Sunday, March 17, 2019

Power distribution

When I was in college, I worked between semesters as an office temp. Several of my jobs were at the power company in San Francisco. The jobs weren't particularly challenging, which meant I was good at them with minimal effort. Along the way, I learned a few things (very few) about electric power generation and distribution.

These look like transmission lines.

There is a difference between power transmission and distribution. The big power lines we see held up high by large steel towers and spanning long distances are usually what are referred to as "transmission lines." They move high tension power from generating plants (gas, coal, hydro, nuclear) to substations where the electrical power is "transformed" to voltages that customers can use. The power is then sent through lower tension "distribution lines" that are strung from common telephone poles, or underground conduits from the substations to customers. Often, that power is once again transformed locally before delivery to residential customers.

That is the sum total of what I learned by answering phones and typing letters for the electric company.


  1. I think the wires may sag when a lot of power is passing through them, but I'm not sure about that.

  2. Walt, can you post a photo (if you have one) of you at the temp job in SF? It would be cute, Roderick

  3. Better than learning nothing at all. Thanks for the wee lesson.

  4. And you use that knowledge so well. (I'm impressed you can remember it after ALL those years.)

  5. All I know about power lines is that the curve they make from tower to tower is a hyperbolic cosine. After reading your post I discovered that "tension" in this context is French for voltage.

  6. evelyn, I wonder.

    roderick, sorry, selfies weren't a thing back in the olden days! LOL

    chris, I worked in the office of one engineer whose job it was to monitor power output from the generating stations and figure out where to send it on the grid. At least, I think that's what he did.

    mitch, there's no guarantee that I remembered correctly! ;)

    tom, we always called transmission lines "high tension lines" when I was a kid, so that must exist in English, too.


Tell me what you think!