Page 5-13
FPU-32 Feeder Protection Unit
Rev.
2-A-103014
Protective Functions
N
OTE:
CT saturation is not detected. Enable overcurrent
protection when fault levels can exceed 15 times the
phase-CT-primary rating.
5.7 D
EFINITE-
T
IME
E
ARTH
F
AULT
Menu:
Setup
|
Protection
|
Ict Def Time
This protection function uses the earth-fault-CT input.
The protection setting range is equal to the earth-fault-
CT-primary rating (I
e
).
Trip Level ................................. 0.01 to 1.00 x Earth-Fault
.............................................. CT primary rating (I
e
)
Trip Delay (D) .......................... 0.00 to 100.00 s
(see Table 5.2)
Alarm Level ............................. 0.01 to 1.00 x I
e
Alarm Delay (D) ....................... 0.00 to 100.00 s
(see
Table
5.2)
Protection ................................. Enable/Disable Trip1, 2, 3
Enable/Disable
Alarm1, 2, 3
Measurement Method ............... DFT c/w saturation
compensation
Set-Point Groups ...................... Group 1 and Group 2
5.8 C
URRENT
U
NBALANCE
Menu:
Setup
|
Protection
|
Unbalance
Menu:
Setup
|
System Config
|
I
2
/I
1
Threshold
Positive-sequence current (I
1
) and negative-sequence
current (I
2
) are used to determine current unbalance (I
2
/I
1
).
The unbalance display range is 0.00 to 1.00 where 1.00 is
100% unbalance—a single-phase condition. Single-phase
loads generate unbalance that may cause false trips when
feeder currents are low. The
I
2
/I
1
Threshold
sets the
current level where unbalance protection becomes active.
The threshold is based on the maximum of the three-
phase currents. Set this value above the single-phase load
value to avoid false trips. Negative unbalance is indicated
when current inputs are connected B-A-C (negative-
sequence current is greater than positive-sequence
current). Severe unbalance may also be indicated if
phase-CT polarity is incorrect.
Trip Level ................................. 0.05 to 1.00
Trip Delay ................................ 1.00 to 100.00 s
Alarm Level ............................. 0.05 to 1.00
Alarm Delay ............................. 1.00 to 100.00 s
Protection ................................. Enable/Disable Trip1, 2, 3
Enable/Disable
Alarm1, 2, 3
Threshold .................................. 0.10 to 0.50 x I
p
Measurement Method ............... DFT
5.9 P
HASE
L
OSS
Menu:
Setup
|
Protection
|
Phase Loss
Phase loss is a severe form of unbalance and can be
used to detect open-circuit faults. When phase loss occurs
on a 3-phase load, negative-sequence current (I
2
) is equal
to positive-sequence current (I
1
). The phase-loss
algorithm considers I
2
/I
1
from 0.90 to 1.00 to be a phase
loss. Set the phase-loss trip delay shorter than the
unbalance trip delay to avoid an unbalance trip in the
event of a phase loss.
The phase-loss threshold is fixed at 10% of the
CT-primary rating (I
p
).
Trip Delay ................................ 1.00 to 100.00 s
Alarm Delay ............................. 1.00 to 100.00 s
Protection ................................. Enable/Disable Trip1, 2, 3
Enable/Disable
Alarm1, 2, 3
Measurement Method .............. DFT
5.10 P
HASE
R
EVERSE
Menu:
Setup
|
Protection
|
Phase Rev
If the current phase sequence is B-A-C, the magnitude
of negative-sequence current will be larger than the
magnitude of positive-sequence current. To maintain
magnitude consistency for set points, the I
2
/I
1
ratio is
inverted for the protection algorithm when phase
sequence is B-A-C. A negative unbalance is indicated in
the meter display for B-A-C sequence.
The phase-reverse threshold is fixed at 10% of the
CT-primary rating (I
p
).
Trip Delay ................................ 1.00 to 100.00 s
Alarm Delay ............................. 1.00 to 100.00 s
Protection ................................. Enable/Disable Trip1, 2, 3
Enable/Disable
Alarm 1, 2, 3
Measurement Method .............. DFT
5.11 PTC T
EMPERATURE
Menu:
Setup
|
Hardware
|
Temp Sensor Type
Menu:
Setup
|
Protection
|
PTC Local Temp
The local-temperature-sensor input is configured for a
positive-temperature-coefficient (PTC) thermistor sensor
using the
Setup
|
Hardware
|
Temp Sensor Type
menu.
The total resistance of series-connected PTC
thermistors must be less than 1,500
at 20°C (68°F). A
trip or alarm will occur when series resistance exceeds
2,800
.
During Emergency Thermal Reset, a PTC trip is reset
and PTC-temperature protection is disabled. See Section
5.2.2.
Protection ................................. Enable/Disable Trip1, 2, 3
Enable/Disable
Alarm1, 2, 3
