ABB Relion 611 Series, Technical Manual

Page: 349 / 536

In the example, the incoming feeder is carrying a load of 2.0 pu and both outgoing
feeders carry an equal load of 1.0 pu However, both HIxPDIF and HZCCxSPVC
consider the current as an increased differential or unbalance current because of the
broken CT wire in phase C. Both HIxPDIF and HZCCxSPVC receive the differential
current of approximately 1.0 pu The main differential protection HIxPDIF cannot
operate because of the higher current setting.
All CTs must have the same ratio.
The
ALARM
output of the CT supervision function can be used to energize an auxiliary
relay which can short-circuit the current CT wires, making the busbar differential
protection inoperative. This arrangement does not prevent unwanted operation of
HIxPDIF if the start setting is below the rated load. For example, if the start setting for
HIxPDIF in the example is set as 0.8 pu HIxPDIF operates before HZCCxSPVC.
6.2.7 Signals
Table 373: HZCCASPVC Input signals
Name Type Default Description
I_A SIGNAL 0 Phase A current
BLOCK BOOLEAN 0=False Block signal for activating blocking mode
Table 374: HZCCBSPVC Input signals
Name Type Default Description
I_B SIGNAL 0 Phase B current
BLOCK BOOLEAN 0=False Block signal for activating blocking mode
Table 375: HZCCCSPVC Input signals
Name Type Default Description
I_C SIGNAL 0 Phase C current
BLOCK BOOLEAN 0=False Block signal for activating blocking mode
Table 376: HZCCASPVC Output signals
Name Type Description
ALARM BOOLEAN Alarm output
Table 377: HZCCBSPVC Output signals
Name Type Description
ALARM BOOLEAN Alarm output
1MRS757454 D
Section 6
Supervision functions
611 series 343
Technical Manual