Protection
12
original point is added to the quadrilateral
characteristic.
The
rectangular
offset
characteristic (illustrated in Figure 6) is
calculated automatically according to the
related
distance
zones
settings.
Furthermore, the memory voltage direction
element, the zero sequence directional
element, and the negative sequence
direction element are applied to determine
the direction together.
X
R
X
Set
R
Set
Φ
Top
Φ
Bottom
Φ
Left
Φ
Right
X
Offset
R
Offset
Figure 6 Extended polygonal distance protection
zone characteristic
Reverse zone characteristic
In addition to the forward characteristic
zones mentioned above, the IED provides
two optional reverse zone characteristics
to protect connected busbar as a backup
protection. The reverse zone characteristic
can be set for zones 4 and 5 individually.
This reverse characteristic has been
shown in Figure 7.
X
R
-X_ZSet
-R_ZSet
Figure 7 Characteristic distance protection
reverse zone
Switch-onto- fault protection
function
Under either auto reclosing or manual
closing process, the protection function is
able to discriminate these conditions to
give an instantaneous tripping once the
circuit breaker is closed on permanent
faulty line.
Power swing (68)
The IED provides a high reliable power
swing
detector
which
discriminates
between fault and power swing with
different algorithm.
Power swing blocking logic
According to the slow behavior of power
swing phenomenon, once one of the two
following conditions is met, the protection
program will switch to power swing logic
process:
Without operation of sudden-change
current
startup
element,
all
phase-to-phase impedances,
Z
AB
,
Z
BC