Siemens siprotec 7SD5 User Manual page 449

Figure 3-2
This results in an upper limit for the resistance dimension, R
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
derived as:
To keep the circuit breaker trip coil energized in the above case, R
If the calculation results that R
the next lowest switching threshold U
the relay using plug-in jumpers (see Section „Hardware Modifications").
7SD5 Manual
C53000-G1176-C169-1
Trip circuit supervision with one binary input — Example for trip circuit 1
Constant current with activated BI (= 1.8 mA)
I
BI (HIGH)
U Minimum control voltage for BI
BI min
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 Control voltage for trip circuit
SP
R DC resistance of circuit breaker trip coil
CBTC
U Maximum voltage on the circuit breaker trip coil that does not lead to trip-
CBTC (LOW)
ping
3.1 Mounting and Connections
< R , then the calculation must be repeated, with
max min
, and this threshold must be implemented in
BI min
, and a lower limit R
max min
is
max
is derived as:
min
449
,