S&C Vista - Overcurrent Protection Setting Definitions; Time Overcurrent Phase Protection

38 S&C Instruction Sheet 681-530
A list of the Overcurrent Protection settings and their denitions follows:
(Time Overcurrent Phase Protection) Protection Element – Select to enable or
disable phase protection settings for the selected interrupter. This element trips the
fault interrupter when current on one or more phases exceeds the pickup value. When
disabled, only the Denite Time settings and/or Ground, Negative Sequence, and
Sensitive Earth Fault settings are used.
Curve Family – Select the TCC Curve Family: IEC, IEEE, Vista Coordination, or Vista
Speed. 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 desired ampere rating from the drop-down menu for the
Vista Coordination and Vista Speed curve families. 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 or Vista Speed 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 (Time Overcurrent Phase Protection)
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.
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.
Definite-Time Phase Protection (Time Overcurrent Phase Protection)
Denite-Time Phase Protection (Element #1 and Element #2) Select to enable or
disable protection settings for the selected way. Denite Time selection is available if
a IEC, IEEE, or Vista coordination phase TCC curve is selected or if no TCC curve is
specied for phase protection. Denite-Time Phase Protection settings will trip the
fault interrupter if the selected current exceeds the setting value for the specied time
setting.
Time Overcurrent
Phase Protection
Overcurrent Protection Setting Denitions