ABB Relion 670 Series Technical Reference Manual page 255

1MRK505222-UUS C
Technical reference manual
The β is derived according to equation
the voltage and current.
X
ϕ
VAB
ZRevPP
ANSI06000469 V1 EN
Figure 121: Operation characteristic for reverse phase A-to-B fault
Phase-to-ground fault
Mho
The measuring of ground faults uses ground-return compensation applied in a
conventional way. The compensation voltage is derived by considering the influence
from the ground-return path.
For a ground fault in phase A, the compensation voltage Vcomp can be derived, as
shown in figure 122.
- ×
= V I
Vcomp
pol A
EQUATION1793-ANSI V1 EN
35 for the mho circle and φ is the angle between
ZPP
ArgNegRes
IAB
ArgDir
en06000469_ansi.ep
Z
loop
Section 6
Impedance protection
R
(Equation 36)
249