6–68 350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION CHAPTER 6: SETPOINTS
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 > S3 SETPOINT GROUP 1(2) > NTRL DIR
NTRL DIR FUNCTION
Range: Disabled, Latched Alarm, Alarm, Control
Default: Disabled
When an Alarm function is selected, the alarm LED will flash upon detection of Reverse
direction, and will drop out when the direction changes to Forward. When Latched
Alarm is selected, the alarm LED will flash upon detection of Reverse direction, and will
stay lit (latched) after the direction changes to Forward. The alarm LED can be reset, by
issuing a Reset command. Detection of Reverse direction when the Control function is
selected, does not trigger the alarm LED.
NTRL DIR POLARIZING
Range: Voltage, Current, Dual
Default: Voltage
This setting specifies the voltage polarizing signal for the detection of Forward and
Reverse directions.
NTRL DIR MTA
Range: 0° to 359° Lead in steps of 1°
Default: 315°
This setting sets the Maximum Torque Angle (MTA), for the Neutral Directional element to
define the regions of Forward and Reverse directions. For Voltage polarizing, enter the
maximum torque angle by which the operating current leads the polarizing voltage. This
is the angle of maximum sensitivity.
MIN POL VOLTAGE
Range: 0.05 to 1.25 x VT in steps of 0.01
Default: 0.05 x VT
This setting affects only cases where voltage or dual polarizing is selected. The minimum
zero sequence voltage level must be selected to prevent operation due to normal
system unbalances, or voltage transformer errors. Set the minimum zero sequence
voltage level to 2% of VT for well balanced systems, and 1% of VT accuracy. For systems
with high resistance grounding or floating neutrals, this setting can be as high as 20%.
The default of 5% of VT is appropriate for most solidly grounded systems.
Table 6-11: Neutral directional characteristics
* Polarizing voltage will be 3V
o
when voltage is measured from the auxiliary voltage
channel.
Dual Undefined Undefined Undefined
FW RV Undefined
RV FW Undefined
Undefined FW FW
Undefined RV RV
FW Undefined FW
RV Undefined RV
Quantity Operating Current Polarizing Voltage
(VT connection: Wye)
Polarizing Current
Neutral 3I
0
= I
a
+I b + I c -V
0
= -(V
a
+V
b
+V
c
)/3
-3V
0
(*)
I
g
Directional type Current direction Voltage direction Result
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