ABB RELION REX640, Техническое руководство, Страница: 843 / 1960

In a drop-off situation, that is, when the value of the negative-sequence current
drops below the
Start value setting, the reset timer is activated and the
START
output resets after the time delay of
Reset delay time for the DT characteristics. For
IDMT, the reset time depends on the curve type selected.
For the IDMT curves, it is possible to define minimum and maximum operate times
with the
Minimum operate time and Maximum operate time settings. The Machine
time Mult setting parameter corresponds to the machine constant, equal to the I
2
2
t
constant of the machine, as stated by the machine manufacturer. In case there is a
mismatch between the used CT and the protected motor's nominal current values,
it is possible to fit the IDMT curves for the protected motor using the
Current
reference setting.
The activation of the
OPERATE
output activates the
BLK_RESTART
output. The
deactivation of the
OPERATE
output activates the cooling timer. The timer is set
to the value entered in the
Cooling time setting. The
BLK_RESTART
output is
kept active until the cooling timer is exceeded. If the negative-sequence current
increases above the set value during this period, the
OPERATE
output is activated
immediately.
T_ENARESTART indicates the duration for which the
BLK_RESTART
output remains
active, that is, it indicates the remaining time of the cooling timer. The value is
available in the monitored data view.
When the
ST_EMERG_ENA
emergency start is set high, the value of the
T_ENARESTART is immediately set to "False". This disables
BLK_RESTART
and in turn
makes the restart of the motor possible.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is
available in the monitored data view.
The
T_ENARESTART
output indicates the duration for which the
BLK_RESTART
output remains active, that is, it indicates the remaining time of the cooling timer.
The value is available in the monitored data view.
When the
ST_EMERG_ENA
emergency start is set high, the value of the
T_ENARESTART is immediately set to "False". This disables
BLK_RESTART
and in turn
makes the restart of the motor possible.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is
available in the monitored data view.
4.4.5.6 Timer characteristics
MNSPTOC supports both DT and IDMT characteristics. The DT timer characteristics
can be selected with "ANSI Def. Time" or "IEC Def. Time" in the
Operating curve type
setting. The functionality is identical in both cases. When the DT characteristics
are selected, the functionality is only affected by the
Operate delay time and Reset
delay time settings.
The protection relay provides two user-programmable IDMT characteristics curves,
"Inv. curve A" and "Inv. curve B".
Current-based inverse definite minimum time curve (IDMT)
In inverse-time modes, the operate time depends on the momentary value of the
current: the higher the current, the shorter the operate time. The operate time
1MRS759142 F Protection functions
REX640
Technical Manual
843