ABB 615 Series ANSI, Technical Manual

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1MAC050144-MB C
Section 4
Protection functions
615 series ANSI 225
Technical Manual
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 trip 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 221: The reset time functionality when the IDMT trip time curve is selected
Type of reset curve Description of operation
“Immediate” The trip timer is reset instantaneously when drop-off
occurs
“Def time reset” The trip timer is frozen during drop-off. The trip timer
is reset after the set
Reset delay time
is exceeded
“DT Lin decr rst” The trip timer value linearly decreases during the
drop-off situation. The trip timer is reset after the set
Reset delay time is exceeded