ABB Relion 670 series, Technical Manual

Page: 233 / 1432

A loop
pol
Vcomp
V I Z
=
- ×
EQUATION1793-ANSI V1 EN-US
(Equation 57)
where
V
pol
is the polarizing voltage (memorized VA for Phase A-to- ground
fault)
Z
loop
is the loop impedance, which in general terms can be expressed
as
( )
1 1
Z +ZN 1 Z KN
= × +
where
Z
1
is the positive sequence impedance of the line (Ohm/phase)
KN is the zero-sequence compensator factor
The angle β between the Vcomp and the polarize voltage Vpol for a A-to-ground fault is
( )
A A
arg V I IN KN ZPE arg(Vpol)
b = - + × × -
é ù
ë û
EQUATION1592 V1 EN-US
(Equation 58)
where
V
A
is the phase voltage in faulty phase A
I
A
is the phase current in faulty phase A
IN is the zero-sequence current in faulty phase A (3I0)
KN Z0-Z1
3 Z1
×
the setting parameter for the zero sequence compensation
consisting of the magnitude KN and the angle KNAng.
V
pol
is the 100% of positive sequence memorized voltage V
A
1MRK 502 066-UUS B Section 7
Impedance protection
227
Technical manual