New Lightning-Dissipation System Keeps Power Plant On Line in the Worst Storms
During peak hurricane season on the East Coast (August 15 through September 30), Auburndale Power Partners, based in Auburndale, FL, can count on one lightning storm per day. Despite a good overall power availability rating, the cogen power plant usually sustained from four to six lightning-related outages per year, each lasting from 12 to 24 hours.
Glenn Weigle, plant engineer at Auburndale Power Partners was concerned about protecting the 150-megawatt power plant from lightning-strike damage. Past damage has included the loss of sensitive controller cards, costing $1,000 each, which has required the plant to shut down. Restarting the plant required using electricity and resynchronizing the steam and combustion turbine-generators to the power grid. The restart required paying overtime and equipment inspection, repair, and replacement cost of $1,000 to $10,000 per outage.
In addition to these costs, thousands of homes and businesses depended on the electricity the Auburndale plant produced and sold to Florida Power Corp. Even minor power outages could compel Florida Power to find replacement electricity, either by buying at open market prices or requiring that other plants produce more electricity.
The Auburndale plant was also under contract to supply 70,000 pounds of steam per hour, 24 hours a day, 365 days a year to some large manufacturers in the area. When Auburndale operations shut down during an outage, these manufacturers also had to stop operations, exposing Auburndale to liability and penalties for being off-line.
Altogether, a single strike could cost the plant up to $25,000. As a result, unscheduled outages became one of Weigle's chief concerns. "The lightning strikes were hurting our availability, productivity, and the bottom line," he says. "When the boiler tripped, the turbines did too, and we were forced to shut down, since all the major equipment is connected in logical series. We had to minimize the unscheduled trips taking us off-line, and that meant minimizing lightning strikes."
After three recent unscheduled lightning outages in less than two months, Auburndale's plant manager asked Weigle to look into upgrading the plant's lightning-rod protection system. The original lightning-rod system providers were out of business, so Weigle hired an electrical consulting firm to reassess the plant.
The firm's three-week study found that the grounding system was routed through the structural steel of the building and the grounding grid was ineffective. Plant personnel had suspected that many strikes were hitting the plant's 160-ft-high steel exhaust stack, and that connecting conduits were transferring energy to places not designed for it, such as the boiler controls. The consulting firm recommended a new preventative lightning strike technology, offered by Lightning Eliminators & Consultants (LEC), Boulder, CO. LEC is the manufacturer of Dissipation Array Systems (DAS).
"The dissipation array concept was so new to us it seemed like magic," says Weigle. "For reassurance, I contacted eight companies from LEC's reference list. They agreed that DAS was money well spent."
Convinced of DAS' effectiveness, Weigle arranged a three-phase project with LEC, designed to protect the most critical plant structures first. He sent LEC engineers drawings of the problematic steel exhaust stack at Auburndale, so LEC could custom engineer a DAS especially for the stack system. Once in place on the stack, the Dissipation Array System's primary function was to collect or "leak off" ions of the same charge as the lightning's electrostatic field and repel the storm away from the plant. This process is called "point discharge."
Since the ionization process creates current flow from the point(s) to the surrounding air, DAS removes the storm-induced charge on the protected site, transferring it to air molecules, which leave the site. DAS prevents strikes by continually lowering the voltage difference between the ground and charged cloud to well below lightning potential, even in the worst storms.
"Where lighting rods are meant to get hit by lighting, the DAS system on our stack is guaranteed to prevent lightning strikes," says Weigle. "In fact, if lightning hits the stack within a year of installation, LEC will upgrade it for free."
In addition to the stack's DAS system, LEC placed six Spline Ball Ionizers (SBIs) on the plant's 90-ft.-high steel boiler. These are hybrid devices that prevent lightning strikes with point discharge ionization as well as collect and redirect any lightning strikes that may get through. LEC also replaced about 50 existing lightning rods with Spline Ball Terminals, which screw into existing lightning-rod sockets. Finally, following LEC's recommendation, Weigle had the plant's grounding upgraded from existing structural steel, which permitted dangerous electrical surges during lightning strikes, to separate copper wires that ran the length of each building into the grounding grid below the facility.
"After implementing phase one with DAS technology, we had just a single outage in the year 2000, during the worst storm of the year," says Weigle. "In reducing the strikes from up to six down to one, we saved about $100,0000. Phase One has already paid for itself, so anything we save this year is pure gold."
Lightning Eliminators & Consultants, Inc., 6687
Arapahoe Road, Boulder, Colorado 80303; call