Part Two: From the Wires in the Neighborhood, to Sub-Station Transformers.
See Part One Here
This journey traces our electrical power to its source – in three parts.
Our house is to the left. That single 7,200 volt wire and the bare ground wire (the latter dificult to see,) come into the picture from the left and join with one of three wires making a turn to the right. The power that is delivered to our house can come from either direction, as multiple loops of triple 7,200 volt lines (and a separate ground wire) form a redundant grid which can be switched in advantageous ways to better insure connectivity – as events occur.
Three wires, and a ground. This is the same configuration comprising transmission from the generator to every local neighborhood. Technically: Long distance transmission is much more efficient with three alternating current phases, each generated 120 degrees apart, and in the case of most of the USA, at 60 cycles per second. It hurts my head to visualize the principles involved, but the effect justifies the need for three conductors, or wires. Overhead: As seen in the first image above, only one of these wires is neccesary to supply each house. The bundle above, however, is typical to efficiently bring the necessary voltage to NEAR our homes.
About a quarter mile away from home is a junction of two routes, again, with three 7,200 volt feeds, and one common ground. The ground is connected as a bare wire down virtually every pole to the soil beneath, or as in this case, serving the dual purpose of a guy wire. (Lower down the pole in this image, 110 volt wires from nearby transformers, feed houses and the streetlight.)
On either side of the junction shown in the previous image, these arrays serve as a computerized reclosure system. The second crossbar down holds six conventional manual circuit breakers. Then, each wire enters the components in the rack, continuing down on the far side of the pole to a control panel at street level. It detects failures, assess the impact and instantly re-directs or cuts off power; and if deemed only a momentary stoppage, re-connects in seconds. A telemetry antenna on the lower side independently transmits info to the utility company via battery back-up. Click to enlarge and see details of this remarkable grid component.
Reclosure Control Panel at Street Level
Sandy and I often walk under two of these reclosure arrays in an area two blocks away from home known locally as “Doggie Triangle!” Two miles away, the three conductors emerge from a small sub-station, as seen below.
Here, are the three 7,200 volt lines coming out of the nearby sub-station after having been ‘stepped down’ from 69,000 volts.
Coming into this same sub-station, we trace three (of six) 69,000 volt conductor wires (faintly seen dipping down from the hi tension mono tower,) with a fourth (ground wire) way on top. These are handled by the framework, right, and drop down in the foreground, entering the transformer area, out of sight below. The transformers step their voltage down to 7,200 each after which they exit the sub-station as shown in the previous photo.
About 6 miles further north, the S. Mahwah sub-station covers several acres with many more transformers, capacitors, reclosures, bus bars and dead squirrels. Coming in from NY State are some serious power towers, possibly carrying 138,000 volts. This image is where that force of power is handled and stepped down to the 69,000 volt towers seen in the previous image, and also several 7,200 volt bundles exiting to local loops which redundently serve as backups spreading out into the region.
At least 138,000 volts in 4 groups of three wires (left towers) come into the S. Mahwah sub-station (in the diatance) from New York State, behind me in this view.
The next Part follows the link another 25 miles or so to the massive Indian Point Nuclear Power Plant, the source, …where electricity is generated from the heat released from Uranium 235 fission.
Part Three? See http://wp.me/p37YEI-1zn
Disclaimer: Not being an electrical engineer or public utility employee, some values and circumstances may be slightly different than stated, but should give a general idea of the actual grid. Any system or statistical corrections will be most appreciated.
As usual, thanks for viewing, and comments are always welcome. M:-)