Functions
2.11 Monitoring Functions
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
212
2.11.2 Trip Circuit Supervision 74TC
Devices 7SJ62/64 are equipped with an integrated trip circuit supervision. Depending on the number of avail-
able binary inputs (not connected to a common potential), supervision with one or two binary inputs can be se-
lected. If the allocation of the required binary inputs does not match the selected supervision type, then a
message to this effect is generated („74TC ProgFail“).
Applications
• When using two binary inputs, malfunctions in the trip circuit can be detected under all circuit breaker con-
ditions.
• When only one binary input is used, malfunctions in the circuit breaker itself cannot be detected.
Prerequisites
A requirement for the use of trip circuit supervision is that the control voltage for the circuit breaker is at least
twice the voltage drop across the binary input (V
ct
> 2 · V
BImin
).
Since at least 19 V are needed for the binary input, the supervision can only be used with a system control
voltage of over 38 V.
2.11.2.1 Description
Supervision with Two Binary Inputs
When using two binary inputs, these are connected according to Figure 2-71, parallel to the associated trip
contact on one side, and parallel to the circuit breaker auxiliary contacts on the other.
Figure 2-71 Principle of the trip circuit supervision with two binary inputs
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