AMES, Iowa - There are approximately 185 million power transmission poles in North America, and more than two million need to be replaced each year.
An Iowa State University professor and a former ISU graduate student have designed what they believe is a better pole that will cost less to install, help prevent power failures after storms, and allow for repair, rather than costly replacement.
Jon "Matt" Rouse, senior lecturer in civil, construction and environmental engineering at ISU, and Casey Faber, currently a project engineer with WHKS & Co. of Ames, developed their design to make transmission poles less susceptible to cascading collapse after a tornado, ice storm, hurricane, earthquake or act of terrorism.
The transmission of power from power plants to substations depends on very large, heavy, tall and expensive poles, Rouse said.
"These poles are typically metal tubular structures or lattice frameworks," Rouse said. "A single pole depending on its size and installation costs can cost up to $150,000."
And every five to 10 miles of a transmission line, there are heavier and more expensive "dead-end" structures to contain any cascading collapse of the transmission poles.
"We wanted to either lessen the possibility of a cascading collapse or eliminate it all together," Rouse said. "The pole that we have designed will bend, but not break, and it will absorb the forces after it is exposed to an extreme overload."
The design involves a hinge, or pivot pin, at the base of the pole and a metal plate on each side that act as fuses. When the pole is under horizontal stress, it will pivot sideways and buckle the plate, but not break and start a chain reaction that takes down other transmission poles.
To repair the pole, utility workers would need to bring the pole upright and replace the buckled plate. Initial installation of the transmission pole also would cost less because it could be raised in place with the same method, as opposed to using large cranes to stack sections of concrete or steel poles.
"We also believe the cost of manufacturing the pole will be less because it will not require as much steel and it will be less expensive to fabricate and transport," Rouse said. "We're building a lot of excess strength in (existing) poles that is not sufficient to prevent a cascading collapse should a catastrophic load be applied."
The new design has been tested with a scale model at ISU, but Rouse said full-scale testing is needed to assure the design performs as expected to meet rigid industry specifications.
"We would need to set up a facility with four full-scale poles and a strong power reaction frame to generate sufficient pulling force," Rouse said. "That's what we really need to demonstrate the design and put fears to rest."
Costs are high
The new design by Rouse, Casey and the ISU engineering team comes as utilities in the United States are projected to spend $2 trillion over the next 40 years on electrical infrastructure and new transmission lines to support green energy generation from solar and wind.
Doug Collins, president of ITC Midwest in Cedar Rapids, said the electric power transmission industry is slow to adapt to new technology.
"Because we're putting assets in the ground for 50 or 60 years, change does not come fast away from what we do that has worked," Collins said. "Certainly, we encourage moving forward with designs that will do things such as improve reliability, reduce outage times when we do have problems, and reduce overall costs."
ITC Midwest, which operates more than 6,800 circuit miles of transmission lines in Iowa, Minnesota, Illinois and Missouri, is a member of the ISU Electric Power Research Center, which financially supports electric utility industry research by professors and graduate students at the university.
Collins said the ISU power transmission pole design initially would be useful to carry up to 161,000 volts of electricity.
"In our industry, you typically start at one level and, as the technology matures, you move it up," he said. "Our customers appreciate that approach because when we build them a line, they don't want to see it come down catastrophically."
Summit Technology Group in Cedar Rapids has signed an agreement with the Iowa State University Research Foundation to commercialize the new power transmission pole design.