Lee Ayers, system engineer for the Mid-Carolina Electric Cooperative, a distribution utility in Lexington, S.C., used to live in dread of the region’s frequent electrical storms. When the phone rang during these tempests, chances were it was a report of damage from another lightning strike on one of the co-op’s substations. Worse yet, if the phone didn’t ring, it could mean that a communications tower was hit, severing its radio and microwave links.
“We were experiencing tremendous losses due to lightning, specifically transformers in five substations. If a single substation was hit, we could lose as many as 4,000 to 5,000 customers in the initial outage,” said Ayers, whose facility serves about 42,000 customers in the Columbia, S.C., area. “In most cases, we could quickly restore power to a good number of customers, but others would be out for many hours if we took major damage and lost a substation transformer. If a communications tower was damaged, we wouldn’t necessarily lose power to any customers, but we wouldn’t have the radios and data communications to support restoration, maintenance and all the other necessary efforts to get people back on line.”
A technician installs the dissipation array system, which is designed to eliminate direct lightning strikes.Click here to enlarge image
Ayers is not alone. Hundreds of electrical facilities are damaged worldwide each year by lightning strikes and related phenomenon, causing untold customer losses and inconvenience from related power outages-not to mention the equipment costs to the facilities themselves.
Even if the facility isn’t directly struck by lightning, secondary effects such as bound charge and electromagnetic pulses can fry sensitive circuitry in the vicinity. The resulting failures range from catastrophic system-wide destruction to merely inconvenient lockups requiring replacement, repair, reprogramming or rebooting.
Compounding its problems, the South Carolina area where Ayers’ facility is located has very high electrical storm activity. The facilities were “protected” by old-fashioned lightning rods at the time, which were barely adequate at best and particularly inefficient in this case due to the area’s highly silicate soils.
“We get a lot of lightning storms in this area,” Ayers said. “In terms of total lightning strikes per year, we’re right behind central Florida. We’re also in a geological zone where it’s extremely difficult to ground our equipment adequately due to sandy soil, which makes the earth less conductive than usual. We think that was a big factor in the number of hits we were getting. The lightning rods we had installed were not protecting our equipment. We experienced both direct hits and collateral lightning damage. Most electrical insulators are silicon composites, and sand is just the same thing.”
These factors added up to major losses for Mid-Carolina-so serious, in fact, that their insurance carrier was demanding preventive actions.
“Total replacement costs for damaged equipment was over $1 million during a five-year period. The transformers cost about a quarter million each,” Ayers said. “Our insurance carrier was constantly raising our rates and pushing us to do something to cut its losses. If our prior track record of lightning damage had held, we might not be insured anymore, and we would definitely be paying much higher premiums. We were at the point where we had to do something.”
Fortunately, Ayers found his solution at an IEEE conference he attended, in the form of the Dissipation Array System (DAS) manufactured by Lightning Eliminators & Consultants Inc. DAS is based on a natural phenomenon known to scientists for centuries as the “point discharge” principle. A sharp point in a strong electrostatic field will leak off electrons by ionizing the adjacent air molecules, providing the point’s potential is raised 10,000 volts above that of its surroundings.
DAS employs the point discharge principle by providing thousands of points that simultaneously produce ions over a large area, thus preventing the formation of a streamer, the precursor to a lightning strike. This ionization process creates a flow of current from the point(s) into the surrounding air. The charge induced on the site by the storm is removed from the protected area and transferred to the air molecules, which then move away from the site. Thus DAS prevents strikes by continually lowering the voltage differential between the ground and the charged cloud to well below the lightning potential, even in the midst of a worst-case storm.
Because it prevents rather than redirects lightning, DAS is possibly the best long-term solution to lightning strike problems. DAS is currently providing complete lightning protection to an extensive list of customers and facility types, including many Fortune 500 firms such as Federal Express, PPG Chemical, Union Camp, Exxon, Mobil Oil and Texaco.
“LEC’s (Lightning Eliminators and Consultants’) talk on dissipation arrays at the conference got our immediate interest,” Ayers recalls.
Mid-Carolina decided to test the technology. Once they were ready, LEC began an extensive survey of its facilities. Ayers said that their professionalism and openness influenced his decision to go with the Boulder, Colo.-based company.
“We chose LEC because of their engineered approach to the problems and solutions at hand. Other vendors that we investigated said, ‘Here’s some widgets. Buy a few, put them up, they’ll help. If you didn’t buy enough, come back and we’ll sell you some more.’ But LEC came in, did an evaluation study and made recommendations, designed a specific group of products for the specific application, and installed them,” he said.
“They were very open and up-front about explaining the theory and the reasons why their product works,” added Ayers. “Other companies seemed to be much less forthcoming with technical data and theoretical explanations that satisfied our requirements. But LEC sat down and showed us the math and physics behind its system so that we understood what they were doing. It made the product much more credible.”
That’s not surprising, as LEC has long been at the forefront of DAS development. In the three decades since LEC introduced DAS into the U.S. marketplace, it has been the only lightning protection system proven to prevent lightning strikes to any protected facility. The system has accumulated over 20,000 system-years of history with 99.7 percent reliability.
After the survey, dissipation arrays were installed on Mid-Carolina’s substations and communications towers, and Ayers reported that the system has dramatically reduced the amount of lightning damage and equipment replacement costs.
“In the five years prior to deploying the LEC equipment, we had probably lost $1.25 to $1.5 million in damaged equipment,” he said. “Over a comparable five-year period afterward, our losses to collateral lightning damage on the protected facilities probably amount to no more than $50,000.”
Ayers also likes the fact that LEC backs up its claims with a guarantee of protection: If its system falls short of total protection, LEC will return and fix it at no charge.
“They don’t just sell a product; they sell a design service as well,” Ayers said. “It’s a very thorough approach, and they stand behind what they design. Their engineered design warranty offers to pay any extra expenses if their design falls short. But for the most part that hasn’t been necessary. In all the time since the system has been in place, we’ve only had one site, a communications tower, that had to be redesigned. We know of no direct hits to the tower since then,” he noted.
Impressed with these results, Mid-Carolina has made the DAS standard on all its new installations, and Ayers has recommended the system to other utilities facing electrical storm damage.
“As we build new substations and communications towers, we budget them in. We don’t wait to have a lightning strike to decide a new site needs protecting; we just protect it from the beginning. Given our loss experience prior to deployment, I have to say that the LEC is doing a great job.”