Composite material is rapidly gaining acceptance for the fabrication of poles and crossarms throughout the utility industry. This technology is considered cutting-edge, avant-garde and ultramodern by much of the industry, but the fact is, it has been on the grid for 50 years. As with other technologies on the intelligent grid, the materials science took a while to catch up with the theories and ideas of the people working in the industry. But again, it has been on the grid for half a century.
The first composite poles were a fiber-reinforced polymer design. Installed on the Hawaiian island of Maui in the early 1960s, the poles were fiberglass and designed as a solution to wood-pole degradation and steel-pole corrosion problems. The problems were caused by the warm, moist, salt-air environment. These fiber-reinforced polymers lasted about 45 years before being replaced. Equally important is the fact they were replaced for “fiber blooming” problems, not for structural reasons.
Blooming is caused by ultraviolet rays, which can cause the resin surface to break down, exposing the fibers. Remember, these were first-generation poles. They did not contain any of the modern ultraviolet inhibitors or veils so common today, but even so, they performed very well.
Advancing Materials Science
Composites are made from thermosetting resins and some form of fiber reinforcement. The resin is combined with fiber and cured into a solid laminate. Resins come from six major family groups: polyester, vinyl ester, acrylic, epoxy, phenolic and urethane. Several fibers are available for reinforcement, with the most common being Kevlar, carbon and glass. Of these, glass is the most common because of its low cost and high strength.
One of the biggest material breakthroughs was the development of specialized polyurethane resins. This material makes a composite pole extremely strong and environmentally inert, and no styrenes are used during the manufacturing process. Not using toxic chemicals is a big plus at a time when environmental issues are attracting a lot of attention from regulators and the public in general.
There are two methods for fabricating composite poles commercially in use: pultrusion and filament winding. The pultrusion process pulls fiber through the wet resins and then through a heated die. After curing, it is then cut to standard lengths. The pultrusion process is used by manufacturers such as Strongwell, Powertrusion International Inc. and Duratel, offering a wide selection of poles.
The filament winding process pulls the fiber through the wet resins also, but then wraps the wet resin-rich fiber around a mandrel where it sets up. Fabricators have developed systems to allow the mandrel to wind the fiber circumferentially, axially or some combination of both. The filament process is used by manufacturers such as Utility Composite Solutions International Inc., RS Technologies Inc. and Shakespeare Composite Structures to make their poles.
A white paper from Utility Composite Solutions estimates the U.S. market for distribution poles is approximately US$9 billion. The report estimates that about 3.6 million distribution poles (mostly wood) have to be replaced each year. In addition, about 2.4 million new poles are added annually. The present U.S. manufacturing capacity for composites is about 20,000 poles annually. This is a huge potential as composites gain utility acceptance.
Composites have a lot going for them. They are extremely lightweight (about two-thirds the weight of steel, one-third the weight of wood and one-eighth the weight of concrete). They also are smaller in diameter compared to wood. In addition, composites do not lose strength over their lifetime. In other words, they have great resilience.
“The small footprint and lightweight design of Duratel composites allow easy installation in areas ranging from remote wilderness to congested backyards,” said Ted Fotos, senior vice president of manufacturing and sales for Duratel. “This can be very important for storm restoration.”
Several Gulf Coast utilities are exploring this aspect to develop a quick-response method for hurricane-damaged distribution circuits using composites.
Another feature gaining attention is that composite poles, although not fireproof, are fire-resistant. Add a coating of fire retardant, and they become very attractive to utilities with service territories containing brushy terrain, forests or combinations of both. Tests have been made using the California Department of Forestry and Fire Protection's fast-moving brush-fire test.
In this test, composite poles are subjected to a propane flame for a specific time and temperature. They only ignite when the flame is directly applied. As soon as the flame is removed, they stop burning or smoldering; they are self-extinguishing. Composite poles have passed the test both in the lab and the field. The industry can expect to see this feature becoming more important in light of the 2011 fire season.
Composites' strength ratings also can be customized to match a utility's specification. If the utility wants a single- or double-pole configuration, that is not a problem. It can be either tapered or non-tapered. This saves the utility money by not having to purchase more pole than is needed for the job.
Another innovation from composite pole manufacturers is the modular pole system. This allows for a wide range of composite pole lengths and strengths to be made from a small number of standard pole sections, much like sectional steel poles.
Also, like sectional steel poles, the modules are joined by being winched together with come-alongs or chain hoists until the joints are tight. This gives a utility a tremendous benefit. They can purchase and stock various pole modules rather than specific pole lengths and classes. Because of the design, smaller-diameter modules can be nested, or stored, inside larger ones, which require less storage space in the warehousing area.
“Composite modular poles are gaining a great deal of interest both domestically and internationally,” said Galen Fecht, director of business development for RS Technologies. “RS has supplied a Norwegian utility with RS modular poles for the first phase of a transmission line — 170 poles. The Norwegians are also very interested in the fact that composite poles do not leach hazardous chemicals into the ground the way treated wood poles do.”
Thinking Outside the Box
The fact that composites poles are hollow has not been missed by innovative thinkers. It solves several problems plaguing utilities. For example, Southern California Edison (SCE) reports that, on a line where wood poles were damaged, they had broken off 5 ft to 8 ft (1.5 m to 2.4 m) above grade and had to be replaced. SCE inspected the stubs and determined they were fine. The stubs were cut to a specific length. Hollow composite poles were installed over the stubs. Through bolts were used to secure the pole to the stub, and a closed-cell foam was injected to fill the void between the pole and the stub. SCE reports that significant savings were realized with this restoration process.
Duratel's Fotos said, “Utilities are using Duratel composite poles for siting wireless, cellular, satellite and radio antennas, devices and dishes. Since the pole is hollow and non-metallic, these devices and all their wiring can be located inside the pole. This puts the installation out of site to the public. These poles have been engineered to operate seamlessly with wireless and cell signals. Utility poles can now become revenue-generating conduits that provide universal, affordable and attractive access to the Internet.”
There also are many applications that require utilities to run a copper ground wire up a pole. In today's troubled economy, copper theft is a growing problem. By installing the copper wire inside the composite, utilities have seen a reduction in copper theft. It is a case of out of sight, out of mind.
“Modular poles are more versatile than single-length, single-strength poles,” said RS Technologies' Fecht. “In the event of an emergency, the utility can mix and match the modules in inventory to create a pole of virtually any length and strength required. This is a big plus and gives the utility an immediate range of pole-replacement options, which is critical during a system outage where downtime is measured in minutes.”
Total Cost of Ownership
Despite all these benefits and extras, utilities are reluctant to deploy composites. Composite poles typically cost more upfront — up to twice the cost of wood poles — for distribution application; however, the price delta diminishes significantly with larger transmission-sized poles. Since many utility purchasing departments are focused on low price and not total life-cycle cost, this is one reason why composite poles are not deployed.
If a cost-benefit analysis is performed, a more complete picture of the total cost of asset ownership becomes apparent. Composites have a longer life span. Installation costs are lower because installation is quicker, and usually only light-duty equipment is required.
Maintenance costs are another evaluated cost, and they are lower for composite poles. There are arguably no maintenance costs for composite poles. These factors all contribute to an overall lower total cost of ownership, but all that is lost when the only purchasing criteria is lowest price.
To appreciate the real evaluated costs versus low first cost, compare the life span with the purchase price. Based on accelerated life testing, the service life of a composite pole is approximately 70 years, which is about twice the life of a wood pole, assuming that factors such as insect infestation, woodpeckers and wood rot do not end the wood pole's service life prematurely.
The utility would have to buy at least two wood poles to reach the equivalent life span of a composite pole, but that is only part of the cost. The utility would have to pay removal costs for the first wood pole and installation costs for the second wood pole. There is also the issue of periodic inspection and chemical treatments of the wood pole. The composite pole does not require chemical treatments and may only need minimum inspections over its life. And that is only one factor in the typical evaluated cost analysis.
Utilities and Composite Poles
There has been a lot of composite pole activity in Canada for transmission rated lines. Great Lakes Power has installed roughly 300 RStandard poles for H-frame construction for its 230-kV transmission system.
BC Hydro has a research and development (R&D) project testing composite pole configurations on its system. It has installed about 90 RStandard composite poles on lines at various voltages. BC Hydro is sharing part of its R&D effort through a video the company recently posted online (www.youtube.com/watch?v=Wnc4HpDsyqY). The video shows the installation of a composite H-frame structure based on its 287-kV transmission line requirements.
Janos Toth, BC Hydro R&D project manager, said, “BC Hydro is committed to investigating how composite poles' technology can be applied to engineering and asset management challenges.”
In the United States, Ameren has installed hundreds of Duratel composite poles systemwide, replacing wood poles damaged by a variety of causes. One area attracting attention is woodpecker abatement, as woodpeckers are protected species. Woodpeckers make softball-sized holes in Ameren's wood poles as they hunt for insects, hide acorns and make nests.
It turns out the surface of the Duratel pole is too slick for woodpeckers to hold on to, so they cannot land and start pecking a hole. Ameren inspectors also noticed climbing animals, such as squirrels, cannot climb these poles, which really improves the utility's system average interruption duration index figures for critter-induced outages. SCE has included a variety of composites in its Circuit of the Future program, and it appears these poles have lowered the utility's total owning costs for distribution poles on these circuits.
It is so exciting. The industry started out with composites reducing costs by being lighter and resistant to many of the problems of wood. Then they were found to be fire-resistant and woodpecker-proof, but who would have thought about squirrels not being able to climb them? Composites can be made in a variety of colors so they can be camouflaged to match the terrain they are traversing — a big plus for improving customer relations. Utilities have found composites can be interspersed with wood poles, in a line, to limit cascading failures so prevalent in hurricanes and ice storms. The applications seem limitless as more composite poles are installed on the grid.