S&C Instruction Sheet 681-530
39
Overcurrent Protection Setting Definitions
The
Definite Time Phase Protection #1
element must be enabled for the
Defi-
nite Time Phase Protection #2
element to be enabled. When programming both the
Definite Time #1
element and the
Definite Time #2
element, the
Definite Time #2
element must be set at a higher current and a faster speed than the
Definite Time #1
element or an error will occur. The
Definite Time #1 and #2
elements also must be
greater than the
Low-Current Cutoff
setting and the minimum trip current. The time
must be faster than the time-overcurrent protection curve.
Definite-Time Current, A
– This is the current at which the
Definite Time
Current
element picks up.
Definite-Time Time, s
– This is the time delay after the
Definite-Time
Current
value
is exceeded at which the
Definite Time
element initiates a trip.
Reset Time Parameters (Time Overcurrent Phase Protection)
Reset Type
– The Reset parameter is a definite time reset method and the
Type
field is
always set to
Timed
mode.
Reset Time, s
– Enter the time delay for the definite time reset, if desired. Accumulated
value will reset to zero after
Reset Time
setting has elapsed.
(Ground Protection) Protection Element
– Select to enable or disable protection
settings for the selected way. The
Ground Protection
element trips the fault interrupter
when the computed residual of the three-phase current exceeds the minimum trip current
for the time value set by the
Inverse Curve
or
Definite Time
settings.
Curve Family
– Select the TCC Curve Family: IEC, IEEE, or Vista Coordination curve.
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 TCCs. 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 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.
Ground Protection
