availability, external errors hours,
calendar hours, etc.



Meteorological data:

Wind speed and d
irection, air pressure, temperature, mean wind speed and
any other project
-
specific data



Grid data:

3 phases and current voltage, active and reactive power and any project
-
specific data

Reports

The WebWPS SCADA system provides both standardized and custo
mized reports. All of them can be easily
exported to Excel allowing quick analysis of these reports within customer organization. Some of the
"standards" include:



Browsing and filtering (date, station, alarm codes, etc.) and historical data



Daily, weekly
and monthly reports on turbine performance, meterological and grid data ‘
22


3.6.5

Figure 15

below is an example of a basic SCADA interface and demonstrates the vital information the
SCADA system displays in a simple format.
It should be noted that the
system can be set up to display desired
information at any time making SCADA an essential ingredient for the entire wind park management team from
the technicians to managers. SCADA data is also being collated by the major manufacturers to asses turbine
mo
del performance in an effort to reduce costs and improve overall reliability.




22

From ‘ Mon
itoring
-

the WebWPS SCADA System’,
http://www.energy.siemens.com/mx/en/power
-
generation/renewables/wind
-
power/wind
-
turbines/
#content=Technology
, accessed 20/04/2011.

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Figure 15



Sample SCADA interface information
23

3.6.4

SCADA maintenance involves the service and replacement of control and IT equipment that is very
rarely fails but when it d
oes redundancy is built in as the SCADA system controls the operation and shut down
of the entire turbine system. Loss of system control through faults occurring is not
desirable

at any stage and
technicians must be fully versed into how to maintain and understand the used SCADA system to be effective
in their roles on site.











23

From ‘Wind Turbine Control’,
http://www.deifwindpower.com/SCADA
-
1.aspx
, accessed 20/04/2011.

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4.0

The Full Service


Having looked at costs, components and maintenance relative to wind turbine O&
M it is sensible to take
account of the standard full servicing and inspection requirements of industrial wind turbines.




Figure 16


12A Inspection List for Wind Turbines
24




24

From ‘ Guideline for the Continued Operation of Wind Turbines 2009’,
http://www.gl
-
group.com/en/certification/renewables/CertificationGuidelines.php
, accessed 2
0/04/2011.

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4.1.1

GL Garrad Hassan offer a full inspection service the
details of which are contained in their
‘Guideline for the continued Operation of Wind Turbines’. The inspection list is illumi
nating and is shown
in figure 16

above.


4.1.2

The inspection list shows all aspects of turbine inspection therefore delivering a

list of
maintenance that must be performed. If a component needs inspecting then it also needs maintained.
From the GL list it is noted that there are 75 inspection points which indicates the complexity of the
system alongside the intensity of manual & sy
stem monitoring that is required.



































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5
.0

Onshore v Offshore Comparison


It is interesting to look at the basic differences between off and onshore which immediately indicate the
extra costs associated with offshore O&M.


Issue

Onshore O&M

Offshore O&M

Location

Often remote but accessible via
purpose built tracks. Access
rarely prevented due to extreme
weather.

Out at sea but easily accessed in normal weather
conditions. Bad/extreme weather can curtail
location access for

days/weeks. Rough seas may
also prevent personnel transfer from boat to
access platform on turbine.

Purpose built offshore accommodation blocks
allow easier access.

Equipment

Motor vehicles and a crane the
most common.

Boat / barge access, Helicopter, se
mi sub crane.

Technicians

Skilled with safety at height and
rope access skills.

Skilled with safety at height, rope access, offshore
survival, helicopter escape, competent swimmer.

Components

Mainly gear driven parks.

Moving to complete Direct Drive
parks.

Size

Majority see no more than 20
turbines.

200+ turbine wind parks in plan for round 3
offshore in 2014.





























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6
.0

Recommendations

6.1

Final Conclusions


This report has summarised the main issues involved in helping to develop a successful
wind park O&M
strategy and from the report the following recommendations can be made






Preventative maintenance

is the single most important activity that the O&M team

can
carry out. Preventing the failure of large components such as the gearbox reduces
downtime, reduces costs and extends the useful life of the turbine.



SCADA data

is absolutely vital in learning lessons about the individual wind park. Generic
data is be
coming more and more available but unique data
for the in
div
i
dual wind park must
be collected and analysed regularly to allow verif
ication of the in place O&M strat
egy and
also to allow changes to be made should any trends be identified.



In order to reduc
e the financial risk of a wind farm, special attention should be given to the
operation and maintenance contract

(long term warranties including availability
warranties in terms of losses in the energy production) and the performance warranties
(wind farm
performance in relation to a reference mast). Enhanced flow models should be
used for the energy yield prediction and the calculation of the wind farm power curve which
are validated for the type of terrain.
25



Technician understanding

of the economics of turbine downtime is essential. Tailoring
salary and bonus payments to turbine availability is a sensible stuff to ensure staff are
committed and motivated to keeping the turbines operational.
The O&M team leader must
motivate the team
and lead by example in going the extra mile in the face of operational
challenges.



Technician service reports

must be analysed and reported on. Alongside SCADA date
this will provide an accurate and useful overall picture of maintenance issues on the
individual site. The information should also be passed to the turbine manufacturer so they
can attempt to engineer

out
problems for the future. The industry is here for the long term
so the more reliable O&M becomes the more viable projects become thus increasing
employ
ment prospects across the board
.


6.2

Pareto


6.2.1

Allied to the information delivered in this repo
rt it is also impossible to ignore the work of Raghav
Raghunathan who has produced an excellent report on O&M strategies. The slide below sums up his
Pareto analysis and simply illustrates, in one slide, the goals a quality O&M strategy should be dictated
towards.




25

From ‘P90


How to reduce the financial Risks of a Wind Farm Project,
http://www.dewi.de/dewi/fileadmin/pdf/publications/Publikations/klug_ewec20
04.pdf
, accessed
01/03/2011

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26

From ‘Wind Turbine Reliability: A Database and Analysis Appraoch, Raghav Raghunathan,
http://www.slideshare.net/karthik451/wind
-
turbine
-
reliability
,

accessed 15/03/2011.