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
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 Rated
current 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.
4.4.4.5 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 IED provides two user-programmable IDMT characteristics curves, "Inv.
curve A" and "Inv. curve B".
1YHT530004D05 D Section 4
Protection functions
615 series 461
Technical Manual
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