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5.3 S2 SYSTEM SETUP
5.3S2 SYSTEM SETUP
PATH: SETPOINTS
S2 SYSTEM SETUP
CURRENT SENSING
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This group of setpoints is critical for all overcurrent protection features that have settings specified in multiples of CT rating.
When the relay is ordered, the phase, ground, and sensitive ground CT inputs must be specified as either 1 A or 5 A.
As the phase CTs are connected in wye (star), the calculated phasor sum of the three phase currents (I
Current = 3I
) is used as the input for the neutral overcurrent. In addition, a zero-sequence (core balance) CT which senses
0
current in all of the circuit primary conductors, or a CT in a neutral grounding conductor may also be used. For this configu-
ration, the ground CT primary rating must be entered. To detect low level ground fault currents, the sensitive ground input
may be used. In this case, the sensitive ground CT primary rating must be entered. For additional details on CT connec-
tions, refer to Section 3.2.1: Typical Wiring on page 3–7 for details.
The setpoint entries are the same for Ground and Phase CTs with 1 A and 5 A secondaries. For correct operation, the CT
secondary must match the relay as indicated on the relay identification label (e.g. 5 A for a xxx:5 CT).
5
PATH: SETPOINTS
S2 SYSTEM SETUP
BUS VT SENSING
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With bus VTs installed, the relay can be used to perform voltage measurements, power calculations, and directional control
of overcurrent elements.
•
VT CONNECTION TYPE: Enter "None" if Bus VTs are not used. If Bus VTs are used, enter the VT connection made to
the system as "Wye" or "Delta". An open-delta connection is entered as "Delta". See Figure 3–9: Typical Wiring Dia-
gram on page 3–7 for details on Delta and Wye wiring.
•
NOMINAL VT SECONDARY VOLTAGE: This setpoint represents the voltage across the VT secondary winding when
nominal voltage is applied to the primary. On a source of 13.8 kV line-line at nominal voltage, with a 14400:120 V VT in
the Delta connection, the voltage to be entered is "115 V". For the Wye connection, the voltage to be entered is 115 /
3
= 66.4 V.
•
VT RATIO: Enter the VT primary to secondary turns ratio with this setpoint. For a 14400:120 VT, the entry would be
"120:1" (since 14400 / 120 = 120.0).
5-16
Courtesy of NationalSwitchgear.com
CURRENT SENSING
ð
ENTER
PHASE CT PRIMARY:
ESCAPE
1000 A
GND CT PRIMARY:
ESCAPE
MESSAGE
50 A
SENSTV GND CT
ESCAPE
MESSAGE
PRIMARY:
1000 A
BUS VT SENSING
ð
VT CONNECTION TYPE:
ENTER
ESCAPE
Wye
NOMINAL VT SECONDARY
ESCAPE
MESSAGE
VOLTAGE: 120.0 V
VT RATIO:
ESCAPE
MESSAGE
120.0:1
750/760 Feeder Management Relay
5.3.1 CURRENT SENSING
Range: 1 to 50000 A in steps of 1
Range: 1 to 50000 A in steps of 1
Range: 1 to 50000 A in steps of 1
5.3.2 BUS VT SENSING
Range: None, Wye, Delta
Range: 50.0 to 240.0 V in steps of 0.1
Range: 1.0 to 5000.0 in steps of 0.1
5 SETPOINTS
+ I
+ I
= Neutral
a
b
c
GE Multilin
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