Overcurrent Feature - ABB Relion 670 Series Technical Reference Manual

Section 6
Current protection
6.8.2.3
204
IRecnInhibit< parameter in order to determine when the capacitor bank is
energized or disconnected. The simplified logic diagram is shown in fig 96.
currentRMS
IRecnInhibit<
IEC08000345 V1 EN
Figure 96: Capacitor bank energization check for one phase. Similar for all
three phases
When SCB is disconnected in all three phases, the reconnection inhibit signal will
be given. This signal will be active until the preset time elapsed and is used to
inhibit the reconnection of charged capacitor bank to live network. The internal
logic diagram for the inhibit feature is shown in figure 97.
CAPDISC Ph1 _
CAPDISC Ph2
AND
CAPDISC Ph3
IEC08000346 V1 EN
Figure 97: Capacitor bank reconnection inhibit

Overcurrent feature

The overcurrent protection feature protects the capacitor bank from excessive
current conditions. The sub function takes the current peakRMS value from the
preprocessing block in the IED as input. The peakRMS value of the current is
compared with the setting of parameter IOC>. Whenever the peakRMS value of
the current crosses the set level the function sends a START signal as output. The
signal is passed through the definite timer for giving the TRIP signal. Each phase
will have its own START and TRIP signals for overcurrent. The internal logic for
the overcurrent feature is shown in fig 98.
a
0.02 s
a>b
t
b
tReconnInhibit
AND
-2
Z
-2
Z
1MRK 505 208-UEN B
CapBank Energised
CAPDISC
Phx
NOT
IEC08000345-1-en.vsd
CAPDISC
RECNINH
AND
en08000346.vsd
Technical reference manual