ABB RELION REX640 Technical Manual page 1044

Section 4
Protection functions
1038
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 parameters Curve parameter A, Curve parameter B,
Curve parameter C and Curve parameter E.
In a drop-off situation, that is, when a fault suddenly disappears before the operation
delay is exceeded, the Timer 1 reset state is activated. The functionality of Timer 1 in
the reset state depends on the combination of the Operating curve type 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, an immediate
reset occurs. The START output is deactivated when the reset timer has elapsed.
The setting Time multiplier is used for scaling the IDMT operation times.
The setting parameter Minimum operate time defines the minimum desired operation
time for IDMT. The setting is applicable only when the IDMT curves are used.
The Minimum operate time setting should be used with great care
because the operation time is according to the IDMT curve, but always
at least the value of the Minimum operate time setting.
Timer 1 calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is available
in the monitored data view.
Level detector 2
The phasewise-compensated unbalance currents I_COM_AMPL_A,
I_COM_AMPL_B and I_COM_AMPL_C are compared to the set Alarm start value. If
the compensated unbalance current in one or more phases exceeds the set Alarm start
value, the Level detector 2 module sends the enabling signal to the Timer 2 module.
Timer 2
Once activated, the timer activates the alarm timer. The timer characteristic is
according to DT. When the alarm timer has reached the value set by Alarm delay
time, the ALARM output is activated.
If the fault disappears before the alarm activates, the alarm timer is reset immediately.
Blocking logic
There are three operation modes in the blocking function. The operation modes are
controlled by the BLOCK input and the global setting Configuration/System/
Blocking mode which selects the blocking mode. The BLOCK input can be controlled
by a binary input, a horizontal communication input or an internal signal of the
protection relay's program. The influence of the BLOCK signal activation is
preselected with the global setting Blocking mode.
1MRS759142 C
REX640
Technical Manual