S&C Vista - Page 43

S&C Instruction Sheet 681-530 43
Overcurrent Protection Setting Denitions
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 (Sensitive Earth Fault )
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 (Sensitive Earth Fault)
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 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 Denite Time #2 elements
also must be greater than the Low-Current Cutoff setting and the minimum trip cur-
rent. 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 (Sensitive Earth Fault )
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 has elapsed.