208V/120V in Lighting Distribution Board(Grounding)

[kimseunghee]

I'd like to know system ground for lighting distribution. The transformer(Dy) 480V/208V is arranged for lighting distiribution and lighting fitting(120V line to neutral) is fed from each mcb(line-neutraL) from lighting distribution board. This mcb(two-pole, L-N) is provided with RCD. I expect that mcb will trip against earth fault.
However, 208V, L-L are fed to each socket from mcb(L-L) at same distribution. This mcb(two-pole, L-L) is provided with RCD as well. Will this mcb trip against earth fault of any phase ? or affect on MCCB at primary side of transformer rather than ?

 

[waross]

I believe that you are referring to what we call a Ground Fault Interrupting Breaker, or GFI.
The devices work by measuring and summing all curent through the device. The currents should sum to zero. Any non-zero current is assumed to be returning through ground instead of through the breaker. If the current diference exceeds the set point, the breaker is tripped off.
These devices will NOT provvide line to line shock protection. If a person contacts two live lines, the device will only trip on ground protection if enough current diverts through the person's body through another path to ground to trip the device.

Bill
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