Timer Characteristics - ABB RELION REX640 Technical Manual

1MRS759142 C
4.4.5.6
REX640
Technical Manual
Timer
Once activated, the timer activates the START output. Depending on the value of the
set Operating curve type, the time characteristics are according to DT or IDMT. When
the operation timer has reached the value set by Operate delay time in the DT mode
or the maximum value defined by the inverse time curve, the OPERATE output is
activated.
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
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.
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.
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.

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
Section 4
Protection functions
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