ABB Relion 670 series, Technical Reference Manual

Page: 253 / 1232

AB
AB
-I ZPP
arg
-(-I ZRevPP)
V
V
×
×
b =
æ ö
ç ÷
è ø
EQUATION1792-ANSI V1 EN
(Equation 35)
where
V
EQUATION1801 V1 EN
is the V
AB
voltage
ZRevPP is the positive sequence impedance setting for phase-to-phase fault in reverse direction
ZPP I
AB
•
AB
comp1
V = V
ß
I
AB
jX
I
AB
R
-
ZPP I
AB
•
vPP Re Z
AB
I •
V
V Vcomp2 =
·
-
=IF
·ZF =V
AB
en07000110_ansi.vsd
ANSI07000110 V1 EN
Figure 119: Simplified offset mho characteristic and voltage vectors for phase A-to-
B fault.
Operation occurs if 90≤β≤270.
Offset mho, forward direction
When forward direction has been selected for the offset mho, an extra criteria beside
the one for offset mho (90<β<270) is introduced, that is the angle φ between the
voltage and the current must lie between the blinders in second quadrant and fourth
quadrant. See figure
120 . Operation occurs if 90≤β≤270 and ArgDir≤φ≤ArgNegRes .
1MRK505222-UUS C
Section 6
Impedance protection
247
Technical reference manual