Siemens siprotec 7SD5

3.1 Mounting and Connections
449
7SD5 Manual
C53000-G1176-C169-1
Figure 3-2 Trip circuit supervision with one binary input — Example for trip circuit 1
This results in an upper limit for the resistance dimension, R
max
, and a lower limit R
min
,
from which the optimal value of the arithmetic mean R should be selected:
In order that the minimum voltage for controlling the binary input is ensured, R
max
is
derived as:
To keep the circuit breaker trip coil energized in the above case, R
min
is derived as:
If the calculation results that R
max
< R
min
, then the calculation must be repeated, with
the next lowest switching threshold U
BI min
, and this threshold must be implemented in
the relay using plug-in jumpers (see Section „Hardware Modifications“).
I
BI (HIGH)
Constant current with activated BI (= 1.8 mA)
U
BI min
Minimum control voltage for BI
19 V for delivery setting for nominal voltages of 24/48/60/250 V;
88 V for delivery setting for nominal voltages of 110/125/220/250 V;
176 V for delivery setting for nominal voltages of 220/250 V
U
SP
Control voltage for trip circuit
R
CBTC
DC resistance of circuit breaker trip coil
U
CBTC (LOW)
Maximum voltage on the circuit breaker trip coil that does not lead to trip-
ping
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