GE UR Series L90, Instruction Manual

Page: 567 / 846

GE Multilin L90 Line Current Differential System 9-21
9 THEORY OF OPERATION 9.3 DISTANCE ELEMENTS
9
9.3.3 DISTANCE CHARACTERISTICS
a) DEFINITIONS
The relay shapes its distance characteristics using phase angle comparators and voltage and current phasors estimated as
described in the previous section.
The following definitions pertain to all of the distance functions:
• I
A
, I
B
, I
C
: phase A, B, and C current phasors.
• I
G
: ground current from a parallel line.
• V
A
, V
B
, V
C
: 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
).
• Z
REV:
reverse reach impedance for non-directional applications (
REV REACH

REV REACH RCA
+ 180°).
• Z
D
: directional characteristic impedance (1

DIR RCA
).
• Z
R
: right blinder characteristic impedance: Z
R
=
RGT BLD

sin (
RGT BLD RCA
)

1

(
RGT BLD RCA
– 90°).
• Z
L
: left blinder characteristic impedance: Z
L
=
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 CHARACTERISTIC
The dynamic 100% memory polarized mho characteristic is achieved by checking the angle between:
• AB phase element: (I
A
– I
B
)

Z – (V
A
– V
B
) and (V
A
– V
B
)_1M
• BC phase element: (I
B
– I
C
)

Z – (V
B
– V
C
) and (V
B
– V
C
)_1M
• CA phase element: (I
C
– I
A
)

Z – (V
C
– V
A
) and (V
C
– V
A
)_1M
• A ground element: I
A

Z + I_0

K0

Z + I
G

K0M

Z – V
A
and V
A
_1M
• B ground element: I
B

Z + I_0

K0

Z + I
G

K0M

Z – V
B
and V
B
_1M
• C ground element: I
C

Z + I_0

K0

Z + I
G

K0M

Z – V
C
and V
C
_1M
The limit angle of the comparator is adjustable enabling the user to shape the characteristic as a mho or a lens as shown in
the figures below.The memory-polarized mho characteristic has an excellent directional integrity built-in as explained in the
Memory polarization section.