Siemens Siprotec 7UM611 Manual page 181

When using only one binary input, a resistor R is inserted into the circuit on the system
side, instead of the missing second binary input. Through appropriate sizing of the re-
sistor and depending on the system conditions, a lower control voltage can often be
sufficient. The resistor R is inserted into the circuit of the second circuit breaker auxil-
iary contact (AuxCont2) to detect a malfunction also when the circuit breaker auxiliary
contact (AuxCont1) is open, and the trip contact has dropped out (see Principle of Trip
Circuit Monitoring with One Binary Input figure). This resistor must be sized such that
the circuit breaker trip coil (CBTC) is no longer energized when the circuit breaker is
open (which means AuxCont1 is open and AuxCont2 is closed). Binary input (BI1)
should still be picked up when the trip contact is simultaneously opened.
This results in an upper limit for the resistance R
the optimal value of the arithmetic mean R should be selected:
In order that the minimum voltage for controlling the binary input is ensured, the result
for R
So the circuit breaker trip coil does not remain energized in the above case, R
derived as:
with
I
U
U
R
U
If the calculation results that R
the next lowest switching threshold UBE min, and this threshold must be implemented
in the device using jumper(s).
For power consumption of the resistance:
7UM61 Manual
C53000-G1176-C127-3
is:
max
Constant current with activated BI ( = 1.8 mA)
BI (HIGH)
minimum control voltage for BI (19 V for delivery setting for nominal
BI min
voltages 24/48/60 V; 88 V for delivery setting for nominal voltages
110/125/220/250 V)
Control Voltage for Trip Circuit
Ctrl
DC Resistance of circuit breaker trip coil
CBTC
Maximum voltage on the circuit breaker trip coil that does not lead to
CBTC (LOW)
tripping
, and a lower limit R
max
< R , then the calculation must be repeated, with
max min
2.29 Trip Circuit Supervision
, from which
min
min
is
181