System Neutral and Earth Bus

This has been covered in earlier CR4 threads, pleas search.

technically the shorting of neutral awith earth is not preferable at user level, nor most of the codes permit this. This is due to the alternate path created to the earth fault to flow through (and also the neutral current will have now two paths to follow, bot at equipotential.

Also it will have a bit problem at substation level, where the neutral is shorted with/without NGR.

Please read the article on earthing systems in Wikipedia.

As earthing is connected to earth the equipment body ,where as neutral is connected for fault current to flow in fault condition means current carring.

We have PE and PEN systems of earthing.

PE is protective earth,which is a seperate earthing method.No neutral is combined.

PEN is protective earth and neutral,where earth and neutral is linked or combined.

Some use PEN and some use PE on their installations,depend on which method is most suitable for your method of installation.Pls,read yr books on protective measures or yr regulations and you will get the best answer to yr question.

Knowing fully well that neutral is a return path for healthy current which goes back to source,earth is a return path for fault current(earth fault) which goes to ground(general mass of earth).

Read more and understand yr earthing system to apply,but in most cases,PE(seperate earthing) is used.

Patrick Whowha

If you are bonding the earth and the neutral "also" at the switchboard apart from at the source, then you are violating the law of the land. You are not permitted by law to do so. If you are bonding the earth and the neutral only at the switchboard, then this also is against the Code, as neutral has to be bonded to earth only at the source end and not at the load end.

Dear all,

1) If the switchboard is the first switchboard from the transformer, this is correct.

2) This is permitted, if your area allows TT system. The regulations for TT system must be followed.

Advantage of 1) over 2)

Against earth-faults

1) is TN system, OCD overcurrent protection also protect the circuit against earth-faults. 2) is TT system and if the earth resistance between two separate earth electrodes is not low enough, overcurrent protection device will not trip on an earth-fault, thus you need additional RCDs (earth-fault or earth leakage relay).

Immunity to nearby lightning strike

1) Transformer and switchboard is equipotential against lightning. 2) Transformer and switchboard may have hight potential difference, which may break the insulation of both transformer and switchgear.

Advantage of 2) over 1)

Earth-fault current in 2) is smaller than in 1). This is the main advantage of 2) over 1). Facility damage by earth-fault in 2) is smaller than in 1). Voltage dip during an earth-fault is smaller in 2) than in 1).

Regards