9-2 D30 Line Distance Protection System GE Multilin9.1 DISTANCE ELEMENTS 9 THEORY OF OPERATION99.1.3 DISTANCE CHARACTERISTICSa) DEFINITIONSThe relay shapes its distance characteristics using phase angle comparators and voltage and current phasors estimated asdescribed in the previous section.The following definitions pertain to all of the distance functions:• IA, IB, I C : phase A, B, and C current phasors.• IG : ground current from a parallel line.• VA, VB, VC : phase A to ground, phase B to ground, and phase C to ground voltage phasors.• ( )_1: positive-sequence phasor of ( ) derived from the phase quantities.• ( )_2: negative-sequence phasor of ( ) derived from the phase quantities.• ( )_0: zero-sequence phasor of ( ) derived from the phase quantities.• ( )M: memorized value of ( ).• Z: reach impedance (REACH RCA).• ZREV: reverse reach impedance for non-directional applications (REV REACH REV REACH RCA + 180°).• ZD : directional characteristic impedance (1 DIR RCA).• ZR : right blinder characteristic impedance: Z R = RGT BLD sin (RGT BLD RCA) 1 (RGT BLD RCA – 90°).• ZL : left blinder characteristic impedance: ZL = LFT BLD sin (LFT BLD RCA) 1 (LFT BLD RCA + 90°).• K0: zero-sequence compensating factor: K0 = (Z0/Z1 MAG Z0/Z1 ANG) – 1.• K0M: mutual zero-sequence compensating factor: K0M = 1/3 x Z0M/Z1 MAG Z0M/Z1 ANG.• : non-homogeneity angle setting (NON-HOMOGEN ANG).b) DIRECTIONAL MHO CHARACTERISTICThe dynamic 100% memory polarized mho characteristic is achieved by checking the angle between:• AB phase element: (I A – IB) Z – (VA – VB) and (VA – VB)_1M• BC phase element: (I B – I C) Z – (VB – VC) and (VB – VC)_1M• CA phase element: (IC – I A) Z – (VC – VA) and (VC – VA)_1M• A ground element: I A Z + I_0 K0 Z + I G K0M Z – VA and VA_1M• B ground element: I B Z + I_0 K0 Z + I G K0M Z – VB and VB_1M• C ground element: IC Z + I_0 K0 Z + IG K0M Z – VC and VC _1MThe limit angle of the comparator is adjustable enabling the user to shape the characteristic as a mho or a lens as shown inthe figures below.The memory-polarized mho characteristic has an excellent directional integrity built-in as explained in theMemory polarization section.
