ABB RER620 Technical Manual page 132

Section 4
Protection functions
126
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
current followed by a non-directional ground fault current, 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.
The pickup value multiplication is normally done when the inrush detection function
(INR) is connected to the ENA_MULT input.
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 added 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
type "Inverse reset", the reset time depends on the current during the drop-off situation. If
the drop-off situation continues, the reset timer is reset and the PICKUP output is
deactivated.
The "Inverse reset" selection is only supported with ANSI or user
programmable types of the IDMT operating curves. If another operating
curve type is selected, an immediate reset occurs during the drop-off
situation.
The setting Time multiplier is used for scaling the IDMT trip and reset times.
The setting parameter Minimum trip time defines the minimum desired trip time for IDMT.
The setting is applicable only when the IDMT curves are used.
1MAC309294-MB F
RER620
Technical Manual