ABB RER620, Technical Manual

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1MAC309294-MB F
Section 4
Protection functions
RER620 173
Technical Manual
Figure 77: Functional module diagram. I
2
represents negative phase sequence
current.
Level detector
The measured negative phase-sequence current is compared with the set Pickup value . If
the measured value exceeds the set Pickup value , the level detector activates the timer
module. If the
ENA_MULT
input is active, the set Pickup value is multiplied by the set
Pickup value Mult .
Timer
Once activated, the timer activates the
PICKUP
output. Depending on the value of the
Operating curve type setting, the time characteristics are according to DT or IDMT. When
the operation timer has reached the value of Trip delay time in the DT mode or the
maximum value defined by the inverse time curve and the Time adder time has expired,
the
TRIP
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 happens, that is, a fault suddenly disappears before the trip delay is
exceeded, the timer reset state is activated. The functionality of the timer in the reset state
depends on the combination of the
Operating curve type , Type of reset curve and Reset
delay time settings. When the DT characteristic is selected, the reset timer runs until the
set Reset delay time value is exceeded. When the IDMT curves are selected, the Type of
reset curve setting can be set to “ Immediate ” , “ Def time reset ” or “ Inverse reset ” . The
reset curve type “Immediate” causes an immediate reset. With the reset curve type “Def
time reset”, the reset time depends on the
Reset delay time setting. With the reset curve
Do not set the multiplier setting Pickup value Mult higher than necessary.
If the value is too high, the function may not trip at all during an inrush
followed by a fault, no matter how severe the fault is.
The relay does not accept the Pickup value or Pickup value Mult setting if
the product of these settings exceeds the Pickup value setting range.