Please note in the picture above that the tripping area is linked to the angle of the positive sequence
voltage
U
1
. The angle of the positive sequence current
I
1
is compared to
U
1
angle, and if the fault is in
the correct direction, it is possible to perform a trip when the amplitude of
I
L1
,
I
L2
or
I
L3
increases
above the pick-up limit.
If the 3LL mode is used without the
U
0
measurement in a single-phase fault situation, the voltage
reference comes from the healthy phase and the current reference from the faulty phase. In a short-
circuit the angle comes from impedance calculation.
Figure. 5.3.4 - 90. Operation sector area when the sector center has been set to -45 degrees.
A
AQ
Q-T215
-T215
Instruction manual
Version: 2.04
112