Bloviating About Grid Outages

The O’Reilly Factor has kept the term “bloviating” alive.

The Factor is usually accurate about its facts, but occasionally it bloviates without the facts. The recent electrical outages after Sandy elicited such an outburst. Why, it asked, isn’t the grid updated to prevent such horrendous outages?

The Factor was not alone in raising questions about the grid.

Others, such as IntelligentUtility magazine and the Union of Concerned Scientists, ranted about global warming. It should be pointed out that if the 1938 hurricane had hit land 60 miles farther to the West, New York City would have experienced greater flooding than it did from Sandy, and that was before Al Gore was born and global warming became a faux issue.

In fact, nearly every hurricane or major storm has invoked similar outbursts.

While it’s reasonable to question why power lines aren’t underground, the inference shouldn’t be that someone hasn’t done their job or that putting power lines underground is an obvious solution.

Actually, the grid, even though most of it was built in the last century, is still in reasonably good shape. Its major failing is a lack of investment in new transmission lines, to accommodate growth. This is primarily because of NIMBY’s, or because environmentalists have objected to transmission lines being built in what they consider to be, environmentally sensitive areas.

It’s true, that new measurement and communication equipment can help improve capacity and more quickly pinpoint faults and other problems on the grid, but the so-called smart grid reflects evolving technological improvements rather than any single effort, such as putting lines underground. No amount of smart meters could prevent the disruption caused by Sandy, or any other natural disaster.

At the core of most criticism about electrical outages after Sandy is why hadn’t transmission and distribution lines been put underground?

To answer that question, it’s necessary to establish what comprises the grid.

Aside from transformers, switchgear, cutouts and other ancillary items, the grid consists of power lines ranging in voltage from around 4,000 volts to as high as a million volts. Table 1 divides these into categories based on their voltage rating.

Table 1

Typical Power Line Voltages,

Thousands of Volts AC (KV)

Distribution 4
7
13
Sub-transmission 33
69
Transmission 115
138
161
230
345
Extra-high voltage transmission 500
765
Over 1,000
  • Categories are somewhat arbitrary, though generally recognized. Some consider 33KV as distribution voltage.
  • DC is a special category and won’t be included in this discussion.

There are two truisms with respect to voltages.

  1. The higher the voltage, the lower the line losses.
  2. The higher the voltage, the more expensive it is to build transmission lines.

There are approximately 800,000 miles of transmission lines in the United States, while there are approximately 6,000,000 miles of distribution lines1. There is, therefore, 7 ½ times more miles of distribution than transmission lines.

Only approximately 6,000 miles of transmission lines, or less than 1%, were underground in 2007.

Approximately 1,000,000 miles of distribution lines, or 18%, were underground in 2007.

Another piece of relevant information is that there were far fewer failures, i.e., customer interruptions, involving transmission lines than with distribution lines. The EEI2 report shows this graphically. A Virginia government report3 showed that out of 128 minutes of average customer loss of power, only 4 minutes were attributable to transmission related incidents.

When looking at underground distribution systems, some, such as in New York, involve underground networks where it’s physically impossible to build overhead lines. Much, if not most, of the remaining 18% of underground distribution was built when new housing communities were constructed and it was a simple matter to dig trenches and install underground distribution in “Greenfield” locations. But even areas where underground distribution was installed are not immune from interruptions, because the distribution feeder to the underground system is overhead and susceptible to wind, ice and other storm damage.

The main reason that more transmission and distribution lines aren’t put underground is cost.

Costs will vary significantly between rural and urban areas, but the cost of putting lines underground are essentially 4 to 10 times more costly in either case.

Transmission line costs are shown in Table 2.

Table 2

Average Cost to Build Transmission Lines4

Overhead, Rural areas $1,200,000 per mile
Overhead, Urban areas $2,200,000 per mile
Underground, Rural areas $6,00,0004 per mile
Underground, Urban areas $10,500,000 per mile

The case is similar for distribution lines as shown in Table 3.

Table 3

Average Cost to Build Distribution  Lines5

Overhead, Rural areas $135,000 per mile
Overhead, Urban areas $197,000 per mile
Underground, Rural areas $409,000 per mile
Underground, Urban areas $560,000 per mile

For these reasons, i.e., a small percentage of outages from transmission line failures, the very high cost per mile of building underground transmission lines and some technical issues, such as heat dissipation, it seems entirely reasonable to leave transmission lines overhead whenever possible.

The situation with distribution lines is somewhat different because of the lower average cost per mile, though in some instances the cost of building underground distribution lines has been as high as $1,100,000 per mile, even in rural areas. Consider the costly impact of granite or rock ledges and areas with high water tables, such as Florida.

The problem with contemplating putting distribution lines underground is that a very large number of miles, approximately 6 million, are involved. Multiplying 6 million miles by $400,000 per mile means the cost of putting all distribution lines underground would be, at a minimum, $2.4 Trillion. This equals 16% of the U.S. GDP.

An argument could be made to put distribution lines underground where there are potential threats, but between hurricanes, ice storms, wind storms, tornados, floods and earth quakes, there are few areas in the United States where some form of catastrophic event isn’t a possibility.

It should be noted that putting distribution lines underground doesn’t eliminate the threat of outages, though they would be substantially reduced. Outages would still occur due to flooding, dig-ins and cable failures. New York City didn’t avoid outages even though the distribution system on Manhattan was underground. Also, all distribution lines in an area would have to be put underground, since any remaining overhead distribution feeder lines would still be susceptible to failure.

Cable life is another uncertainty. The history of overhead lines is that they last for 80 years, while the history for underground cross-linked polyethylene (XLPE) 6 cables indicates a life of 35 years, though, because of their relative newness, this history is incomplete.

The issue of whether to put power lines underground has been studied on numerous occasions, such as by Houston Texas, Florida, Oklahoma, Virginia and North Carolina.

In general the conclusion has been, “Complete undergrounding of all electrical facilities is not the solution to the outage problems caused by storms.”

The impact of failures should be considered when evaluating the issue. Hospitals and other emergency installations need to have reliable backup power no matter what decision is reached … no system will be perfect. Perhaps, gas stations should also have back-up generators.

Getting FEMA to do its job would alleviate the hardship caused by any natural disaster.

Undoubtedly, the issue of putting power lines underground will be studied again after Sandy.

Until now, utilities and governmental bodies have acted in good faith and with considerable knowledge of the problems associated with putting transmission and distribution lines underground.

Before bloviating about the issue, it’s worthwhile gathering the facts and recognizing that a great many highly talented people have examined the issue on numerous occasions.

There’s no quick solution, such as installing smart meters as some would suggest.

NOTES:

  1. An Updated Study on the Undergrounding of Transmission Lines, Edison Electric Institute, 2009.
  2. ibid
  3. Report of Joint Legislative Audit and Review Commission to the Governor and the general assembly of Virginia, 2006
  4. An Updated Study on the Undergrounding of Transmission Lines, Edison Electric Institute, 2009.
  5. Ibid
  6. Cross-linked polyethylene (XLPE) cable is a more recent development, with many utilities still using High-pressure, fluid-filled pipe (HPFF). The advantages and disadvantages are described in a paper Underground Electric Transmission Lines, published by the Public Service Commission of Wisconsin.

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0 Replies to “Bloviating About Grid Outages”

  1. Don, liked your article, I found it informative. However, there are two things that I feel that need to be explored that I have not seen written about.

    First, has anyone really explored the effects of deregulation on the utility business? Deregulation, in my opinion it has actually weakened the companies that distribute electricity. They have cut back their operations in order to squeeze out profits and therefore have reduced manpower, reduced spare parts and have made minimized capital investment in the grid. In order to make profit from flat revenue, instead of increasing rates they have reduced their spending which is why they cannot handle the recovery to the storms.

    Secondly, tree trimming and line maintenance are reactionary, not proactive (another cost saving idea-sarcasm intended). I remember growing up on Long Island in the late 60’s, there was a tree planting boom. Those trees are now mature 45 year olds and are entangled in the power lines. There are so many that any wind related event wreaks severe havoc on the community. Go down any neighborhood block and look up at the wires that carry power to see what I am talking about. Something has to be done about it and it would be a heck of a lot cheaper than putting power lines underground.

    Here is an ironic story. A friend of mine told me that he wanted to take down two trees on his property. He had to apply for a permit…the town sent someone out to inspect them and said they were fine and denied the permit. Those two trees came down in Sandy knocking the wires off his house and blacking out his block. Why have we allowed this to happen to us?

  2. Tom:
    Thanks for your comments.
    Not surprised about the trees that were felled by Sandy after the town denied permission to have them removed. I lived in Reston, Virginia for several years where the homeowners association was sometimes overly zealous in preventing trees from being taken down. It’s a green thing.
    Tree trimming needs greater attention, because, as you noted, there has been a concerted effort to plant more trees. Awards are given to cities and towns for planting trees, which is a good thing if attention is paid to their effect on power lines and the town’s are open to removing trees when appropriate. It should be noted that utilities are frequently criticized for doing too much trimming.
    I can’t comment on the effect of deregulation. I’m not certain that deregulation is really applicable in situations where there are monopolies, which is another issue.

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