Shock From Neutral?

It depends. If the phase loads are unbalanced, the neutral will carry current. And if it is ungrounded, it may also present a shock danger. And that's even before addressing harmonics.

The neutral usually is earthed at some point or other. So theoritically the voltage neutral to earth is zero.

If the loads are true 3 phase, then by KCL the phase current phasors will add up to zero and hence no neutral current.

If you have either individual phase to neutral (ie single phase loads) then depending on the amount of unbalance the neutral will carry the current (again KCL) , only here the current will be at the maximum equal to the maximum phase current (ie equal to the maximum of the 3 phase currents), however it will be usually much lesser than that unless it is only one phase loaded.

This may happen even in case of some faults, with the same effect.

In these cases the current flowing through the neutral will generate some voltage at the user end (the distribution point is earthed + IR drop between that and user terminal)

However these currents, usually, will generate very low voltage may be of the order 10-20V at max, assuming the other things (earthing, loading etc) are in order.

"In theory, theory and practice are the same. In practice, they are not." -- Lawrence Peter Berra

In practice, a percentage of the phase loads are switching mode power supplies so neutral carries their harmonic current, plus any imbalance. This harmonic neutral current is only eliminated by delta-wye wired transformers, which I never find on residential utility poles (mid-west US). Furthermore, the majority of residential power is provided by single phase circuits where the neutral current equals the phase current.

So there are hundreds of thousands of miles of neutral conductors that have some IxR voltage drop.

Where the neutral conductor is earthed, that made electrode has a resistance in the ballpark of 300 ohms. So, in practice, the earth is pulled closer to neutral voltage around each grounding electrode. Measured from anywhere else on Earth - remote from grounding electrodes - neutral still has a voltage.

This is why the Code is so "obsessed" with bonding all conceivable electrodes to equipment ground and creating grounding electrodes from swimming pool foundations, domestic animal housing, etc. We are trying to avoid providing a circumstance where our body is the connection between equipment ground (utility company neutral) and remote contact with Earth (away from grounding electrodes).

P.S. You mentioned "10-20V", this is a frightening high (abnormal) voltage for neutral.

As long as the neutral is properly connected to the circuit, it is safe to touch, the electricity is taking the easiest path, and our bodies have a lot of resistance, on a dry day.

Like posted, if the neutral is disconnected, it has the potential of the whole load, and will shock you to death.

Don't be presumptuous and always consider neutral safe. Many maintenance calls have been for a bad connection on a neutral, and until properly connected, that wire is as dangerous as any.

It has already been mentioned, I just want to emphasize about the second part of the question: Will any one get shock from neutral?

The answer is

No for a solidly and properly grounded system

Not No (YES) for solidly but improper ground system

Not No (YES) for HRG (High Resistance Grounding), or LRG or ungrounded system

If a ground fault occurs to a phase in a HRG (or ungrounded) system, the system doesn't trip and the faulted phase gets the same potential as ground. With this condition, phase to neutral voltage exists between the neutral and ground and touching neutral will cause severe shock to death.

In the process plant, where tripping a load is not desirable for simply a single phase to ground fault, the HRG system is used with a ground fault monitoring system (if a ground fault occurs for a process pump, the operator identify it from the monitoring system and change over to the standby pump before stopping the faulty one for maintenance without disturbing the process). However, this system is not permitted where single phase load is used because of the safety issue.

The bottom line is 'Never assume the neutral is safe to touch in a live system'.

-MS

The neutral of your building is properly tied to the equipment ground and grounding electrodes at the service entrance. In turn, this is tied to the neutral conductor of the utility distribution system. If there is any net current flow on this utility conductor, or on the neutral conductor of the building circuit, there will be a voltage drop.

Let's say the I*R drop is one volt within the building, and three volts on the utility neutral conductor. You will have a voltage difference of between two and four volts from neutral to earth ground. Even two volts RMS is enough to get a sensation if you skin is not dry. It will be positively painful if you are soaking wet, like sitting on wet concrete at the edge of the pool.

Please note that if you touch only equipment ground, the voltage difference from you to earth ground in this instance is three volts!

<...The neutral ... is properly tied to the equipment ground and grounding electrodes at the service entrance...>

Not in TT earthing systems, it isn't!

And TN-S, TN-C and TN-C-S systems don't have a local ground electrode.

http://en.wikipedia.org/wiki/Earthing_system

I stand corrected on TT earthing systems.

<... And TN-S, TN-C and TN-C-S systems don't have a local ground electrode. ...> Here I disagree. I have always found a made electrode and/or all existing local ground electrodes (water pipes, etc.) tied to equipment ground at the main service disconnect of every TN-S, TN-C and TN-C-S system I have viewed. I also recall a "shall" statement in the NEC about a made electrode where there are no existing electrodes... Has this been waived recently? Anyone?

Yes, there are many circunstances that a nuetral will carry current. you should always handle a nuetral as a potential conductor.

Greetings.

In older buildings the neutrals of multiple circuits were sometines bunched together in a conduit box.

If the neutrals from two circuits are bunched together and you have your first circuit turned off you can get zapped by the neutral of the second hot other circuit when you pull the bundle apart to work on it. The hot side of the second circuit through the appliance or even a light bulb thru the second neutral and You become the neutral's circuit completion when you separate the neutrals.

This has happened to many times to Experienced Electricians and Technicians.

I know im going to get hate for this one but it must be said

IGNORE ALL THE ENGINEERS! Dont even bother reading their replies....

Always treat the neutral as it is live. The only time you dont have to is you flip the main disconnect. As an electrician and then an electrical engineer I can tell you of countless fatalities from people who assume a balanced system or neutral carries no voltage/current.

Betterto be safe, remember it only takes 50mA to stop your heart! Thats the current from a 6watt bulb

Most of the engineers who have responded to this topic have pointed to several ways in which the neutral can carry current or be (unintentionally) ungrounded, and therefore live (i.e., potential to ground).

So what is this drivel about "ignore all the engineers", coming from a no-name guest?

Nonetheless, despite the insults, you are correct to note that supposed neutrals might not actually BE neutral. And don't necessarily depend on the color of the wire, by the way. If it becomes disconnected, its "real color" may change....

Hi, this is Bhavesh (India)

It is known that the Earth is bigest conductor and considering Neutral as return is to ensure the electrical path completion to the supply line, infact Neutral is connected to Earth and since when you touch the Neutral you should not get shock, this is because you hold same electrical potential and there is no current flowing through your body (the body part which is touching the Neutral line and the Earth..)

Hope this may help you..

Thanks

bye

I must disagree, Bhavesh. As I said (in message #6), There is usually a voltage difference between the utility company's "ground" and the true earth potential. This is what your building equipment ground and grounding electrodes are connected to. (This difference is what makes cows unproductive if milked with powered equipment.) If all the loads on the utility company equipment are between phases (as mandated in California, US), the neutral conductor no longer carries any load current except during fault conditions. This is the only condition I am aware of when neutral potential matches the earth potential.

The neutral is a current carrying conductor. In multiwire branch circuits is carries the imbalance. It you should break the neutral under load it will arc and if you are unfortunate to get across the gap, you will become the conductor. Very Dangerous.

Dear,

There may be two cases.

Case1. Three Phase balanced System

In this case parameters like line voltages, phase voltages, phase impedences are same with respect to other phases. So current meeting at point becomes zero as per KCL .In this way we get neutral at star point i.e. its potential difference w.r.t. earth becomes zero in this case if u touch neutal definitely u will not get shock.

Case 2. Three phase Unbalanced system

In this case parameters like line voltages, phase voltages, phase impedences are not same with respect to other phases. So current meeting at point doen't become zero so it will show some voltage w.r.t. earth. Now if u touch such neutral u will definitely get shock if the neutral is not properly grounded.