ABB RED650 Technical Manual page 137

1MRK 505 394-UEN A
Line differential protection RED650 2.2 IEC
Technical manual
•jX
I
L1

3 I 0

I Z 1
L 1 set
IEC15000059 V1 EN-US
Figure 51: Simplified offset mho characteristic and vector diagram for phase
L1-to-earth fault
Operation occurs if 90°≤β≤270°.
Offset mho
The condition for operation of offset mho at phase-to-earth fault is that the angle β
between the two compensated voltages is equal to or greater than 90°, see figure
52. The angle will be 90° for fault location on the boundary of the circle.


   
arg U ( I 3 0 I K
L 1 L 1 N
IECEQUATION15022 V2 EN-US
U
comp

K Z 1
N set
U
L 1



    
) Z 1 arg U ( I 3 0

set L 1 L 1
Section 7
Impedance protection
    
U ( I 3 I 0 K ) Z
L 1 L 1 N

U
pol
I
L1
IEC15000059-1-en.vsdx
GUID-B1EF3931-7B86-4C7B-BCEA-3034482BA240 v2


 
I K ) Z 1

N set
1
set
•R
(Equation 12)
131