ABB RED650 Technical Manual page 132

Section 7
Impedance protection
126
X
(a)
Rset
Xset
R
Forward
(d)
X
Rset
Xset
R
Xset
Rset
R
Forward
(a) and (c) are for Zone 1, Zone 2 and Zone 3-5 when DirModeZ3-5 = Forward.
(b) and (d) are for ZoneRV and Zone 3-5 when DirModeZ3-5 = Reverse
(c) and (f) are for Zone 3-5 when DirModeZ3-5 = Non-Directional
IEC15000055 V2 EN-US
Figure 48: Mho and offset Mho characteristics
For each zone, the impedance is set in cartesian coordinates (resistance and
reactance) which is the same as for quadrilateral characteristic.
The ZMFPDIS function has only one set of reach setting so the reverse will be the
same as for the forward reach, meaning that the non-directional offset mho
characteristic will always be centered around the origin. In detail, for Zone 1, the
resistive and reactance reaches for phase-to-earth fault and phase-to-phase fault are
set individually using the settings R1PPZ1, X1PPZ1, R1PEZ1, X1PEZ1, X0Z1 and
R0Z1. In Zone 2-5 and Zone RV, the same zone reach settings are used for phase-
to-earth fault and phase-to-phase (R1Zx, X1Zx, X0Zx and R0Zx, x=2-5 or RV).
Theory of operation
The mho algorithm is based on the phase comparison of an operating phasor and a
polarizing phasor. When the operating phasor leads the reference polarizing phasor
by 90 degrees or more, the function operates and gives a trip output.
Phase-to-phase fault
Mho
X
(b) (c)
R
Xset
Rset
Reverse
Mho Characteristics
(e) (f)
X
Rset
Xset
R
Xset
Xset
Rset
Reverse
Offset Mho Characteristics
1MRK 505 394-UEN A
X
Rset
Xset
R
(a)-(f)
For phase-to-phase fault
Rset
Non-directional
Xset
For phase-to-earth fault
Rset
Xset
X
XNZx
RNZx
Rset
Xset
R
Rset
Non-directional
GUID-D162893C-918A-4DDA-AAC2-0D0A814D85C1 v1
Line differential protection RED650 2.2 IEC
Technical manual

R Zx 1

X Zx 1
 
R Zx RNZx 1
 
X Zx XNZx 1

X Zx X Zx 0 1

3

R Zx R Zx 0 1

3
IEC15000055-2-en.vsdx
SEMOD154224-46 v6
SEMOD154224-240 v2