ABB Relion 670 Series Technical Reference Manual page 228

Section 6
Impedance protection
222
The characteristic for FDPSPDIS (21) function at phase-to-ground fault is according to
figure 102. The characteristic has a fixed angle for the resistive boundary in the first
quadrant of 60°.
The resistance RN and reactance XN are the impedance in the ground-return path
defined according to equation
-
R 0 R 1
=
RN
3
EQUATION1256 V1 EN
-
X 0 X 1
=
XN
3
EQUATION1257 V1 EN
RFItRevPG
RFItRevPG
60 deg
RFItRevPG
Kr·(X1+XN)
ANSI06000396 V1 EN
Figure 102: Characteristic of FDPSPDIS (21) for phase-to-ground fault (setting
parameters in italic), ohm/loop domain (directional lines are drawn as
"line-dot-dot-line")
Besides this, the 3I residual current must fulfil the conditions according to equation
0
and equation 28.
25 and equation 26.
X (ohm/loop)
Kr·(X1+XN)
RFItFwdPG
X1+XN
60 deg
RFItFwdPG
R (Ohm/loop)
X1+XN
Kr
RFItFwdPG
en06000396_ansi.vsd
1MRK505222-UUS C
1
=
tan(60 deg)
Technical reference manual
(Equation 25)
(Equation 26)
27