4 Protection Functions and Specifications
D02706R02.30
L-PRO 4000 User Manual
4-21
Close Command
This method can be applied where the relay can get the Breaker Close com-
mand from control panel manual close switch (TNC) or SCADA Close com-
mand. This Close command should reach the relay as an External Input or a
Virtual Input or ProLogics to initiate SOTF logic.
This method ensures that all the poles or any one pole are in dead condition for
more than the A1 timer by checking the current level (i.e. lower than 4% of
nominal), then it will enable the SOTF function.
Status Monitoring
This method can be applied where the relay can get Breaker status (52A). This
Breaker Status Monitoring signal should reach the relay as an External Input
or a Virtual Input to initiate SOTF logic.
This method will monitor all the pole statuses as well as each pole load current.
The SOTF function is enabled whenever current value is changing from 0 to
more than 4% of nominal or any pole Breaker status is changing from open to
close.
Both options have a common Pick-up delay (i.e. timer B1), which will allow
to extend the SOTF function enabled up-to the desired settable duration. Typ-
ically, this timer value shall be equal to Zone 2 time delay setting.
During SOTF Enabled condition, if any 50 Trip or 50N Trip or Zone 2 (21N2
or 21P2) alarm picked up condition happens, then the relay will go for an in-
stantaneous 3-pole SOTF Trip.
In addition to the above options, the SOTF function has a second harmonic re-
straint logic which allows the line to be more easily energized if the line is T-
tapped with an online reactor or transformer. Energization of the line with the
T-tapped device results in second harmonics that allows the line to be ener-
gized. If a fault exists that exceeds the line high set overcurrent devices, the line
is allowed to trip.
Table 4.7: Switch On To Fault Settings
Switch On To Fault
Enable/Disable
Breaker Signal
Close Command/ Status Monitoring
Close Pulse
EI1 to EI 20, PL1 to PL24, VI1 to VI30 (This setting shall
be enabled when the Breaker signal setting is selected
as Close Command)
Pole Dead Pick-up Timer (A1,
Pick-up timer)
0.0 to 999.9 Seconds (This setting shall be enabled
when the Breaker signal setting is selected as Close
Command)
Main Breaker Status
EI1 to EI 20, PL1 to PL24, VI1 to VI30 (This setting shall
be enabled when the Breaker signal setting is selected
as Status Monitoring)
Summary of Contents for L-PRO 4000
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