Herald JournalHerald Journal, June 21, 2004

Lightning: a high voltage headache for power companies

By Lynda Jensen and Liz Hellmann

Lightning might be nature’s form of electricity, but for the three area power companies, it can be a high voltage headache.

“Lightning has a mind of its own,” commented Bruce Huderle of McLeod Cooperative Power.

In fact, all three of the power companies that serve the Herald Journal area – Xcel Energy, Wright-Hennepin Cooperative Electric Association, and McLeod Cooperative Power Association – do what they can with the natural phenomena.

A single bolt of lightning can contain as much as 100 million volts of electricity, according to the National Weather Service (NWS).

For electric companies, this is a payload of unwanted energy, which can cause major problems if the lightning strikes power equipment or the ground near ground cables.

“Lightning is electrical and it’s an electrical system,” admitted Ed Legge of Xcel Energy.

“You’re talking about thousands of volts,” Huderle agreed.

There are an estimated 22 million cloud-to-ground lightning strikes each year in the United States, according to the NWS.

Lightning can wipe out equipment immediately, or strike near cables, causing them to fail weeks later, Legge said.

“Usually it likes to follow back to the substation,” Huderle said, noting that McLeod Power sections off its lines to limit damage.

For this reason, all three companies keep crews on standby for severe weather and power outages.

“Utilities are pretty used to dealing with lightning; it’s something you can’t eliminate,” commented Sheila Knop of Wright-Hennepinn.

Wright-Hennepin responds to more than 100 outages each year, a majority of which are caused by lightning and severe weather conditions, she said.

In fact, the Howard Lake-Waverly area is particularly prone to lightning strikes, she said.

McLeod deals with a similar number of cases, about 100 to 150 strikes per year, Huderle said.

The average flash of lightning could light a 100-watt light bulb for three months, Knop noted.

A bolt of lightning may carry 10,000 amps of electricity. In comparison, a common electrical service into a home carries 240 volts with around 200 amps of current according to the weather service.

In recent years, the average number of lightning strikes in the seven-county (Hennepin, Anoka, Ramsey, Washington, Carver, Scott, Dakota) metro Twin Cities area is 20,000 to 25,000 per year, Legge said.

Apparently there were considerably more strikes than average in 2002 – more than 118,000, he noted.

Lightning can strike electrical equipment at either the generation or transmission level.

Where the lightning strike takes place and the extent of its damage determines who and how many people experience a power outage, and for how long.

If lightning damages equipment at a larger distribution substation, a bigger area will be affected. Whereas, if a smaller substation or transmission line is hit, a smaller number of people will lose power. It could also take longer to repair the damage if a substation is hit in contrast to an individual power line pole.

Minnesota registers about 406 lightning strikes per year that cause some kind of damage.

Prevention with surge arrestors

Home owners may protect themselves by buying something called a surge arrestor, Huderle said.

The surge arrestor can be mounted on the pole outside the home, or behind the main meter on the house.

There are also smaller devices, depending on the load being served, that can be bought for protection of specific items such as phones, or a big screen TV.

“It will take most of it out, not all,” Huderle said.

Point-of-use surge protectors can be hooked up to electric outlets, phone lines, cable outlets and garage door openers.

Meter protectors can also be installed by the electric company on an electric meter outside the home to protect certain appliances such as refrigerators, freezers, washers and dryers.

Staying ahead of the strikes

All three power companies are constantly upgrading equipment to head off problems with power outages.

Lightning is actually only one problem of many related to severe weather, Legge said.

“We try to minimize these problems as much as we can. We’re constantly upgrading our equipment,” Knop said.

Wright-Hennepin has also set up insulators on transmission lines which take the power from substations to homes and businesses.

These insulators minimize the type of hit on the equipment and can protect against small lightning strikes.

“Some can take a hit and blink, but you won’t even lose power; there are other times when it takes a solid hit,” Knop said.

The biggest challenge can be pinpointing which poles where hit. Wright-Hennepin encourages home and business owners to report all power outages so they can pinpoint the problem efficiently.

“We have strategically installed lightning arrestors, which serve the same purpose as surge protectors, on our equipment throughout our service territory,” Legge said.

Lightning arrestors are devices that help to mitigate the impact of lightning.

Strong winds can blow tree branches and other items into cables as well.

Wright-Hennepin keeps an aggressive tree trimming program to address this problem.

Trees can also be dangerous when then are too close to power lines because they could fall into them during a wind storm or other severe weather.

Problems can develop in heavily wooded areas where lightning and strong winds topple trees onto overhead power lines, creating a higher number of storm related power outages in those areas.

More power lines are being buried underground as well, according to Knop, especially in high construction areas. “Underground power lines can help reduce weather related interruptions but nothing is fool-proof when it comes to lightning and severe storms,” she said.

In areas where power lines need to be above ground, the company keeps surrounding trees trimmed and encourages their customers to plant trees a safe distance away from power lines.

Now is a good time for property owners to inspect their property for overgrown trees which are too close to power lines, before more summer storms hit, Knop noted.

Wright-Hennepin recommends a clearance of a minimum of 15 feet on all sides of the center conductor or pole-line.

There are also other steps property owners can take as well.

“With all the electronics in people’s homes today, surge protection can be a very good thing to have,” Knop said. There are many different types of surge protection devices available.

For more information regarding power outages and safety instructions concerning lightning strikes, visit Wright-Hennepin’s web site at www.whe.org, Xcel Energy’s home web site, www.xcelenergy.com, or McLeod Cooperative Power at www.mrea.org/members/co-op_pages/mcleod.htm.

For more information about lightning statistics, go to the National Weather Service online at www.nws.noaa.gov.

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