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Why Don't We Bury More Power Lines?

Scott Sklar, The Stella Group Ltd.
March 24, 2009  |  19 Comments

I was wondering if we changed the way we transmitted electricity from high voltage to high current, wouldn't that make it easier to bury the lines underground thereby mitigating the objection to spoiling the scenery for the new eco-power plants that will be constructed? The Sunrise Powerlink project for San Diego Gas & Electric is having a tough time with this aspect of the project. This is a real shame because I think the Sterling Energy System is the best technology out there. -- Terry B., Paso Robles, California

Terry,  Many people believe correctly that burying power lines solves lots of problems like the icing of powerlines and the avoidance of falling tree limbs on windy days that knock down lines. On the other hand, buried power lines make them more susceptable to damage from floods, earthquakes mudslides and can limit how quickly they can be repaired.

But the real limiting factor is that the cost of ditching and burying lines can be more than US $10 per foot. In fact, the state Public Service Commission staff found that burying Louisiana's utility lines to protect them from hurricane-force winds could cost $70 billion — far too much for the state's 2 million electricity customers to pay. Plans to go underground often hit a brick wall nationally, because burying existing overhead power lines costs about 10-15 times more than stringing them from poles.

Washington State's Puget Sound Energy has about 50 percent of the 20,000 miles of power lines underground — about 20 percent for Seattle City Light, mostly in downtown, the University District and about 40 percent of lines in Snohomish County's Public Utility District are underground. PSE may also use other approaches, such as installing more "tree wire," a cable with a coating that makes it more resilient during a storm.

In Florida and North Carolina, statewide initiatives to bury power lines would have prompted a rate increase of 80 to 125 percent, according to a report by the Edison Electric Institute, the utility industry trade group.

All of that said, the national trend in cities is to bury lines when the city's infrastructure is being upgraded. Now that billions from the just-passed Stimulus package will be going into upgrading infrastructure, you will probbaly see smarter grids that are buried, at least in cities.

Scott Sklar of the Washington, DC-based, The Stella Group, Ltd. which is a strategic marketing and policy firm for clean distributed energy users and companies. Sklar was also appointed in April 2007 to the National Advisory Council for Environmental Policy & Technology (NACEPT) of the United States Environmental Protection Agency (EPA) and is Chair of the Steering Committee of the Sustainable Energy Coalition. He also serves on several clean energy national non-profit Boards of Directors.

19 Comments

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Stuart Karlan
Stuart Karlan
September 11, 2011
What options are available for containing high-voltage power lines in some kind of conduit, perhaps made of reinforced concrete, that would rest on or slightly above the ground? This system might provide easy access for repair and maintenance, ease and perhaps lower cost of construction than line burial, and would not destroy the viewplane.
Lauri Garber
Lauri Garber
June 27, 2009
The issue is not the cost of burying the lines compared to the status quo. The issue is the cost in dollars and lives due to fires. I think the power companies should be held liable for the fires caused by downed power lines. It is not as if the fires of the last few years are the first ones caused by downed power lines. This is a known hazard that the power companies have not corrected.

I realize that there are lawsuits pending in San Diego. Are there any other class action suits against the power companies and what is the status of these suits?

I realize that there are also threats caused by burying the power lines, but maybe these could be worked out. Also consider what is the greatest public health hazard and what should be done about it.
Vanessa Rusczyk
Vanessa Rusczyk
April 5, 2009
Warren,

Where is this 500MWe SES installation east of San Diego? And where is the construction of the 300MWe facility in Imperial County taking place exactly? I think you are confusing proposed projects with actual installations. The CPUC has not even approved these projects. Currently Southern Cal Edison has a contract with SES for a 500MWe system, and with SDG&E for a 300MWe system, but that is all. There is no large scale SES system anywhere.

Also, the SES system might be very efficient (although this data is based on a single dish in the high desert in NM), but you need to factor in the cost of building the transmission line, line loss, and the environmental cost of both projects. There are better ways to get renewable energy without so much destruction to the environment. We are destroying the planet in order to save it.
John Carr
John Carr
March 30, 2009
Warren,
There are two instances steel jackets are used.

1. For distribution voltage of 15kV or less: Steel jacketed conduits are used when cable are placed under highways, canals, or railroads. This is to prevent undermining the overlying structure with weak plastic conduits. In the $750/lf case discussed above, (12) 6" PVC conduits are placed in spacers and slid into the steel jacket. Once in place, the jacket, with the PVC conduits in place, is filled with grout. Grouting provides better heat transfer and strength under crossings. Any type of wire can be placed in the conduits.

2. Underground 250kV or higher transmission cables are place in a schedule 40 steel pipe. Oil is circulated through the pipe to keep the cable cool. Any type of wire can be placed in the conduits.

Burying cable will prevent damage from wind and ice. It will not prevent damage from lightning strikes, water, or solar flare activity.

Lightning regularly penetrates the ground, striking u/g utilities. This is why grounding wires are run along with power cables both above and below the ground.

Water: Properly sheathed cables stand in water for decades without damage. Damage normally occurs when transformers and switchgear get wet. These are placed underground in urban environments regularly. However, doing so increases the risk of flooding a transformer. This usually happens when someone breaks a water main nearby.

Solar activity: The earth's magnetic field PENETRATES the Earth. The cables are in the earth. Need I say more?

I've been designing underground electric utilities for years.
It's better to ask questions and learn.
Jan Konigsberg
Jan Konigsberg
March 29, 2009
I'm wondering (as in pipe-dream) what the feasibility might be of integrating electric transmission with highways/freeways to power vehicles ? Conceptually, trolleys come to mind, but whether it is possible to have vehicles moving freely on the road (shifting lanes) and stay connected to a grid (automatic attaching and detaching boom?)?? Further, if engineering (mechancial and electrical) is indeed feasible, would the economic benefits of using existing right of ways for electric transmission/distribution and (potentially) solving (or minimizing) the battery problem exceed the costs of such a scheme? Just wondering . . .
Scott Evans
Scott Evans
March 29, 2009
As implied by John Carr, the UG cables also tend to be co-located so any heating and failure problems are multiplied up. Maintenance and then fault finding are also much more difficult than OH.

For now construction, High Voltage DC seems to be the next generation of technology.
Warren Reynolds
Warren Reynolds
March 29, 2009
John:

Let us see: $1.5 billion in homes destroyed divided by the $750/foot cost for steel jacketed buried power lines = 378.9 miles. The lawsuits that SDG & E are facing will more than have paid for their 130 mile Sunrise grid tower link.
One would not use steel jacketed cables anyway due to rust. It is far cheaper to use PVC jacketed Teflon coated power lines under ground at
$280/foot. The constant underground temperature of 55 deg. F certainly would aid any thermal heating of the power lines with proper thermal fins.
David Bainbridge
David Bainbridge
March 29, 2009
Another missing disadvantage is that above-ground high voltage lines are much more susceptible to geomagnetic storms. In 1989 a geomagnetic storm caused the collapse of the Hydro-Quebeces power grid for 9 hours. Just think of of the economic costs if there is a large enough storm to take out a larger area. It would make the cost of burying the lines pale in comparison.
william hughes
william hughes
March 26, 2009
Cutting through the gorgons not, in the end part of the solution to the distribution of power is to generate locally with renewables, reducing the need to transmit power. Lets hope Obama's initiative to make Solar Electric far cheaper bears fruit.
John Carr
John Carr
March 25, 2009
Watch overhead transmission lines in the summer. Have you noticed they are hanging lower? It's because they are hot and have lengthened under the heat.
The real problem with burying transmission lines is heat. When you bury a high capacity line it gets hot. Real hot. The ground acts like a thermal insulator. Oil must be pumped through the protective steel casing to cool the conductors. On high load days an uncooled, buried transmission line can burn through. Very nasty.
This is not usually the case with 15kV distribution lines, although I have seen it happen where cables get kinked or pinched.

FYI, a 36", steel jacketed bore, for 9, 6" conduits will cost up to $750/lineal foot. Cost is a factor.
Nick Cook
Nick Cook
March 25, 2009
I think the argument for lower voltages is probably because burried cables require insulating and the insulation thickness is proportional to voltage but because it wraps the conductor the volume of insulation is proprtional to the voltage squared. Also because the stiffness of a material is propotional to the witdth and the cube of the thickness, for a given cable design its stiffness is proportional to forth power of the voltage so if you double the voltage the stifness increases by 16 times. Like many things in life its a question of finding the best compromise.
The answer for burried cables is ultimately HTSC (high temperature super conductors) but they're not quite there yet, particularly for long haul lines, I think the logest currently installed is about a mile. They are generally based around copper oxides and use about 1% of the volume of material of copper cables (for the same current density) of which only a portion is copper, and for some types of HTSCs the other ingredients are more abundant and cheaper than copper, so when we crack the manufacturing problems HTSCs could end up cheaper.
Warren Reynolds
Warren Reynolds
March 25, 2009
Vanessa/Dan:

Solar Stirling engines are very cost competitive with 31% efficiency. SES, Inc. just finished its 500 MWe Stirling installation just east of San Diego with a contract price of $0.06/kw-hr to SDG & E. They are now building another 300 MWe installation for SDG&E in Imperial county at the same contract price. They are also building 500 MWe installation east of L.A. at $0.06/kw-hr contract price.
Imperial Valley around El Centro is excellent for solar. Our group is considering building in that area for a 24/7 solar-hydrogen power plant (500 MWe). I have been at the intended site in El Centro area and it is excelleint for solar.

Al:

Need to add one more disadvantage to overhead power lines: Fires !
A recent report (20 March) by SDG & E has shown that 17 fires have been caused by lightning strikes of overhead power lines over the past 5 years in So. California. A total of $1.5 billion in homes have been burned.

Warren
Thomas Blakeslee
Thomas Blakeslee
March 25, 2009
The US is amazingly behind in undergrounding electric power. High voltage DC can be cheaper than above ground AC in new installations-- Particularly if existing roadway shoulders are used instead of buying expensive right-of-ways. Here is a recent article: http://www.renewableenergyworld.com/rea/news/article/2009/03/invisible-underground-hvdc-power-costs-no-more-than-ugly-towers
Al Lewandowski
Al Lewandowski
March 25, 2009
Having worked for a number of Public Utilities over the years, the reason give are for the most part B.S. What would N.Y.C. or other major cities look like today if the lines were not buried? From Maine to California to Washington State to Florida the same excuses are given as to why not. No one says to do it overnight but as roads a renovated or added then there is no excuse in the 21st century to allow ice storms, tornadoes or hurricanes to take down communications and power and provide a national security risk potential for terrorists.
Max Roberto
Max Roberto
March 24, 2009
Why would changing voltage lines from high voltage to high current make them easier to bury? I don't understand the line of thought here.

I think that poster #1 has it right- power lost as heat due to resistance is I^2*R, so you'll lose a lot of power as heat if you use high current transmission lines.

But I still don't understand why high current is better than high voltage for the purpose of burying them!
Joel Myer
Joel Myer
March 24, 2009
Mason County PUD No. 3 in Washington State has 61% of its distribution underground. This is always a surprise for folks with whom I've talked about undergound and overhead power lines. For a rural utility, I think that's pretty good. Peninsula Power and Light in Gig Harbor is working towards having nearly all of its lines underground.
Dan Perkins
Dan Perkins
March 24, 2009
Previously as the Energy Chair for the San Diego Chapter of the Sierra Club I was involved early in the "Sunrise Powerlink" proceedings. SDG&E moved the path here there and everywhere before pressure from the enviros got them to put it parallel to the existing500 kv line along I-8 near the Mexico border. The battle has been furious for over four years and it's not over.

Europe has several years of history for underground 500 kv lines. Underground is more expensive but works just fine. A company that does it applied to install Sunrise but was turned it down, as their proposal was not timely. Power lines that size are paid for by the entire customer base in California so monthly cost to the ratepayers is small and distributed over years. Estimates are three times the cost for underground as overhead.

The Stirling Engine is not a proven technology on a large scale. Tracking the sun is not keeping a focus on the Stirling head and unless it's dead center on target the heat will melt the outer edge of the focal bar. The tracking devise for large solar arrays is not cost effective in today's' market.

Unfortunately the private sector is not installing sufficient solar or energy efficiency to show effective savings or generation where the demand is. That creates fuel for the utilities to fetch all the energy they can, based on California laws specifically the RPS (Renewable Portfolio Standard). And indeed that includes moving Sempra's energy from its' power plants in Mexico, Arizona and California into or out of the California market. SDG&E said using the line exclusively for renewables is not practical and I agree. At the same time Sempra, the parent company of SDG&E, will sell their natural gas to the generators all along the line. So far we were able to preserve the Anza Borrego State Park from a blight that would be there long after the line is needed. Now it's time to do in basin solar rooftops and seriously do energy efficiency.

Dan Perkins
Vanessa Rusczyk
Vanessa Rusczyk
March 24, 2009
SDG&E has led the public, such as Terry B. from Paso Robles above, to believe that the Sunrise Powerlink is about bringing renewable energy to San Diego. However, they have refused to be required to carry ANY renewable energy on the line, and have even said that if such a requirement was made they would not build it. The Powerlink is sited just across the US-Mexican border from SEMPRA's (SDG&E parent company) fossil fuel plants, with more planned. In addition, there are not Stirling Solar suystems built, and the technology on a large scale is untested and unproven. Imperial Valley is a terrible place for a large solar array due to dust and pollution. SDG&E is using the current political climate to ram this destructive and dangerous line through some of the most pristine backcountry in Southern California, placing thousands of homes and lives in danger of more catastrophic wildfires. Please read more about the project before deciding this is the future of green technology in this country. I sincerely hope it is not.
Dennis Houghton
Dennis Houghton
March 24, 2009
Power losses are proportional to the square of the current times resistance. High voltage reduces current and therefore line loss due to resistance. Insulation costs for high voltage lines will be far exceeded by conductor cost for high current transmission.

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Scott Sklar

Scott Sklar

Scott, founder and president of The Stella Group, Ltd., in Washington, DC, is the Chair of the Steering Committee of the Sustainable Energy Coalition and serves on the Boards of Directors of the Sustainable Buildings Industry Council, the...
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