Functions
2.8 Motor Protection
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
169
Behavior in Case of Power Supply Failure
Depending on the setting in address
235
ATEX100
of Power System Data 1 (see Section 2.1.3.2) 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 fail-
ure. In the latter case, when power supply is restored, the thermal replica uses the stored value for calculation
and matches it to the operating conditions. The first option is the default setting. For further details, see /5/.
Emergency Start
If, for emergency reasons, motor starting that will exceed the maximum allowable rotor temperature must take
place, the motor restart inhibit signal can be removed via a binary input (
„>66 emer.start“
), thus allowing
a new starting attempt. The thermal rotor profile, however, continues to function and the maximum allowable
rotor temperature will be exceeded. No motor shutdown will be initiated by the motor restart inhibit, but the cal-
culated excessive temperature of the rotor can be observed for risk assessment.
Blocking
If the motor restart inhibit function is blocked via binary input
„>BLOCK 66“
or switched off, the thermal replica
of the rotor overtemperature, the equilibrium time
T Equal
and the minimum inhibit time
T MIN. INHIBIT
are reset. Thus any blocking signal that is present or upcoming is disregarded.
Via another binary input (
„>66 RM th.repl.“
) the thermal replica can be reset independently. This may be
useful for testing and commissioning, and after a power supply voltage failure.
Logic
There is no pickup annunciation for the restart inhibit and no trip log is produced. The following figure shows
the logic diagram for the restart inhibit.
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