R
R
X
R
X
R
R
X
R
Forward
Reverse
Non-directional
(a)
(b)
(c)
X
X
Rset
Xset
Rset
Xset
X
R
Rset
Xset
(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
(d)
(e)
(f)
Mho Characteristics
Offset Mho Characteristics
1
1
0
1
3
0
1
3
Rset
R Zx
RNZx
Xset
X Zx
XNZx
X Zx
X Zx
XNZx
R Zx
R Zx
RNZx
Rset
Xset
Xset
Rset
Rset
Xset
Xset
Rset
Rset
Xset
Xset
Rset
(a)-(f)
For phase-to-phase fault
For phase-to-earth fault
Forward
Reverse
Non-directional
1
1
Rset
R Zx
Xset
X Zx
IEC15000055-2-en.vsdx
IEC15000055 V2 EN-US
Figure 36:
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
SEMOD154224-46 v6
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
SEMOD154224-240 v2
Mho
GUID-D162893C-918A-4DDA-AAC2-0D0A814D85C1 v1
Section 6
1MRK 506 382-UEN A
Impedance protection
102
Line distance protection REL650 2.2 IEC
Technical manual
Summary of Contents for RELION 650 SERIES
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