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.

Flying High

Last week I took a field trip to substation 4 with some of the engineers to check out the new safety features, environmental upgrades, and daredevil starlings. (Ok, I really just wanted an excuse to wear safety goggles and a hard hat.)

Hanging out in a substation is rather exciting--especially if you have an engineer telling you about all of the high voltage surrounding you (and it's potential danger). Apparently no one has told the birds. They just fly through without a care in the world, oblivious to the fact that they are just millimeters away from doom!

Electrified

A behind the scenes explanation of some of the repairs we were dealing with last week...

The power transformers found in our substations are the key principle element in our electrical system. Each transformer has a specific software and relay protection scheme that does its best to shield the transformer from a daily onslaught of power surges caused by lightning, system switching, and breaker cycling opening and closing due to tree limbs and debris.

A transformer is in effect a huge electromagnet. When it sees a huge current spike, it transforms this into a massive magnetic pulse that causes its interior coils to repel each other with unbelievable force. Each power transformer has its own dedicated breaker that serves as its last line of defense. After years of constant diligence even the best equipment may be pushed past it limit.


This was the case for a power transformer at substation 67 shortly after the storm on June 13th. A power transformer and its related breaker and buswork were destroyed when they could no longer keep its 161,000 volts under control. You can see from the pictures that the failure was catastrophic. The event took place in about a minute and a half.

The most surprising damage was found atop the breaker where the high voltage porcelain bushings were reduced to cinders. This would take a blast of ~3500 F.

The overall system typically has a backup for every element. When one part is damaged beyond repair, MLGW replaces it quickly. In this case no one lost power and the repair and restoration of this substation began almost immediately. A spare transformer and breaker were brought in within a couple of days, and the buswork has been rebuilt.


In a few weeks this substation will be even more robust than before and ready for the future storms to come.

I Feel the Earth Move Under My Feet...

U.S. Senators Lamar Alexander (R-Tenn.) and Bob Corker (R-Tenn.) and U.S. Representatives Steve Cohen (D-Tenn. 9th), Marsha Blackburn (R-Tenn. 7th), and John Tanner (D-8th) today announced a $2 million Department of Homeland Security grant for earthquake protection of Memphis Light, Gas, and Water (MLGW) electrical substations in Shelby County.

“An earthquake on the New Madrid Fault line could prove disastrous for the Shelby County area,” Alexander said. “This funding will help protect nearly one million West Tennesseans on the MLGW grid from power outages should an earthquake hit. I’m glad to see the Department of Homeland Security recognizing the threat of an earthquake in the Greater Memphis Area, and I will continue to work with the rest of the Tennessee delegation to ensure we are prepared.”

“The New Madrid fault could pose a potential risk to the Memphis-Shelby County area in the unlikely event of a major earthquake. Loss of electrical power, in particular, during an earthquake could hinder the rescue and recovery effort. This funding from DHS will help secure the electrical system from shock so it does not fail,” Corker said. “I appreciate the commitment of DHS to helping Tennessee communities prepare for natural and manmade disasters before they occur.”

“This funding is absolutely essential for the safety and well-being of residents in the Mid-South,” said Cohen. “I am pleased that the Department of Homeland Security is taking the necessary steps to ensure that our critical infrastructure is protected in the event of a catastrophic event such as an earthquake. The 9th District lies along the New Madrid fault line and we must be ready for an earthquake at any time. Having witnessed the consequences of unpreparedness for Hurricane Katrina, my Tennessee delegation colleagues and I are even more aware of the importance of pre-disaster preparation.”

"We know that our area is vulnerable to earthquakes because of our geographic location," Tanner said. "It is imperative that we have the resources in place to keep West Tennesseans safe if such a disaster were to occur."

"What we have seen in the past month is how critical solid preparation is to a community's ability to weather a natural disaster,” Blackburn said. “Unlike a hurricane, devastating earthquakes strike without warning. I am gratified to know that in the event of disaster, the preparations that this grant facilitates will allow essential services to continue for Shelby County."

The Memphis-Shelby County area lies within the New Madrid Seismic Zone, which has more seismic activity in any other place in the United States east of the Rocky Mountains. This funding goes toward the seismic anchoring of 110 critical high voltage transformers in the MLGW service area to protect them from failure during a potential earthquake. High voltage transformers are the most critical points of failure for the MLGW electric power system.

Memphis Light, Gas, and Water (MLGW) is a private nonprofit organization. The Pre Disaster Mitigation Program does not grant federal funds directly through nonprofit organizations, so Memphis-Shelby County will be responsible for assisting in the directing and monitoring of the project.

source

The Billy Positioning System (BPS)

A little "engineer humor" from one of our Power and Structures engineers...Enjoy!

It’s the 21st century and most of us have either used GPS on our phone, NAV in our car, or some other type of directional system to help find our way around town. However, William L. Allen Jr. (Billy), an engineer here at Memphis Light, Gas and Water has shunned those technologies, and has created his own positioning system utilizing over 10,000 network connections to produce geographical results in a matter of yoctoseconds. It is known as the Billy Positioning System, or BPS for short.

Billy has memorized the location of over 60 substations in the MLGW system. He also knows how they are all connected via 161 kV (kilovolt) transmission lines and 23 kV or 12 kV distribution circuits. When Billy needs to determine which direction he is headed in, he looks at the transmission lines along the road and says something like, “That’s a 161 kV transmission line because it uses the larger insulators and thicker conductor, and if we’re in the Cordova area, it must connect Substation 39 to Substation 72 from the north side, therefore quite simply, we’re heading west.” (Billy’s wife does not appreciate the power of BPS as much as his fellow engineers.)
So, the next time you’re lost and the NAV in your car goes kaput, give Billy a ring, describe the nearest transmission line to him, and he’ll get you going in the right direction!

Sonic Booms & Black Buzzards in Lakeland

The latest news from our bird-watching substation engineer...


Friday, July 18th, Substation 85 in Lakeland quietly came on line. But it was anything but quiet the day before when the new substation was locked into its sister station, Substation 39.

A 161 kV high-strength insulator failed inside the substation – literally blowing its top - and a sonic boom was heard in Lakeland. It was like July 4th fireworks going off at ground level, only mid-day and later in the month. No personnel were hurt, the protection scheme saved all of the power equipment and the six foot insulator was quickly replaced.

This new substation was necessary due to the load expansion in the area. The initial installation has two 161 to 23 kV power transformers with the yard designed to accept a third transformer when the localized demand warrants. The Metal-Clad Switchgear Complex was designed and ordered in four sectional units with the future requirements in mind, since it is difficult to add on to or retrofit a switchgear years after an installation. This foresight saves a great deal in future expansion costs but forces the designers to look deeply into their crystal ball.

The official mascot of the station is a black buzzard and its family which soars over the station and seems to keep track of the construction progress. One of the other substation engineers has named her “Subby.” Most see her as a good omen.

Safety First

Happy Fourth of July! I thought I'd share some safety related technical info with you today so that when you get around to setting off your fireworks, staying safe will seem easy!

This is a substation:



A substation is where power is transformed from high voltage (161kV) into low voltage (23kV) for meter use.

I've already touched on the hazards for birds, but substations are also one of the most dangerous places that a human can be. MLGW utilizes a variety measures to keep people and equipment safe.

Here's a peek of just one small piece of the pie, breaker repair, compliments of one of our substation engineers.

Substation 67, Power Circuit Breaker 67651

Electricity is like invisible fire. It is extremely useful but must be monitored continuously and shut down immediately if it strays outside manageable parameters. That is the job of power circuit breakers, the silent sentinels of our substation system.


It is estimated that the blink of an eye takes 0.1 to 0.15 seconds or 100 to 150 milliseconds. Newer era power circuit breakers can open a circuit in 50 milliseconds. This means that the breaker can interrupt a problem or fault in the system in half an eye blink.

Breakers are extremely reliable and once in service they usually last decades. Some are still in service after seventy years and are functioning fine; these are the original breakers from the beginning of time, MLGW time. Equipment such as this have been improved over the decades and are no longer manufactured. (Often the only reason it is retired is the unavailability of replacement parts--quite a testament to the original equipment and system designers of the early 1900s.)

Recently, a critical breaker at Substation 67 that serves a number of large industrial customers started showing signs that it was approaching the end of its practical life. All replacement tasks—demolition, foundation, ground grid, electrical equipment, control conduits and protection installation—must be coordinated.

The demolition requires no wrecking ball. It involves the removal of the old breaker and its associated conduits and cables. More often than not the old foundation cannot be used. Field crews use a Ditch Witch with a hydraulic ram to bust the old foundation out. (Old breakers are stored as spare parts for breakers that are still in the grid.)

The next order of business is the new foundation. Memphis is in a seismic zone 3 and all foundations have to meet the requirements dictated by this reality. This particular installation is on very sandy soil at the end of President’s Island which adds another complication. The breaker in this case weighs about 11,000 pounds and is approximately 11 x 14 x 19 feet high and must be anchored solidly to a stout foundation.

After the breaker is set it has to be properly tied into the station grounds. All substation equipment and structures are bolted and bonded onto a huge underground grounding net called the ground grid. This grid is made up of buried conductor that is about ¾ inches in diameter. This provides a low resistance path to ground for any sparks that get unruly and again protects equipment and personnel from electrical shock.

It is the “invisible” safeguards that we all depend on. Engineers have termed this protection “the dark arts”. If they don’t get it right, we’re all in the dark – literally.

The next time you blink your eyes, think of the thousands of breakers working thanklessly for you.

Home Sweet Home

Another installment from our birdwatching Substation Engineer...

House Finch Versus 161 kV – Substation 31

Why doesn’t a bird get electrocuted when it sits on an overhead conductor?

The bird and the conductor are at the same voltage so there isn't a deadly current that flows through the bird. Electrical transmissions and substations are designed so that the conductors are clear of ground to such an extent the electrons cannot jump the gap.

Consider this House Finch nest; it is inside the end of a three inch aluminum pipe carrying 161,000 volts (or 161 kV).


This is the highest voltage used in the MLGW system. The finch is so small that it will never bridge the gap, so it is free to go about its bird business in peace. What a place to live and raise a family!

So what do we know about our newest resident?


The House Finch is called the “embarrassed” finch or the “Hollywood” finch since they were once only found wild in the west. A California fancier trapped some in 1939 and tried to sell them in New York. The rub was that the Migratory Bird Treaty Act protects all native songbirds from being kept captive. In 1940 a fateful raid by the U.S. Fish and Wildlife Service on a pet store in Long Island allowed them to fly free in the east. The law came in the front door and the birds were released out the back. They have been spreading westward ever since. They love Tennessee and our power substations.

Now that the technical question is answered, let's turn to the philosophical one. Is this the most unsafe nest in Memphis, or the safest?

Damage Report

Substation 71 in the Hickory Hill area was de-energized last night due to damage from debris. Nearby warehouses were completely destroyed and the fence of the substation had collected cars, trees and roofing materials.














Downed power transmission towers just south of the airport/north of Stateline Road are unable to bring power into the station.














Substation 71 is at least 5-7 days from being re-energized, and even then the distribution will not be completed. It could be three weeks before that area is restored.

The reason for the long restoration time is that much of our electric system has been completely wiped out and must be completely rebuilt. This is different from the wind storm of 2003 because in that case, we had fairly significant damage over a wide area. In this case, we have complete devastation, but in a smaller area.

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.