Phase Overvoltage Protection (59P) - GE 845 Instruction Manual

PROTECTION
Phase Overvoltage
Protection (59P)
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The 845 relay provides two identical Phase Overvoltage (OV) elements per protection
group, or a total of 12 elements. Each Phase Overvoltage element may be used to protect
voltage sensitive loads and system components against sustained overvoltage conditions.
The Phase Overvoltage element may be set as an instantaneous element with no time
delay or may be set as a definite time element. The input voltages are the three phase to
phase voltages from delta connected VTs or three phase to ground voltages from wye
connected VTs.
The settings of this function are applied to each of the three voltage inputs to produce
Pickup and Trip flags per voltage input. The OV Pickup flag is asserted when the voltage on
any voltage input is above the PKP value. The OV Trip flag is asserted if the element stays
picked up for the time defined by the Pickup time delay and that number of voltages
required for operation is equal to the number defined by voltages required for the
operation setting. The element drops from Pickup without operation if the measured
voltage drops below 97 to 98% of the Pickup value before the time for operation is
reached.
Path:
Setpoints > Protection > Group 1(6) > Voltage > Phase OV 1(X)
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
MODE
Range: Phase to Ground, Phase to Phase
Default: Phase to Ground
This setting provides the selection of phase to ground and phase to phase voltages for a
Wye VT connection (phase to phase for delta connected VT connection).
Only Phase to Phase mode shall be selected when the delta is programmed for Phase VT
connection under System/Voltage Sensing.
PICKUP
Range: 0.02 to 3.00 x VT in steps of 0.01 x VT
Default: 1.50 x VT
The setting sets the phase overvoltage pickup level to specified per times VT.
For example, a Pickup setting of 1.10 x VT with 13800:115 VT translates into 15.18kV. If
the mode selection is phase to phase and Setpoints/ System Setup/ Voltage Sensing/
Phase VT Connection selection is Wye, the previous example translates to the phase to
phase voltage value of 15.18kV x 1.732 = 26.29kV.
PHASES FOR OPERATION
Range: Any One, Any Two, All Three
Default: Any One
The setting defines the number of voltages required for operation of the Phase OV
protection function.
PICKUP DELAY
Range: 0.000 to 6000.000 s in steps of 0.001 s
Default: 1.000 s
DROPOUT DELAY
Range: 0.000 to 6000.000 s in steps of 0.001 s
Default: 1.000 s
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS