EET&D : According to the US Energy Information Agency there has been a five-fold increase in transmission investment over the last decade or so in North America. What has driven this?

Bryant : Actually a number of things. Following World War II there was surge in generation and transmission investment to serve growing demand. In the late 1960’s the infrastructure adequately supported demand and things stabilized. Transmission investment then declined until the late 1990’s. The Western Energy Crisis of 2000 was a bit of a wake-up call, but it wasn’t until the major east coast outage of 2003 that really captured everyone’s attention.

EET&D : What happened as a result of the outage?

Bryant : It reminded us that our grid was substantially aged and vulnerable. The cascading outage was triggered by a series of events that started with inaccurate telemetry data, a race condition computer bug, a subsequent reboot failure and a lack of effective communication that led to a series of sag-trip outages on a number 345 and 138 kV lines. The economic impact was estimated at $8 to $10 billion which captured the attention of policy makers. The Energy Policy Act of 2005 in the US, for instance, was a significant call to action.

EET&D : In what way?

Bryant : For one, it strengthened the resolve of grid operators and utilities to improve their interaction and communications, but more importantly, it provided incentives (and loan guarantees) to inspire ‘risk-adverse’ utilities to leverage new technologies that could improve the ‘efficiency, capacity and reliability of the grid.’

This included new composite core conductors such as ACCC that were developed to increase grid capacity, reduce congestion costs and mitigate thermal sag that ultimately caused the major blackout of 2003.

EET&D : Can you explain grid congestion?

Bryant : Grid congestion is a situation that occurs when sections of the grid (usually the wires themselves) are not capable of carrying the required current. This generally occurs during warmer months when demand is high. The effect is that grid operators have to reroute power from alternate sources of generation that are typically more expensive. The impact can substantially increase the price of delivered power to the consumer. In recent years these costs have been measured in the billions of dollars annually. Fortunately entities such as the PJM Interconnect (and other RTO’s and ISO’s) and their associated utilities are targeting congested lines and upgrading them to substantially mitigate the problem.

EET&D : You mentioned composite core conductors. Can you elaborate?

Bryant : Composite core conductors were developed primarily to mitigate thermal sag due to the fact that their coefficient of thermal expansion (CTE) is less than that of a conventional steel reinforced conductor. In the early 1900’s most bare overhead conductors were made with copper wire. During World War I, copper was diverted to the war effort and aluminum was subsequently used in its place. Because aluminum is relatively weak, steel core strands were incorporated in many conductor designs to enable greater spans between fewer structures. The composite core conductors take it a step further as they are stronger and lighter than steel. They also resist corrosion and fatigue better than steel, and, due to their lighter weight, they can incorporate more aluminum without a weight penalty. The added aluminum content not only serves to increase line capacity, it also reduces electrical resistance which reduces transmission line losses under any load condition.

EET&D : Transmission line losses in North America are relatively low. Is reducing them further that beneficial?

Bryant : Surprisingly yes. While the cost of line losses are typically passed through to the consumer, what many utilities are now realizing is that a reduction in line losses can essentially ‘free-up’ generation capacity that is otherwise wasted. This energy can then be sold. From another point of view, a reduction in line losses can reduce fuel consumption and associated emissions from non-renewable resources. While line losses in North America are a relatively low three to four percent, you’d be astonished at the impact a thirty percent reduction actually offers. In developing countries like India, technical losses are well over twenty percent and closer to thirty percent when you factor in commercial losses.

EET&D : Are the utilities focusing on line loss reductions in North America?

Bryant : Not typically as a first tier priority, however, a great deal of effort is being make to alleviate grid congestion, improve grid reliability and, in the wake of several super storms, improve grid resiliency, by ‘hardening’ the grid so that damage can be avoided or quickly repaired. While the benefits of these priorities are obvious, at the end of the day, the efficiency of the grid is also improving through these efforts. This is, in part, due to the fact that modern high-capacity low-sag conductors offer decreased electrical resistance. While they are typically installed to increase the capacity of existing transmission and distribution lines, their improved efficiency and ability to carry increased current also serves to reduce load levels on adjacent lines allowing them to operate cooler and more efficiently.

EET&D : Regarding ‘first tier’ priorities, what are some other reasons we are seeing an increase in T&D investment?

Bryant : In addition to activities focused on linking renewables, hardening the grid, and modifying lines found to be out of compliance due to excessive conductor sag, uncertainties associated with deregulation have dissipated and market improvements and regulatory clarifications are helping utilities better understand their potential returns on investment. With that said, securing permits to build new lines is still very challenging and most utilities and regulators have trouble recognizing, measuring and conveying the numerous but less obvious benefits of transmission investment that could ultimately reduce the burden.

EET&D : Can you explain?

Bryant : Generally a number of transmission projects are proposed or drafted to accommodate a variety of needs. While circumstances often change, projects are periodically evaluated and reprioritized. When priorities and economics are sorted, the ‘green light’ is given to projects that offer the greatest cost benefit ratio. Unfortunately, not all benefits are generally considered. For instance, if a new line is proposed to link a new source of generation, the project has obvious value. However, additional benefits might include improving grid reliability, reducing emissions and increasing market competition that could lead to reduced consumer prices, among many other societal benefits. Fortunately organizations such as EPRI, EEI, the Energy Future Coalition, WIRES, The Brattle Group, and several other entities are developing new methods to assess and analyze the true value of transmission investment.

EET&D : This sounds positive, but what are the utilities doing in the meantime?

Bryant : In the past, utilities spent billions of dollars improving the efficiency of generation to reduce operating costs and improve profitability. More recently they have supported improvements in efficiency of demand side appliances in an effort to minimize the need for additional generation investment. Lately, much effort has been directed at ‘Smart Grid’ strategies to carry this further. Today, utilities are also investing in modern conductors to improve grid efficiency, capacity and reliability. The ACCC conductor, for instance, has already been deployed to over 300 projects in 30 countries. This is a good thing for everyone because without access to affordable and reliable power no society can possibly flourish.

EET&D : We can’t thank you enough Dave for spending some of your valuable time with us. Your in-depth explanations with a glimpse at the past and the view going forward regarding this important issue are a valuable lesson for our readers.

About the Author

Dave Bryant, Director Technology, CTC Global was one of the original developers of the ACCC conductor and ancillary hardware components. His background in composite materials, testing and industrial design helped expedite the commercialization of the ACCC conductor.