Code related Theory question
- Thread starter crossman
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jwelectric
Senior Member
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- North Carolina
Re: Code related Theory question
I personally think that everyone that has replied to this post should take a closer look at the question. People who might read this and try to prove the posted answer might get hurt of even death. Part three of his question doesn?t require a lot of math to see that grounded or not this guy is hurt bad.
Both exposed ends of the conductor will have 480 volts present after the cut. When he touches both ends simultaneously he becomes the connecting link on a parallel 200 anp load at 480 volts and his body has just become extra crispy.
3) After cutting the cable (assuming he survived), he REMOVES HIS GLOVES and reaches in and touches both ends of the cut cable simultaneously (remember, he is not grounded). Does he get shocked?
Do you concur?
I personally think that everyone that has replied to this post should take a closer look at the question. People who might read this and try to prove the posted answer might get hurt of even death. Part three of his question doesn?t require a lot of math to see that grounded or not this guy is hurt bad.
Both exposed ends of the conductor will have 480 volts present after the cut. When he touches both ends simultaneously he becomes the connecting link on a parallel 200 anp load at 480 volts and his body has just become extra crispy.
3) After cutting the cable (assuming he survived), he REMOVES HIS GLOVES and reaches in and touches both ends of the cut cable simultaneously (remember, he is not grounded). Does he get shocked?
Do you concur?
petersonra
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- Semi-retired engineer
Re: Code related Theory question
1. No arc. The current just transfers to the other conductor.
2. No arc-no damage.
3. he will see whatever voltage drop there is across the uncut conductor. probably not a whole lot.
[ January 05, 2005, 03:31 PM: Message edited by: petersonra ]
1. No arc. The current just transfers to the other conductor.
2. No arc-no damage.
3. he will see whatever voltage drop there is across the uncut conductor. probably not a whole lot.
[ January 05, 2005, 03:31 PM: Message edited by: petersonra ]
Re: Code related Theory question
Pete is right. The inductance of the wire is insignificant. You merely double the resistance by cutting one cable. This doubles the drop over the length of said cable. This drop now appears across the cut. I doubt that the worker would feel more than a tingle (if that) by touching the cut ends. Now if he cuts both cables and grabs the cut ends, it would knock him on his butt, but perhaps not kill him--just teach him a lesson.
Pete is right. The inductance of the wire is insignificant. You merely double the resistance by cutting one cable. This doubles the drop over the length of said cable. This drop now appears across the cut. I doubt that the worker would feel more than a tingle (if that) by touching the cut ends. Now if he cuts both cables and grabs the cut ends, it would knock him on his butt, but perhaps not kill him--just teach him a lesson.
physis
Senior Member
Re: Code related Theory question
Now that the wire's cut (this guy stopped and took off his gloves) the two wires left connected at either end of the intact conductor aren't much different than your meter's test probes. So set it to a low voltage setting and see who's done the math right for voltage drop.
Now that the wire's cut (this guy stopped and took off his gloves) the two wires left connected at either end of the intact conductor aren't much different than your meter's test probes. So set it to a low voltage setting and see who's done the math right for voltage drop.
jwelectric
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Re: Code related Theory question
Voltage drop, everyone has done well on voltage drop, I guess, I haven?t done any math
There will only be a difference of potential on voltage between the two cut leads of the amount of resistance of the volt meter. There will be a low voltage reading on the meter. So far I guess we will all agree.
Don?t see any reason to do a whole lot of math because the basic principles of electricity are: A series circuit is a voltage divider and a parallel circuit is a current divider. What we feel while being shocked is all them little electrons running through our body and this is know as current flow. Now somebody do the math of the amount of current that this poor lass will be feeling and then tell me that he will feel a tingle. Oh yea, the voltage applied to a parallel circuit is the same through out the circuit I Think.
[ January 05, 2005, 06:16 PM: Message edited by: jwelectric ]
Voltage drop, everyone has done well on voltage drop, I guess, I haven?t done any math
There will only be a difference of potential on voltage between the two cut leads of the amount of resistance of the volt meter. There will be a low voltage reading on the meter. So far I guess we will all agree.
Don?t see any reason to do a whole lot of math because the basic principles of electricity are: A series circuit is a voltage divider and a parallel circuit is a current divider. What we feel while being shocked is all them little electrons running through our body and this is know as current flow. Now somebody do the math of the amount of current that this poor lass will be feeling and then tell me that he will feel a tingle. Oh yea, the voltage applied to a parallel circuit is the same through out the circuit I Think.
[ January 05, 2005, 06:16 PM: Message edited by: jwelectric ]
jwelectric
Senior Member
- Location
- North Carolina
Re: Code related Theory question
Good deal Physis you are on a roll. Let?s not forget that this entire math has been voltage drop or the amount of voltage we subtract from the applied voltage. Noting that this is on a three phase load that has an equal current load on all phases can we now ascertain that we are dealing with a constant load on all three phases. This being true we are not dealing with a phase current of 277 but a line current of 480, yes? The second that he touches both ends of the cut conductor there is now a difference of potential between the two conductors, the resistance of his body, and current will flow. What you think? What part of the 200 amps will his body conduct?
[ January 05, 2005, 07:03 PM: Message edited by: jwelectric ]
Good deal Physis you are on a roll. Let?s not forget that this entire math has been voltage drop or the amount of voltage we subtract from the applied voltage. Noting that this is on a three phase load that has an equal current load on all phases can we now ascertain that we are dealing with a constant load on all three phases. This being true we are not dealing with a phase current of 277 but a line current of 480, yes? The second that he touches both ends of the cut conductor there is now a difference of potential between the two conductors, the resistance of his body, and current will flow. What you think? What part of the 200 amps will his body conduct?
[ January 05, 2005, 07:03 PM: Message edited by: jwelectric ]
Re: Code related Theory question
You guys are making this difficult. His body will conduct virtually no current because only a couple of volts will appear across the cut. And, we cannot calculate this miniscule current because we don't know the area of contact, the condition of his skin, etc., etc., etc.... It should be obvious that the voltage across the cut will be identical to the drop across the 100 foot uncut cable. Voltmeter resistance would have no effect even with a cheapo 5Kohm/volt job.
You guys are making this difficult. His body will conduct virtually no current because only a couple of volts will appear across the cut. And, we cannot calculate this miniscule current because we don't know the area of contact, the condition of his skin, etc., etc., etc.... It should be obvious that the voltage across the cut will be identical to the drop across the 100 foot uncut cable. Voltmeter resistance would have no effect even with a cheapo 5Kohm/volt job.
jwelectric
Senior Member
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- North Carolina
Re: Code related Theory question
Just ran this on multisim 7 simulator. I used 2.5 ohm for 200 amp load, 480 volt divided by 200 amps. I used a 150k ohm for man paralleled with .26 ohm for 3/0 conductor and energized the circuit. This is the analysis I saw; at the 150k resistor I had 79.325 volts at .617 amps. This is for what ever it is worth to who it is worth anything.
Just ran this on multisim 7 simulator. I used 2.5 ohm for 200 amp load, 480 volt divided by 200 amps. I used a 150k ohm for man paralleled with .26 ohm for 3/0 conductor and energized the circuit. This is the analysis I saw; at the 150k resistor I had 79.325 volts at .617 amps. This is for what ever it is worth to who it is worth anything.
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