if neutral point is missing...

[electrics]

Hi, in the electrical installation code of my country says something like this:
if a neutral point is missing or can not be found, one of the phases are grounded and used as a neutral line. (not mot a mot but roughly so)
so what do you think ? is it possible or just a mistranslation from german standards?

 

[Dennis Alwon]

I cannot make heads or tails of it

 

[Smart $]

Hi, in the electrical installation code of my country says something like this:
if a neutral point is missing or can not be found, one of the phases are grounded and used as a neutral line. (not mot a mot but roughly so)
so what do you think ? is it possible or just a mistranslation from german standards?

I believe from an NEC Code perspective, if the source has no neutral point AND all other connection points isolated from ground, one connection point can be grounded... but it cannot be used as a neutral connection; it can only be used as a grounded conductor connection.

 

[electrics]

what do u mean with other connections? a delta connection has three connection for example.
and what do u mean when you say "can not be used as neutral connection"?

 

[electrics]

ooh, I found the same discussion here, this guy is german
http://forums.mikeholt.com/showthread.php?t=130393

 

[Smart $]

ooh, I found the same discussion here, this guy is german
http://forums.mikeholt.com/showthread.php?t=130393

Seems to me you started that discussion about2 1/2 years ago... and I don't believe anyone else is German (i.e. a native national).

 

[electrics]

from book of giridharan electrical system design ,

 

[augie47]

Your first post quoted incorrectly by saying the phase wire would be a neutral.
Your last post (quote) indicates that if no neutral is available, one phase conductor will be grounded.
It will not, however, be a neutral per the definition of "neutral".
I see no problem.

 

[electrics]

what I can not understand is , how is a phase conductor is grounded , can you show me?

 

[JoeStillman]

Here in the USA, we call that a "Corner Grounded Delta". The grounded (earthed) phase is not a neutral, just a grounded circuit conductor. When you're not corner grounded, you have what I call a "floating delta" which is not ideal because your voltage to ground can be almost anything, and ground fault currents don't trip any breakers until you get another ground fault on another phase.

 

[augie47]

If you have a power supply such as a transformer with a 2 wire or 3 wire delta secondary you have no ground reference until you make a ground connection... nothing is connected to earth.
You can take one of those phase and treat it just as you would the neutral if one was present, Simply bond it to your grounding electrode system as if it were a neutral

 

[electrics]

maybe but what about pen conductor ? is it possible that you can imagine a phase conductor can be used as PEN conductor. In an old code it is said it is possible but here above it is forbidden in modern days.
So you talk about delta, but here it is not said wye or delta. What you said senses true though.
Anyway , I will be very glad to learn what you all think in this issue..

 

[augie47]

In the above diagram, remove the "N" wiring completely....
You then have a straight delta. Now connect "B" to ground.

 

[electrics]

you mean with grounding phase conductor the point at which two winding connects or what? What I can not understand is how can you ground a phase conductor downstream. If what you talk is upstream with reference to transformer secondary windings than what I asked first is valid true?

 

[electrics]

so sayinG grounding a phase conductor you mean the neutral line dividing a phase winding in two or the B point grounded which is in fact not a phase conductor but just a connection point of two phase conductor. ?

 

[electrics]

yes, as always, no one knows what does "phase conductor shall not serve as pen conductor" mean. I am accustomed to this

 

[electrics]

Reference to IEC/EN 60364-4-41 413.1.3
All exposed conductive parts of the installation must be connected to the earthed point of the power system
by protective conductors which must be earthed at or near to each relevant transformer or generator.
Exposed conductive parts that are accessible at the same time must be connected to the same earthing
system, either individually, in groups or collectively.
Normally the earthed point of the power system is the neutral point. If a neutral point is not available or
accessible, a phase conductor must be earthed. The phase conductor must not serve as a PEN conductor.
In fixed installations a single conductor may serve both as a protective conductor and a neutral conductor
(PEN conductor).

 

[JoeStillman]

All they are saying is that the grounded phase conductor may not serve double duty as a PE conductor. You must have a dedicated PE conductor when the system is corner grounded. A PEN conductor serves as a neutral and an earth conductor. Since the grounded phase conductor is not connected to any neutral point, it may not serve as the PE conductor.

Here in the USA, the only place we use a PEN conductor is between the utility and the service disconnect. From that point onward, PE and N must be separate.

 

[jim dungar]

yes, as always, no one knows what does "phase conductor shall not serve as pen conductor" mean. I am accustomed to this

Translating technical language is very difficult. Translating technical slang can be even harder.

Most of the participants on this forum are not familiar with the technical terms used in most European countries. For example we use the phrase WYE instead of STAR to describe a particular transformer connection.
When you include the number of different voltage systems used regularly in the US, and the fact that we do not have a single national standard method for describing all of them, I am not surprised there is as much misunderstanding as we have.

In the US we do a very poor job of describing our reference points. for the most part we only use the term Grounded and Grounding. A Grounded conductor is a voltage system conductor (e.g. neutral) that has been purposely connected to a reference plane (about the same as your PEN). A Grounding conductor is an extension of the reference plane (about the same as your protective conductor PE). In most situations this reference plane is dirt, although that is not always possible such as in ships, airplanes, space stations and other isolated systems in which case I believe our grounding conductor may be called 'application frame' in some translations.

 

[Sahib]

I think the purpose of grounding a phase conductor, when no other means for grounding service conductors exists is an attempt at discharging lightning surge current to ground through the service conductors.

Obviously, it can not used as a PEN, because its potential at a given point, where its connection to ground is broken accidentally, can raise to its rated high value with respect to remote ground, unlike a 'true neutral' whose potential would not raise to such high value under such similar condition.