Getting rid of our present electrical system

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kwired said:
A lot of people don't respect 120 volts. This is because they have been shocked by things supplied by a 120 circuit or at least a 120 to ground circuit, and survived, usually with little noticeable damages.

If most common voltages here were 240 or more to ground I think there would be more respect to the dangers.

277 to ground is a fairly common voltage and does get more respect to the dangers then 120 does. It is not as common at our homes and many smaller businesses though.

Can't tell you how many times I have heard "it is only 110".

Can't tell you how many times I have heard that "220 really hurts" even though most of those incidents were likely only 120 to ground incidents and they just don't realize what it was they were dealing with when they got shocked.

Also heard many stories of how getting shocked from an open neutral is the worst, thing is there is no more then 120 volts involved a lot of the time, I think it is the fact they got hit by something they didn't expect to be "live" really plays a mind game on you to some extent.
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No disagreement with that.
We commonly used 110Vac for controls in our panels. It was derived from the secondary of typically a 500VA 400V/110V tranny with one seondary leg connected to earth (ground). It did all the control relays, contactors, pushbuttons, indicator lamps both panel mounted and in the field.

Now and again we'd be asked to provide a centre tap and earth that so there was maximum 55Vac to ground. No problem. Safer for the operators was the driver. Electrical safety courses I have attended suggest that 70 V is the lowest voltage that could result in a fatality.
 
Besoeker said:
No disagreement with that.
We commonly used 110Vac for controls in our panels. It was derived from the secondary of typically a 500VA 400V/110V tranny with one seondary leg connected to earth (ground). It did all the control relays, contactors, pushbuttons, indicator lamps both panel mounted and in the field.

Now and again we'd be asked to provide a centre tap and earth that so there was maximum 55Vac to ground. No problem. Safer for the operators was the driver. Electrical safety courses I have attended suggest that 70 V is the lowest voltage that could result in a fatality.
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For a dry skin, point contact situation.
Even single digit voltages (touch potential) in a pool of water may be fatal.
 
IMHO the chance of a wholesale change away from 120/240V is vanishingly small.

More plausible is stepping away from using a combined neutral and ground for the electrical service entrance, and then 're-grounding' at each facility. This would eliminate problems such as large current flow on common metal piping systems or communications cabling.

This change would not require different hardware, different appliances, or even much of a change in training; simply wire the 'main' like a 'subpanel'. We've already moved away from this for 'detached structures', and if the utilities followed the NEC rather than the NESC my bet is that this change would happen eventually.

I'm not holding my breath, but having the neutral-ground bond at the transformer and only at the transformer IMHO has a small but non zero change of happening.

Other 'small chance of happening' changes would be moving to resistance grounded residential service, where all breakers would be GFP or GFCI.

-Jon
 
winnie said:
IMHO the chance of a wholesale change away from 120/240V is vanishingly small.

More plausible is stepping away from using a combined neutral and ground for the electrical service entrance, and then 're-grounding' at each facility. This would eliminate problems such as large current flow on common metal piping systems or communications cabling.

This change would not require different hardware, different appliances, or even much of a change in training; simply wire the 'main' like a 'subpanel'. We've already moved away from this for 'detached structures', and if the utilities followed the NEC rather than the NESC my bet is that this change would happen eventually.

I'm not holding my breath, but having the neutral-ground bond at the transformer and only at the transformer IMHO has a small but non zero change of happening.

Other 'small chance of happening' changes would be moving to resistance grounded residential service, where all breakers would be GFP or GFCI.

-Jon
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Perhaps, but keep in mind the NEC acknowledges MGNs, and even BS7671 let you use MEN/TN-C up to the first disconnect when served by an outdoor supply.

Now, that does not mean that I think it should not change. But in all honesty as time passes I think there will be a gradual shift over the decades.
 
mbrooke said:
Perhaps, but keep in mind the NEC acknowledges MGNs, and even BS7671 let you use MEN/TN-C up to the first disconnect when served by an outdoor supply.

Now, that does not mean that I think it should not change. But in all honesty as time passes I think there will be a gradual shift over the decades.
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It has progressed some. First the elimination of allowing to bond the frames of ranges and clothes dryers to the grounded circuit conductor (with exceptions for existing installations) then the elimination of using the grounded conductor for bonding on outdoor feeders to separate structures (again with exceptions for existing installations).

I don't think the NEC can go much further then that other then to remove exceptions for existing installations. To make us run a separate grounded and grounding conductor for services would mean other standards used by the utility companies need to change. The most NEC can do for services would be to require separate grounded/grounding conductors up to the "service point". Which in some cases is pretty near the service disconnecting means and wouldn't really have much significant impact anyway.
 
kwired said:
It has progressed some. First the elimination of allowing to bond the frames of ranges and clothes dryers to the grounded circuit conductor (with exceptions for existing installations) then the elimination of using the grounded conductor for bonding on outdoor feeders to separate structures (again with exceptions for existing installations).

I don't think the NEC can go much further then that other then to remove exceptions for existing installations. To make us run a separate grounded and grounding conductor for services would mean other standards used by the utility companies need to change. The most NEC can do for services would be to require separate grounded/grounding conductors up to the "service point". Which in some cases is pretty near the service disconnecting means and wouldn't really have much significant impact anyway.
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Correct, but my point in addition to services is that the NEC lets you use an MGN for a private overhead feed.
 
We have been keeping grounds and neutrals separate back to the yard pole for a while now. What happens when the poco isolates the primary and secondary neutrals?
 
winnie said:
IMHO the chance of a wholesale change away from 120/240V is vanishingly small.

More plausible is stepping away from using a combined neutral and ground for the electrical service entrance, and then 're-grounding' at each facility. This would eliminate problems such as large current flow on common metal piping systems or communications cabling.

This change would not require different hardware, different appliances, or even much of a change in training; simply wire the 'main' like a 'subpanel'. We've already moved away from this for 'detached structures', and if the utilities followed the NEC rather than the NESC my bet is that this change would happen eventually.

I'm not holding my breath, but having the neutral-ground bond at the transformer and only at the transformer IMHO has a small but non zero change of happening.

Other 'small chance of happening' changes would be moving to resistance grounded residential service, where all breakers would be GFP or GFCI.

-Jon
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It will make sense to change after the first nuclear war, as much stuff will need to be rebuilt anyway.
 
next to impossible to say what v or i is fatal

the IEC has a study on body Z for various scenarios
wet, dry, large or small contact, arm to foot, arm to arm, etc
in general % of the population
25% ~750 ohm
<50% 1000 ohm
<95% 1400 ohm

lethal i (mA) = 175 / sqrt t or t = (175/i)^2 (fibrillation)
say 120 V and 1000 ohm if it clears in 2.1 sec survivable
say 240 and 1000, 0.53 sec
say 240 and 750, 0.3 sec

the key is a good ground/earth fault rtn path for fast clearing
 
Besoeker said:
Who wants to?
My view is that your system is complicated by the number of different voltages. Your residences alone have two different voltages compared to Europe where it is all 230V.
But it is what it is. I think that the costs of making it a single voltage for domestic means it won't happen any time soon.
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Now we both know that is a bit of a white lie. Brussels decreed the European “declared voltage” was to be 230V, each country changed their tolerance to -6% +10%.

Basically, nothing changed. UKPN are still fitting 433/250V transformers.
 
Galt said:
We have been keeping grounds and neutrals separate back to the yard pole for a while now. What happens when the poco isolates the primary and secondary neutrals?
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Take a transformer - they bond the housing to the primary grounded conductor so that if there is a fault in the transformer it has a low resistance path to help facilitate overcurrent protection.

They also do the same thing for the secondary if it is to be a grounded system. That leaves both tied together. Not using the primary neutral for current carrying purposed would be a potential solution to get rid of voltage rise on the MGN. Don't count on seeing that happening anytime soon.
 
kwired said:
A lot of people don't respect 120 volts. This is because they have been shocked by things supplied by a 120 circuit or at least a 120 to ground circuit, and survived, usually with little noticeable damages.

If most common voltages here were 240 or more to ground I think there would be more respect to the dangers.

277 to ground is a fairly common voltage and does get more respect to the dangers then 120 does. It is not as common at our homes and many smaller businesses though.

Can't tell you how many times I have heard "it is only 110".

Can't tell you how many times I have heard that "220 really hurts" even though most of those incidents were likely only 120 to ground incidents and they just don't realize what it was they were dealing with when they got shocked.

Also heard many stories of how getting shocked from an open neutral is the worst, thing is there is no more then 120 volts involved a lot of the time, I think it is the fact they got hit by something they didn't expect to be "live" really plays a mind game on you to some extent.
Click to expand...

If you are the ground point for an open neutral you pull the amps of that circuit (refrigerator) and your body load, if you are the ground point of an open hot you pull your bodies load only.
 
sameguy said:
If you are the ground point for an open neutral you pull the amps of that circuit (refrigerator) and your body load, if you are the ground point of an open hot you pull your bodies load only.
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Better think about that some more. The body has very high resistance so very little current flows. In the case of an open neutral you now have a series circuit with your body and whatever other loads are on the circuit. Because of the high resistance of the body, very little current flows, thus there is very little voltage drop through the other resistors/loads. Thus there is essentially no difference in a hot shock vs an open neutral shock.
 
electrofelon said:
Better think about that some more. The body has very high resistance so very little current flows. In the case of an open neutral you now have a series circuit with your body and whatever other loads are on the circuit. Because of the high resistance of the body, very little current flows, thus there is very little voltage drop through the other resistors/loads. Thus there is essentially no difference in a hot shock vs an open neutral shock.
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This is correct. If there's any difference, the current would be a hair less in series with a load.

I had someone question my suggestion of checking for open fuses by reading for voltage across a fuse with a solenoid tester. He thought the load would force enough current through the tester to destroy it, until I explained that, if it can withstand line-to-line testing, series testing wouldn't hurt it. He realized what I was saying after a few minutes.
 
Tony S said:
Now we both know that is a bit of a white lie. Brussels decreed the European “declared voltage” was to be 230V, each country changed their tolerance to -6% +10%.
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That's why I usually call the 230V/400V "nominal".
But you get differences in different locations and different times of the day. At home, the single was a little over 240V the last time I measured it. One of our 3-phase test supplies at work was about 390V.
 
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