Siemens siprotec SJ62, Руководство пользователя

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2.8 Motor Protection (Motor Starting Protection 48, Motor Restart Inhibit 66)
162
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
Thus the total inhibit time T
Reclose
can become equal to the minimum inhibit time if it is
longer than the sum of the two first mentioned times:
T
Reclose
= T
Equal
+ T
Restart
for T
Min Inhibit
< T
Equal
+ T
Restart
T
Reclose
= T
Min Inhibit
for T
Min Inhibit
≥
T
Equal
+ T
Restart
, if the calculated exces-
sive temperature > restarting limit
The operational measured value T
Reclose
(visible in the thermal measured values) is
the remaining time until the next restart is permissible. When the rotor excessive tem-
perature is below the restarting limit and thus the next restarting attempt is permitted,
the operational measured value for the waiting time has reached zero.
Extension of Cool
Down Time Con-
stants In order to properly account for the reduced heat exchange when a self-ventilated
motor is stopped, the cooling time constants can be increased relative to the time con-
stants for a running machine with the factor
K τ at STOP
(address
4308
). The criterion
for the motor stop is the undershooting of a set current threshold
BkrClosed I MIN
.
This understands that the motor idle current is greater than this threshold. The pickup
threshold
BkrClosed I MIN
affects also the thermal overload protection function
(see Section 2.10).
While the motor is running, the heating of the thermal profile is modeled with the time
constant
τ
R
calculated from the motor ratings, and the cool down calculated with the
time constant
τ
R
x
K τ at RUNNING
(address
4309
). In this way, the protection caters
to the requirements in case of a slow cool down (slow temperature equilibrium).
For calculation of the restarting time T
Restart
the following applies:
with
k
τ
at STOP
– extension factor for the time constant =
K τ at STOP
,
address
4308
k
τ
at RUNNING
– extension factor for the time constant =
K τ at
RUNNING
, address
4309
Θ
pre
– thermal replica at the instant the motor is switched off
(depends on operational condition)
τ
R
– rotor time constant, calculated internally
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 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 "Additional In-
formation on the Protection of Explosion-Protected Motors of Protection Type In-
creased Safety "e", C53000-B1174-C157"/5/). For further details, see /5/.