6–56 350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION CHAPTER 6: SETPOINTS
MIN POL VOLTAGE
Range: 0.05 to 1.25 x VT in steps of 0.01
Default: 0.05 x VT
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.
The following table shows the operating current, and the polarizing signals used for
directional control:
Table 6-9: Ground Directional characteristics
* Polarizing voltage will be 3Vo when voltage is measured from the auxiliary voltage
channel.
BLOCK OC DIR UN
Range: Disabled, Enabled
Default: Enabled
This setting establishes the procedure under undefined direction. If enabled, ground OC
elements with “Forward” or “Reverse” setting are blocked; otherwise, they are not.
OUTPUT RELAY X
For details see Common setpoints
.
BLOCK 1/2/3
For details see Common setpoints
.
Quantity Operating Current Polarizing Voltage
Ground Ig -Vo/-3Vo*
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