Siemens SENTRON 3WA1 Manual page 190

Description
2.10 Zone-selective interlocking ZSI
In the example below, the B+ and B- connections of the ZSI200 modules of the circuit
breakers -Q2 to -Q4 are connected to the A+ and A- connections of the ZSI200 module
of the upstream circuit breaker -Q1. All connections of a grading level are connected in
parallel.
Circuit breakers in switchgear couplings as well as an upstream protective device of the
medium voltage can be integrated into the ZSI system. Both are shown in the examples,
see Chapter Application examples (Page 191).
Up to 20 circuit breakers can be connected to each ZSI interface. The maximum distance
of the circuit breakers is determined by the control line used, see Chapter Technical
specifications (Page 361).
Mode of operation
The ZSI function is available for ST short-time-delayed short-circuit protection and GF
ground-fault protection.
If the electronic trip unit detects a short-circuit or ground fault, a control signal is sent to
the upstream circuit breakers (feeding side) and these circuit breakers are informed
about the pick-up. At the same time, the ETU600 electronic trip unit checks whether a
control signal is received from a downstream circuit breaker (load side).
If no control signal is received from a downstream circuit breaker, the circuit breaker is
opened after the delay time t
characteristics, delay time t
for the ground-fault protection GF. The delay times t
t
g
the short-time-delayed short-circuit protection ST and the ground-fault protection GF,
correspond to a guaranteed non-trip time.
If a signal is received and there is no disconnection of the pick-up current by a
downstream circuit breaker, the circuit breaker is opened according to its set response
characteristic.
188
. This is done independently of the delays of its response
ZSI
for the short-time-delayed short-circuit protection ST, and
sd
, which can be set separately for
ZSI
3WA1 air circuit breaker
Equipment Manual, 02/2023, 92310000002-06