IMG: Let’s start with a simple question: How does electricity get into your house?
Q&A: Eugene Suchyta
Director of System Operation, DTE Energy
: We generate electricity at our power plants. Most of our power plants are coal-fired, but we do have a nuclear power plant, a gas fired power plant, and, of course, we have renewable energy sources as well -- some solar, but most of it is wind.
That electricity leaves the power plant and gets put on what we lovingly refer to as the grid. The grid is kind of like the energy super highway. It runs from kilovolts up to kilovolts in the state of Michigan.
It is analogous to a road system. If you think about a highway, the more lanes you have on the highway, the more cars you can get going from Point A to Point B. The higher the voltage, the more electrons you can transport.
The grid is much the same way. When we get to a local distribution point, we transform that down to lower voltage, much like when you get onto your major surface streets. You’re now off the freeway and you’re on, let’s say, a five-lane or perhaps a six-lane divided highway. We would characterize that more or less as the sub-transmission, at slightly lower voltage, 24 to 40 kilovolts.
Then we get even lower than that. The poles and wires that most people see going down their road between the three lane highways are what we call our distribution system, and that is either the 13.2 or 4.8 kilovolts, so still plenty high.
Then, finally, we transform that down to the usable voltage that you have inside your home. You can think of that as like your driveway or those minor surface streets that you have going through your subdivision. The higher the voltage, the more capacity it can carry.
IMG: When the electricity is generated, how does it first get on to the grid from the generation source?
: Transformers are the device that sit between the generation and the grid. So there’s a transformer that sits just outside the generator house. The generator sits inside the generator house, and the transformer that sits there changes that voltage, which is usually fairly low, sometimes around 20 kilovolts up to 120 to 345 kilovolts. Then just on the other side of that, is usually a fairly good size switchyard that helps distribute that energy to the other large substations that are sitting on the grid.
When you get to the next substation there’s lines that go to other large substations. It’s all an interconnected network, so that there’s some redundancy and there’s some fault tolerance in it, so that if we need to work on something we can shut it down and all the lights stay on. Let’s say a car hits a pole, or you get a really bad windstorm or something like that, you can still lose some of those lines and the lights still stay on.
There’s a lot of redundancy that’s built into the system much like the freeway system and the traffic system has redundancy built into it. If you shut down a road you can still get from Point A to Point B by traveling down a different road. It’s a networked type connection like that.
Some of those substations will have transformers that will then transform that voltage into the lower voltages that will then eventually get to your house. Step up transformers are what we have at the power plants. Step down transformers are what we would have at large stations and substations as well as on poles and in your backyard
IMG: And then how exactly does electricity get off the grid and into your house?
: It depends on where you live, if you have underground service in your backyard, you can’t see any of the wires. Those little green boxes that are around, those are underground transformers.
If you’re in an area where you’re predominantly fed by overhead wires and you have a wire going from, let’s say, the pole to your house, there’s a pretty good chance that there’s a thing that looks like a trashcan sitting out on one of those poles. That’s an overhead transformer.
And then, finally, the line enters the service box and into the electrical wiring in your home.