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During a pass hurricane, I had a chance to speak to a lineman.
I did not have trouble. He was just checking the neighborhood.
At my house he grab all three wires one at a time, with gloves and rubber boots on and did not receive a shock. The power was on. I was amazed.
The 3 lines that come off the power pole into the house are 220/115/ neutral into
The main breaker box. Is this correct.
Why didn't the lineman get shocked?
If I understand correctly:
Means... that the lineman did not touch two lines simultaneously.Quote:
Originally Posted by Oneill474
If he did, he would complete a circuit, and get shocked :eek:
That's why birds on a wire survive, they can't touch two lines at the same time, although a squirrel routin' 'round a transformer has enough length to span two lines, and BOOM! :eek: you have a transformer explosion.
The gloves and boots are there for protection in case of an accidental touch, but if there is high enough voltage/amperage it will go through even that protection.
! I strongly advise against this practice !:
"Some" homeowners will not lock out a breaker when they change a switch or receptacle.
As long as they don't touch a white, green, or bare wire when they touch a black one their okay... that sure sounds like an oxymoron.
BUT, They are playing with fire!.....Literally!
K
Actually, besides not touching two wires, wearing the rubber gloves act as a ___________ (I forget the word), to keep from getting shocked. As long as you are not touching the wires together and touching metal or anything that could send the electric into your body then you should be okay.
Also the wiring has to be grounded.
That is why they say do not touch metal in your car during a thunderstorm.
While it is true birds can sit on electric wires because they are touching only one wire, therefore not completing the circuit, One wire at the service is connected to the ground. If he was in contact with the earth while he touched the other wire, he WAS touching two wires at the same time.
The lineman did not get shocked because he was wearing protective rubber boots and gloves. (the same reason you do not get shocked when you pull a plug out of a receptacle, there is a layer of insulation between you and the conductor.)
Warning: The lineman does not wear just any kind of rubber boots and gloves. His safety equipment is designed for touching live wires, he is trained in its use, and the equipment is tested regularly. DO NOT TRY THIS AT HOME!
That's why I asked if I understood him correctly.
Can we please wait until that is verified?
For N0help4u, the word is insulator
K
The real reason he did not get shocked is because the live wires coming from the pole are insulated. If the lines were live and not insulated they would instantly trip a breaker or fuse seeding that branch. We take great care not to touch bare live wires together.
The gloves and boots are special pieces as ohb0b said. They are specifically designed to be used on live wires and circuits, not to protect from accidental contact. Same goes for the tools we use for working live.
I am required to use 1000v rated gloves and tools when making up service drop taps. I just today did this exact thing for a service upgrade.
YES, if approved, we are allowed to make up our own taps.
When did the 1000v rating come into effect?Quote:
Originally Posted by stanfortyman
15 years ago I witnessed a lineman get burned even though he was wearing shoulder length gloves.
For the sake of brevity accidental contact was a poor choice of words.
Sorry if I implied that I was a lineman. I am an electrician, and in my area we can make service taps if on an approved list.
Our utility mandates that we use Class 0 gloves since all we can work with is 120/240v secondary.
The utility linemen work with primary, 13,200 volts and even higher.
Not a problem.
I have seen two instances of what High Voltage can do. The one I mentioned, and a Econoline Van get its roof split in half while being carried on a R.R. auto-carrier.
The Plasma cloud was awesome! :eek:
[QUOTE=KUXJ;1825708]When did the 1000v rating come into effect?
15 years ago I witnessed a lineman get burned even though he was wearing shoulder length gloves.
Stan is also correct, the lineman probably did not touch the un-insulated part of the wires (except for the Neutral, which is at the same potential as ground)
Also, I'm not a lineman, I'm an industrial electrician. (That's why I never answer ceiling fan questions) I have a pair of 1KV (1000V) gloves and 5KV (5000V) gloves. The 5KV gloves are thicker rubber, and as KUXJ noted, have longer cuffs. I often have to work 480 volts hot, for which I wear the 1KV gloves.
I don't work on higher voltages hot, other than to open or close a switch, and to check for voltage. AS KUXJ suggests, if the voltage is high enough, "hot-gloves" gloves do not fully protect. You have to maintain a physical distance from the energized equipment. In addition to gloves, the electrician has to use insulated tools, and wear a flame resistant overgarment, a hard hat, special face shield, and use a long "hot-stick." We have voltage detectors and tools that attach to the end of the hot stick.
http://en.wikipedia.org/wiki/Hot_stick
I think part of your question was "The 3 lines that come off the power pole into the house are 220/115/ neutral into
the main breaker box, I sthis correct?" and no one has answered that. The lines coming in are not 220 but rather 120 lines, two of them. In most cases the third line is a cable carrying the weight of the wire. Maybe the electrcians here can further explain where the home gets ist ground and its neutral.
A residential service is typically 120/240v.
This is a 240v secondary with a center tapped "neutral". The center tap is what gives us 120v.
The neutral is called the grounded conductor because it is intentionally connected to earth. This is a reference point and to stabilize the voltages. A transformer will function just fine without this connection to earth, but it should be there.
This is NOT where the ground comes from which is connected to the little round hole in a typical receptacle.
The safety ground (bare or green wire) connected to the center hole of a receptacle comes from the neutral bond in the MAIN panel or disconnect. This is the only place that neutrals and grounds are sharing a common connection point, and this is what creates the safety ground that causes breakers to trip during a fault or short circuit.
The neutral, or grounded conductor, is intentionally bonded to the panel box which is also connected to the grounding electrode system. Again, the earth connection is a reference point and to help dissipate high voltage surges such as lightning or transformer problems.
Clear as mud?
I think you gave us a start but Oneill will still have trouble with"This is a 240v secondary with a center tapped "neutral". The center tap is what gives us 120v" because I did too. Can you re-explain what each of the third wires carries from the pole?
I had a feeling I was not very clear.
Here are some great images that will help explain it:
Wiring a House - Google Books
Scroll up to pages 8 & 9
In addition to being a support (or "messenger") wire, the uninsulated wire from the pole is connected to the center tap of the transformer secondary. It is intentionally connected to ground (Earth) thus becoming the "grounded" conductor in the system. (commonly called the "neutral.") Since this wire is at the same voltage as the earth reference, you can touch it without being shocked. This is the same principle as the bird sitting on the overhead wire.Quote:
Originally Posted by ballengerb1
In North America, a residential service is powered by a 240/120 volt transformer. There are three wires coming from the transformer. One connected to each end of the coil, and one connected to the center of the coil. There are 240 volts between the two ends of the secondary coil, and 120 volts between either end and the center tap.
A person would receive a shock of 120 volts if he were in contact with the earth and touching one of the wires from the end of the transformer. If he were touching both end wires, he would receive a 240 volt shock. Ohms law will determine how much current will pass through his body.
The grounded neutral is different from the grounding conductor, (green or bare) which bonds together all the metallic, non-current carrying components of the system, such as pipes and boxes. The grounded conductor normally carries current, the grounding conductor only carries current if there is a short circuit. The grounding and grounded conductors are connected together at the service panel, and also connected the earth at this point.
Both the grounded and grounding wires are necessary for a safe installation, but they protect against different hazards. It would take half a semester of electrical theory, so I won't attempt to discuss it here.)
In the US and Canada, remember the Green is the GroundinG, the White is the GroundeD conductor.
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