CHAPTER 7: PROTECTION
GROUPED PROTECTION ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
259
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 220: Negative-sequence directional characteristics
The forward-looking function is designed to be more secure as compared to the reverse-
looking function, and therefore, should be used for the tripping direction. The reverse-
looking function is designed to be faster as compared to the forward-looking function and
should be used for the blocking direction. This allows for better protection coordination.
The above bias should be taken 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 item to open the negative-sequence directional overcurrent
configuration window.
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