VOLTAGE TO GROUND WITH THE NEUTRAL GROUNDED

[LarryFine]

Neutral VD will make difference and under certain conditions may be deadly,

Would you consider it safe to touch your meter, main disco, and/or breaker panel enclosure while barefoot?

 

[LarryFine]

What do you think is the reason why the man will not be electrocuted if one line is connected to ground and somebody touched this current carrying conductor?

Because the impedance of the intended current pathway of the grounded conductor is so low in comparison to the average, dressed person standing on most surfaces.

 

[LarryFine]

Are you sure that it is not the voltage that drives the current in electricity? Ever wonder why code warns against voltage not current? DANGER HIGH VOLTAGE? Will you be electrocuted with very low voltage?

Voltage does indeed drive current. The average person might not be scared by DANGER: HIGH CURRENT!

 

[Hv&Lv]

Perhaps I'm missing something that Larry saw but I've got to say yes he would in the very least feel it. Current takes all available paths back to source in proportion to resistance.
The graphic was to show that a seconday path was going from the arm through the body exiting the foot. Showing potential to have an impact on the heart, and possible cardiac arrest.

I would say in this instance it would be no different than touching a three wire dryer or stove casing.
think transformer, if you have a dry pot energized and touch the case what happens?

Remember the calls we all got at least once where someone complained a washing machine was shocking them?
Polarized plug backwards..

 

[Fred B]

Have you analyzed where the 80 volts came from? Is the source 3 phase ungrounded delta in your real life experience? Did you measure the line to ground voltage for each line?

80 volts was a result of the splitting of the current between 3 circuit neutrals all tied together in a jbox. Additionally resistance of the equipment that the lighting circuit was turned on. And by metering between the neutral and grounding conductor at the switch that was being rewired it was measuring another conductor potential back to source. When the offending light was turned off no current present. Made a repair at attic jbox and no more shock and no more N/G voltage reading. Just continuity on N/G that would be expected on the home run.

 

[bobby ocampo]

Would you consider it safe to touch your meter, main disco, and/or breaker panel enclosure while barefoot?

I will check the voltage to ground first using a voltmeter. If the voltage is zero will you be electrocuted?

 

[Fred B]

To me, ptonsparkey's "bird on a wire" is the simplest illustration. A bird sitting on a bare distribution wire receives no shock as both feet are at the same potential (if you measured voltage between the two points it would be zero).
To a degree, your drawing is the same situation. In theory, with the system grounded (connected to earth via grounding electrode), his feet and hand are the same as the birds legs...same potential.
In reality, due to resistance and other factors there will be potential. The value dependent on many factors, so there could be enough potential to cause a shock

That would be valid if there was no means for the persons body to be grounded. The illustration cleadly indicates a means by which the person is grounded, in order for the current to also travel in the means shown.

 

[bobby ocampo]

80 volts was a result of the splitting of the current between 3 circuit neutrals all tied together in a jbox. Additionally resistance of the equipment that the lighting circuit was turned on. And by metering between the neutral and grounding conductor at the switch that was being rewired it was measuring another conductor potential back to source. When the offending light was turned off no current present. Made a repair at attic jbox and no more shock and no more N/G voltage reading. Just continuity on N/G that would be expected on the home run.

The explanation is in the system capacitance from an imaginary neutral for a delta connected ungrounded system. Chapter 1 IEEE 142. You can verify it with a voltmeter as you have experienced it. Based on my calculation it will be 70 volts neutral to ground

 

[Sea Nile]

Work out the current and voltage assuming 25 Ohms of resistance for ground rod, 1000 ohms of resistance from hand to foot. And the conductor resistance of 14 AWG copper.

I would bet the current and voltage would be so insignificant that it wouldn't be a concern at all

 

[Fred B]

Would you consider it safe to touch your meter, main disco, and/or breaker panel enclosure while barefoot?

I will check the voltage to ground first using a voltmeter. If the voltage is zero will you be electrocuted?

I was taught to approach and touch such (absent metering) with the back of hand just in case, if significant enough voltage present, muscle contraction would cause you to literally grab onto the source.
If zero volts there us nothing to shock or electrocute you.

 

[ptonsparky]

Would you consider it safe to touch your meter, main disco, and/or breaker panel enclosure while barefoot?

Mine, yes. A customers, no. I've had a couple learning experiences to justify a No.

 

[Sea Nile]

If we are trying to keep the perspective on learning theory. In the controlled example, yes it's safe to touch.

But in the real world, you can't know ahead of time what state the system is in, so follow the advice of the veterans to be safe.

But for the sake of understanding theory, no a person will not be electrocuted.

 

[LarryFine]

I will check the voltage to ground first using a voltmeter. If the voltage is zero will you be electrocuted?

Zero volts = zero current = zero shock.

 

[LarryFine]

80 volts was a result of the splitting of the current between 3 circuit neutrals all tied together in a jbox. Additionally resistance of the equipment that the lighting circuit was turned on. And by metering between the neutral and grounding conductor at the switch that was being rewired it was measuring another conductor potential back to source. When the offending light was turned off no current present. Made a repair at attic jbox and no more shock and no more N/G voltage reading. Just continuity on N/G that would be expected on the home run.

The neutral joint must have been opened for that to have happen, and it would be expected.

The explanation is in the system capacitance from an imaginary neutral for a delta connected ungrounded system. Chapter 1 IEEE 142. You can verify it with a voltmeter as you have experienced it. Based on my calculation it will be 70 volts neutral to ground

A voltage from an open current pathway is very different from a voltage from capacitance.

 

[LarryFine]

I was taught to approach and touch such (absent metering) with the back of hand just in case, . . .

Mine, yes. A customers, no. I've had a couple learning experiences to justify a No.

I was, of course referring to normal circumstances. If I was on a fluctuating-voltage service call, definitely not.

 

[LarryFine]

If we are trying to keep the perspective on learning theory. In the controlled example, yes it's safe to touch.

But in the real world, you can't know ahead of time what state the system is in, so follow the advice of the veterans to be safe.

But for the sake of understanding theory, no a person will not be electrocuted.

Thank you for bringing this up. Just like with discussions such as why current sometimes rises with rising voltage vs sometimes lowering with rising voltage, we are of course talking in the theoretical, all-else-being-equal sense.

Yes, the caveats of the real world do apply, and it's even good to mention them sometimes. But, as an aside, and not to the point of discrediting the simple, to-the-point responses given as direct answer to the question as asked.

 

[bobby ocampo]

Voltage does indeed drive current. The average person might not be scared by DANGER: HIGH CURRENT!

Most are scared of high current because current is emphasized as the danger. With mA being used as the guide but not specifying that the range of current was at 120 volts in the experiment. Touch and step potential to prevent shock and electrocution is based on voltage calculation. IEEE 80

 

[bobby ocampo]

Would you consider it safe to touch your meter, main disco, and/or breaker panel enclosure while barefoot?

For the purpose of safety protocol you may not just want to touch any equipment that may be energized. You may want to use your voltmeter first to make sure that the panel is not energized before touching.

 

[bobby ocampo]

Because the impedance of the intended current pathway of the grounded conductor is so low in comparison to the average, dressed person standing on most surfaces.

Can you possibly show your comment by illustration please?

 

[bobby ocampo]

I would say in this instance it would be no different than touching a three wire dryer or stove casing.
think transformer, if you have a dry pot energized and touch the case what happens?

Remember the calls we all got at least once where someone complained a washing machine was shocking them?
Polarized plug backwards..

Why do you think someone is complaining on washing machine shocking them? Is it because of no return path to the source that the circuit breaker won.t trip? Or was it because the ungrounded conductor is suddenly touching the non current carrying part of the equipment?