P54x/EN OP/La4 Operation
(OP) 5-56
MiCOM P543, P544, P545 & P546
OP
P1239ENa
P1134ENa
Z
L1
Z
R1
Z
S1
Z
L2
Z
R2
Z
S2
Z
L0
Z
R0
Z
S0
I
F1
I
F2
I
F0
I
1
I
2
I
0
V
1
V
2
V
0
I
F/3
E
voltage
generator
represents
voltage
change
at fault
location
Figure 31 Sequence networks connection for an internal A-N fault
(Distance option only)
The fault is shown near to the busbar at end R of the line, and results in a connection of the
positive, negative, and zero sequence networks in series. Drawing the delta diagram, it is
seen that any fault is effectively a generator of , connected at the location of fault inception.
The characteristics are:
1. The I generated by the fault is equal to the total fault arc current;
2. The I will split into parallel paths, with part contribution from source “S”, and part from
remote end “R” of the line. Therefore, each relay will measure a lower proportion of
delta I;
3. The V generated by the fault is equal to the fault arc voltage minus the prefault
voltage (and so will be in antiphase with the prefault voltage);
4. The V will generally be smaller as measured at the relay location, due to the voltage
collapse being smaller near to the source than at the fault itself. The delta V
measured by a relay is effectively the voltage drop across the source impedance
behind the relay location.
If a fault were to occur at any point on the protected line, the resulting I and V as
measured at the relay location must be greater than the Delta I Fwd and Delta V Fwd
settings, in order that the fault can be detected. (Scenarios (2) and (4) above must be
verified for all fault types: Ph-G, Ph-Ph, Ph-Ph-G, and 3-phase)
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