For a detailed description of the voltage IDMT curves, see the IDMT
curves for overvoltage protection section in this manual.
When the operation timer has reached the value set by Trip delay time in the DT mode or
the maximum value defined by the IDMT, the TRIP output is activated.
When the user-programmable IDMT curve is selected, the trip time characteristics are
defined by the parameters Curve parameter A, Curve parameter B, Curve parameter C,
Curve parameter D and Curve parameter E.
If a drop-off situation occurs, that is, a fault suddenly disappears before the trip delay is
exceeded, the reset state is activated. The behavior in the drop-off situation depends on the
selected trip time characteristics. If the DT characteristics are selected, the reset timer runs
until the set Reset delay time value is exceeded. If the drop-off situation exceeds the set
Reset delay time, the Timer is reset and the PICKUP output is deactivated.
When the IDMT operate time curve is selected, the functionality of the Timer in the drop-
off state depends on the combination of the Type of reset curve and Reset delay time
settings.
Table 510: Reset time functionality when IDMT operation time curve selected
Reset functionality
Setting Type of reset
curve
Setting Type of time
reset
Setting Reset delay
time
Instantaneous
reset
Operation timer is
“Reset
instantaneously”
when drop-off
occurs
“Immediate”
Setting has no
effect
Setting has no
effect
Frozen timer Operation timer is
frozen during drop-
off
“Def time reset”
“Freeze Op timer” Operate timer is
reset after the set
Reset delay time
has elapsed
Linear decrease
Operation timer
value linearly
decreases during
the drop-off
situation
“Def time reset”
“Decrease Op
timer”
Operate timer is
reset after the set
Reset delay time
has elapsed
Section 4 1MAC059074-MB A
Protection functions
612 615 series ANSI
Technical Manual
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