ABB REL650 series Technical Manual page 175

1MRK 506 335-UUS A
Technical manual
X
ANSI05000722 V1 EN
Figure 79: Setting angles for discrimination of forward and reverse fault for
quadrilateral characteristic
The reverse directional characteristic is equal to the forward characteristic rotated by 180
degrees.
ZDNRDIR (21D) gives binary coded directional information per measuring loop on the
output STDIRCND.
The code built up for release of the measuring fault loops is as follows: STDIRCND =
L1N*1 + L2N*2 + L3N*4 + L1L2*8 + L2L3*16 + L3L1*32
Example: If only L1N start, the value is 1, if start in L1N and L3N are choosen, the value
is 1+4=5.
The polarizing voltage is available as long as the positive-sequence voltage exceeds 5%
of the set base voltage VBase. So the directional element can use it for all unsymmetrical
faults including close-in faults.
For close-in three-phase faults, the V1AM memory voltage, based on the same positive
sequence voltage, ensures correct directional discrimination.
The memory voltage is used for 100ms or until the positive sequence voltage is restored.
After 100ms, the following occurs:
• If the current is still above the set value of the minimum operating current (between
10% and 30% of IBase) the condition seals in.
AngNegRes
AngDir
R
en05000722_ansi.vsd
Section 6
Impedance protection
169