ABB RELION REX640 Technical Manual page 1030

Section 4
Protection functions
1024
The amplitude I_AMPL_COMP and the angle I_ANGL_COMP of the compensated
I
unbalance current
CompUnb
Level detector 1
The calculated compensated unbalance current I_AMPL_COMP is compared to the
set "Start value". If I_AMPL_COMP exceeds the set "Start value", the Level detector
1 sends an enabling signal to the Timer 1 module.
Timer 1
Once activated, the Timer 1 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 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 operate
delay is exceeded, the Timer 1 reset state is activated. The functionality of the 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 and reset 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.
The Timer 1 module calculates the start duration value START_DUR, which
indicates the percentile ratio of the start situation and the set operation time. The value
is available in the monitored data view.
In a typical double-Y-connected configuration
every phase and hence six individual counters COUNT_BR1_A, COUNT_BR2_A,
COUNT_BR1_B, COUNT_BR2_B, COUNT_BR1_C and COUNT_BR2_C are
maintained. Based on the phase angle of the compensated unbalance current
I_ANGL_COMP, the phase and the branch of the element failure location is detected.
However, the element failure location also depends on the type of capacitor banks, that
is, whether internal or external fuses are used. The setting Fuse location is used to set
the capacitor bank type as "External" or "Internal".
are available in the monitored data view.
(Figure
1MRS759142 C
553), there are two branches in
REX640
Technical Manual