The conditions of the two binary inputs are scanned periodically. A query takes place about every 500 ms. If
three consecutive conditional checks detect an abnormality, an annunciation is reported (see Figure 2-74).
The repeated measurements help to determine the delay of the alarm message and to avoid that an alarm is
output during short-time transition periods. After the fault in the trip circuit is removed, the alarm is reset
automatically after the same time.
[logikdiagramm-auskruebrwchg-2-be-wlk-310702, 1, en_US]
Figure 2-74 Logic diagram of the trip circuit monitoring with two binary inputs
Monitoring with One Binary Input
The binary input is connected in parallel to the respective command relay contact of the protection device
according to Figure 2-75. The circuit-breaker auxiliary contact is bridged with a high-ohm substitute resistor R.
The control voltage for the circuit breaker should be at least twice as high as the minimum voltage drop at the
binary input (V
Ctrl
> 2·V
BImin
). Since at least 19 V are necessary at the binary input, this supervision can be used
with a system control voltage higher than 38 V.
A calculation example for the resistance shunt R is shown in the configuration notes in Section “Mounting and
Connections”, margin “Trip Circuit Supervision”.
[prinzip-ausloesekrueb-1-be-wlk-010802, 1, en_US]
Figure 2-75 Principle of the trip circuit monitoring with one binary input
TCR Relay trip contact
52 Circuit breaker
52TC Circuit-breaker trip coil
52a Circuit-breaker auxiliary contact (NO contact)
52b Circuit-breaker auxiliary contact (NC contact)
V-Ctrl Control Voltage for trip circuit
V-BI Input voltage for binary input
R Bypass resistor
VR Voltage at bypass resistor
During normal operation, the binary input is activated (logical condition “H”) when the trip contact is open and
the trip circuit is intact, because the monitoring circuit is closed by either the circuit-breaker auxiliary contact
Functions
2.14 Monitoring Functions
164 SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
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