A polarised-mho phase comparator connected for red-phase-to-earth faults on a single-end line is supplied with inputs: S = IZR-V S = V-k/60 VB where voltage V = VR-N and current I=IR + KI resid. (ie current includes earth-fault compensation) so that in terms of system impedance the comparator inputs can be shown to be: S = ZR-Z S = 3k ( /-30 + p /30)Zs 2+9 Zso where p =- and q =. Zs Zo Y/N + (1+k) Z Zs and Z are positive-sequence source and line impedances. Zso and Zo are zero-sequence source and line impedances. Construct the polar diagram for this relay assuming k = 0.2, IZSI/IZRI = 5, p =3/0, q = 2.5/0 and that the argument of Zg is 90 and of ZR = 70