Wind-Electric System Maintenance: Page 2 of 4

Electronics

• For grid-tied inverters, test the ability to disconnect when the grid goes down by turning off the inverter breaker and verifying “0 voltage” at the inverter output. After turning the grid breaker on, verify the 5-minute delay before the inverter reconnects to the grid.
• For battery-charging controllers, confirm that the charging set point programming is appropriate for the batteries. Verify the controller’s ability to perform this function—by checking a voltmeter to make sure power is diverted when the high battery voltage set point is reached.
• When applicable, test the electrical integrity and operation of the turbine diversion loads.
• Make sure there is no flammable material near the diversion loads. Inspect any heat shields for physical damage and signs of overheating.
• Clean dust or other obstructions from any cooling fans and vents. Heat dissipation is essential for proper electronics operation and has a direct effect on the equipment’s life expectancy.

Batteries

Battery maintenance could be the subject of a complete article (see “Flooded Lead-Acid Battery Maintenance” in HP98 for more information). Owners of battery-based systems will need to follow a basic maintenance procedure:

• Check all battery connections for tightness and clean corrosion from them; then grease or coat connections with an anticorrosion coating.
• Clean battery tops with water and a rag.
• Check electrolyte level and fill as needed with distilled water.
• Check settings on battery monitor.
• Check settings on charge controller(s).

On-the-Ground Tower Inspection

Safety First

Before climbing or lowering a tower, fully inspect all components accessible from the ground. Any serious problems must be corrected before climbing the tower.

Most home-scale wind installation companies receive several calls each year from system owners with turbines that have been orphaned by their original installer but still need inspection or repair. Although we apply the following procedures on all inspections, we always take a much harder look at an unknown installation.

Before You Climb

• Foundations: Check for excessive anchor movement. This may be the only indication of a failed or failing foundation system. Look for deterioration of the anchor rods or other attaching points, especially where they contact the concrete or the ground.
• All towers: Examine the overall appearance of the tower. Check that it is straight and plumb. Small discrepancies are OK, but a seriously out-of-plumb tower can be an indication of a more significant problem. At the very least, it could be dangerous to climb or tilt. Also check it for rust, since deep-rooted rust can affect the tower’s structural integrity. Minor surface rust is to be expected. Probe the rusted area with a sturdy screwdriver or similar tool. Look for broken welds or structural components that are bent or missing. Bent or missing tower parts may be easy to spot, but cracked welds are not. Rust streaking around galvanized welded joints may be an indication of a cracked weld. If a safety-climb system such as a Lad-Saf is installed, check the cable and tensioner integrity. Fall-arrest systems should not be used for support at all until the entire fall arrest assembly is checked.
• Guyed towers: Inspect all hardware: turnbuckles, equalizer plates (which equalize the tension on each set of guy wires), cable clamps, etc., for deterioration, excessive movement, and tightness. Look for loose or missing lock nuts, Palnuts, and turnbuckle safety loops—these things can bring down a tower. Check guy wires for rust and broken or frayed strands. Pay close attention to the area where the cable passes around the thimble at the guy ends. This is a high-stress area, subject to vibration, susceptible to corrosion, and perhaps very difficult to see. Minor surface rust or the occasional missing guy cable strand may not present a major issue now, but bears watching. Once corrosion starts, it can accelerate quickly, especially in salt-air environments. Some tower grounding conductors are connected directly to the guy wires. Galvanic reaction from dissimilar metals may be causing corrosion inside the attaching hardware. Remove, inspect, and replace if needed.
  
  Check for proper guy tension and adjust as needed. This varies between tower manufacturers, so follow the proper procedure for your tower. The tangential intercept method (using a bit of geometry and the sag of the cable) is often used for tilt-up towers; the oscillation method (using some math and a controlled shaking of the cable) is routinely used for fixed guyed lattice towers. Wind turbine installation manuals are great sources for this type of information.
• Freestanding towers: Inspect the hardware that secures the tower to the foundation. Look for signs of unusual movement around the hardware and leg flanges, such as misalignment, weathering patterns, or cocked bolts. If grout was used under the tower legs, check the drain-holes for blockage and clean as necessary. Moisture buildup inside hollow tower legs can lead to freeze damage and eventual tower collapse.
• Grounding: Never climb an ungrounded tower—look for proper grounding of the tower and guy wires. There are many different tower grounding methods, but they are beyond the scope of this article (for more information, see “Get Grounded: Renewable Energy System Grounding Basics” in HP118.) Again, review the tower manuals! Inspect the grounding wire and hardware. The most common problems found are loose and missing ground-rod clamps.
• Brake: Inspect and test the tower-mounted turbine disconnect and shorting brake. If applicable, check the furling or brake mechanism for proper operation. (This should not be done in a high wind.) Brake, short, or otherwise secure the turbine before ascending the tower.