ABB Relion 650 Series Technical Manual page 116

Section 5
Impedance protection
I • Z
AB
ANSI09000116 V1 EN-US
Figure 58: Simplified mho characteristic and vector diagram for phase A-to-B fault
Offset Mho
The characteristic for offset mho is a circle where two points on the circle are the setting
parameters
the angle for
The condition for operation at phase-to-phase fault is that the angle β between the two
compensated voltages Vcomp1 and Vcomp2 is greater than or equal to 90° (figure 59). The angle
will be 90° for fault location on the boundary of the circle.
The angle β for A-to-B fault can be defined according to equation 14.
β =
Arg
EQUATION1792-ANSI-650 V1 EN-US
where
V
EQUATION1801 V1 EN-US
ZRev
110
I X
AB ·
Z and ZRev . The vector Z in the impedance plane has the settable angle LineAng and
ZRev is LineAng+180° .
 
− ⋅
V I Z
AB
 
( )
− − ⋅
 
V I Z Re v
AB
is the V voltage
AB
is the positive sequence impedance setting for phase-to-phase fault in reverse direction
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V I Z
V - •
= AB AB
comp
ß
V
pol
V
AB
I ·R
AB
ANSI09000116-1-en.vsd
1MRK 506 326-UUS B
SEMOD154224-242 v3
(Equation 14)
Line distance protection REL650
Technical manual