GE P444

Application Notes
P44x/EN AP/Hb
6
MiCOM P40 Agile P442, P444
(AP) 5-
21
S >5 x (10% x Vn x 20% x In x cos (85°)
This sum is calculated on five successive samples.
the RCA angle of the delta algorithms is equal to 60° (-30°) if the protected line is not serie
compensated (otherwise RCA is equal to 0°).
2.2.5 Phase Selection
Phase selection is made on the basis of a comparison between the transition values for the
derivatives of currents IA, IB and IC:
∆I'A, ∆I'B, ∆I'C, ∆I'AB, ∆I'BC, ∆I'CA
Note: The derivatives of the currents are used to eliminate the effects of the DC current
component.
Therefore:
∑
+≥
∆=
40
0
i
AAN
)²'(
S
nni
n
I
∑
+≥
∆=
40
0
i
AB
)²'( S
nni
n
AB
I
∑
+
≥
∆=
40
0
i
BBN
)²'(
S
nni
n
I
∑
+≥
∆=
40
0
i
BC
)²'( S
nni
n
BC
I
∑
+≥
∆=
40
0
i
CCN
)²'( S
nni
n
I
∑
+≥
∆=
40
0
i
CA
)²'( S
nni
n
CA
I
The phase selection is valid if the sum (S
AB
+S
BC
+S
CA
) is higher than a threshold. This sum is
not valid if the positive sequence impedance on the source side is far higher than the zero
sequence impedance. In this case, the conventional algorithms are used to select the faulted
phase(s).
Sums on one-phase and two-phase loops are performed. The relative magnitudes of these
sums determine the faulted phase(s).
For example, assume:
If S
AB
<S
BC
<S
CA
and If S
AB
<<S
BC
, the fault has had little effect on the loop A to B. If
S
AN
<S
BN
<S
CN
, the fault declared as single phase fault C.
If the fault is not detected as single-phase by the previous criterion, the fault conditions are
multi-phase.
If S
AN
<S
BN
<S
CN
and If S
AB
<<S
BC
, the fault is B to C.
If S
AN
<S
BN
<S
CN
and If S
AB
≈S
BC
≈S
CA
and if S
AN
≈S
BN
≈S
CN
, the fault is three-phase (the fault
occurs on the three phases).
2.2.6 Summary
A transition is detected if
∆I > 20% x In or ∆V >10% x Vn
Then three tasks are starting in parallel:
• Fault confirmation:
∆I and ∆V (3 consecutive samples)
• Faulty phase selection (4 consecutive samples)
• Fault directional decision (5 consecutive samples)