CBCT Connection

ryt.

Rong. http://cr4.globalspec.com/comment/1068109

ryb ?

Three phases. Should be "cables". Neutral needed in case loads aren't exactly balanced.

The problem here is interpreting these TLAs and FLAs.

If there is a difference between the three phases, a neutral current will flow. There will be an imbalance in the RYB

The fourth, neutral cable must pass through the residual current detection. If there is then an earth fault, there will be an imbalance to operate the protection.

Do you have access to your national wiring standard? If so, read it. If not, then why not?

All four conductors have to pass through the CBCT. You don't want unbalance to trip the ELCB. Only earth leakage. That will happen only if the vector sum of the entire current is zero normally. Any earth leakage will make the vector sum no longer zero, so the ELCB (or RCD/ RCBO) trip. This is the reason that it is called "Core-Balance-Current-Transformer"

Not sure what a CBCT is (I doubt your working on dentistry scanners). Circuit breaker current transformer perhaps?

I don't know what type of electrical and grounding system you have so cannot say (they vary from country to country and even state to state).

Refer to your local Indian electrical standard and electrical codes of practice, the answer will be in there.

A simple reply is:

if there is a neutral conductor (TPN or 4-wire supply) - Yes.
if there is no neutral conductor (TP or 3-wire supply) - No.

Any protective earth continuity conductor should be outside the CBCT

Their are specific requirements in various electrical codes for switching the neutral. You probably need to consult with a local electrician who knows the local requirements. Most of the time you do not switch the neutral in most codes, but again codes vary. -- JHF