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S2 SYSTEM SETUP
Voltage sensing
6–26
PATH:
SETPOINTS > S2 SYSTEM SETUP > VOLTAGE SENSING
VT CONNECTION
Range: Wye, Delta
Default: Wye
The 350 provides three-phase VT inputs, that can be wired to either bus VTs or feeder
VTs. Select the "Wye" connection, if phase-neutral voltages are wired to the relay VT
terminals. Select "Delta" connection, if phase-phase voltages from either Delta or Open
Delta VTs are connected to the three-phase VT terminals. See the VT connections per the
Typical Wiring Diagram in Chapter 2.
VT SECONDARY
Range: 50 V to 240 V
Default: 120 V
This setting defines the voltage across the VT secondary winding when nominal voltage
is applied to the primary. On a source of 13.8kV line-line voltage, with a VT ratio of
14400:120 V delta connection, the voltage to be entered is "115 V". For a Wye
connection, the voltage to be entered is 115/ √3 = 66 V.
VT RATIO
Range: 1.0:1 to 5000.0:1
Default: 1.0:1
This setting defines the VT primary to secondary turns ratio. For a 14400: 120 VT, the
entry would be "120.0:1" (14400/120 = 120).
AUX VT INPUT
Range: V
VT, V
VT, V
ab
bc
ca
Default: V
VT
ab
The 350 relay provides a voltage input (AUX VT INPUT), where a single feeder/line VT can
be connected. The aux. VT voltage can be used for setting up auxiliary under- and over-
voltage feeder protection, as well as one of the voltage inputs for the synchrocheck
function. Select the phase-neutral, or the phase-phase voltage connected to the Aux VT
input terminals.
The auxiliary voltage input can also be connected to an open corner delta VT
arrangement for the Wattmetric ground fault protection. This arrangement is also
known as a broken delta. Connection should be as shown in the following figure, where
polarity is critical.
VT, V
VT, V
VT, V
VT, V
an
bn
cn
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS
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