12
SERIAL
PORT
SGR/1
U2
U3
U3
1111
DCBA
+-
Uaux
E
+
-
(~)
(~)
A
N
da
dn
SGR
100V
110V
19 20 21 10 11 61 62 70 71 72 77 78 80 81 68 69 65 66
7
5324 68
SPAU 130 C
START1 SIGNAL1 TRIP2 TRIP1IRF
100V
110V
16 1718
100V
110V
1314 15
IRF
3U<
TS2
TS1
SGB/5
SS1
SS2
U1
I/O
t<
t>,k>
3U>
BS
-
M
MOTOR
FEEDER
CB TRIP
MAIN CB TRIP
Fig. 5. Motor feeder undervoltage protection with relay SPAU 130 C. The selector switch positions
are shown in the table on the following page.
The undervoltage stage of the relay trips the
circuit breakers of the motor feeders connected
to the busbar. In this way the motors are pre-
vented from restarting at the same time on
recovery of the voltage. The operate time setting
of the undervoltage stage is to be longer than the
dead time of the high-speed auto-reclose cycle of
the transmission network. This prevents motors
from tripping during short voltage interrup-
tions.
An unwanted operation of the undervoltage
stage when the miniature circuit breaker (MCB)
trips has been inhibited by routing a control
voltage from the auxiliary contact of the MCB
to the control input 10-11 of the relay. Switch
SGB/5 on the printed circuit board of the volt-
age relay module should be in position 1 as
should also switch SGR/1.
Example 2.
Motor undervoltage
protection
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