ABB RELION REX640 Technical Manual page 360

Section 4
Protection functions
354
Voltage and input control mode
If Control mode is set to "Voltage and input Ctrl", both the "Voltage control" and
"Input control" modes are used. However, the "Input control" functionality is
dominant over the "Voltage control" mode when ENA_LOW_LIM is active.
No voltage dependency mode
When Control mode is set to "No Volt dependency", the effective start value has no
voltage dependency and the function acts as a normal time overcurrent function with
effective start value being equal to the Start value setting.
Level detector
The measured phase currents are compared phasewise to the calculated effective start
value. If the measured value exceeds the calculated effective start value, the Level
detector reports the exceeding value to the phase selection logic. If the ENA_MULT
input is active, the effective start value is multiplied by the Start value Mult setting.
Do not set the multiplier Start value Mult setting higher than
necessary. If the value is too high, the function may not operate at all
during an inrush followed by a fault, no matter how severe the fault is.
The start value multiplication is normally done when the inrush detection function
INRPHAR is connected to the ENA_MULT input.
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 measured current exceeds the setting. If the phase
information matches the Num of start phases setting, the phase selection logic
activates the Timer module.
Timer
Once activated, the Timer module activates the START 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
Operate delay time in the DT mode or the maximum value defined by the inverse time
curve, the OPERATE output is activated.
When the user programmable IDMT curve is selected, the operation time
characteristics are defined by the settings Curve parameter A, Curve parameter B,
Curve parameter C, Curve parameter D and Curve parameter E.
In a drop-off situation, that is, when a fault suddenly disappears before the operating
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
1MRS759142 C
REX640
Technical Manual