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A Case for Modern Power Line Conductors

image credit: AEP by permission

As regulators in the U.S. move away from a “risk based” approach to a “consumer benefits” approach when considering ROI’s for transmission investment, the case for deploying modern powerline conductors has never been stronger.

Classic 100 year old steel reinforced (ACSR) conductors are now being replaced worldwide by composite core conductors such as ACCC. Developed initially to carry twice the current of conventional steel reinforced conductors to alleviate congested transmission lines, reduce thermal sag, associated sag-trip outages, fire hazards, and other reliability issues, modern ACCC Conductors offer far more than meets the eye.

Though classified as a High-Temperature, Low-Sag (“HTLS”) conductor, The ACCC Conductor actually operates much cooler than other conductors of the same diameter and weight under equal load conditions.

There is nothing magic about it:

The ACCC Conductor’s carbon and glass fiber core is 70% lighter than its steel counterpart and 50 to 100% stronger. The lighter weight core allows nearly 30% more aluminum to be incorporated without any weight or diameter penalty. The added aluminum content serves to lower the conductor’s electrical resistance which reduces line losses by 25 to 40% or more.

Here’s why it matters:

Reduced line losses serves to reduce fuel consumption and associated emissions. This helps reduce the cost of delivered power for the utility and the consumer. And it can help Utilities meet their Emission Reduction Initiatives when taken into consideration during the design phase.

Check this out:

The magnitude of reduced line losses and associated emission reductions offered by the ACCC Conductor is not insignificant. So remarkable is this attribute that the Asian Development Bank, World Bank and others are actually funding dozens of ACCC transmission projects, worldwide, not only to deliver more power to support economic development, but specifically to help them achieve their carbon emission reduction objectives. On top of this, other entities are providing project grant funds to further support emission reduction benefits. Here in the U.S., Green Bond Financing should play a major role in modernizing and expanding our transmission system using modern conductors such as ACCC for the same reasons. Reduced line losses not only reduces fuel consumption and associated emissions, it also frees up generation capacity that is otherwise wasted. This can help a wind or solar farm deliver more power (and increased ROI) for a given investment or reduce upfront capital costs.

But wait, there’s more:

Did you know that thermal generation and nuclear power plants consume anywhere from 10,000 to 60,000 gallons of clean filtered water for every megawatt hour of electricity generated? Line loss reductions can effectively reduce clean water consumption.

Classic Project Example:

In 2016, American Electric Power won the Edison Award for Transmission Project of the Year. They replaced two 120 mile long 345 kV circuits of ACSR conductor with ACCC Conductor with a goal of nearly doubling line capacity without having to rebuild or replace existing structures (to save time and money). The project was completed while the line remained energized. While the primary goals were achieved and the project completed eight months ahead of schedule, the use of ACCC Conductor also reduced line losses by 30%.

Reduced line losses in this case translates into a 300,000 MWh savings per year (~$15 million @ $50.00 / MWh). It also reduces CO2 emissions by ~200,000 metric tons per year (the equivalent of removing 34,000 cars from the road). This also freed-up 34 MW of generation (assuming base generation operating at 100%). Translated, if the same benefit was desired considering wind generation at a capacity factor of ~40%, the savings would equate to roughly 80 MW (an additional ~$80 million dollar savings).

Though the cost of the conductor was only a small percentage of the overall project cost (which included substation upgrades), the use of ACCC Conductor benefited AEP, their customers and the environment and saving over 3.6 million gallons of clean filtered water every year – the amount of water consumed by over 68,000 people!

As regulators in the U.S. move away from a “risk based” approach to a “consumer benefits” approach when considering ROI’s for transmission investment, the case for deploying modern power line conductors has never been stronger and these are the business cases that our Utilities should argue for.


Bob Meinetz's picture
Bob Meinetz on Sep 13, 2020

Interesting, Dave. Despite the current push toward "distributed generation", hopefully California and other states with immense electricity loads will invest in ACCC cables, and make utility electricity - already the most efficient and equitable way to distribute electricity to everyone - even more so.

Line losses in California are currently estimated at 9% - higher than most states.

  1. What's the estimated service life of a 350kV ACCC cable?
  2. Is there any structural difference between AC vs. HVDC cables, except for their gauge?
Dave Bryant's picture
Dave Bryant on Sep 14, 2020

Bob, Thanks for your feedback. I think DG is also an important part of the mix. The anticipated service life of conductors is generally considered to be around 40 years. However, in some severe environments, it can be much less. We have replaced copper, ACSR and ACSS Conductors ranging from 8 to 80 years old +/-. Because the ACCC Conductor's composite core will not corrode (and is highly immune to cyclic load fatigue), computer modeling and lab testing suggests its service life could be much longer. Regarding your second question, we have ACCC bare overhead conductors operating at voltages from 11 kV (AC) to 1100 kV (DC). AC systems use three phase conductors (often bundled at higher voltages), while DC systems use only two (sometime only one if the ground (or water) is used as the return. I helped write a book about these topics you can find at the following link:

Happy to answer any other questions you might have. Thanks

Dave Bryant's picture

Thank Dave for the Post!

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