GE D90 Plus - Page 272

262 D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUPED PROTECTION ELEMENTS CHAPTER 7: PROTECTION
validated, neither forward nor reverse indication is given. In addition, the negative-
sequence current (or zero-sequence current) must be greater than the
Current Cutoff Level
setting value specified in the Protection > Power System > AC Inputs – Current menu. The
following figure explains the usage of the voltage polarized directional unit of the element.
Figure 224: Negative-sequence directional characteristics
The forward-looking function is designed to be more secure as compared to the reverse-
looking function, so use the forward-looking function for the tripping direction. The
reverse-looking function is faster compared to the forward-looking function and is to be
used for the blocking direction. This allows for better protection coordination. Take this bias
into account when using the negative-sequence directional overcurrent element to
directionalize other protection elements.
Select the Settings > Protection > Elements > Group 1 > Current > Negative Sequence
Directional OC menu to open the negative-sequence directional overcurrent
configuration window.
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