Siemens SENTRON 3WA1 - Page 64

Description
2.3 Protection system
3WA1 air circuit breaker
62 Equipment Manual, 02/2023, 92310000002-06
Note
The maximum voltage at the measuring input of the electronic trip unit is 150
V
rms. This
must not be exceeded. A varistor or other suitable voltage limitation device must be
connected in parallel to the load for this reason.
Note
Proper operation of the combination of current transformers and the load is not
monitored by the ETU600 electronic trip unit.
The ETU600 LSIG Hi-Z electronic trip unit can differentiate between an infeed-side
ground fault and an outgoing-side ground fault. In countries where British standards are
used, the areas before and after the circuit breaker are referred to as the "restricted
zone" and "unrestricted zone" respectively. Derived from this, this type of ground-fault
protection is called "Restricted Earth Fault (REF)" and "Unrestricted Earth Fault
(UREF)".
Please note that ground-fault protection with ETU600 LSIG Hi-Z differs from high-
resistance neutral point grounding and must not be confused with it.
(1)
Restricted zone of protection
(2)
Unrestricted zone of protection