Trip Circuit Supervision 74TC
Devices 7SJ61 are equipped with an integrated trip circuit supervision. Depending on the number of available
binary inputs (not connected to a common potential), supervision with one or two binary inputs can be
selected. 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
conditions.
•
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.
Description
Supervision with Two Binary Inputs
When using two binary inputs, these are connected according to Figure 2-46, parallel to the associated trip
contact on one side, and parallel to the circuit breaker auxiliary contacts on the other.
[prinzip-ausloesekreisueberwachung-2-binein-150502-kn, 1, en_US]
Figure 2-46
Principle of the trip circuit supervision with two binary inputs
Supervision with two binary inputs not only detects interruptions in the trip circuit and loss of control voltage,
it also supervises the response of the circuit breaker using the position of the circuit breaker auxiliary contacts.
Depending on the conditions of the trip contact and the circuit breaker, the binary inputs are activated (logical
condition "H" in Table 2-5), or not activated (logical condition "L").
In healthy trip circuits the condition that both binary inputs are not actuated (”L") is only possible during a
short transition period (trip contact is closed but the circuit breaker has not yet opened). A continuous state of
2.8.2
2.8.2.1
Functions
2.8 Monitoring Functions
126 SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016
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