Siemens SENTRON VL Series

Zone Selective Interlocking
5.2 Examples
3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02
117
5.2.2.7 Circuit breakers without ZSI function
Circuit breakers without ZSI function can be integrated into a system equipped with ZSI.
However, they must have no delay time since otherwise the selectivity of the circuit breakers
cannot be guaranteed.
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PRGXOH
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Short-circuit at circuit breaker ①
● t
sd
= 100 ms
Short-circuit at circuit breaker
①. Circuit breaker ① will switch off the short-circuit with a
delay time t
sd
of 100 ms. The short-circuit is also detected by circuit breaker ② and since
no ZSI-IN signal is detected, switch-off is executed with a delay time t
ZSI
of 50 ms.
t
sd
> t
ZSI
100 ms ① > 50 ms ②
⇒ circuit breaker ② trips before circuit breaker ①.
The short-circuit is switched off non-selectively.
● t
sd
= 0 ms
Short-circuit at circuit breaker
①. Circuit breaker ① will switch off the short-circuit with a
delay time t
sd
of 0 ms (instantaneous). The short-circuit is also detected by circuit breaker
② and since no ZSI-IN signal is detected, switch-off is executed with a delay time t
ZSI
of
50 ms.
t
ZSI
> t
sd
50 ms ② > 0 ms ①
⇒ circuit breaker ① trips before circuit breaker ②.
The short-circuit is switched off selectively.