Lightning Detection Protects Wind Farm Crews and Maintains Productivity
Lightning can strike at any time, and wind farms-with their tall towers and turbines-are particularly at risk for lightning strikes when severe weather moves through an area.
By Don Leick
Lightning can strike at any time, and wind farms-with their tall towers and turbines-are particularly at risk for lightning strikes when severe weather moves through an area. Crew safety is a priority for wind farm operators, as is efficiency, while dealing with severe weather threats. Stopping outdoor operations every time severe weather is forecast is neither realistic nor productive; but, waiting to act until someone sees lightning or hears thunder is dangerous because lightning can strike up to 10 miles from the main storm cell.
This prompts the question: How can wind turbine maintenance crews strike the right balance between keeping crews safe and maintaining productivity?
Monitor Lightning Accurately
The first step is to implement a reliable and accurate lightning monitoring system. Common lightning detection methods are inaccurate and risky. The flash-to-bang method, for example, which attempts to measure how far away lightning is by counting the time between the lightning flash and the sound of thunder, is inaccurate and dangerous. When multiple flashes occur during a short time span or when it is difficult to hear distant thunder because of wind or machinery noise, this method cannot provide an accurate measurement of distance. It's also dangerous because it requires the storm cell to be close before any calculation can be performed-and, as mentioned earlier, lightning can strike up to 10 miles from a storm. In addition, those responsible for making safety decisions might not be outdoors, and, therefore, might not see lightning or hear thunder to make those decisions.
For wind farms, it is critical to receive lightning strike warnings far enough in advance-considering it can take technicians 10 to 20 minutes to climb down a tower. The best monitoring option is a real-time lightning detection service that automatically provides alerts when lightning strikes are detected within a pre-determined distance from the facility. Such lightning warning services leverage the latest technology in the lightning detection networks that have been established throughout the U.S., such as the Vaisala North American Lightning Detection Network (NALDN).
Telvent's MxVision WeatherSentry Online, a Web-based weather monitoring service, offers real-time, accurate lightning detection and alert systems. When strikes occur within a pre-determined radius of a prescribed location, crews in the field receive immediate alerts through email or text message. Through Telvent's system, wind farm operators usually set up three automatic alerts to help warn workers and prepare them to take action:
• Caution-indicates lightning within 50 miles of a site. No new technicians should go up any towers and any current "up tower" work should begin to close down.
• Warning-indicates lighting within 30 miles and calls for evacuation to the safety of an enclosed vehicle.
• All Clear-indicates no lighting within 50 miles for 15 minutes and it is now safe to resume work.
In addition, services such as Telvent's MxVision WeatherSentry Online allow users to customize their alert ranges and provide real-time map displays of current lightning strikes in their areas.
The bottom line is that wind farm operators need the best possible information to make the most informed safety decisions in a timely manner, and that means having access to real-time, reliable lightning tracking.
Have a Plan
The next step in balancing crew safety and maintaining productivity is to develop a lightning safety plan with the following components:
1. Determine which operations put personnel at risk for lightning-related injuries.
2. Determine where they can take shelter if lightning threatens (buildings, enclosed vehicles).
3. Determine the amount of time it takes to get from the at-risk operations to the associated shelters.
Determining the time needed for personnel to reach safety helps wind farm operators understand how large of a geographic radius needs to be monitored and how much advance warning should be incorporated into the lightning monitoring technology.
Communicate the lightning safety plan. Let all affected employees know what the safety protocol is and how to follow the protocol so there is no misinterpretation or debate when lives are at stake.
Know When to Let Workers Go Back to Work
As important as it is to know when to evacuate workers, it's equally important to know when it's safe to allow them to resume their outdoor work. If sent outside too soon, they are as much at risk as if they had never been evacuated; but, unnecessarily keeping workers inside lowers productivity and cuts into the bottom line.
Because of new technology, there are better options than first-hand observation. Weather monitoring services that provide real-time lightning detection also can provide an all-clear notification when it is safe to resume outdoor activities. An all clear is issued when no lightning has occurred within the alerting range within a specified time period-usually 15 to 30 minutes.
Lightning is a significant safety issue, and it must be taken seriously. Effective safety requires a clear protocol for employees to follow when a lightning threat is detected. Make it known in advance that this plan will be adhered to if lightning occurs so there is no debate when prompt action needs to be taken.
Equally important to lightning safety is the implementation of threat detection tools. Personal powers of observation are no match for technology. A lightning detection system that provides reliable, real-time warnings and avoids false alarms is crucial to ensuring employee safety and maintaining operational efficiencies.
About the author: Don Leick is a senior product manager at Telvent and is responsible for all aspects of WeatherSentry and other weather products. Leick has more than 25 years experience in software and technology companies, with the last 15 years in product management.