Animal Mitigation at Work

As you can see from our masthead, birds love our substations. Unfortunately, they can be a dangerous place to nest.

We put things in place to protect wildlife from untimely deaths, and one of substation engineers was thrilled to see that the barriers are working. Look at this sweet mother robin and her two chicks. The animal mitigation barrier (the plastic disk you see) acts as a parasol.

Squirrel Uprising

Both the Commercial Appeal and Channel 3 have done stories today about the outage that affected Substation 6 in Midtown this morning. The outage was caused by a squirrel getting into equipment and causing a short circuit. The outage affected 4,800 customers and was quickly restored in about an hour and a half. Many CA commenters fear a squirrel uprising.

Here are some things to remember:

• MLGW was able to quickly restore power in this case, with many customers getting restored within an hour.

• This outage was caused by a squirrel getting into electrical equipment and causing a short circuit that affected part of Substation 6, which serves part of Midtown.

• Squirrels are actually very nice creatures who normally mind their own business.

• Animal related issues are something that every utility deals with, and they are very rare at the substation level.

• This is the 4th animal-related substation outage this year. There were four in all of last year, three in 2008 and only two in 2007.

• Since the 90’s, MLGW has implemented an extensive animal mitigation program for overhead transformers involving the installation of guards to keep squirrels and raccoons clear of energized components.

• Our substation animal mitigation program has been in place since 2006. It is ongoing, though MLGW has stepped up its efforts in recent months to add additional protection.

• This particular piece of equipment did not have animal mitigation protection. However, other equipment at Substation 6 is protected, and MLGW will seek to make improvements.

• Sometimes there are limits to what can be covered and/or shielded, because it must still be accessible for construction crews to perform routine maintenance and make repairs.

• Substations are a particular challenge because they usually occupy an area of several acres and are virtually impossible to keep completely free of small animals. In addition, there are hundreds of locations in each station that may be vulnerable.

• At newer substations, we have designed to provide greater clearances between live pieces of equipment, making it less likely that an animal can bridge the energized equipment.

Critters in our Midst

Today's paper has a good article on our animal mitigation efforts and a great picture of our in-house critter expert. Mike Waldrop. Check it out here.


Photo by Brandon Dill

Blame the Squirrel, not the Doves

This is a stock photo, not the actual perpetrator.

Not too long ago, a raccoon wreaked havoc in the Medical District. On Friday, it was a squirrel that caused a stir, this time downtown. (There were reports of several dead doves, possibly pigeons, in the area, but they were either victims of the squirrel's shenanigans or their own at an earlier date.)

Memphis has been the victim of two unusual events in as many months.

Friday's outage was caused by a flash over, or an unintended electric arc, like a bolt of lightning that jumps past an insulator. This is made possible through a temporary "bridge" such as an animal, in this case, a squirrel. Rarely does it cause a long outage. Usually it is just a millisecond flicker. If the equipment monitoring system sees a long event - say two eye blinks - it opens special high speed switches to separate the problem area from the rest of the system.

Last Friday was an odd event that we don't have often. A squirrel bridged some bus insulators, which are nonconducting standoffs that keep the high voltage from jumping like a lighting bolt through the air. (We must have a thousand of these in our system.) It was repaired quickly, but SUB 3 is a network station with underground transmission and it takes a little longer to get the power flowing again.

Read more about our animal mitigation efforts here.

Havoc Wreaking Obese Raccoons

Last week, an alleged 40lb raccoon made headlines when he caused a major outage in the Medical District. The major hospitals affected had back up generators and were fine. However, the Commercial Appeal's generator wasn't strong enough to run its printing presses, so the Friday paper didn't go out until mid day. That sure got people's attention!

Naturally we've had some questions about how a rodent could cause so many problems. As you can see from our masthead, we have several animal friends who like to make their homes in our substations, play on our electrical wires, and occasionally wreak havoc.

So here's what happened. A giant raccoon was scurrying along on the substation structure. When he (allegedly a "he") decided to climb across a switch that was ~30 ft off of the ground, he became an unwitting conductor for a few milliseconds. Some times (most times) the protective service equipment breaks (opens) the affected circuit and the offending bridge falls away and the circuit can be closed in again. In this case, a lightning-like spark formed over and through the raccoon and destroyed portions of the switch which had to be replaced. This is what caused the long outage. It was a really unusual situation--you might even say it was the perfect storm because it was a critical switch at this particular station and one of the last ones you would think an obese raccoon could get across!

As far as animal mitigation goes, we have a systematic, economical plan in place. We start with the big ticket items, like transformers and breakers, which also add up to long outages. Much like chess, we protect the king and queen first, but we have to choose which of the "back" pieces to protect. (Switches might be considered rooks or knights.) And well, the pawns are often on their own. (i.e. The station class insulators - there are so many of them and they are typically much shorter than a raptor, squirrel or raccoon.)



Breaker with "Big Red Covers"


Before we started our Animal Mitigation Program, we looked at historical records and chose the stations that had the most animal outages. We have stored animal mitigation stock on hand and the field workers cover equipment that is put back into service because animals think alike and will likely use the same path to shelter or food.

Basically, we try to increase the distance between high and low voltage typically around insulators and bushings so that an animal cannot initiate an arc "over" the insulator. All of the possibilities are considered, but economics play heavily into the extent of the implementation. The animal mitigation components are not cheap because they have to have huge insulation properties and have to survive being in the elements for decades without degradation.


Switches with "Clear Polycarbonate Bushing Barriers"

To read more about our efforts, click here.

Animal House

As you can see from our masthead, we literally deal with birds on electrical wires everyday. Memphis is right in the middle of the Mississippi Flyway—a major bird migration corridor that is a narrow strip just a few miles east and west of the river.

There are two major flock onslaughts in the spring and fall. Electrical substations provide nesting places similar to tree canopies, which causes many birds to want to stop and stay awhile. Large stations usually have the same types of birds—-Red-tailed Hawks, American Kestrels, House Finches, Rock Pigeons, Killdeers and an occasional Mockingbird or Northern Flicker.

Birds are not the only inhabitants of our substations. The warm areas, like the tops of power transformers and capacitor enclosures, attract raccoons and squirrels. Raccoons try to build dens in the underground systems so they can get bird eggs from nests in the substation superstructures. Squirrels typically use the structures as a high pathway to and from food sources – much like the way they move through trees. Domestic cats looking for bird snacks and an occasional snake also make their way into substations.

Unfortunately, by choosing to call a substation home, animals risk injury to themselves and others. The inadvertent contact or “bridging” of energized equipment can cause system outages and possible equipment damage. There is always the possibility of momentary or sustained safety breaches caused by these electrical faults.

Even a small bird can have a huge impact; the best example is the Monk Parakeet. These non-indigenous birds love to build their communal nests around warm transformers and have given other utilities fits. Some nests have been reported to be 10ft in diameter and weigh 150lbs. Substation engineers are constantly on the lookout for these little rascals. (Sometimes the animals combine forces to wreak havoc, like in New Mexico.)

Professional Engineers are to hold paramount the protection of people and property before all else. Substation Engineering is systematically analyzing and covering the secondary bushings on the power transformers, bushings on sectionalizing and feeder breakers, station service equipment, and key switches and capacitor bank structures at problematic substations. They try to achieve a balance between service, science, economics, and environment.