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SIF5600 - Manual - 03 - 2008
Pilot wire breakage transforms the protection system into two distinct systems, still using acceler-
ated logic, but not coordinated chronometrically with one another; particularly in the case of inter-
ruption of the pilot wire close to the supply point, the entire system would be put out of service.
SIF5600 relays have a diagnostic function which detects any pilot wire breakages so as to allow
maintenance of the selectivity, even in the case of interruption of the pilot wire.
T
he function is based on periodic continuity checking of the twisted pair cable by sending impulses
from the block output circuits of the downstream protective devices.
Whenever any interruption in the pilot wire is detected, the relay self-test command (if envisaged)
is initiated.
Pilot wire connections
Connections must be made using shielded twisted pair cable, observing the polarities indicated in
the diagrams.
Note:
switching the polarities produces an effect equivalent to the short-circuiting of the pilot wire with the consequence of keeping the relay recei-
ving the signal blocked (until the timer tB expires).
It is indispensable that only the shield at the end of the cable close to the block input circuit (Blin1)
be connected to ground.
C
onnection of the shield to ground avoids any induced voltages arising caused by capacitive and/or
inductive effects which are difficult to quantify and depend on the configuration of the system.
It is recommended that separate routes be arranged for the pilot wires with respect to power ca-
bles.
Any cabling differing from the above instructions may cause malfunctioning and/or damage to the
block circuits with consequential loss of efficiency of the protection system.
E2
E1
Q2
E3
E4
SIF5600
Q1
A
SIF5600SIF5600
B
C
Q3
E5
E6
E3
E4
E2
E1
E6
E5
E2
E1
E6
E5
E4
E3
BLIN1+
BLIN1-
BLOUT1-
BLOUT1+
BLOUT2-
BLOUT2+
BLIN1+
BLIN1-
BLOUT1-
BLOUT1+
BLOUT2-
BLOUT2+
BLIN1+
BLIN1-
BLOUT1-
BLOUT1+
BLOUT2-
BLOUT2+
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