Zero sequence current protection specific applications in three-phase line

Zero sequence current protection specific applications can be installed one each on the three-phase line current transformer (CT), or let the three phase wires together through a  Circuit breaker  CT, can also be installed on a neutral line N zero sequence CT, the use of these CT to detect the phase current vector and that the zero-sequence current Io, IA + IB + IC = Io, when the line is connected to the three-phase load on the full balance (without ground fault, and does not consider the lines, electrical  electric meter  leakage current), Io = 0; when the line connected on the three-phase load imbalance, then Io = IN, at this time of the zero-sequence current  electric transformer  current iN; when one phase ground fault occurs, inevitably produce a single ground fault current Id, at this time the detected zero-sequence current IO = IN + Id, a three-phase and single-phase unbalanced current vector sum of currents.