timer is activated. If the fault reoccurs during the reset time, the tripping calculation is
made based on the effects of the period when PICKUP was previously active. This is
intended to allow a tripping condition to occur in less time to account for the heating
effects from the previous active pickup period.
When TRIP becomes active, the reset time is based on the following equation.
reset time
PICKUP DUR
Cooling time=
⋅
_
100
GUID-14537CFF-A8C8-49DF-A0D3-02FF269FE516 V2 EN (Equation 121)
For the IDMT curves, when the fault disappears, the integral value calculated during
PICKUP is continuously decremented by a constant that causes its value to become zero
when the reset time elapses during the reset period. If a fault reoccurs, the integration
continues from the current integral value and the pickup time is adjusted, as shown in
Figure 321. The pickup time becomes the value at the time when the fault dropped off
minus the amount of reset time that occurred. If the reset period elapses without a fault
being detected, the saved values of the pickup time and integration are cleared.
GUID-47898DF5-3AC0-4EFC-AC30-23A0BBECE133 V1 EN
Figure 321: An example of a delayed reset in the inverse time characteristics. When
the pickup becomes active during the reset period, the trip time counter
continues from the level corresponding to the drop-off (reset time = 0.50 ·
Cooling time)
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 647
Technical Manual
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