GE P742

A
pplication Notes P74x/EN AP/N
a7
MiCOM P74
1, P742, P743 (AP) 6-
13
AP
2.1.1.6.1 VT(s) connected to the Bar(s) and the Central Unit,
This device calculates the required voltage information and sends the release information to
the Central Unit via an output contact to opto input communication link. The required logic is
made in the P741 PSL.
The 87BB trip order can be blocked in the CU using 2 logic input sets, one to block the
phase element, the second to block the SEF element and that per zone:
• INP Block 3Ph Z1 to Z8
• INP Block SEF Z1 to Z8
If 2 bus section are included in the same zone (isolator bus section or during double
switching), an OR gate between the 2 voltage criteria from the different bus sections is used
to confirm the fault detection.
Example:
Q
Q Q Q QQQ
Q
Q
Q QQ
C
B
C
B
C
B
C
B
C
B
C
T
C
T
C
T
C
T
C
T
Feeder
1
Feeder
3
Bus1b
Bus1a
Bus2b
P3985ENa
Bus2a
Feeder
2
Feeder
4
• When the isolator bus sections are open:
− The faults in zone 1a are confirmed by the VT connected to the bus section 1a
− The faults in zone 1b are confirmed by the VT connected to the bus section 1b
• When the isolator bus sections are closed:
− The section 1a and 1b are in the same zone, the faults are confirmed by the VT
connected to the bus section 1a OR the VT connected to the bus section 1b
• When the isolator bus sections are open and during double switching, when both
isolators of a feeder are closed:
− The faults in zone 1a / 2a are confirmed by the OR between VT connected to bus
1a and 2a
2.1.1.6.2 VT(s) connected to the Line(s) and a Peripheral Unit,
This device calculates the required voltage information and sends the release information to
a Peripheral Unit via an output contact to opto input communication link. The required logic is
made in the P742 or P743 PSL.
The 87BB trip order can be blocked in the PU using 2 logic inputs, one to block the phase
element, the second to block the SEF element:
• INP Block 87BB/P
• INP Block 87BB/N
If some PUs are connected to Voltage device and not the other ones, some PU can trip
whereas the other ones are blocked by the voltage criteria coming from the Voltage device.