Table of Contents
Advertisement
4. PT Protection Settings
Table 7. Source and Zero Sequence Current Ground
Settings
PT20/25
Adjustable range: 0.2~1.0, with interval of 0.01
PT10
0.2
0.4
Ig=
0.2x400
160
4.6 Advanced Protections (PT25 only,
unless specified elsewhere)
The PT25 provides a set of advanced protection features that
can be configured to OFF (by default), Alarm or Trip.
Refer to Table 3 for the adjustment range and interval of the
pickup and time delay parameters of the following advanced
protection features.
4.6.1 Over-Voltage
The trip unit continuously monitors the line voltage rms
values (VAB, VBC, VCA). If the line voltage at any phase is
greater than the over-voltage setting, and the corresponding
delay time setting is exceeded, the trip unit will act (OFF,
Alarm or Trip).
4.6.2 Under-Voltage
If the line voltage at any phase is lower than the under-
voltage setting, and the corresponding delay time setting is
exceeded, the trip unit will act.
Note: If both over-voltage and under-voltage protection are
enabled, the under-voltage setting should always be lower
than the over-voltage setting.
4.6.3 Phase Sequence Protection
The phase sequence protection can be set to positive
sequence (A-B-C), or negative (A-C-B) sequence action. When
the phase sequence of the three phase voltages is the same
as the setting, the trip unit will act.
Note: When the phase voltages at all three phases are
greater than 100V, phase sequence metering will be
activated.
4.6.4 Demand Protection
Current demand protection (PT20/25).
Current demand protection is a type of current protection
mechanism for each phase. Different thresholds can be set
for different phases (independent from each other), and the
same time delay parameters are used for all three phases.
When the current of any of the three phases is greater
than the protection threshold of that phase and the
corresponding time delay setting is reached, the trip unit will
act.
14
PT UNIT USER MANUAL APRIL 2023 www.eaton.com.cn
0.6
0.8
1.0
240
320
400
Power demand protection.
When the detected active power is greater than the defined
power demand setting, and the corresponding time delay
setting is reached, the trip device will act.
4.6.5 Frequency Protection
Over-frequency protection
When the frequency detected by the trip unit exceeds the
over-frequency setting, and the corresponding time delay
setting is exceeded, the trip device will act.
Under-frequency protection
If the frequency detected by the trip unit is lower than the
under-frequency setting and the corresponding time delay
setting is exceeded, the trip unit will act.
Note: When Phase A's phase voltage is greater than 100V,
the frequency protection will be activated.
4.6.6 Voltage Unbalance
If the difference between the maximum and minimum values
of the line voltage in three phases is greater than the voltage
unbalance's voltage setting, and the corresponding time delay
setting is exceeded, the trip unit will act.
Note: Voltage unbalance protection is effective only when
the line voltage in at least one phase is greater than 84V.
The voltage unbalance protection is calculated as follows:
Max(Vab,Vbc,Vca)- Min(Vab,Vbc.Vca)
Max(Vab,Vbc,Vca)
4.6.7 Current Unbalance (PT20/25)
The trip unit continuously monitors the rms current value of
each item (Ia, Ib, Ic). Unbalance protection prevents partial
or complete absence of current in one or two phases. If the
difference between the maximum and minimum values of the
three-phase current is greater than the current unbalance's
current setting, and the corresponding time delay setting is
exceeded, the trip unit will act.
Note: Current unbalance protection is effective only when
at least one phase current is greater than 50% of the Long
Delay Pickup (LDPU or I
) value.
r
The current unbalance and phase loss protection is
calculated as follows:
Max(la,lb,Ic)-Min(la.lb.lc)
Max(la,lb,Ic)
x 100%
x 100%
Advertisement
Table of Contents
