Why the technologies, developed half a century ago, have suddenly
Wood poles – the workhorse of the electric utility – have a predicted 30-year life expectancy. Nevertheless, even in the advanced United States, many poles have been in service upward of 80 years. Replacement typically comes only after a pole is damaged, but it’s easy to understand. An electric company might have tens of thousands of poles in its jurisdiction, and replacing every component on a regular cycle would take significant time and money.
Although many states carry out periodic inspections of their utility infrastructure, sometimes you can find poles still in service that were set in the 1940s!
The windstorms of 2011 in Southern California knocked over transmission lines and ultimately started a fire in one county and major power outages in others. Then, in 2012, Hurricane Sandy left more than 8 million electric customers along the East Coast without power.
The severity of these incidents forced to take a closer look at the electric grid and start to search how these failures could have been prevented.
Some companies were obviously put in an impossible position, such as for instance Appalachian Power Co. (APCO) from West Virginia, which lost approximately 1,000 wood utility poles in December 2009. «Many of these poles were located in very rough terrain. Getting heavy equipment to some of these locations was almost impossible”, says Tim Brammer, senior electrical engineer for the company.
The lifting capacity of helicopters is limited, so the weight of wood poles prevented the company from delivering the poles of required length and thickness.
To solve the problem, АРСО risked replacing several dozen damaged poles with composite structures of necessary size. The company is currently conducting a cost comparison study and doesn’t preclude using more composite poles in the future.
Crossarms – those horizontal supports actually holding the power lines – are the component seeing the biggest shift from wood to composites, although wood still dominates the crossarm market.
But one of the main reasons why composite utility poles have not yet completely replaced wood structures – is their cost. However, there are areas where obvious composite advantages outweigh the necessity to pay for these benefits in advance. For example, woodpeckers kept attacking several pole structures in a valley crossing. Patching and bird deterrents did not help to get rid of the birds’ “attention”. Only the replacement of wood to composite helped to protect the poles from woodpeckers’ damage.
The coastal areas appreciated corrosion resistance of composite materials. Prior to composites being better known, the choices were concrete or steel, but in a coastal environment eventually you’re faced with a deterioration of both materials caused by moisture, sea salt and sun. The composites provide solutions that are extremely reliable and long-lasting, and these competitive products virtually sell themselves using “world of mouth”.
And so rather than waiting for the electric suppliers to arrive at the conclusion that composite components can help solve reliability challenges, manufacturers are also actively working on standards for their products. In just over a year, ASTM International committee D20.18 on Reinforced Thermosetting Plastics drafted and published ASTM D8019, Standard Test Methods for Determining the Full Section Flexural Modulus and Bending Strength of Fiber Reinforced Polymer Crossarms Assembled with Center Mount Brackets.
A standard does two things: firstly it legitimatizes the materials and eliminates various kinds of speculations. Secondly, it gives an opportunity for manufacturers and customers to speak the same language. The person manufacturing the product knows how to check its compliance with the standard, and the person using the product knows exactly how it’s being tested. The standard is now available through ACMA at acmaeducationhub.org.