All machinery that contains moving parts requires attention on a regular schedule. A wind generator's hours of operation can be compared to the miles of an automobile. In order to keep your turbine healthy and assure safety and energy efficiency, a once per year minimum for inspection and maintenance is a good rule to follow. Even better: twice a year, especially if you have frequent and turbulent winds. An up-close check from the bottom to the top is recommended.

The types of things to check on a modern wind turbine are the result of forces of the wind and the spinning of the turbine which causes vibration and can loosen or damage hardware, turnbuckles and other tower or turbine components. Prepare all of your equipment such as climbing gear, tools, and supplies you might need for the job. Have a checklist prepared and bring a digital camera to document problems you may find. Read the equipment manuals - you might be surprised at what they may tell you!

The four areas to focus on include the on the ground electronics, batteries, the tower and foundation, and the wind generator itself.

The Ground Electronics

1. Examine all conduit, wire runs, junction boxes and conduit fittings for water intrusion, condensation, chew marks from animals, cracks, frost-heaving.
2. Check for tightness and signs or arcing or degradation on all wire terminals on junction boxes, inverter, controller.
3. Use a continuity tester on a multimeter to check for any deterioration on fuses and circuit breakers, and to check all surge arrestors.
4. By checking the wire runs for ground faults as a result of skinned or cracked wire insulation, you can prevent shock hazard and a decrease in system performance. Use a megohmmeter for checking the underground wiring in the conduit.
5. If three-phase output is applicable, check for balance when the turbine is operating. Allow for varying wind speeds - consider it a problem if you see variations of 10 per cent or more between phases. Run the test at least three times to allow for wind speed variations.
6. Follow all other turbine-specific testing as directed by the turbine manufacturer's recommendations.
7. Test the disconnect in a grid-tied inverter to make sure the grid goes out by turning off the inverter breaker. Verify that the voltage goes to zero. Verify the five minute delay before reconnection to the grid. For battery-connected controllers, make sure that the charge set point is appropriately programmed for the batteries and verify that the controller can perform the function of diverting the power when the high battery voltage setting is reached.
8. Check the diversion loads if present, for integrity and operation. Make sure there is no sign of overheating, and keep flammable material away from the diversion loads.
9. Clean cooling fans and vent to make sure they are free of dust and other obstructions

The Batteries

1. Check battery connections for corrosion and grease or coat connections with an anticorrosive. Make sure battery connections are tight.
2. Clean the top of each battery with a damp rag.
3. Check the electrolyte level and top off as needed with distilled water.
4. Check battery and charge controller settings.

Tower Inspection

1. All tower maintenance begins with tower safety. For owners of tilt-up towers, managing the tower safety involves inspection of the foundation, bolts and hinge mechanism on the tower before tilt-down. Otherwise, a manlift can be utilized, keeping in mind that proper tie-off in a manlift is necessary. For large lattice or monopole towers equipped with ladders or climbing pegs, it is best to hire a company to climb your tower, unless you have had specialized training in tower climbing safety and rescue.
2. Inspect the foundation of your tower for excessive anchor movement, which could indicate a failed foundation. Make sure the anchor rods or other attaching points are sound, especially where connected to the concrete or the ground.
3. Look at the overall appearance of the tower, making sure that is appears straight and plump, which can indicate a dangerous situation if you attempt to climb or tilt it. Make sure there is not significant rust affecting the integrity of the tower. Check for bent or missing tower parts. Rust streaking around galvanized welds at the joints could be an indication of a cracked weld. Make sure the safety-climb system is sound.
4. Guyed towers depend upon their cables for structural safety before climbing. All hardware such as the turnbuckles, equalizer plates and cable clamps should be tight without excessive movement. Inspect for loose or missing lock nuts, Palnuts or turnbuckle safety loops - all three can bring down a tower. Guy wires should be free of rust and broken or frayed strands, especially the area where the cable passes around the thimble at the guy ends. Make sure the guy tension is good and adjust as needed, following the tower manufacturer's procedure manual.
5. A tower must be properly grounded before it is climbed for any reason. Review the tower manufacturer's manual for grounding procedure. Commonly the problems found are loose or missing ground-rod clamps.
6. Test the tower mounted turbine disconnect and shorting brake. With little or no wind, check the furling or brake mechanism for proper operation. Be sure that the brake to the turbine is on or otherwise secure it before climbing the tower.
7. Assemble an array of bolts, nuts, and other small parts before ascending the tower. Carry a climber's tool bag. As you climb, look for missing or loose bolts nuts and lock nuts. Torque several sample spots on the tower, and comply with the manufacturer's recommended torque specs and hardware sizes. A wire brush can be used to clean rusted tower parts and the spots can be sprayed with cold-galvanizing spray.
8. Check all cable and conduit integrity by inspecting their clamps and wire ties. All tower-mounted data such as for the anemometer and wind vane hardware should be secure and operational.

The Wind Generator

1. Modern wind generators can have bearing problems. A telltale signs of bearing failure would be rust streaking, caused by moisture entering and exiting the bearing leaving a rust colored residue behind. A fine black powder seen around the bearing or grease and oil where it shouldn't be is a sure sign that sealed bearings are no longer sealed.
2. Vibration and movement from loose hardware may have worn away protective coatings, allowing oxidation.
3. Turbine mounting should meet proper torque, and should be void of cracking and other signs of stress on welds. Verify that the blade is mounted securely, and inspect the blades for loose or missing hardware. Blades should be free of cracks, pits, erosion, leading edge wear, or damaged/missing leading edge tape. Spin the rotor and listen for unusual noise or resistance, which can be caused by grit on magnets rubbing on the stator. Check for bearing slop by lifting upward on the rotor.
4. Inspect all bearing and pivot points, which typically include rotor and yaw bearings, furling bearings or pivot, furling or brake assembly and friction areas.
5. With Jacobs and Kestrel turbines, make sure the governor assembly is intact. On the endurance S-250, check brake pads for wear. Check the flexible hoses in the air brake system and the color of the brake fluid. Moisture absorbed changes the color and indicates when replacement is needed.
6. Inspect the slip-ring and brush assembly for pitting or roughness and uneven wear. Look inside the assembly for black dust, metal shavings or excessive grease from bearing failure. Check the wire connections for wear and loose terminals from vibration.
7. Lubricate some sealed bearings with a grease gun attachment, being careful to seal any openings created during the process using handheld tubes of sealant. Grease all fittings and change the gearbox oil on endurance and Jacobs turbines, following the manufacturer's manual instructions.

Information for the educational material above was obtained from an article in "Homepower Magazine", Issue 135, pp. 98-103 by Ian Woofenden and Roy Butler.