S&C Vista - Page 40

40 S&C Instruction Sheet 681-530
Overcurrent Protection Setting Denitions
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.
Definite-Time Phase Protection (Ground Protection)
Denite-Time Protection Elements (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.
The Definite Time Phase Protection #1 element must be enabled for the Definite
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 Definite Time #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 at which the Denite Time Current
element picks up.
Reset Time Parameters (Ground 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. Accumulated value will
reset to zero after the Reset Time setting has elapsed.