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
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)
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
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