ABB RELION REX640 Technical Manual page 1136

Protection functions
are selected, an immediate reset occurs. The START output is deactivated when the
reset timer has elapsed.
The setting
The setting parameter
operation time for IDMT. The setting is applicable only when the IDMT curves are
used.
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
unbalance current in one or more phases exceeds the set
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
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
The
mode, the operation timer is frozen to the prevailing value. In the "Block all" mode,
the whole function is blocked and the timers are reset. In the "Block OPERATE
output" mode, HCUBPTOC operates normally but the OPERATE output is not
activated.
4.12.3.6 Application
Shunt capacitor banks (SCBs) are widely used in transmission and distribution
networks to produce reactive power support. Located in relevant places such as
in the vicinity of load centers, SCBs have beneficial effects on power system
performance: increased power factor, reduced losses, improved system capacity
and better voltage level at load points.
The capacitor bank terminology 'Bank', 'Unit' and 'Element' is shown in
1136
Time multiplier is used for scaling the IDMT operation times.
Minimum operate time defines the minimum desired
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
Blocking mode setting has three blocking methods. In the "Freeze timers"
Minimum operate time setting.
Alarm start value . If the compensated
Blocking mode .
1MRS759142 F
Alarm start value , the Level
Alarm delay
Figure 636
REX640
Technical Manual
.