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CHAPTER 6: SETPOINTS
Phase overvoltage
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
An overvoltage on a running motor with a constant load results in decreased current.
However, iron and copper losses increase, causing an increase in motor temperature. The
current overload element will not pickup this condition and provide adequate protection.
Therefore, the overvoltage element may be useful for protecting the motor in the event of
a sustained overvoltage condition. The 339 provides 2 Phase Overvoltage elements. Each
element can be set to either cause a trip or generate an alarm when the input voltage
exceeds the pickup level for a specified time delay. If it is desirable to have an alarm before
a trip occurs, the user can set the function of one Phase Overvoltage element to ALARM,
and the function of the other element to TRIP. For wye-connected VT, the input voltage is
phase-to-ground voltage; for delta-connected VT, the input voltage is phase-to-phase
voltage. The Phase Overvoltage operation can be set for phase combinations including
"Any One", "Any Two" and "All Three". If overvoltage tripping is enabled, and the setting PH
OV PHASES is set for "Any One", a trip will occur once the magnitude of any input voltage
(wye-connected VT: phase-to-ground voltage; delta-connected VT: phase-to-phase
voltage) exceeds the pickup level for a period of time specified by the time delay. On the
other hand, if overvoltage trip is enabled, and the setting PH OV PHASES is set for "All
Three", a trip will occur only when the magnitudes of all three input voltages exceed the
pickup level for a period of time specified by the time delay.
The following path is available using the keypad. For instructions on how to use the
keypad, please refer to Chapter 3 - Working with the Keypad.
PATH:
SETPOINTS > S3 PROTECTION > PHASE OV1(2)
PH OV FUNCTION
Range: Disabled, Alarm, Latched Alarm, Trip
Default: Disabled
The selection of the Latched Alarm, Alarm, or Trip setting enables the Phase
Overvoltage function. If the operating condition is satisfied when Trip is selected as the
function, the logic operand ANY TRIP OP will be asserted, which in turn will activate the
"TRIP" LED and operate the "Trip" output relay. If Alarm is selected, the "ALARM" LED will
flash upon Phase Overvoltage operation, and will automatically reset when the
activating condition clears. If Latched Alarm is selected, the "ALARM" LED will flash upon
Phase Overvoltage operation, and will stay "ON" after the condition clears, until a reset
command is initiated. The TRIP output relay will not operate if the Latched Alarm or
Alarm function is selected. Any assignable output relays can be selected to operate
when the setting PH OV FUNCTION is selected as Latched Alarm, Alarm, or Trip.
PH OV PKP
Range: 0.00 to 1.25 x VT in steps of 0.01
Default: 1.25 x VT
This setting defines the Phase OV pickup level.
PH OV DELAY
Range: 0.1 to 600.0 sec in steps of 0.1
Default: 2.0 s
This setting specifies the time delay before Phase OV operation.
PH OV PHASES
Range: Any One, Any Two, All Three
Default: All Three
This setting selects the combination of overvoltage conditions with respect to the
number of phase voltages over the overvoltage pickup setting.
S3 PROTECTION
6–93
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