Generally for healthy and earth faulted conditions in 4 wire system, we can write: a- Healthy condition : ir+is+it+in=0 b- Earth faulted condition: ir+is+it+in=ie (earth fault current which cause ELCB tripping) In health condition, when you remove neutral current, you force the neutral current to zero amount and ir,is,ir changing, but you have already : Ir+is+it=0 and in=0 and consequently ie=0 (ELCB no tripping) In fact in all earth faulted conditions we face to unbalance current systems but its vice versa is not correct.