ABB RER620 Technical Manual page 198

Section 4
Protection functions
192
Timer
Once activated, the timer activates the respective phase PICKUP(ST_A_AB) as shown
typically above for respective phase output as well as the common PICKUP (START)
output . Depending on the value of the set Operating curve type, the time characteristics
are selected according to DT or IDMT.
For a detailed description of the voltage IDMT curves, see the General
function block features 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 (OPR_A_AB) for respective phase as
well as the common the OPERATE output are 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 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 201: The reset time functionality when the IDMT trip time curve is selected
Type of reset curve
"Immediate"
"Def time reset"
"DT Lin decr rst"
Description of operation
The trip timer is reset instantaneously when drop-off
occurs
The trip timer is frozen during drop-off. The trip timer
Reset delay time
is reset after the set
The trip timer value linearly decreases during the
drop-off situation. The trip timer is reset after the set
Reset delay time
is exceeded
1MAC309294-MB F
is exceeded
RER620
Technical Manual