Alstom MiCOM P54 Series, Technical Manual

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P54x/EN OP/La4 Operation
(OP) 5-68
MiCOM P543, P544, P545 & P546
OP
A B
Z
Z
Z o ne 1
Z o ne 2
Z o ne 3
Z o ne 1
Z o ne 2
Z o ne 3
Z o ne 4
Z o ne 4
Opti o na l feat u res o f sc h e m e
TZ1
TZP
TZ2
TZ3
TZ 4
Z1
ZP
Z2
Z3
Z 4
1
Trip A
TZ1
TZP
TZ2
TZ3
TZ 4
Z1
ZP
Z2
Z3
Z 4
1
Trip B
&
&
Fast Z 4
C Rx C Rx
C Tx C Tx
&
&
Fast Z 4
P11 5 2 E Nb P113 4E Na
Figure 40 Distance blocking scheme (BOP) (Distance option only)
1.23.7 Distance schemes current reversal guard logic (Distance option only)
For double circuit lines, the fault current direction can change in one circuit when circuit
breakers open sequentially to clear the fault on the parallel circuit. The change in current
direction causes the overreaching distance elements to see the fault in the opposite direction
to the direction in which the fault was initially detected (settings of these elements exceed
150% of the line impedance at each terminal). The race between operation and resetting of
the overreaching distance elements at each line terminal can cause the Permissive
Overreach, and Blocking schemes to trip the healthy line. A system configuration that could
result in current reversals is shown in Figure 41. For a fault on line L1 close to circuit
breaker B, as circuit breaker B trips it causes the direction of current flow in line L2 to
reverse.