GE MiCOM P747 Agile Technical Manual page 158

Chapter 5 - Protection Functions
● The allocation of current transformer numbers (CT1, CT2, etc.), are defined by the input circuit to
which they are connected.
● The current transformers are assumed to have the polarities shown but you can invert the polarity in
the settings.
● The method used to label the switches is:
▪ QBusn is the bus section isolator on busbar 'n'
▪ QnZx indicates that terminal 'n' connects to zone 'x'
To Set The Configuration:
1. In the Protected Phase setting, confirm which phase is protected.
2. In this scheme there are 8 current transformers so set Terminal Number to 8.
3. Using the Zn CT Dir and Zn CT Inv Dir settings (where n = the number of the zone), map the CT
connections to the zones they are protecting.
Refer to CT directions in the diagram: if a CT looks into a zone, set the relevant bit in the Zn CT Dir
setting; if a CT looks out of a zone, set the relevant bit in the Zn CT Inv Dir setting.
The Zn CT Dir and Zn CT Inv Dir settings are 18-bit fields where the least significant bit corresponds
to terminal 1 and the most significant bit corresponds to terminal 18.
a. In this example, zone 1 is protected using terminals (CTs) 1, 2, and 7, and they all look into the
zone, so you set:
Z1 CT Dir to 000000000001000011
Z1 CT Inv Dir to 000000000000000000
b. In this example, zone 2 is protected using terminals (CTs) 1, 2, and 8. Terminals 1 and 2 look
into the zone but terminal 8 looks out from the zone, so you set:
Z2 CT Dir to 000000000000000011
Z2 CT Inv Dir to 000000000010000000
4. Apply the same method to allocate the terminals for the other zones, for the check zone terminals, for
the bus coupling terminals, and for the bus section terminals.
a. The check zone for this example is defined by terminals 1, 2, 3, and 4, so you set:
ChZONE Terminal to 000000000000001111
b. In this example there are two bus couplers, both protected by two CTs. This is reflected in the
Coupling 2CT-1 and the Coupling 2CT-2 settings. The Bus Coupler 1CT setting is used in
applications where a single CT protects a bus coupler.
c. The Bus Section 1 and Bus Section 2 settings are used to set which zones are connected to
the bus section isolator.
5. Once the configuration settings are complete, map digital inputs in the Programmable Scheme Logic
(PSL). Map the status of all switches on the busbar using the PSL. The following diagram shows
mapped bus section isolators for this example.
Qbus1 52B (open)
Qbus2 52B (open)
E00722
1. If a bus coupler has one circuit breaker protected by two current transformers, map the circuit breaker
to both current transformers. The following diagram shows bus coupler circuit breakers for the worked
example.
138
Input L1
DDB #
Input L1
DDB #
MiCOM P747
Qbus Sect1 Clo
DDB #
Qbus Sect2 Clo
DDB #
P747-TM-EN-1
P747-TM-EN-1.1