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S4 CONTROLS
VT fuse fail (VTFF or 60VTS)
6–140
The 339 relay includes one VT Fuse Failure element. The measured voltages from the
installed phase VTs are monitored and compared against user programmable levels. If one
or two of the three voltages drops to less than 70% of nominal, and at the same time any
of the three voltages is greater than 85%, either an Alarm or a Trip and Start Inhibit will
occur after a 1 second delay. The 70% threshold allows for the possibility that the
downstream voltage from a blown fuse is pulled up above zero by devices connected
between the open fuse and another phase. The VT reference for the VTFF element is the
phase to neutral voltage for Wye-connected VTs, and the phase-phase voltage for a Delta-
connected VT. The VT Connection, VT Ratio and VT Secondary voltage are user
programmable values under
PATH:
SETPOINTS > S4 CONTROL > VT FUSE FAILURE
FUSE FAIL FUNCTION
Range: Disabled, Alarm, Trip
Default: Trip
For details see
Common
SETPOINTS > S2 SYSTEM SETUP > VOLTAGE SENSING
setpoints.
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS
.
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