Neutral distributed / Neutral no

[pintodacosta]

Good afternoon,

Can anyone explain me the defirence between a 3phase system with neutral not distributed and with neutral distributed.

Always made big confucion on that.

tx

 

[waross]

Three wires or four wires.
Some designers will not run a neutral if there is no possibility that phase to neutral loads will ever be installed. Some designers will run the neutral even if it may never be used.
Example: A plant with a number of 480 Volt breaker panels. Some panels have 277 Volt line to neutral loads connected. All panels in the plant will have neutrals installed.
A plant with a mix of 120:208 Volt panels and 480 volt panels. A design decision is made that all single phase loads will be connected either to 120 Volts or phase to phase at 480 Volts. All 120:208 volt panels will have neutrals. No 480 Volt panels will have neutrals.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[pintodacosta]

waross:

if we have:

- 3phase system 3 wire,there is no neutral, this means no distributed neutral;

- 3phase system 4 wire (L1+L2+L3+N), this means the neutral is distributed

in my case i have a TNS earthing system, and i have a 3 phase 5 wire (l1+L2+L3+N+PE), i consider this neutral distributed??

i am feedinn a 3phase board from a feeder in the substation, and due to the fact that in the plant is TNS, i will run a 5 wire system rom the feeder to the board, in order to calculate the Lmax for this circuit, i use the formula for neutral distributed, or neutral not distributed??

 

[waross]

I am not sure that I understand your question.
Often the neutral is installed to the first or main panel for the purpose of system grounding. It depends on circumstances whether the neutral is run to any or all sub panels.
If you are calculating the inductance under fault conditions, then use the neutral calculations for faults involving neutral current.
What are you trying to do and what is your application? I may be answering a completely different question than the question that you are asking.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[pintodacosta]

hi,

I am sizing a cable that comes from a 3ph distribution board to distribution board lets call him Board 1 that will feed 3phase and 1 phase loads.

In order i can make some calculations i need to know the Iminshortcircuit.

Please take a look at the example, that i attach, and tell me please what is the meaning of neutral distributed and neutral not distributed.

Tx for the support

 

[itsmoked]

No attachment found!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

If you use 4 conductor cable (Four power cores and one smaller grounding/bonding core) The neutral will be the same size as the line conductors.
If you are feeding phase to phase single phase loads you may not need a neutral. If you are using conduit and individual wires, your codes may allow you to reduce the size of the neutral core or wire.
We are a little confused by what exactly do you mean by "distributed neutral".
Waiting for the attatchment

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[pintodacosta]

Please take a look at the 2 screenshots

 

[waross]

I don't think that we have been answering the question that you have been asking. Sorry.
I am wondering:
In the case of multiple parallel conductors does this refer to an installation with multiple conductors per phase with one neutral conductor as opposed to an installation with parallel neutral conductors, one conductor included in each group of three phase conductors.
It is hard to grasp the context.
Possibly someone familiar with those calculations may be able to help.
It seems that example #1 is using a 100A breaker and a full size neutral.
Example #2 is using a 200A breaker and a 50% neutral.
??????

Bill
--------------------
"Why not the best?"
Jimmy Carter