ABB RED650 - Page 133

The plain Mho circle has the characteristic as in figure 49. The condition for
deriving the angle β is according to equation 6.
β = −
( )
−
( )
⋅arg argU I Z U
L L L L set pol1 2 1 2
1
IECEQUATION15027 V1 EN-US (Equation 6)
where
U L1L2
EQUATION1790 V2EN-US
is the voltage vector difference between phases L1 and L2
I L1L2
EQUATION1791 V2EN-US
is the current vector difference between phases L1 and L2
Z set1 
is the positive sequence impedance setting for phase-to-phase fault in zone direction
For Zone 1,
Z R PPZ j X PPZ
set
1 1 1 1 1= + ⋅
IECEQUATION15011 V1 EN-US (Equation 7)
where
R1PPZ1 is the positive sequence resistive reach for phase-to-phase fault for zone 1
X1PPZ1 is the positive sequence reactance reach for phase-to-phase fault for zone 1
For Zone 2-5 and RV
Z R Zx j X Zx
set
1 1 1= + ⋅
IECEQUATION15012 V1 EN-US (Equation 8)
where
R1Zx is the positive sequence resistive reach for zone x (x=2-5 and RV)
X1Zx is the positive sequence reactance reach for zone x (x=2-5 and RV)
Upol
is the polarizing voltage
Operation occurs if 90°≤β≤270°
1MRK 505 394-UEN A Section 7
Impedance protection
Line differential protection RED650 2.2 IEC 127
Technical manual