74Tc Trip Circuit Supervision; Method Of Operation - Siemens SIPROTEC 7SD80 Manual

2.14.2

74TC Trip Circuit Supervision

The 7SD80 line protection is equipped with an integrated trip circuit supervision function. 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 routing of the binary inputs required for this does not comply with the selected
monitoring mode, an alarm is given („TripC1 ProgFAIL ...", with identification of the non-compliant circuit).
When using two binary inputs, malfunctions in the trip circuit can be detected under all circuit-breaker condi-
tions. When only one binary input is used, malfunctions in the circuit breaker itself cannot be detected. If single-
pole tripping is possible, a separate trip circuit supervision can be implemented for each circuit-breaker pole
provided the required binary inputs are available.

2.14.2.1 Method of Operation

Monitoring with Two Binary Inputs
When using two binary inputs, these are connected according to Figure 2-73, parallel to the associated trip
contact on one side, and parallel to the circuit-breaker auxiliary contacts on the other.
A precondition for the use of the trip circuit supervision is that the control voltage for the circuit breaker is higher
than the total of the minimum voltages drops at the two binary inputs (V
needed at each binary input, the supervision can only be used with a system control voltage higher than 38 V.
Figure 2-73 Principle of the trip circuit monitoring with two binary inputs
RTC
52
52TC
52a
52b
V-CTRL
V-BI1
V-BI2
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
Relay trip contact
Circuit breaker
Circuit-breaker trip coil
Circuit-breaker auxiliary contact (NO contact)
Circuit-breaker auxiliary contact (NC contact)
Control Voltage (tripping voltage)
Input voltage for first binary input
Input voltage for second binary input
2.14 Monitoring Functions
> 2·V ). Since at least 19 V are
Ctrl BImin
Functions
179