Alstom MiCOM P54 Series, Technical Manual

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P54x/EN OP/La4 Operation
(OP) 5-74
MiCOM P543, P544, P545 & P546
OP

A current reversal guard timer is included in the signal send logic to prevent unwanted
trips of the relay on the healthy circuit, during current reversal situations on a parallel
circuit.

To allow time for a blocking signal to arrive, a short time delay on aided tripping,
Delta dly
, must be used.
This scheme is similar to that used in the LFDC relay, and is shown in Figure 49.
Send logic:

Fault Reverse
Trip logic:

Fault Forward, plus Channel NOT Recieved, delayed by Tp.
DI R F WD
Z (T)
DI R F WD
Z (T)
R R
DI R RE V
DI R RE V
G
H
CT X
C RX
S ignalling
E q ui p ment
CT X
C RX
S ignalling
E q ui p ment
DI R RE V
DI R RE V
& &
DI R F WD DI R F WD
1 1
T ri p G T ri p H
EN D G EN D H
t
t
0
0
Z
Z
T Z (T)
T Z (T)
P1233 E Na
P1019 E Na
Figure 49 delta directional comparison BLOCKING scheme
1.24 Zone 1 extension and loss of load schemes (Distance option only)
The MiCOM P54x offers additional non-channel distance schemes, notably Zone 1
extension, and loss of load.