GE MiCOM P40 Agile - Figure 55: Offset Mho Characteristics - Voltage Domain

R
Xj
Z
90°
-plane
LP
Z
phNZN
IIkZ 
replica
Z
replicaphph
ZIV 
Z

phNZN
IIkZ 

replica
Z

replicaphph
ZIV


V02714
V
p
h
/
I
p
h
Figure 55: Offset mho characteristics – voltage domain
where: Z
replica
is the replica forward reach and Z'
replica
is the replica reverse reach.
With mutual compensation applied:
Z
replica
= Z(1+k
ZN
.I
N
/I
ph
+ k
ZM
.I
M
/I
ph
)
Z'
replica
= Z'(1+k
ZN
.I
N
/I
ph
+ k
ZM
.I
M
/I
ph
)
If the healthy phase currents are much less than the current of the faulty phase, then the neutral current is
approximately the same as the phase current, and the terms can be simplified as follows:
Z
replica
= Z(1+k
ZN
+ k
ZM
.I
M
/I
ph
)
Z'
replica
= Z'(1+k
ZN
+ k
ZM
.I
M
/I
ph
)
If the healthy phase currents are much less than the current of the faulty phase, and mutual current compensation
is not applied, then these terms can be simplified as follows:
Z
replica
@ Z(1+k
ZN
)
Z'
replica
@ Z'(1+k
ZN
)
So, as with the Directional Self-Polarized Mho characteristic for earth-faults, the Z
LP
plane representation of the
characteristic becomes static.
P543i/P545i Chapter 7 - Distance Protection
P54x1i-TM-EN-1 143