|
Faunsdale, AL | I think the important part is that if there’s a short circuit inside the building, the grounds are tied to everything that is available for the live wires to touch.
The importance of the grounds is to make a breaker trip quickly. They do this by creating a path of least resistance for current to flow back to the transformer winding. This is an attempt to avoid short circuits that allow current to flow but not enough to trip a breaker/blow a fuse. Keeps you from touching something that is energized by tripping it off when it faults. However it also creates the potential for higher current flow if your body makes the connection between the hot wire and the grounded/bonded steel. I guess the thinking is that people will be smart enough not to let that happen. I know it’s possible to be standing on wood floor in house and touch something that’s energized and just get a tingle because you’re so poorly grounded. If you’re also touching a metal object that’s bonded/grounded, you get the full effect of the current only limited by the conductivity of your body!
The 3rd (bare) neutral conductor coming into the building from the transformer is bonded to the ground system at the first disconnecting means after the meter, which is usually at a main breaker in the panel supplying the building. There is usually a ground rod driven for that purpose or it can be tied to building steel or concrete slab reinforcing steel.
There will also be a ground at the transformer pole and every pole on down the line back to the substation unless you’re way out and there’s a single wire supplying your transformer. That (single wire earth return) is really rare. Almost all utilities supply power with one or more high voltage lines and a neutral that’s grounded at every pole .
The common misconception is that the electricity “wants” to go to ground. No, it doesn’t, it wants to return to the transformer that created it. That transformer is almost always bonded to ground for several reasons (lightning mitigation for one), so you can get some current potentially flowing through the earth but generally not high amperages………… Because there’s a wire connection that’s supposed to carry all of it that’s a much better conductor than the earth.
At any rate, the safety grounds are all tied back to the transformer neutral through the WIRES and having the building metal and slab steel included in that is a good thing.
Edited by ccjersey 1/16/2025 08:51
| |
|
New shop electric grounded to frame?
