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FRP Poles - Ducument

FRP Poles - Ducument

FIRST FRP POLES INSTALLED ON THE HAWAIIAN ISLAND.

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Composite Transmission and Distribution Poles: A New Trend

Posted on October 16, 2013

Posted By: SRIRAM KALAGA Ph.D., PE

Topic: Grid Operations

 

Introduction

The first composite pole used as transmission structure was a fiber-reinforced polymer (FRP) design. Installed on

the Hawaiian island of Maui in the early 1960s, the poles were made of fiberglass and replaced wood and steel

poles, which suffered degradation (wood) and corrosion (steel) problems caused by warm, moist, salty air. These

fiber-reinforced poles lasted about 45 years. Since then, fiberglass, carbon pultruded, and spun poles have gained

worldwide acceptance. Composite materials are rapidly being considered for the fabrication of poles and cross

arms throughout the utility industry in the United States and elsewhere.

This article discusses the advantages and issues related to composite transmission poles and how they highlight a

growing trend in the industry.

 

Material Advantages

At ¾ the density of wood, 1/10 of steel and 1/3 of concrete, the FRP pole offers utilities an attractive choice.

Compared to wood, they are smaller in diameter. A fiberglass pole is lightweight, strong and has low

conductivity properties; it also resists corrosion, rot, UV rays, water absorption, insects, and woodpeckers.

Unlike wood poles, composite poles do not lose strength as they age so maintenance is minimal. Engineers also

like the electrical properties of the FRP poles and their ability to withstand heavy wind loads and impacts.

The table below gives a comparison of various materials (values are typical).

Property Steel Concrete Wood Composite
Density (pcf) 490 150 60 45
Mod. of Elasticity E (ksi) 29,000 5,000 to 6,000 1800 to 1900 20, 000 – 22,000 ***
Expected Service Life (years) 60 * 50 45 ** 70 to 100
Coefficient of Thermal Conductivity (BTU/hr/ ft/ in/ oF) 25 to 40 10 0.8 to 1.2 5

 

 

 

 

 

 

 * galvanized         ** treated     *** depending on manufacturing process

 

Operational Advantages

Composite poles, although not fireproof, are fire resistant. With just one coat of fire retardant, they become

attractive to utilities with service territories containing brushy terrain, forests, or combinations of both.

Composite poles’ strength ratings can be customized to match a utility’s specification. Utilities can achieve a

single- or double-pole configuration and/or tapered or non-tapered form. This saves the utility money by not

having to purchase more pole than is needed for the job. For a given set of material properties, Composite poles

can also be modeled on popular software, such as PLS-POLE and CADD.

Another practical advantage is woodpecker abatement; woodpeckers, a protected species, make softball-sized

holes in wood poles as they hunt for insects, hide acorns and make nests. The surface of a composite pole is too

slick for woodpeckers to grab. Utility inspectors also noticed that animals, like squirrels, cannot climb these

poles, which reduces interruptions caused by critter-induced outages. A composite pole does not require

chemical treatments and may only need minimum inspections throughout its life.

Recent advances also facilitate detachable and permanent climbing steps to be used on composite transmission

poles, just as in steel and concrete.

 

Strategic Advantages

The fact that composites poles are hollow has not been missed by innovative thinkers. Being hollow solves

several problems. Utilities now use composite poles for siting wireless, cellular, satellite and radio antennas,

devices, and dishes. Because the pole is hollow and non-metallic, wiring can be located inside the pole.

Additionally, many applications 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 pole, utilities can reduce

instances of copper theft.

The small footprint and lightweight design of composite poles allows for easy installation in areas ranging from

congested backyards to remote wildernesses. Several Gulf Coast utilities are exploring this aspect to develop a

quick-response method for hurricane-damaged distribution circuits using composites.

Composites can be made in a variety of colors so they can be camouflaged to match the terrain they are

traversing — a major advantage for improving customer relations. Utilities have found composites can be

nterspersed with wood poles in a transmission line to limit cascading failures often prevalent in hurricanes and 
ice storms.

 

Modular Poles

Another innovation from composite pole manufacturers is the modular pole system. This allows for a range of

composite pole lengths and strengths to be made from a small number of standard pole sections, much like

sectional steel poles. 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 offers the utility an immediate range of pole

replacement options, which is critical during a system outage where downtime is measured in minutes. Even

though the maximum modular pole size possible now stands at 120 feet, proposals are being evaluated to

ncrease that to 160 ft. and beyond.

 

Usage Trends

The first composite distribution pole was installed in 1993 and the first transmission pole (about 70 feet tall) in

1996. In 2009, a 125-foot fiberglass composite pole was erected. The latest innovation is the fabrication of Iso-

Truss transmission structures using lattice framework technology.

Composite poles have been used in various situations: self-supporting, angle, and dead end designs. These poles

have proven they can accept most industry hardware and provide a compelling case as an alternative to wood,

steel, and concrete. Composites are also now used in substations.

Fiberglass cross arms are fast becoming the choice of utilities adding under-build distribution circuits to existing

high-voltage transmission lines. PUPI tangent and dead end cross arms have been used on several projects in OK

and elsewhere. They have also been successfully modeled in PLS-POLE.         

Great Lakes Power in Ontario, Canada, has installed roughly 300 poles for H-frame construction for its 230 kV

transmission system. BC Hydro also tested various composite pole configurations on its system and installed

about 90 composite poles on lines at various voltages, including composite H-frame structures on a 287 kV

transmission line. BC Hydro is also focused on investigating how composite pole technology can be applied to

engineering and asset management challenges.

In the United States, Ameren has installed hundreds of Duratel composite poles system-wide, replacing wood

poles damaged by a variety of causes. BTES in Tennessee installed 144 FRP poles on two transmission projects;

other utilities, such as TVA, SCE, Allegheny Power, DVP etc., are known to be considering using Strongwell

Corp’s FRP poles on their transmission lines.

 

Cost of Ownership

Despite all these benefits and advantages, utilities have been reluctant to deploy composites. Composite poles

typically cost more upfront — nearly twice the cost of wood poles — for distribution application; however, the

price difference diminishes significantly with larger transmission-sized poles. Because many utilities and their

purchasing departments are focused on low price and not total life cycle cost, composite poles are not deployed

as much as they could be.

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 only

light-duty equipment is required. Maintenance costs are negligible or low for composite poles.

 

Research

Recent years has seen rising academic interest in composite poles. Theoretical and computational mechanics

approaches are being developed in conjunction with the FE method to analyze composite power poles.

 

Market Potential

The United States market for distribution poles is approximately $9 billion. It is estimated 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 annual United States manufacturing capacity for composites is about 20,000 poles.

This is a huge potential as composites gain utility acceptance. The applications seem limitless as more composite

poles — both transmission and distribution — are installed on our ever-expanding power grid.

 

References

1.    FRP Composite Poles are the Future of Transmission Lines, Transmission and Distribution World, June 2003.

2.    Composites Take the Field, Transmission and Distribution World, October 2011.

3.    Use of Composites Increases in the Utility and Telecommunications Markets, Utility Products, website, June 2011.

4.    Duratel, Chicago, Illinois, USA

5.    Strongwell Corp., Bristol, Virginia, USA

6.    Shakespeare Composite Structures, Newberry, South Carolina, USA

7.    Resin Systems (RI), Inc., Novi, MI.

8.    Powertrusion Products, Alum Bank, Pennsylvania.

9.    PUPI (Pultruded Utility Products International), Stewartville, MN.

10.  Lindsey Manufacturing Company, Azusa, CA.

11.  I.G. Raftoyiannis and D.J. Polyzois, “Dynamic Analysis of Tapered Composite Poles with Flexible

Connections using the Finite Element Method”, 5th International Congress of Computational Mechanics,

Limassol, Cyprus, 2005.

 

Authored By:

SRIRAM KALAGA Ph.D., PE

Sriram Kalaga, Ph.D., PE, SECB is a Senior Civil-Structural Engineer based at Ulteig Engineers, St. Paul, Minnesota. He specializes in 

the design of electrical transmission and distribution structures, foundations and lines. He is a licensed engineer in several states and has

published extensively on various topics in Structural Engineering such as Finite Elements, Stability of Beam-Columns, Non-linear 

Analysis, Low-Cost Composites and Reliability-based Design of transmission structures.

See complete profile

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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