UNESCO Desire – Net Project Wind Farm Performances Monitoring and O&M Issues Marco Parletta

UNESCO Desire – Net Project Wind Farm Performances Monitoring and O&M Issues Marco Parletta ENEL – GEM - AdB ER marco.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 get an idea of how to calculate them and which tools are necessary • To mention which are the components of a WTG, the main problems they could suffer and the technique to investigate them • To give a hint of the O&M organization and the relevant costs

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 • Missed Production • Power Curve • Plant Losses • Capacity Factor • Average Wind Speed • 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

External Availability WTG’s Availability Total Availability Availability - Calculation TTOT TAEXT = TTOT – TUE TUEI TUEE TAWTG = TAEXT - TUWTG TUWTG • 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 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

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 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 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: • 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 • 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 them • 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 Parameters Once 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 KIV=15,6% KICE=43,8% KIAP=11,9 • 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 KIAP=3,6% KICE=0% KIV= -10,8% -

Manual Data Entry Work Magt. Spare Parts Mngt. Accounting Performance Analysis 4 3 2 Remote Diagnostic 1 Remote Control 0 The Tools The importance of the data appears clear but what tools can support their processing and managent ? Level 4. HW and SW devices used to support work and spare parts management and to monitor accounting aspects Level 3. HW and SW devices doing calculations, aggregations and representations of production data, availability data, etc., aiming to do performance analysis Level 2. HW and SW devices used to store, to retrieve and to process data aiming to do remote diagnostic 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 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

Hub Nacelle Blade Tower Foundation 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

Let’s go in the Nacelle 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 V52 - 850 kW

Main Component - Blades The 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: • The bearings, because of lack of lubrication or wrong grease or material defect or ageing • 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 Components • Many 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 Develop Electric 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

Your Eyes Your Ears Your Nose 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:

WTGs Substations Civil Works Maintenance Needs 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 Costs It 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 • 10 - 12 €/MWh • 20 - 25 €/kW/Year • 1,5% - 2%/Year of the original turbine investment • In case of O&M done on one’s own • 6 -15 €/MWh • 12 - 30 €/kW/Year • 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

UNESCO Desire – Net Project Wind Farm Performances Monitoring and O&M Issues Marco Parletta