S&C Vista - Negative Sequence

S&C Instruction Sheet 681-530 41
(Negative Sequence) Protection Element – Select to enable or disable protection
settings for the selected way. The Negative Sequence element trips the fault interrupter
when the negative-sequence component of the three-phase currents exceeds the pickup
value for the time value set by the Inverse Curve or the Denite Time settings.
Curve Family – Select the TCC curve family: IEC, IEEE, or Vista Coordination. For
more details on the curve families, see the “Overcurrent Control Settings” section on
page 56 for the curve families available. The TCC curves available can also be found in
S&C Information Bulletin 680-211, “Time-Current Characteristic Curves.”
Inverse Segment – Select the desired segment from the drop-down list of curves.
Ampere Rating – Select the ampere rating from the drop down menu for Vista
Coordination TCC curves. The IEEE and IEC curves do not use the ampere rating eld.
Minimum-Trip Current, A – This is the current at which the inverse curve begins timing.
When using Vista Coordination curves, the minimum-trip current is set automatically
according to the ampere rating selected. For IEEE and IEC curves, enter the Minimum
Trip Current value in increments of 1 ampere. The value should always be equal to or
lower than the low-current cutoff.
Time Multiplier – This is the time multiplier for the inverse curve. The time multiplier
is only used with IEEE and IEC curves.
Time Adder, s – This is the time adder for the inverse curve. The time adder is only used
with IEEE and IEC curves.
Low-Current Cutoff (Negative Sequence)
Low-Current Cutoff - Select to enable or disable the low-current cutoff. It is not
possible to enable the Low-Current Cutoff setting if the associated Time-Overcurrent
Protection element is disabled. The Low-Current Cutoff setting will not change
automatically when a different curve family is selected. This value will only change
when modied by the user.
Low-Current Cutoff, A – This is the current at which the TCC curve begins timing.
This value must be equal to or greater than the lowest pickup value of the inverse curve.
Negative Sequence
Overcurrent Protection Setting Denitions