GE P444 User Manual

P
44x/EN AP/Hb6
Application Notes
(AP) 5
-24 MiCOM P40 Agile
P442, P444
2.3.3 Phase Selection
If the fault currents are high enough with respect to the maximum load currents current-
based phase selection is used; if not, impedance-based phase selection is required.
Current Phase Selection
Amplitudes I'A, I'B, I'C are derived from the three measured phase currents IA, IB, IC. These
values are then compared to each other and to the two thresholds S1 and S2:
• First threshold is S1= 3 x I'n
• Second threshold is S2 = 5 x I'n
Example:
If I'A< I'B < I' C:
• If I'
C
> S2 and I'
A
> S1, the fault is three-phase.
• If I'
C
> S2, I'B > S1 and I'
A
< S1, the fault is two-phase, on phases B and C.
• If I'
C
> S2 and I'
B
< S1, the fault is single-phase, on phase C.
• If I'
C
< S2, the current phase selection cannot be used. Impedance phase selection
should then be used.
Impedance Phase Selection
Impedance phase selection is obtained by checking the convergence of the various
measuring loops within the start-up characteristic, as follows:
• T = Presence of zero-sequence voltage or current (logic Information: 0 or 1).
• Z
AN
= Convergence within the characteristic of the loop A (logic Information).
• Z
BN
= Convergence within the characteristic of the loop B (logic Information).
• Z
CN
= Convergence within the characteristic of the loop C (logic Information).
• Z
AB
= Convergence within the characteristic of the loop AB (logic Information).
• Z
BC
= Convergence within the characteristic of the loop BC (logic Information).
• Z
CA
= Convergence within the characteristic of the loop CA (logic Information).
In addition, the following are also defined:
• R
AN
= Z
AN
x
BCZ
where ZBC = convergence within the characteristic of the loop
BC (Logic Information).
• R
BN
= Z
BN
x
CA
Z
where ZCA = convergence within the characteristic of the loop
CA (Logic Information).
• R
CN
= Z
CN
x
ABZ
where ZAB = convergence within the characteristic of the loop
AB (Logic Information).
• R
AB
= Z
AB
x
CNZ
where ZCN = convergence within the characteristic of the loop
C (Logic Information).
• R
BC
= Z
BC
x
ANZ
where ZAN = convergence within the characteristic of the loop
A (Logic Information).
• R
CA
= Z
CA
x
BNZ
where ZBN= convergence within the characteristic of the loop
B (Logic Information).

GE P444 Specifications

General

Brand	GE
Model	P444
Category	Protection Device
Language	English