Electric utilities are in the business of providing cost effective, reliable electric power to customers and with that comes the responsibility of keeping the lights on. Reliable power is a requirement in today’s world. According to the U.S Energy Information Administration (EIA), on average, U.S. electricity customers experienced just over eight hours of electric power interruptions in 2020, the most since EIA began collecting electricity reliability data in 2013. The average U.S. electricity customer experienced nearly twenty more minutes of power interruptions in 2020 than in 2017, the year with second-longest duration of interruptions in EIA records.
The true cost of power outages is difficult to determine. A major weather event can easily cost utilities millions of dollars to restore power. According to a report from the PEW Charitable Trusts, the U.S. Department of Energy estimates power outages are costing American businesses around $150 billion per year, and while the rise in the number and intensity of weather events is a major contributing factor to power outages, there is no doubt that aging, antiquated power infrastructure also contributes to the increased number of outages. The weather cannot be controlled, but aging, antiquated power infrastructure can be addressed.
An aging infrastructure in need
It is easy to underestimate the seriousness of the aging electric transmission infrastructure in the United States. Over a quarter of the grid is 50 years old or older and the average age is 40 years old. It is estimated that over the next three decades, nearly a 140,000 miles of transmission line will need to be replaced. To simply upgrade this infrastructure and maintain the status quo would require an investment of more than 700 billion dollars, as calculated by Oliver Wyman Energy.
A resilient solution: ductile iron
Ductile iron poles offer the physical strength of steel with the corrosion resistance of cast iron, creating a versatile pole that has benefits of both.
Ductile iron poles have a service life of 75+ years and, similar to steel and concrete, are completely resistant to rot, insects, and woodpeckers. Bare ductile iron will not slowly rust away and will last longer than weathering steel. Ductile iron, or any other metal product, is most exposed for material degradation at the ground line or below grade. For maximum embed protection, the ductile iron poles are coated with a ceramic epoxy coating called Permasafe, patented in 1979 for corrosive environments with an excellent record of performance. Ductile iron poles are exceptional for storm hardening and extreme weather events as they are designed to withstand 142% of class load before ultimate failure. The conductors will come down before the pole fails. A 50’ class 1 pole was tested to 173% of class 1 load (5.1 kips) with 103-inch deflection prior to failure.
Ductile iron poles are approximately 45% lighter than wood, much lighter than concrete, and approximately 25% heavier than steel for an equivalent size and class of pole. The heaviest ductile iron pole is a 110’ H-3, weighing 9,806 pounds. Installation can be performed using standard distribution or Transmission equipment, depending on the size of the pole.
Ductile iron poles are considered “green” as they are made of 96% recycled cars, appliances, and other metals. They are 100% recyclable and made in the USA. Poles up to 70’ are shipped as a single poles and poles over 70’ are shipped in sections depending on the length. Field installation is easy and jacking kits are provided. Ductile iron poles can be pre-drilled up to 20 through-hole penetrations, included in the price of the pole and, if more holes are required, they can be pre-drilled to specifications for a nominal charge. If field drilling is required, they are much easier to drill than steel and concrete using a carbide-tipped hole saw bit or a step type bit.
The properties of ductile iron poles are a yield strength of 42,000 psi, ultimate strength of 62,000 psi, modulus of elasticity of 24,000 ksi, and a minimum elongation of 10%. Conductivity testing was performed by American Electric Power Company Inc. (AEP)on a 45’ ductile iron pole and resulted in approximately 2,000 micro-ohms impedance – equivalent to the resistance of a 4/0 copper ground. The pole is self-grounded; therefore, no copper ground wire is required.
Case study: Central Virginia Electric Cooperative
Central Virginia Electric Cooperative (CVEC) is a member-owned, not-for-profit electric utility headquartered in Colleen, Virginia, nestled next to the Blue Ridge mountains. CVEC serves approximately 38,800 active residential, agricultural, commercial and industrial member accounts in the rural portions of 14 Virginia counties. CVEC’s infrastructure is similar to many other cooperatives and other electric utilities, with some facilities approaching 50+ years of age.
The CVEC-owned transmission system consists of 46 kV, 115 kV, and 138 kV. By 2025, CVEC will own a very small portion of 230 kV. Most CVEC owned transmission structures are single wood pole or wood H-frame construction. CVEC has some steel and composite transmission structures with more steel than composite structures.
At the time of bid opening, the ductile iron pole bid cost 37% less than the second lowest bid and almost 67% less than the highest bid. In addition, the ductile iron poles had a lead time of 6-8 weeks after drawing approval, which was almost one-half the next best lead time at 14 weeks. Based on the bid results, CVEC chose to use ductile iron poles for the construction.
CVEC undertook three projects: a 48-year old 46 kV transmission line that was replaced in 2022, a 39-year old 115 kV transmission line that was replaced in 2022 as well, and a 59-year-old 138 kV transmission line that is currently being replaced this year.
Summary
CVEC is implementing changes and technologies into the design of transmission and other projects to improve reliability, operations efficiency, and resilience to last a lifetime and beyond. Some of the changes and technologies are as follows:
- Utilizing ductile iron poles for transmission lines.
- Implementing and utilizing fiber connectivity.
- Implementing fiber connected SCADA controlled devices, such as, fault indicators, MOABS, reclosers, and other devices.
- Moving forward to implement FLISR on the transmission system and subsequently on distribution.
- Implementing Corona rings on transmission lines 115 kV and above.
- Utilizing drone technology for inspections and rights-of-way management.
- Implementing use of satellite imagery to assist in right-of-way management.
- Utilizing polymer insulators where possible.
- Procuring more than sufficient rights-of-way.
Within the next five years, CVEC is currently planning to complete three additional transmission line projects, totaling approximately 20 miles and implementing the changes and technologies listed above, Through access to power and connectivity, communities can have a higher quality of life. CVEC believes this fundamental connection in our ever-changing world will transform lives.
