By MICK SAGRILLO February 4, 2014
When working around small wind turbines, a frequently-overlooked safety issue is voltage in wires running up the tower as well as at the turbine. Turbine installers and maintenance personnel often have to check continuity of wire runs or circuits at the wind turbine. If the tower must be climbed, three critical aspects demand the utmost attention: gravity, proper use of the safety harness, and the potential for an electrical shock. Even if a shock is not fatal, it can be disorienting enough to cause a fatal fall.
The American Wind Energy Association (AWEA) and OSHA have jointly developed lock-out/tag-out procedures (LOTO) for utility-scale wind projects. While not specifically intended for small wind, they offer some valuable lessons.
LOTO is an OSHA-required procedure for anyone working on live and potentially live electrical circuits, devices or wiring. The person doing the work must shut down the equipment and place a padlock on a disconnect switch or electrical box. The purpose is to deactivate all energy sources downstream of the disconnecting device and ensure that no one else can re-energize the circuit. This assures that wiring or equipment can be installed, serviced or repaired without the threat of an electrical hazard.
AWEA stipulates the following practices and procedures for LOTO:
1. Only authorized workers may lock-out or tag-out machines or equipment in order to perform servicing or maintenance.
2. Lock-out locks and tag-out devices must be used only for controlling energy and may not be used for any other purpose—locking your toolbox, for example.
3. The LOTO procedure requires that only one key for each lock is in circulation, that the key is only accessible by its owner, and that a tag or similar marking clearly shows who has control of the lock.
4. All energy sources to equipment being serviced must be identified and electrically isolated.
5. After the energy is isolated from the machine or equipment, the isolating device(s) must be locked out or tagged out in the off position only by the person working on the equipment.
6. Following the application of the lock-out or tag-out devices to the energy isolating devices, any stored or residual energy (for example, from capacitors) must be safely discharged.
7. Prior to starting work on the equipment, the worker shall verify that the equipment is isolated from the energy source (for example, by operating the on/off switch on the equipment).
8. The lock and tag must remain on the machine until the work is completed.
9. Only the worker who placed the lock and tag may remove his/her lock or tag.
Most small wind installations have a disconnect switch at the base of the tower, a logical place for anyone (worker, homeowner, utility lineman or fire or rescue personnel) who needs to shut the wind turbine down for any reason. Situations exist where, for example, a worker locks-out a turbine at the bottom of the tower, then proceeds up the tower to troubleshoot the wind turbine. Oftentimes, re-energizing the turbine is helpful for troubleshooting. Utility-scale equipment is no different, and a logical question arose from AWEA about requiring a tower-top worker to climb up and down a tower any time they need to lock-out or unlock the wind turbine. This can be a real pain and quite fatiguing for the person climbing to do the work. The logical solution seemed to be to allow a worker at ground level apply a lock at the direction of the tower-top worker.
AWEA developed a protocol whereby a ground worker, under the supervision only of the tower top worker, could lock-out the wind turbine, a seemingly logical solution to this problem. OSHA’s response was an emphatic “no” (see https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=27656 ).
So, how do you resolve a problem that every small wind worker has encountered at some time or other atop a tower? OSHA actually suggests an excellent solution around this dilemma: install an energy isolating device—a disconnect switch—in a safe location at the top of the tower. The best time to do this is at the time of initial installation. And while this disconnect needs to be outdoor rated, and therefore costly, it will pay for itself on the first tower-top service call.
While this may be great for new installations, what about existing turbines? Does “grandfathering” exist here, or could someone get cited by OSHA? Could an electrical inspector deny energization of a turbine because of the lack of a disconnect switch at the turbine itself? Since these questions are as yet unresolved, the prudent practice would be to retrofit any existing wind turbine with a disconnect atop the tower.
A portal to OSHA’s LOTO rules and regulations can be found at:
This article appears in the January/February issue of SOLAR TODAY. Subscribe now!