- 94 -
impedance and negative-sequence impedance are the same and that the influences of the fault
resistance are ignored.
where,
V
1
: Relay point positive-sequence voltage
V
2
: Relay point negative-sequence voltage
V
0
: Relay point zero-sequence voltage
V
1
F: Fault point positive-sequence voltage
V
2
F: Fault point negative-sequence voltage
V
0
F: Fault point zero-sequence voltage
I
1
: Relay point positive-sequence current
I
2
: Relay point negative-sequence current
I
0
: Relay point zero-sequence current
I
0
m: Adjacent line zero-sequence current
Z
1
: Fault point - relay point positive-sequence impedance
Z
0
: Fault point - relay point zero-sequence impedance
Z
0
m: Adjacent line zero-sequence mutual impedance
Considering the faulted phase voltage V
a
F at the point of fault is,
Phase-A voltage V
a
at the relay is calculated from the following equation:
Where, I
a
is the current of phase-A at the relay and is defined in the following equation
by the symmetrical component of the current:
Here, defining the current synthesized using the phase-A current at the relay as I
a
', and
Then equation (2.10-11) can be re-written in the following form:
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