Okay so you are saying that even if we touch the frame, since its conductivity is much higher, the current will keep flowing through it and then to the earth and not our body?Which has the path of least resistance? A grounded chassis or you standing in shoes? Hint, your bodies resistance is much higher than a copper wires.
Thanks a lot for the effort, but I am only a beginner who is trying to study electricity and electronics himself. Are you able to simplify your answer for a lay person? I couldn't understand it...It's not so much a matter of grounding a circuit to a frame as bonding the frame back to the source.
By bonding one point in the transformer secondary supplying the system to the equipment grounding conductor - most often a neutral conductor which is common between all phases - that system becomes solidly ground-referenced. That is to say, there is deliberate electrical continuity between the equipment grounding conductor (green wire or green/yellow in EU) and the ungrounded circuit conductors ("hot" wires) through the transformer windings.
In this way, if a fault occurs between one of the ungrounded conductors and an equipment frame which has been solidly bonded back to the transformer via the equipment grounding conductor, a complete circuit having very low impedance will be formed. The voltage to ground experienced at the frame will be minimized due to the low impedance back to the source, and sufficient current will flow to operate the overcurrent protective device protecting that circuit. Once the overcurrent protective device opens, the (relatively) low shock potential will be eliminated.
Much better than the alternative of an un-bonded frame sitting at line voltage indefinitely until someone wanders past and happens to touch it as was often the case prior to the 1960's.
As they say, code books and engineering standards are written in blood.
Well, I've worked with more people than I can count who think it's a good idea to splice circuits live, so there may just be something to that argument, lol.I wonder if people in 230V countries get fewer shocks because they are more careful?
It pays to work with a colleague. Not just so that when you recoil from the shock, they can point and laugh and say "Was that a bit live, then?"Well, I've worked with more people than I can count who think it's a good idea to splice circuits live, so there may just be something to that argument, lol.
As far as common shocks, it varies widely. I've heard tell of someone getting bits of their ear blown off when they touched a 277V circuit because said ear was touching a metal stud. People being unable to let go of a live conductor because their other hand is latched onto the panel tub, etc...
Nasty all around.
People take shortcuts, I understand that. My primary live electrical safety shortcut at this point in my career is to have another person do the job.I've had several of the plant electricians tell me that they touch feel for 120V live circuits. I didn't argue, just walked away with the willies thinking about it and shaking my head. Luckily in my career none of them were ever electrocuted. Suspect their supervisor may have had something negative to say about the practice and not all of them were prone to do so.
Back in the early 1900's the code book suggested exactly that sort of practice if I'm not mistaken. It also suggested that some people might not have the pain tolerance for it and should wear leather shoes or stand on rubber while doing it.I've had several of the plant electricians tell me that they touch feel for 120V live circuits.
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