• Transmission Infrastructure
  • Transmission Upgrades
  • Overhead Conductor
  • Utility Transformations

Advanced Conductors Are Changing the Economics of New Transmission Line Builds—and Existing Line Upgrades

Richelle Elberg
Oct 03, 2018

Overhead Power Lines 1

For more than a century, utilities have been building their overhead transmission and sub-transmission (33 kV and higher) networks with traditional aluminum conductor steel reinforced (ACSR) conductor. Today, that age-old practice is shifting and investment in newer advanced conductors is accelerating worldwide. 

While advanced conductors still cost more than traditional options, the total cost of ownership—which considers improved efficiency and structural and environmental benefits—is often lower than traditional options. A growing number of utilities now consider advanced conductors to be invaluable tools in their toolbox for transmission line upgrades, rebuilds, and, increasingly, new line builds.

The use of lighter weight advanced conductors allows utilities to reconductor along existing corridors, doubling capacity while making use of existing support infrastructure and rights of way (ROW). Reconductoring projects not only cost roughly half what a new line or a rebuilt line may cost, they can also be executed in a fraction of the time and with fewer regulatory and permitting burdens.

Overhead Conductor Evolution, Categories, and Key Characteristics

In the late 1800s, copper’s value made its use within overhead transmission conductors cost-prohibitive. Aluminum made for a relatively cheap, technically comparable alternative. This led to the invention of the all aluminum conductor (AAC). In the early 20th century a steel core was added for strength and the ACSR conductor was invented. ACSR has been the standard transmission conductor of choice for utilities ever since.

A variety of improved conductor technologies were subsequently introduced, including several in the high temperature low sag category. These not only raise capacity but also maintain higher sagging clearances at elevated temperatures.

More recently, high performance advanced conductors were introduced. These conductors, using strong, lightweight composite cores, not only reduce thermal sag but also increase line efficiency and length between structures, resist cyclic load fatigue, maintain self-dampening characteristics, and more. This class includes ACCR, ACCC, ACFR, LoSag, and C7. The table below summarizes the major categories of traditional, improved, and advanced conductors described here, and lists example vendors. 

Traditional, Improved, and Advanced Overhead Transmission Conductors

Traditional, Improved, and Advanced Overhead Transmission Conductors

(Source: Navigant Research)

It’s Not Just about Price Anymore

Advanced conductors offer varying degrees of capacity increase, sag reduction, and improved efficiency versus ACSR conductor. The global market for advanced transmission conductors is expanding—Navigant Research projects annual investment to quintuple over the next decade—and is driven by several drivers. 

In mature markets, such as North America and Europe, market drivers for advanced conductors include aging infrastructure, a need for higher transmission capacity to support load growth, the need to interconnect new renewable generation sites, and growing difficulties of accessing new or widened ROWs. 

In emerging markets, the operational benefits of advanced conductors increasingly factor in—even for new electrification and new line builds. For example, in Bangladesh, CTC Global’s patented ACCC® conductor has become the de facto standard in an aggressive national electrification upgrade project.
The following table compares traditional, improved, and advanced conductors in terms of capacity (relative to ACSR), their ability to withstand high temperatures, to reduce sag, improved efficiency, and installed base worldwide.

Performance Characteristics of Common Traditional, Improved, and Advanced Overhead Conductors

Performance Characteristics of Common Traditional, Improved, and Advanced Overhead Conductors

* Defined as >25% improvement in line losses.

(Source: Navigant Research)

Advanced Conductors Change the Value Equation for Utilities

The challenges faced by utilities today cannot all be met by traditional steel core conductor in the transmission grid. The market has evolved and several types of advanced conductors are now available with demonstrated benefits to the utilities who deploy them.
The benefits of and market drivers for advanced composite core conductors are described more fully in a new Navigant Research white paper, sponsored by CTC Global