Startco FPU-16 - Mode 2 - Instantaneous Overcurrent; Mode 3 - Current Unbalance

Startco Engineering Ltd. Page 10
FPU-16 Feeder Protection Unit Rev. 0
Pub. FPU-16-M, November, 1997 Downloaded from the Internet, see Disclaimer.
3.4 MODE 2 — INSTANTANEOUS OVERCURRENT
This mode is used to enter instantaneous overcurrent set points and to
annunciate instantaneous overcurrent alarms and trips. The instantaneous
overcurrent trip-and-alarm time is fixed.
Set-Point Range.................................... 1 to 9 x CT-Primary Rating
Set-Point Step Size............................... 0.1 x CT-Primary Rating
Trip-and-Alarm Time.............................. 0.25 to 3 cycles
Display Codes:
Trip............................................. 2FFF
Alarm.......................................... 2AAA
Set Point Deleted........................ 2ddd
Default Values:
Trip............................................. Deleted
Alarm.......................................... Deleted
3.5 MODE 3 — CURRENT UNBALANCE
This mode is used to enter current-unbalance set points and to annunciate
current-unbalance alarms and trips. Two equations are used to calculate
current unbalance.
For I
max
≤ 0.5 x I
n
:
()
[]
Unbalance I I I
n
=− ×
max min
/ 100% (3.1)
For I
max
> 0.5 x I
n
:
()
[]
Unbalance I I I=− ×
max min max
/ 100% (3.2)
Where: I
max
= maximum phase current
I
min
= minimum phase current
I
n
= rated current
Set-Point Range.................................... 5% to 75%
Set-Point Step Size............................... 1%
Trip Time............................................... 5 s
Alarm Time............................................ 1 s
Alarm Hysteresis ................................... 2%
Display Codes:
Trip............................................. 3FFF
Alarm.......................................... 3AAA
Set Point Deleted........................ 3ddd