6–74 350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION CHAPTER 6: SETPOINTS
Figure 20: Open Delta VT connection
The fault is detected in the Forward direction when the direction of the operating current Ig
is within ± 90° of the polarizing signal. Otherwise the direction is detected as Reverse.
In the case where the voltage drops below the setting of the minimum polarizing voltage,
the ground directional element defaults to the Forward direction.
The diagram below shows the regions for detection of ground current Forward and
Reverse directions with respect to the zero sequence voltage and the selected Maximum
Torque Angle (MTA).
Courtesy of NationalSwitchgear.com
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