The Dreadful Impact of Inefficient Transmission Lines – A Texas Example

The amount of energy lost as electricity travels over powerlines from a generation asset to a distribution substation is greater than most people realize. While the power grid in the United States is more efficient than it is in many other countries (despite our ‘not great’ D+ rating by the American Society of Civil Engineers), the unrealized impact of the U.S. grid’s inefficiency should no longer be overlooked.

In Texas, for example, extreme weather events and fettered generation assets have wreaked havoc on the cost and availability of electricity for residential, commercial, and industrial consumers. While the average consumer cost of electricity is 12 cents per kWh ($120.00 per MWh), prices have soared on a number of days to over $1,000.00 per MWh. While many positive changes are underway to curtail these rare events, more can and should be done.

Here is an example based on a similar project that American Electric Power completed in the Lower Rio Grande Valley in 2016:

Consider a 100 mile long 345 kV transmission line operating at a 50% load factor that is rated for 3,000 amps, we are going to compare the use of ACCC® Conductor – which uses a composite core, versus ACSS conductor that uses a steel core. The ACSS conductor was introduced around 1975 and the ACCC® Conductor was introduced around 2005. Both conductors are approximately one inch in diameter and weigh approximately one pound per lineal foot. However, because the composite core is about 70% lighter than the steel core, the ACCC® Conductor contains about 28% more aluminum – the conductive stuff.

While the ACCC® Conductor is much stronger than the ACSS conductor (41,200 lbf vs 25,900 lbf) and much more resistant to corrosion and fatigue and can be used to upgrade existing lines using existing structures - improved efficiency is the primary purpose of this comparison.

Using a double bundled configuration (two wires per phase) to accommodate the 3,000 amp and 345 kV voltage requirements and, considering an ambient temperature of 25° Celsius (96° Fahrenheit) and other environmental assumptions, the ACCC® Conductor would exhibit a steady state temperature of 141° Celsius vs ACSS at 173° C. Keep in mind that the load factor of 50%, these conductors would rarely if ever reach these temperatures. Nevertheless, the ACCC® Conductor’s cooler operating temperature at peak load strongly reflects improved efficiency.

Let’s look at the numbers:

The ACCC® Conductor offers a reduction of line losses of 28%, saving 195,079 MWh per year. At a cost of $120.00 per MWh, that equates to a savings of $23.4 million dollars per year – every year. If you think about the cost of the conductor for a minute, this 100 mile line would require 600 miles of conductor – as it is a standard three phase AC line that uses a double bundle configuration. If the ACCC® Conductor was twice the cost of ACSS – which it’s not – the price delta would be about $9.5 million dollars. Considering that the use of ACCC® Conductor saved $23.4 million during its first year of operation, the payback time for the added cost would be less than six months.

Looking closer, the ACCC® Conductor’s reduction in line losses compared to ACSS conductor would also free-up 22.27 MW of generation capacity wasted to support line losses. Freeing up generation capacity, rather than building it, saves big money and time and can help Utilities and Consumers get through severe weather events.

From another viewpoint, using the U.S. national average CO₂ emissions for all combined sources of electricity, the ACCC® Conductor’s reduction in line losses would also reduce CO₂ emission by 121,405 metric tons every year. That is the emission equivalent of removing 26,221 cars from the road. Can you imagine how much money it would take to buy 26,000 electric cars – that would most likely still require some amount of non-renewable energy supply?

The bottom line is that there is tremendous room for improving the efficiency, capacity, reliability, and resilience of the U.S. grid by simply replacing existing steel core conductors with modern composite core ACCC® Conductors. This is a technology that has already been proven on more than 1,000 transmission line projects in 62 countries, including AEP’s EEI award winning 345 kV live-line ACCC Reconductoring project in the Lower Rio Grande Valley in Texas.

A special thanks to CTC Global’s Application Engineers Soraya Ostowari and Hemed Khodadadfar for running their comparison analysis that you can view at this LINK.