GE Multilin 850

4–156 850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION CHAPTER 4: SETPOINTS
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