Neutral Line

NGR?

To the best of my knowledge .. "NGR" means Neutral Grounding Resistor and obviously, a neutral is required.

Answer is already in your question. It is necessary to have Neutral in a system to have NGR. You are hereby advised.

Rather it is the other way round. If you don't have a neutral you need not have an NGR.

NGR will be connected to the star point, could it be possible to have 3phase 4wire system.

Ronald,

It seems that you are asking if it is OK to earth the star point, or neutral point at the source through a Neutral Grounding Resistor and then only run a 3 wire system out to the loads without including a neutral conductor. If that is your question, then yes it is electrically functional.

The effect will be current limited earth faults, reduced damage upon fault, and improved fault protection. Treat the system protection and metering as if you were supplying all 4 wires to the loads.

CJM

thanks, another setup of question, let say i will connect the star point to NGR then to earth, is it possible to get another neutral line from star point going to load, to have a system of 3phase, 4wire.

It is not advised. If the neutral is taken before NGR the earthfault current flow will bypass NGR, thus the purpose will be defeated.

If you connect the start point to the NGR then the NGR is grounded so that you have a resistor beteen the star point and the ground.... If I understood well(?) it is OK to run a Neutral line from the start point to the loads. You will now have a 4 wire system. If a fault occurs between phase and ground the short circuit current will be limited by the NGR resistor.

If the requirement of the NGR is to limit drastically the ground - Neutral fault current, then the Neutral 4th wire can be a problem.

BUT THEN A FAULT BETWEEN PHASES IS ALSO GOING TO BE A HIGH CURRENT PROBLEM!

NGR are not normally required when grounding the star point at a transformer. You need the earth resistance to be minimum and within the norms.

You may find this paper informative, please download and study:

schneider-electric ect177.pdf

Dear Mr. Ronald A,

Yes. The answer is YES for your Quiery, The role of NEUTRAL is different from that of NGR.

An electrical system can be properly designed such that there will be little current flow through Neutral, but Neutral is a Must.

DHAYANANDHAN.S

CR4 MEMBER,

INNDIA.

where can I buy this neutral? is it available in the same shop where I bought the NGR?

Dear Guest,

For smaller capacity, the same wire size will work as neutral.

For larger capacity, 1/2 Core, i.e 50 % of the cable size will work as NEUTRAL CORE.

DHAYANANDHAN.S

But some places, i noticed that double size neutral is used. why?