GE Multilin D60 Line Distance Protection System 6-256 ACTUAL VALUES 6.3 METERING6Loop impedance is defined as Z##=|Z##| Angle=R##+jX##, in secondary ohms and ## is the loop indication (AB, BC, CA,AG, BG, and CG respectively).They are calculated as per the following equations.Where VA, VB, VC are phase voltage phasors in secondary volts; IA, IB, IC are current phasors in secondary amps, I0 isthe zero sequence current phasors in secondary amps; and IG is the ground current from the parallel line scaled to thesource phase CT in secondary amps.Z0/Z1 is the zero sequence impedance to positive sequence impedance ratio, and Z0M/Z1 is mutual zero sequence imped-ance to positive sequence impedance ratio, both are settings taken from the first enabled ground distance zone (count fromzone 1 to zone 5).ZAG, ZBG, ZCG are calculated only if at least one ground distance zone is enabled; otherwise all the metering quantities forground distance impedance (ZAG, ZBG, and ZCG) are reset to zero, including magnitude and angle. Note that VTs of thedistance source must be connected in Wye if the ground distance element is enabled.MESSAGE CG LOOP REACTANCEXCG: 0.00 OhmsMESSAGE CG LOOP IMPEDANCEZCG: 0.00 OhmsMESSAGE CG LOOP IMPEDANCEANGLE: 0.00 DEGZAB VA VB–IA IB–---------------------- ZBC = VB VC–IB IC–----------------------- ZCA VC VA–IC IA–-----------------------==
