Siemens SIPROTEC 4 Manual page 148

Functions
2.10 Thermal Overload Protection 49
when the motor currents drop below a programmable minimum current setting BkrClosed I MIN (refer to
"Current Flow Monitoring" in Section
transformers, the Kτ-FACTOR = 1.
Blocking
The thermal memory may be reset via a binary input (
ture value is thus reset to zero. The same is accomplished via the binary input (
the entire overload protection is blocked completely, including the current warning element.
When motors must be started for emergency reasons, temperatures above the maximum permissible over-
temperatures can be allowed by blocking the trip signal via a binary input (
thermal replica may have exceeded the tripping temperature after initiation and dropout of the binary input,
the protection function features a programmable run-on time interval (T EMERGENCY) which is started when
the binary input drops out and continues suppressing a trip signal. Tripping via the overload protection is
suppressed until this time interval has elapsed. The binary input affects only the trip command. There is no
effect on the trip log nor does the thermal replica reset.
Behavior in Case of Power Supply Failure
Depending on the setting in address 235 ATEX100 of Power System Data 1 (see Section
Data 1) the value of the thermal replica is either reset to zero (ATEX100 = NO) if the power supply voltage
fails, or cyclically buffered in a non-volatile memory (ATEX100 = YES) so that it is maintained in the event of
auxiliary supply voltage failure. In the latter case, the thermal replica uses the stored value for calculation and
matches it to the operating conditions. The first option is the default setting (see
the protection of explosion-protected motors of protection type increased safety
The following figure shows the logic diagram for the overload protection function.
148
2.1.3 Power System Data 1). For externally-cooled motors, cables and
>RES 49 Image ) and the current-related overtempera-
>BLOCK 49 O/L ); in this case,
>EmergencyStart ). Since the
2.1.3 Power System
/5/ Additional description for
"e").
SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017