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S&C Instruction Sheet 681-530
A list of the
Overcurrent Protection
settings and their definitions 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
Definite 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
field.
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)
Definite-Time Phase Protection (Element #1 and Element #2)
Select to enable or
disable protection settings for the selected way. Definite Time selection is available if
a IEC, IEEE, or Vista coordination phase TCC curve is selected or if no TCC curve is
specified for phase protection.
Definite-Time Phase Protection
settings will trip the
fault interrupter if the selected current exceeds the setting value for the specified time
setting.
Time Overcurrent
Phase Protection
Overcurrent Protection Setting Definitions
