Siemens siprotec SJ62, Руководство пользователя

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2 Functions
157
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
2.8.1.2 Setting Notes
General Motor starting protection is only effective and accessible if address
141 48
=
Enabled
is set. If the function is not required
Disabled
is set. The function can be turned
ON
or
OFF
under address
4101 48
.
Startup Parameter The device is informed of the startup current values under normal conditions at
address
4102 STARTUP CURRENT
, the startup time at address
4103 STARTUP
TIME
. At all times this enables timely tripping if the value I
2
t calculated in the protection
device is exceeded.
If the startup time is longer than the permissible blocked rotor time, an external rpm-
counter can initiate the definite-time tripping element via binary input (
„>Rotor
locked“
). A locked rotor leads to a loss of ventilation and therefore to a reduced
thermal load capacity of the machine. For this reason the motor starting time monitor
must issue a tripping command before reaching the thermal tripping characteristic
valid for normal operation.
A current above the threshold
I MOTOR START
(address
1107
) is interpreted as a
motor startup. Consequently, this value must be selected such that under all load and
voltage conditions during motor startup the actual startup current safely exceeds the
setting, but stays below the setting in case of permissible, momentary overload.
Example: Motor with the following data:
The setting for address
STARTUP CURRENT
( I
STARTUP
) as a secondary value is calcu-
lated as follows:
For reduced voltage, the startup current is also reduced almost linearly. At 80 %
nominal voltage, the startup current in this example is reduced to 0.8 ·
I
STARTUP
= 2.5.
The setting for detection of a motor startup must lie above the maximum load current
and below the minimum start-up current. If no other influencing factors are present
(peak loads), the value for motor startup
I MOTOR START
set at address
1107
may
be an average value:
Rated Voltage V
Nom
= 6600 V
Nominal Current I
Nom
= 126 A
Startup Current (primary)
I
STARTUP
= 624 A
Long-Term Current Rating I
max
= 135 A
Startup Duration T
STARTUP
= 8.5 s
Current Transformers I
Nom CTprim
/ I
Nom CTsec
= 200 A /
1 A