S&C Instruction Sheet 681-530
43
Overcurrent Protection Setting Definitions
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 modified 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)
Definite-Time Protection Elements (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.
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 cur-
rent. The time must be faster than the time-overcurrent protection curve.
Definite-Time Current, A
– This is the current at which the
Definite Time
element
picks up.
Definite-Time Time, s
– This is the time delay at which the
Definite Time
Current
element picks up.
Reset Time Parameters (Sensitive Earth Fault )
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. Accumulated value will
reset to zero after the reset time has elapsed.
