GE 845 Instruction Manual page 283

CHAPTER 4: SETPOINTS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
POLARIZING VOLTAGE
Range: Calculated V0, Measured VX
Default: Calculated V0
Selects the polarizing voltage used by the directional unit when "Voltage" or "Dual"
polarizing mode is set. The polarizing voltage can be programmed to be either the zero-
sequence voltage calculated from the phase voltages ("Calculated V_0") or supplied
externally as an auxiliary voltage ("Measured VX")
POS SEQ RESTRAINT
Range: 0.000 to 0.500 in steps of 0.001
Default: 0.063
This setting controls the amount of the positive-sequence restraint. Set to zero to
remove the restraint. Set higher if large system unbalances or poor CT performance are
expected.
ECA
Range: –90° to 90° in steps of 1°
Default: 75°
This setting defines the element characteristic angle (ECA) for the forward direction in
"Voltage" polarizing mode. "Current" polarizing mode uses a fixed ECA of 0°. The ECA in
the reverse direction is the angle set for the forward direction shifted by 180°.
FORWARD LIMIT ANGLE
Range: 40° to 90° in steps of 1°
Default: 90°
This setting defines a symmetrical (in both directions from the ECA) limit angle for the
forward direction.
FORWARD PICKUP
Range: 0.050 to 30.000 x CT in steps of 0.001 x CT
Default: 0.050 x CT
This setting defines the Pickup level for the overcurrent unit of the element in the
forward direction. When selecting this setting it must be kept in mind that the design
uses a 'positive-sequence restraint' technique for the "Calculated 3I0" mode of
operation.
REVERSE LIMIT ANGLE
Range: 40° to 90° in steps of 1°
Default: 90°
This setting defines a symmetrical (in both directions from the ECA) limit angle for the
reverse direction.
REVERSE PICKUP
Range: 0.050 to 30.000 x CT in steps of 0.001 x CT
Default: 0.050 x CT
This setting defines the Pickup level for the overcurrent unit of the element in the reverse
direction. When selecting this setting it must be kept in mind that the design uses a
'positive-sequence restraint' technique for the "Calculated 3I0" mode of operation.
BLOCK
Range: Off, Any operand from the list of FlexLogic operands
Default: Off
EVENTS
Range: Enabled, Disabled
Default: Enabled
PROTECTION
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