ABB SACE Tmax XT2 User Manual page 49

VU Protection Function
The protection is activated in the event of an imbalance between the line-to-line voltages read by
the Trip unit. If the detected imbalance exceeds the U14 threshold for a time greater than t14,
the protection sends the TRIP command.
The protection automatically cuts out if the maximum line-to-line voltage value is less than 0.3
Un.
To verify and simulate the trip times based on all the parameters, see:


Parameters
Parameter
Enable
Trip Enable
Threshold
I14
Time t14
Constraints, limitations, and additional functions
From the service connector (with Ekip Connect) or with system bus communication it is also
possible to access the block functions, see page70.
1SDH002031A1002 ECN000092998
Protection summary table with the operating characteristics (page 79)
Chart with tripping curve (page 88)
Description
Enables/disables protection and availability on menu of the
parameters
Activates/deactivates the open command: if disabled, the alarm
and the lapsing of the protection time are managed only as
information
Defines the unbalance value that activates the protection.
The unbalance is expressed as a percentage value and is
calculated as follows:
in a range: 2 % .. 90 %, with 1 % step.
NOTE:
voltages by comparing each network voltage with the
average value;
U : average value of the network voltages
mi
This is the trip time of the protection; the value is expressed in
seconds, which are settable in a range:
0.5 s .. 60 s, with 0.5 s step
Rev. B
% Sbil = 100 x (max U

max U : maximum deviation between the three
mi
Default
OFF
OFF
) / U
mi mi
50 %
5 s
SACE Tmax XT2 – XT4 | 49