S&C Vista SD - Ground Protection

32 S&C Instruction Sheet 695-535
Overcurrent Protection Setting Denitions
The Denite Time Phase Protection #1 element must be enabled for the Denite
Time Phase Protection #2 element to be enabled. When programming both the Denite
Time #1 element and the Denite Time #2 element, the Denite Time #2 element
must be set at a higher current and a faster speed than the Denite Time #1 element or
an error will occur. The Denite 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.
Denite-Time Current, A – This is the current at which the Denite Time element
picks up.
Denite-Time Time, s – This is the time delay after the Denite-Time current value
is exceeded at which the Denite Time element initiates a trip.
Reset Time Parameters (Time Overcurrent Phase Protection)
Reset Type – The Reset parameter is a denite time reset method and the Type eld is
always set to Timed mode.
Reset Time, s – Enter the time delay for the denite 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 Denite 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 47 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 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 (Ground 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. 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.
Ground Protection