Safety - Critters Awire

Public Power
Author: William Atkinson
Published on: July - August 2004

squirrel affecting power lines

Animal interference with electric power facilities account for 12 percent of all electricity outages, according to Richard Harness, a wildlife biologist with EDM International, a utility consulting firm in Fort Collins, Colo. Weather causes 67 percent of outages.

Utilities can prevent, or at least reduce, animal-caused outages. Unlike outages caused by severe weather, outages caused by animal interference generally occur in isolated locations and the public cannot see the cause. This often leads to anger and frustration among customers.

Today, utilities are focusing on increased reliability. "Fifteen years ago, homes weren't filled with computers, digital clocks, digital stoves, and sensitive, programmable electronic entertainment equipment," said Bob Hartman, general manager of Kaddas Enterprises of Salt Lake City, a manufacturer of devices to reduce animal-related outages. "Now, if the power goes out, homeowners have to go through their homes and reprogram everything. The cost of re-fusing a transformer may only be $300, but the cost of an outage is a lot greater in terms of consumer anger."

"We began looking hard at reliability improvement in 2000, as a result of a high number of outages in 1999," said Bill Ewer, customer services and marketing manager of Longmont Power & Communications in Colorado."We adopted a reliability improvement plan in 2001 and set some goals, as well as some specific measures to improve reliability." Many of these focused on reducing animal outages.

Squirrels are the third leading cause of power outages in the United States, after direct storm damage and tree damage, according to Douglas Wulff, marketing director for Critter Guard, Inc., Columbia, Mo.
In one report on outages, the Electric Power Research Institute referred to squirrels as "Public Enemy Number One" for utilities.

Squirrels, raccoons and birds are the three leading causes of outages for Colorado Springs Utilities, said Kirsta Scherff-Norris, a wildlife biologist with the utility. Longmont's Ewer said animals, chiefly squirrels, account for 38 percent of the utility's outages.

For Wayne Daniel, manager of the electric department at Tullahoma Utilities Board in Tennessee, squirrels are an even more serious problem. "Animals cause about 60 percent of our outages, and most of those are squirrels," he said. "We also have what seems to be a rare problem. Squirrels in the Tullahoma area eat our aluminum connectors." At first, Daniel thought they were just sharpening their teeth, but there are never any shavings or chips anywhere. "They actually eat the aluminum," he said. EPRI is studying this phenomenon to find out why.

To reduce animal-related outages, utilities need to develop strategies for living in harmony with the critters. Protecting animals is a "corporate philosophy" for Sumter Electric Cooperative in Florida. "We have always believed you can run a utility and have it operate in harmony with nature," said Barry Bowman, director of public affairs. "We don't like outages, and we don't like to see wildlife injured." The utility's monthly customer newsletter always has an educational article on wildlife. "The articles are designed to help make the public aware of animals and the environment," said Bowman. If the utility is constructing a new substation, it engages wildlife biologists to relocate any gopher tortoises that might inhabit the area.

Underground distribution lines reduce the incidence of animal-caused outages. "Only about 32 percent of our distribution lines are overhead," said Colorado Springs's Scherff-Norris. "The rest are underground, and about 95 percent of our new lines are also going in underground."

An aggressive tree-trimming program can also reduce animal-caused outages. This is a major component of Longmont Power's overall program to improve reliability. "Trees can be a direct cause of outages, around 11 percent for us," said Ewer. "In addition, they can also make it easier for squirrels to jump to the lines." Three years ago, the utility implemented an aggressive five-year tree-trimming program, where 20 percent of trees along the lines are trimmed each year. To accomplish this, the utility increased its tree-trimming budget from $120,000 to $180,000 a year. "Before, we focused on trimming trees just where specific problems existed," said Ewer. "Now, we are doing systematic trimming, focusing on the main feeder areas." By doing a better job of trimming trees, the utility is starting to see reductions in direct tree-related outages and squirrel-related outages.

Another strategy is to make it difficult for squirrels and other animals to climb poles to get to power lines. One option here is steel poles. "They make it more difficult for animals to climb poles," said Richard F. Aichinger, PE, manager of engineering, utility products, for Valmont Industries, Valley, Neb., a steel pole manufacturer. "Squirrels can still get to your lines from trees, but the problem there would be lack of proper tree-trimming."

Squirrel access to power lines is reduced when utilities band wooden poles with slippery hard sheets of plastic, called "animals slides" or "pole bands."

"We use hard plastic bands about 30 inches wide, wrapped around the poles about half-way up," said Longmont's Ewer. The utility installed 1,700 bands in the last two years, and they have been very effective in preventing climbing animals from getting up poles, he said.

Critter Guard sells pole guards and line guards that keep squirrels from gaining access to equipment. Most utilities use the product only on their more expensive equipment, such as reclosers and pole-top switches, said Wulff. The guards are not cost-effective for transformer protection, but are for substation protection. "Some of our clients have purchased over 3,000 of our line guards to do all of the overhead getaways coming into their substations," he said.

Utilities can also discourage squirrel exploration by covering electrical equipment on poles. "If you want to prevent animal-caused outages in above-ground distribution systems, you can install covers for fuse disconnects, transformer bushings, recloser bushings, breaker bushings, lightning arrestors, and so on," said Kaddas's Hartman. The company also designs and builds products for unique situations.

EDM's Harness sees value in this approach. "If you're having problems with animal-related outages, you should change your construction standards for new installations," he said. For example, if squirrels are a problem, he recommends purchasing transformers with wildlife caps already installed, so squirrels cannot reach up from a transformer and grab the top of the bushing or energized wire and complete the circuit. In addition, when installing a jumper to a transformer, Harness recommends using insulated or covered wires.

Sumter Electric installs squirrel guards on transformers near large squirrel populations. "They aren't very expensive, and they can be installed very quickly," said Bowman.

"We are installing fuse cut-out covers, transformer bushing covers, ceramic cap covers, and some other products," said Longmont Power's Ewer.

Quality and durability are important when purchasing products designed to reduce animal-related outages, Hartman said. "Some products are inexpensive, but they may not last very long," he said. Most of the cost involved in the protection is for installation labor. "You will lose money if you constantly have to replace damaged or broken products," he said.

The effectiveness of these strategies for discouraging squirrel interference with power facilities varies. Hartman of Kaddas Enterprises stays in touch with utilities that have installed the company's products. "We have not been made aware of any cases where they have had problems with animal interactions after installing our products," he said. "In other words, they are virtually 100 percent effective. If squirrels are a problem, though, you may need to invest in a lot of products and labor. You have to do all of the jumpers or stingers, and all of the exposed metal parts.

Longmont Power's comprehensive program has been working. In 2001, the utility experienced 458 outages, including 155 caused by animals or birds. In 2003, that number dropped to 320 outages, only 73 caused by animals or birds.

Tullahoma has not had great success with its installations of wildlife protectors, which are round disks that slide over insulators. "We have installed these around the bushings on the transformers, so animals can't go from ground to hot," said Daniel. The utility purchased 3,300 protectors over the last five years for about $35,000. "They have helped, but just a bit," he said. In 1997, the utility had 148 squirrel-related outages. The number had decreased only to 136 by 2002. Daniel said better tree-trimming practices, not animal-guard equipment, led to the reduction. "There are cases where we have had six or seven of these disks on one pole, but the squirrels have still managed to trip the line out," he said

The continuing problems leave Daniel with a new perspective on squirrels. "Before I got into the utility business, I used to like squirrels," he said. "In fact, I was on an Air Force base for 37 years and used to feed them. I wouldn't do that anymore, though."