UNESCO UNESCO Desire – Net ProjectDesire – Net Project

Wind Farm Performances MonitoringWind Farm Performances Monitoring

andandO&M IssuesO&M Issues

Marco ParlettaMarco ParlettaENEL – GEM - AdB ERENEL – GEM - AdB ER

marco.parletta@enel.itmarco.parletta@enel.it

The Aim of the Lesson

• To understand what parameters are

necessary to keep under control the

performances of a wind farm

• To give a hint of the O&M organization

and the relevant costs

• To mention which are the components of

a WTG, the main problems they could

suffer and the technique to investigate

them

• To get an idea of how to calculate them

and which tools are necessary

Wind Farm Performance Monitoring…a key issue

Every wind farm operator is entitled to know how his plants are performing

… but what is the way ?

If your plants are operated and maintained by a global server and you are not

interested in knowing the details about their performances you could just look at

the energy production and check that it matches with your expectations

Pros

• You don’t need to monitor any other parameter

• You don’t need any particular technical skill

• You can establish incentives for the global server

simply linking them up with over budget production

Cons

• Your plant will be a sort of “black box” of which you

won’t know anything about problems, potential

performances, etc.

• It is difficult to set penalties for under-performances of

the global server owing to lack of proper parameters

Wind Farm Performance Monitoring – Parameters to check

If you want a more clear picture of your plants performances, besides the energy

produced, you have to look at other parameters

• Availability

• Power Curve

• Capacity Factor

• Average Wind Speed

• Missed Production

• Plant Losses

• Statistics of Breakdowns

As all the wind turbines have the same basic components and behaviour an important goal is

to standardize the measure of the performances overcoming the differences due to multiple

turbine types and manufacturers.

Everything can be organized into regular time basis reporting

Availability - Definitions

The IEC 61400 standards define the Availability as the:

“Ratio of the total number of hours during a certain period, excluding the

number of hours that the WTGs could not be operated due to

maintenance or fault situations, to the total number of hours in the period,

expressed as a percentage”

Definitions of availability could be subject to variations and to represent different

things to different people

For example for some WTGs manufacturers the availability is the percentage of

time a turbine is available during the time the wind blows between the cut in and

cut out speeds

These variations can became a point of contractual contention between

manufacturers and customers

Availability - Calculation

TTOT

TUEITAEXT = TTOT – TUE TUEE

TUWTGTAWTG = TAEXT - TUWTG

This is valid for a single WTG, but the calculation

can be extended to sets of WTGs (wind farm) or

sets of wind farms through appropriate averages

Legend:

• TTOT is the observation time

• TUEE (Time of Unavailability External External) is the time during which the WTG cannot to run because of causes external to the WTG and external to the plant (e.g. grid outages, weather conditions, curtailments, etc.)

• TUEI (Time of Unavailability External Internal) is the time during which the WTG cannot to run because of causes external to the WTG but internal to the plant (e.g. substation problems, internal grid problems, etc.)

• TAEXT (Time of Availabilty External) is the time during which the external conditions allow the WTG to run correctly

• TUWTG (Time of Unavailabilty of WTG) is the time during which the WTGs are stopped because of maintenance or faults

• TAWTG (Time of Availabilty of WTG) is the time during which the WTG is ready (available) to produce power

EXT

TOTWTG A

AA

TOT

AEXTEXT T

TA External Availability

AEXT

AWTGWTG T

TA WTG’s Availability

TOT

AWTGTOT T

TA Total Availability

Power Curve – Definition and Measurement

The Power Curve represents, through a table or a

graph, the relation between the wind speed at hub

height and the power produced by the WTG

The proper measure of Power Curve requires a pretty

complex procedure described in the IEC 61400-12. It

requires the installation of an anemometer mast and very

often a site calibration.

This procedure is justified for the acceptance test of

WTGs but normally it is not applied to check the power

curve during the plant operation

If you have several same model WTGs the easiest check is to built up their power curves using wind speed and power

measured by the WTGs and compare them.

This procedure implies error but they are the same for all WTGs and all power curves should appear the same, otherwise

there is some problem that you have to investigate deeper

Capacity Factor and Equivalent Hours

The Capacity Factor is the ratio, expressed as a percentage, of the energy produced during a certain

period of time and the energy that the plant would have produced ideally if it had worked at full power

TOTN

Pf TP

EC

A different way to express the Capacity Factor is through the Equivalent Hours; they are the number of

hours during which the plant should work at full power to produce the same energy it has produced during a

certain period of time that normally is one year

8760 fTOTfN

PEQ CTC

P

EH

Good sites should have a Capacity Factor at least 24%-25% that means Equivalent

Hours over 2000

Average Wind Speed

Once you have installed your wind farm, a good practice is to continue to monitor the wind speed

through a permanent met station.

This allow you to check the actual wind speed vs the expected, and to monitor the correct production of

your plant

Missed Production

Each downtime gives rise to missed production. Until you

don’t evaluate how much energy and revenues you are

losing you have not the right feeling and the spur to reduce

as much as possible the downtimes

You can evaluate the missed production in two ways:

1. Using the wind data from your permanent met station; this is the most correct way but it

is also the more complex and you need the correlation among met station and WTGs

2. Using the energy produced by near WTGs; this method is the easiest and it gives

satisfactory results, but it can be applied only for single turbine downtime in a multiple

turbine site

Plant Losses

The plant losses are basically due to the energy

dissipated in the power cables and transformers

windings, and to the iron losses of the transformers

The simplest way to

monitor these losses is

comparing the produced

energy measured at the

WTGs with that

measured at the delivery

point in the substation.

Typically the plant

losses will be around 3%

Statistics of Breakdowns

A good practice is to monitor the breakdowns and downtimes resulting from

themRatio

Hours Nr. Hours Nr. Hours Nr. Hours Nr. Hours Nr. Hours Nr. Hours Nr.Entire WTG 160 20 160 20 7% 13% 8,0 Rotor/Blades 336 2 336 2 14% 1% 168,0 Gearbox 480 1 50 1 530 2 22% 1% 265,0 Generator 240 1 24 3 240 1 504 5 21% 3% 100,8 Hydraulic Sys. 30 10 30 10 1% 6% 3,0 Yaw System 480 1 480 1 20% 1% 480,0 Pitch System 15 3 6 3 21 6 1% 4% 3,5 Drive Line 0 0 0% 0% - Brake System 14 7 10 10 24 17 1% 11% 1,4 Controller 60 20 15 12 10 3 85 35 4% 23% 2,4 El. System 25 5 30 7 12 2 67 14 3% 9% 4,8 Sensors 30 13 18 9 16 4 64 26 3% 17% 2,5 Tower 20 2 20 2 1% 1% 10,0 Nacelle/Chassis 10 1 10 1 0% 1% 10,0 MV Equipment 48 1 48 1 2% 1% 48,0 Other 10 6 10 4 7 3 27 13 1% 8% 2,1 Total 1432 68 180 22 76 15 97 35 621 15 2406 155Total % 60% 44% 7% 14% 3% 10% 4% 23% 26% 10%Ratio 21,1 8,2 5,1 2,8 41,4

Pa

rt In

vo

lved

Total Total %WeatherFailure Maintenance Wear Grid Outage

Cause of Stop

• The amount of hours gives indication about the responsibility of downtimes and missed production

• The number of events gives indication about the work load of the service teams

• The ratio gives indication about the importance of the specific cause or part involved

Other ParametersOnce you have all the mentioned parameters you can “play” with them as you want or, if

needed, you can define others, i.e.:

• Energy Producible: maximum energy you can milk

from your plant with the actual wind, supposing 100%

of Total Availibility

• Ratio of Unavailability due to Maintenance and

Faults (KIAP): ratio between Missed Production

because of scheduled maintenance plus faults (EIAP)

and Energy Producible. This gives an idea of the

efficiency of the service

Plant "A"

3,803,20

1,42

0,38

1,40

0,60

0,7

1,2

1,7

2,2

2,7

3,2

3,7

ExpectedEnergy

ProducedEnergy

EIAP EICE ProducibleEnergy

EIV

GWh

KIAP=11,9

KICE=43,8%

KIV=15,6%

Plant "B"

1,83

1,95

2,02

0,07

0,19

0,00

1,75

1,85

1,95

2,05

ExpectedEnergy

ProducedEnergy

EIAP EICE ProducibleEnergy

EIV

GWh

KIAP=3,6% KICE=0% KIV= -10,8%

-

• Ratio of Unavailability due to

External Causes (KICE): ratio

between Missed Production

because of causes external to the

plant (EICE) and Energy Producible

• Ratio of Unavailability due to

Wind (KIV): ratio between the

Missed Production, compared to the

expected, because of less wind

(EIV), and the expected production

The ToolsThe importance of the data appears clear but what tools can support their processing and

managent ?

1

Remote Control

Remote Diagnostic

Performance Analysis

Manual Data Entry

Work Magt.Spare Parts

Mngt.Accounting

2

34

0Level 0. Plants level: the tools required are suitable data acquisition network and data transmission equipment. All WTGs and substations must be be connected to the network

Level 1. HW and SW devices collecting all data from the plants; part of the data are used for remote control and part of them are stored

Level 2. HW and SW devices used to store, to retrieve and to process data aiming to do remote diagnostic

Level 3. HW and SW devices doing calculations, aggregations and representations of production data, availability data, etc., aiming to do performance analysis

Level 4. HW and SW devices used to support work and spare parts management and to monitor accounting aspects

The Subject of Discussion

The Wind Turbine Generator

(WTG) is the main subject of a

wind farm and it requires most

of the attention

We have also power cable grid and

substations but they are pretty the

same of those used for othe

applications and power plants

Nacelle

Foundation

Blade

Hub

Tower

1. Service Crane

2. Generator

3. Cooling System

4. Top Controller

5. Gearbox

6. Main Shaft

7. Rotor Lock System

8. Blade

9. Blade Hub

10. Spinner

11. Blade Bearing

12. Machine Frame

13. Hydraulic Unit

14. Gear Torque Arm

15. Yaw Ring

16. Brake

17. Tower

18. Yaw Gear

19. Coupling

Let’s go in the Nacelle

V52 - 850 kW

Main Component - BladesThe components of wind turbines are designed to last about 20 years, but the actual lifetime depends both on the quality of

the materials and local climate conditions, e.g. intensity and turbulence of wind.

For the blades, in particular, an important element causing the shortening of their lifetime are lightings

Protection agaist lightnings normally consists in a lightning receptor at the

tip of the blade and a copper cable running inside the blade and connecting

the receptor with metal parts of the hub

Unfortunately this is not always enough and sometimes the lightings create

damages to the blades, some of them repairable but some of them not.

Main Component - Generator

Lightings, overvoltages,

overloads, defective

insulation, can be the

cause of damage to the

generator windings

Other possible damages could involve:

1. The bearings, because of lack of

lubrication or wrong grease or material

defect or ageing

2. Connectors, because of poor connection

heating cable and insulation

Main Component - Gearbox

Possible damages

can concern the

gear wheels

teeth…

…..or the bearings.

The reason of the faults can be various: lubrication

problems, wrong oil, material defect, dust and water

contamination, fatigue, ageing, etc.

Other ComponentsMany other devices are in the turbine:

• Electric (contactors, breakers, fuses, transformers, etc.)

• Electronic (converters, sensors, controllers, etc.)

• Hydraulic (mechanical brakes and pitch)

• Mechanical (yaw system, drive train, brakes, etc.)

All of them can be affected by various faults

How Damages DevelopElectric damages can be due to overvoltage (e.g. lightings) or evercurrent. In the first case you haven’t

any development but it happens when the cause is there.

In the second case you have sign of heating (change in color of copper and insulation, signs of charring,

etc.) that, if discovered at an early stage, can help to avoid more severe damages.

Mechanical damages normally

have an evolution that, with

appropriate check, can be

detected in an early stage

avoiding catastrophic damages.

An interesting relationship is that

between the time of first noticing

a potential failure and

breakdown

Tools and Techniques to Predict Damages

• Thermography is used to

discover “hot points” mainly

for electric devices, but

sometimes also for

mechanical components

• Vibrational analysis is used to investigate the status of mechanical rotating parts (gear wheels, bearings, bushings, etc.)

Furthermore don’t forget the following other important and always available tools:

Your Eyes Your Ears Your Nose

Maintenance Needs

WTGs Civil WorksSubstations

Scheduled and unscheduled maintenance is required by all the following “parts” of the plants

Some activities are pretty simple and don’t require special skill and tools so that it is thinkable to do them from himself, but

other can be complex so that it is necessary to ask for qualified technicians

This implies that there is not a formula about how to organize their own O&M activities but it results from several factors

The quickness in repairing faults and restarting stopped turbines or entire plants is the way

to maximize output and revenues, so you have to keep in your mind this very clearly when

you set your O&M organization

WTGs O&M CostsIt is not possible to indicate precisely the costs of O&M because of many factors can affect them,

furthermore they can be expressed in different way. An indication is in the following ranges:

In case of O&M with a Global Service contract

1. 10 - 12 €/MWh

2. 20 - 25 €/kW/Year

3. 1,5% - 2%/Year of the original turbine investment

In case of O&M done on one’s own

1. 6 -15 €/MWh

2. 12 - 30 €/kW/Year

3. 1% - 3%/Year ofthe original turbine investment

This is the end for now, I hope the time we have spent together has been useful for you

Goodbye and thanks for your attention