Versatile Protection by ELCB- e.g. 4-pole type, Even when fed with 3 Single-Phase Independent Power Supply Sources
1. A 4-pole ELCB, providing passage to balanced 3 phase & 1 neutral through it’s torroid forming the primary winding of the sensitive current transformer, serves very effectively to guard against leaking current of the order of 5 mA – 30 mA -50 mA and beyond , with prompt clearance of the leaking circuit in a matter of 30-50-100….m.seconds.The consumer side is distributed 3-phase loads plus some single-phase loads. Problem arises when the main 3-phase, 4 wire balanced supply line is switched off by the supply agency and alternative stand-by 3-phase balanced supply is not available.
The gap may be asked to fulfill with 3 Nos separate sources of 1-phase diesel generators, the voltage of which shall be unequal, unbalanced in phase, rather placed at random phase displacement, may be filled with harmonics and even some d.c. components, connected in star with common neutral (earthed) as shown in below vector diagram.