Lighting Design

The three phases AND the neutral MUST go through the ELCB. The vector sum of all three phase currents + neutral is zero. When there is any earth fault/leakage, that current will flow outside the summation CT in the ELCB, so it will trip. As long as there is no current flowing to earth, it will not trip. You can relax.

Sorry for the incomplete answer.. RCD and ELCB operate on the same principle, that they sum up vectorially all healthy currents - the three phase currents and the unbalanced part through the neutral. Any aberration from this indicated an earth leakage, and it will trip.

this is theory. not the answer for my question. well, you said RCD and ELCB works on same princople. Then what is the difference between them and why they called so??

Oh sorry ... i didn't know you wanted that. There are earlier threads in CR4 which touch on this..

Here is a link anyway .. http://en.wikipedia.org/wiki/Residual-current_device

u jus cant use rcd at the incomer. it has to be connected in series with a mcb.....if u r talking abt rcbo then i take back my point.................now abt phase unbalance.......if phase unbalance s more thn 4% then it s really a bad thing.....so the circuit has to be opened........the rcd has setting of 30mA , 100mA, 300mA, 500mA and 100mA ......based on tht if there s unbalance in the phase currents around this range then certainly it will trip...and u should be happy for tht....also before rcd , your mcb will trip due to overcurrents as a result of unbalances......

Are you sure RCD/RCBO/ELCB will trip on unbalanced currents ?

My knowledge is that all four wires (RYB&N) pass through the core of the summation CT. The vector sum of all four currents, even with unbalance, is always zero. If an earth leakage happens (usually due to insulation failure) the vector sum of the 4 currents is no longer zero, and the power is cut off.

Im design electric for the building but I dont no arangement the emegency lingt in basement 1 and 2 of the building-21 floors. Do you hepl me?