Operations and maintenance of wind turbines

19-Nov-12

Professor: By:Peter Lund Ishtiaq MuhammadAdvanced wind power technology Msc Mech Student

Asst Professor:Juuso Lindgren

Three parts:

1- Operation of wind turbine

2- Maintenance of wind turbine

3. Condition monitoring

Topics discussed Today

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1. Operations of wind turbine

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Inside of wind turbine

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NacelleHeart of wind turbineTop of TowerConsists the gear box, low-

and high-speed shafts, generator, controller, and brake.

gears increase the rotational speed of the blades to the generator speed of over 1,500 RPM

Generato produced electricity frequency must be 60 CPS for feeding into grid

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Gear Boxlow-speed shaft to

the high-speed shaft30-60 rpm to 1000-

1800 rpma costly (and heavy)

part of the wind turbine

Drives generetor to produce electricity at max rotational speed

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BladesUpto 3 to 4 blades in a

wind turbine, mostly 3Converts wind energy to

mechanical energyblades spin at a slow

rate of about 20 RPM, although the speed at the blade tip can be over 150 miles per hour.

Length upto 40-50 mMaterial: fiberglass ,

Aluminum

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Towermade from tubular

steel, concrete, or steel lattice

about 150 to 200 feet tall and 10 feet in diameter

ladder running up the inside for maintenance and services

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Working principle of wind turbine

Wind Mechanical energy Electricity

A video clip (3,5 minutes) for better show up :)

http://www.youtube.com/watch?v=LNXTm7aHvWc&feature=related

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2. Maintenance of wind Turbine

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Purpose of Maintenance?» Minimizing operational and maintenance costs

» Improving turbine performance/yield

» Lowering insurance risk

» Protecting assets

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Maintenance as two parts

• Mechanical repair

• Electrical repair

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Mechanical repair• Generator and gearbox housings• Wind generator and gearbox repair• Bearing change outs and upgrades• Slip ring change outs, upgrades & turning• Grounding system upgrades• Rotor lead change outs• Housing and component rebuilds• Brush holder upgrades• Wind turbine and blade cleaning – via rope access• Wind turbine main shafts• Heat exchangers• Blade inspection–via rope access

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Wind turbine main shaft repair and Wind generator bearing change out

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Heat exchangersBlade inspection–via rope accessWind generators up to 3+ MWElectric motorsCooling fansHydraulic pumpsMain breakersElectronie boards

Electrical repair:

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Complete rewind of wind turbine generators

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Offshore VS onshore maintenance• Offshore maintenance is much and more difficult than onshore maintenance• Offshore is much and more costly than onshore maintenance because of the usage of heavy ships, helicopters and cranes etc.• Weather conditions matter too both in offshore and onshore

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Typpical gear box problems1- Highly variable load and speed: 

Wind is an intermittent energy source. It alternates between gusting and still. Therefore, the load that these gearboxes are trying to transmit is a lot more variable than it is in a plant operation (causes accident)

2- Low gearbox safety factors: The drive system in wind turbines is designed to be compact. "They try to make things as small as they can, so that means the safety factors are lower than usual.

3- Flexible foundation: Typically, a plant gearbox and motor are mounted on a large concrete foundation or a steel structure that’s bolted to a concrete foundation. The nacelle is flexing and the rotor itself is causing lots of loads in the whole structure. This causes misalignment between the generator and the gearbox."

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4- Extreme operating environment: 

The turbines have to operate in extremely cold or extremely hot settings. Although the gearbox is in a nacelle and protected from rain it can still be subjected to extreme temperatures.

5- High operating temperature: 

Manufacturers are resistant to adding large radiators to wind turbines. They allow these gearboxes to run pretty hot, and that means the oil viscosity gets low. When they’re rotating slowly, you don’t get a thick oil film between bearings and gears, so you get metal-to-metal contact — and that’s a problem.

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3. Condition monitoring

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What is Condition monitoring?Condition monitoring is a strategy where by physical parameters (such as vibration,temperature, lubrication particles and others) are measured regularly to determine equipment condition.

This procedure makes it possible to detect machine and component problems before they can result in unexpected downtime and the high costs associated with maintenance and interrupted production.

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Today's monitoring systems can handle any number of turbines and multiple data points. Using vibration sensors mounted on a turbine's main shaft bearings, gearbox and generator, systems (in tandem with software) will continuously monitor and track a wide range of operating conditions for analysis. Wireless capabilities allow operators to review data from any location with a computer or hand-held device with Internet access

How condition monitoring works?

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Online condition monitoring system

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Condition monitoring system in nacelle

An integrated on-line condition monitoring system within a typically difficult-to-reach wind turbine nacelle (like the one shown in Fig on next page) offers a powerful tool for managing day-to-day maintenance routines and consolidating risky, costly maintenance activities.

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Online condition monitoring system within nacelle

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Why condition monitoring is done?Condition monitoring is done to detect:

• Unbalanced turbine blades • Misalignment • Shaft deflections • Mechanical looseness • Foundation weakness • Bearing condition • Gear damage • Generator rotor/stator problems • Resonance problems • Tower vibrations • Blade vibrations • Electrical problems • Inadequate lubrication

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Condition monitoring techniquesThe following techniques, available from different applications, which are possibly applicable for wind turbines, have been identified:

1. Vibration analysis 2. Oil analysis3. Thermography4. Physical condition of materials5. Strain measurement6. Acoustic measurements7. Electrical effects8. Process parameters9. Visual inspection10. Performance monitoring19-Nov-12

Some common condition monitoring techniques

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. Vibration Analysis

Vibration analysis is the most known technology applied for condition monitoring, especially for rotating equipment. The type of sensors used depends more or less on the frequency range, relevant for the monitoring:- Position transducers for the low frequency range- Velocity sensors in the middle frequency area- Accelerometers in the high frequency range

Examples can be found for safeguarding of:1. Shafts2. Bearings3. Gearboxes4. Compressors5. Motors

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. Oil analysis

Oil analysis may have two purposes:

- Safeguarding the oil quality (contamination by parts, moist)- Safeguarding the components involved (characterization of parts)

Oil analysis is mostly executed off line, by taking samples. However for safeguarding the oil Quality, application of on-line sensors is increasing.

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. Thermography

Thermograhy is often applied for monitoring and failure identification of electronic and electric components. Hot spots, due to degeneration of components or bad contact can be identified in a simple and fast manner. Thermals cameras are used for thermography purpose

. Strain measurementStrain measurement by strain gauges is a common technique, however not often applied for condition monitoring. Strain gauges are not robust on a long term. Especially for wind turbines, strain measurement can be very useful for life time prediction and safeguarding of the stress level, especially for the blades.

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This is what happens when maintenance is not done in

time (Last topic)A short video clip (1 min)

http://www.youtube.com/watch?v=ppLh5pGX3qQ&feature=related

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So the Maintenance and Condition Monitoring of

Wind Turbine is as Important as Life

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That’s it

Thanks for listening :)

Any Question?

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Following list of references was used for this presentation.

http://www1.eere.energy.gov/wind/wind_how.htmlhttp://www.ecw.orghttp://ecmweb.com/http://www.maintenanceworld.comftp://ecn.nl/pub/www/library/report/2003/c03047.pdfhttp://sine.ni.com/cms/images/casestudies/cartifb.png?sizehttp://www.ips.us/industries/wind-power/

Refrences:

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