GE Multilin 850 Instruction Manual page 288

PROTECTION
4–156
The zero-sequence (V_0) or auxiliary voltage (V_X), accordingly, must be greater than
0.02 x VT to be validated for use as a polarizing signal. If the polarizing signal is invalid,
neither forward nor reverse indication is given.
• If Current polarizing mode is selected, the element uses the angle of the ground
current measured on the ground current input. The ground current must be greater
than 0.05 x CT to be validated as a polarizing signal. If the polarizing signal is not valid,
neither forward nor reverse indication is given.
For a choice of current polarizing, it is recommended that the polarizing signal be
analyzed to ensure that a known direction is maintained irrespective of the fault
location.
• If Dual polarizing mode is selected, the element performs both directional
comparisons as described above. A given direction is confirmed if either voltage or
current comparators indicate so. If a conflicting (simultaneous forward and reverse)
indication occurs, the forward direction overrides the reverse direction.
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")
FORWARD 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: 0.005 to 3.000 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.
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: 0.005 to 3.000 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.
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS