5
Compensation for
natural unbalance
Usually there are some natural unbalance in a
three phase reactive compensation capacitor
bank. An unbalance compensation facility has
therefore been implemented in the protective
relay. A compensation setting area from 0 to
20.0%
∆
I
n
is used. The capacitor bank natural
unbalance current is compensated for both
amplitude and phase angle. Phase current in-
put I
L1
is used as synchronizing input for the
compensation.
Block diagram
IL1
IL3
SGR2 / 3
1
RESET+.
PROGRAM
1
RESET+.
PROGRAM
1
1
SS1
SS2
TS1
TS2
SS3
RESET
TRIP
AR2
AR1
SGB1 / 6
SGB1 / 7
COMPLETE RELAY RESET
SGB1...3 / 8
SGB2...3 / 7
SGB2...3 / 6
TRIP INDICATOR RESET
BS1
BS2
RRES
SGB1..3 / 1
TRIP IND OUTPUT RELAY RESET
IL2
Ia>
ta
70 ms
k
Ib>
∆
I1>
t
∆
1
∆
I2>
k
∆
2
70 ms
SGB1...3 / 2
SGB1...3 / 3
I<
SGB1...3 / 5
SGB1...3 / 4
SGR1 / 1
SGR2 / 1
SGR1 / 5
SGF / 1
SGR1 / 2
SGR2 / 2
SGR1 / 6
SGR1 / 3
SGR2 / 4
SGR2 / 7
SGR1 / 8
SGF / 2
SGR2 / 6
SGR1 / 7
SGR1 / 4
SGR2 / 5
SPCJ 4D40
RECONNECTION INHIBIT
EXTERNAL TRIP
SGR2 / 8
t<
200ms
t rec
COMP
∆
Ics
∆
Ic
∆
I
Fig 2. Block diagram for capacitor bank module type SPCJ 4D40
I
L1
, I
L2
, I
L3
Measured phase currents
∆
I
Measured phase unbalance
∆
I
c
Compensated phase unbalance
BS1, BS2 and RRES
External blocking or resetting signals
SGF, SGB1...3 and SGR1...2
Programming switchgroups
SS1...SS3,
TS1...TS2
Output signals
TRIP
Red trip indicator