Littelfuse MPS - Phase Loss-Current; Phase Reverse-Current; Undercurrent

Page 5-6
MPS Motor Protection System Rev. 6-F-022117
Protective Functions
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
I
P
Threshold .......................... 0.10 to 0.50 x CT-primary
rating (I
P
)
Measurement Method ........... DFT
5.9 PHASE LOSS—CURRENT
OPI Menu: Setup | Protection | Phase Loss (I)
Phase loss is a severe form of unbalance. When phase
loss occurs, negative-sequence current (I
2
) is equal to
positive-sequence current (I
1
) and current unbalance is
100% or 1.00 pu. The phase-loss algorithm considers I
2
/I
1
from 0.90 to 1.00 to be a phase loss. This occurs when
one phase is open resulting in two current vectors at 180°.
Set the phase-loss-trip delay lower than the unbalance trip
delay to avoid an unbalance trip in the event of a phase
loss.
NOTE: An open CT will result in I
2
/I
1
=0.5 because the
phase angle between the other two phases remain at 120°.
This is not considered a phase loss.
Trip Delay ............................. 1.00 to 100.00 s
Protection .............................. Enable/Disable Trip1, 2, 3
Measurement Method ........... DFT
5.10 PHASE REVERSE—CURRENT
OPI Menu: Setup | Protection | Phase Rev (I)
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.
Trip and Alarm Delay
(1)
....... 1.00 to 100.00 s
Protection .............................. Enable/Disable Trip1, 2, 3
Enable/Disable Alarm1, 2, 3
Measurement Method ........... DFT
(1)
Single set point applies to Trip and Alarm.
5.11 UNDERCURRENT
OPI Menu: Setup | Protection | Undercurrent
Undercurrent protection is loss-of-load protection and
is active when the motor is in the Run mode. A trip or
alarm is initiated if current remains below the set point for
the programmed delay.
Trip Level ............................. 0.10 to 1.00 x FLA
Trip Delay ............................. 1.00 to 100.00 s
Alarm Level .......................... 0.10 to 1.00 x FLA
Alarm Delay ......................... 1.00 to 100.00 s
Protection .............................. Enable/Disable Trip1, 2, 3
Enable/Disable Alarm1, 2, 3
Measurement Method ........... DFT
5.12 OVERVOLTAGE
OPI Menu: Setup | Protection | Overvoltage
A trip or alarm occurs if the maximum line-to-line
voltage exceeds the set point.
Trip Level ............................. 1.00 to 1.40 x System
Voltage Rating (V
p
)
Trip Delay ............................. 1.00 to 500.00 s
Alarm Level .......................... 1.00 to 1.40 x V
p
Alarm Delay ......................... 1.00 to 500.00 s
Protection .............................. Enable/Disable Trip1, 2, 3
Enable/Disable Alarm1, 2, 3
Measurement Method ........... DFT
5.13 VOLTAGE UNBALANCE
OPI Menu: Setup | Protection | Unbalance (V)
Positive-sequence voltage (V
1
) and negative-sequence
voltage (V
2
) are used to determine voltage unbalance
(V
2
/V
1
). The unbalance display range is 0.00 to 1.00
where 1.00 is 100% unbalance—a single-phase condition.
A negative unbalance will be indicated if voltage inputs
are connected B-A-C.
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
Measurement Method ........... DFT
5.14 PHASE LOSS—VOLTAGE
OPI Menu: Setup | Protection | Phase Loss (V)
Phase loss is a severe form of unbalance. When phase
loss occurs, negative-sequence voltage (V
2
) is equal to
positive-sequence voltage (V
1
) and voltage unbalance is
100% or 1.00 pu. The phase-loss algorithm considers
V
2
/V
1
from 0.90 to 1.00 to be a phase loss. Set the phase-
loss trip delay lower than the unbalance trip delay to
avoid an unbalance trip in the event of a phase loss.
Trip Delay ............................. 1.00 to 100.00 s
Protection .............................. Enable/Disable Trip1, 2, 3
Measurement Method ........... DFT
5.15 PHASE REVERSE—VOLTAGE
OPI Menu: Setup | Protection | Phase Rev (V)
If the voltage phase sequence is B-A-C, the magnitude
of the negative-sequence voltage will be larger than the
magnitude of the positive-sequence voltage.
Trip and Alarm Delay
(1)
....... 1.00 to 100.00 s
Protection .............................. Enable/Disable Trip1, 2, 3
Enable/Disable Alarm1, 2, 3
Measurement Method ........... DFT
(1)
Single set point applies to Trip and Alarm.