GE L90 Instruction Manual page 553

9 THEORY OF OPERATION
 Z + I_0  K0  Z  K0M  Z
I + I
A L L G
 Z + I_0  K0  Z
I
A L L
Overcurrent supervision: | 3  I_0 | = 4.09 A  3 A
•
Reactance difference angle = | –3.9° – 24.8° | = 28.7°  75°
•
Zero-sequence difference angle = | –19.8° – 0.0° | = 19.8°  75°
•
Negative-sequence directional difference angle = | –19.8° – 0.0° | = 19.8°  75°
•
Right blinder difference angle = | –93.0° – (–109.2°) | = 16.2°  90°
•
Left blinder difference angle = | 82.9° – 108.7° | = 25.8°  90°
•
Fault-type comparator difference angle = | 19.8° – 19.8° | = 0.0°  50°
•
All six comparators and the overcurrent supervision are satisfied.
The Quad Phase A ground element will operate for this fault.
GE Multilin
= 57.0 V 108.7°
– V
L A
= 45.8 V 82.9°
L90 Line Current Differential System
9.3 DISTANCE ELEMENTS
9-29
9