Electric Power in Stephens Valley

 Edition 1. Issue 4.

 

Electric Power in the Valley

In the first three issues, I urged the SV residents to organize and develop positions on issues such that they could be presented to the SV Board as the wishes of the collective. Since that really hasn’t happened yet, this issue will pause on the organization pleas and, instead, provide some simple background information which might be of interest to all SV residents. So, let’s talk about how electric power is distributed to Stephens Valley.

Everyone here gets their electricity from Nashville Electric Service (NES). In turn, NES buys that power wholesale from Tennessee Valley Authority (TVA). In my opinion, we are very lucky to have TVA as the supplier to NES. TVA has a very diverse set of generation resources they use to supply electricity to its 153 local power companies, like NES. They use area dams to generate hydroelectric power (the original renewable energy resource for electricity generation) and those dams provide about 11% of the power we use here, they use nuclear plants to produce about 39% of our energy, they burn natural gas to get about 26% of our needs, they still burn coal to produce 19% of our energy, the rest comes from wind, solar and energy efficiency programs. It is great to have so much diversity on our supply because if something crazy happens to one source, or fuel, it doesn’t cripple TVA.

TVA was born of the Great Depression and FDR’s intent to make the economy and living conditions of the southeastern US better by seeing to it that electric power was democratized – made cheap and available to all. TVA is also tasked with managing the flow of the Tennessee River system, and the economic and environmental stewardship of the region. TVA is owned by the United States, but they get no financing from the public coffers. They raise their own capital completely apart from the federal government, and they pay their debt service with revenues they generate. You can read a lot more about TVA at www.tva.gov.  NES was created in 1939 and is a non-profit, owned by Nashville Metro. NES policies are set by a Board consisting of five members, appointed by Nashville’s Mayor. You can read more about them and sign up to see their meetings at https://www.nespower.com/about-nes/.

NES is one of the largest municipally owned utilities in the US. They serve 420,000 meters over a 700 square mile area, using 5,900 miles of transmission and distribution lines in the process. But once NES purchases this TVA power and uses its distribution circuits to transport it, how does the power get to our homes in Stephens Valley?

Now NES hasn’t shared their mapping with me, but by riding around and observing I can tell that SV is normally served by a high voltage circuit that originates at the NES McCrory Lane substation. The good part about that is we are not too far from the source substation. The bad part is that a lot of that circuit comes down McCrory Lane, which is completely infested with trees that are looking for an opportunity to fall and damage the overhead circuit! As that circuit comes up Pasquo Road, there is one pole in front of the SV West Townhome project where the circuit goes underground to serve us. There is another pole near the original SV entrance on Sneed Road where the other half of the SV underground distribution starts. This is a good design that NES has implemented. Underground cables can fail, and the repair time can be many, many hours. Having redundant feeds into SV means that NES could reconfigure a failed underground component and get nearly all customers back on while repairs are taking place. This is a good thing!

I’ve only discussed about 8 miles of NES grid here. Since NES has about 5,890 other miles of plant to maintain, it is clear we are way out on the edge of their system. For now, being on the edge isn’t what we really want, but as the electric grid changes over the next few years, perhaps we will wind up in a very good position. You’ve likely noticed that we do have sporadic power outages in SV. The most common interruption to our electricity is a simple momentary interruption. Those are the events that send us scurrying to re-boot computers and reset the time on our garage door openers. These occurrences are from transient faults on the McCrory Lane circuit. A tree branch, an animal contact (think birds and squirrels), a lightning strike, or a car accident causes fault current to flow to ground. This fault current is recognized by a relay at the substation and the circuit breaker at the substation opens (just like a circuit breaker in our garages) the circuit to eliminate the overload. Now, when that happens at a substation the relays are fast and smart, and they immediately tell the circuit breaker to reclose. When that happens, and if the fault is gone, we only experience a sub one second blink. Of course, when one of our garage breakers trips, we must go find it and physically reset it. That normally takes a bit longer, but the principle is identical.

As the future unfolds, SV might find a way to become a “microgrid” and, if so, we may be able to cruise through outages by using our own stored energy right here in SV. There are exciting times coming in the electric power world, but more discussion about that will have to wait for another issue of The Valleyist.

It is hoped that this column will appear monthly, at a minimum, and it will attempt to illuminate the SV opportunities for creativity and partnership with our pseudo government right here in our beautiful valley. But I am not going to go it alone on authoring these essays. If you like to write, please join me in this endeavor.

William Ray - Author