GE Multilin D60 Line Distance Protection System 9-59 THEORY OF OPERATION 9.1 DISTANCE ELEMENTS9j) FAULT-TYPE CHARACTERISTICThe fault-type characteristic applies to ground elements only and is achieved by checking the angle between:A ground element: I_0 and IA_2;B ground element: I_0 and IB_2C ground element: I_0 and IC _2The limit angle of the comparator is not adjustable and equals 50°. The fault-type characteristic is intended to block theground distance elements during double-line-to-ground faults.k) ZERO-SEQUENCE DIRECTIONAL CHARACTERISTICThe extra zero-sequence characteristic applies to ground zones 2 and higher and is achieved by checking angles between:A ground element: I_0 × Z D and –V_0B ground element: I_0 × Z D and –V_0C ground element: I_0 × Z D and –V_0The limit angle of the comparator is not adjustable and equals 90°. The zero-sequence directional characteristic improvesdirectional integrity for time-delayed operations after the memory expires.l) OVERCURRENT SUPERVISIONThe overcurrent supervision responds to the following currents:AB phase element: (IA – I B) /BC phase element: (IB – I C) /CA phase element: (IC – I A) /A, B, C ground element: | 3 × I_0 – 0.05 × I_1 |The following tables summarize the characteristics of the distance elementsTable 9–1: DIRECTIONAL MHO PHASE DISTANCE FUNCTIONSCHARACTERISTIC COMPARATOR INPUTS LIMIT ANGLEVariable mho I × Z – V V_1M COMP LIMITReactance I × Z – V I × Z COMP LIMITDirectional I × ZD V_1M DIR COMP LIMITTable 9–2: DIRECTIONAL MHO GROUND DISTANCE FUNCTIONSCHARACTERISTIC COMPARATOR INPUTS LIMIT ANGLEVariable mho I × Z – V V_1M COMP LIMITReactance I × Z – V I_0 × Z COMP LIMITDirectional I_0 × Z D V_1M DIR COMP LIMITDirectional I_2 × Z D V_1M DIR COMP LIMIT (removed when 3I_0 > OC SUPV andI_2 < CUTOFF)Fault-type I_0 I_2 50° (removed during open pole conditions or when 3I_0 > OCSUPV and I_2 < CUTOFF)Zero-sequence I_0 × Z D –V_0 90° (zones 2 and higher only; removed for zones 2 and higherduring open pole conditions)Table 9–3: DIRECTIONAL QUADRILATERAL PHASE DISTANCE FUNCTIONSCHARACTERISTIC COMPARATOR INPUTS LIMIT ANGLEReactance I × Z – V I × Z COMP LIMITDirectional I × ZD V_1M DIR COMP LIMITRight Blinder I × ZR – V I × Z R 90°Left Blinder I × Z L – V I × ZL 90°333
