Measured impedance at source node of a distribution feeder for inter phase faults

Distance protection is not utilized in distribution networks, unlike the transmission systems, due to the inherent characteristic of the distribution networks and the additional required facilities of the distance protection, compared with over-current protection, which is in use in the distribution systems. This paper presents the measured impedance at the source node of a distribution feeder in the case of inter phase, phase to phase and three phase, faults. The ideal tripping characteristic is presented for distribution feeders. The variation of the measured impedance and consequently the distance relay ideal tripping characteristic is investigated as a function of the distribution system conditions.