ABB RELION REX640 Technical Manual page 775

1MRS759142 C
REX640
Technical Manual
Phase selection logic
If the fault criteria are fulfilled in the level detector, the phase selection logic detects
the phase or phases in which the fault level is detected. If the number of faulty phases
match with the set Num of start phases, the phase selection logic activates the Timer.
Timer
Once activated, the Timer activates the 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
curves for overvoltage protection
When the operation timer has reached the value set by Operate delay time in the DT
mode or the maximum value defined by the IDMT, the OPERATE output is activated.
When the user-programmable IDMT curve is selected, the operate 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 operate
delay is exceeded, the reset state is activated. The behavior in the drop-off situation
depends on the selected operate 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 START
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, Type of time reset
and Reset delay time settings.
Table 705: Reset time functionality when IDMT operation time curve selected
Reset functionality
Instantaneous Operation timer is
reset "Reset
instantaneously"
when drop-off
occurs
Frozen timer Operation timer is
frozen during
drop-off
Linear decrease Operation timer
value linearly
decreases during
the drop-off
situation
Protection functions
section in this manual.
Setting Type of Setting Type of time
reset curve reset
"Immediate" Setting has no
effect
"Def time reset" "Freeze Op timer"
"Def time reset" "Decrease Op
timer"
Section 4
IDMT
Setting Reset delay
time
Setting has no
effect
Operate timer is
reset after the set
Reset delay time
has elapsed
Operate timer is
reset after the set
Reset delay time
has elapsed
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