ABB REG670 - Page 195

1L loop
pol
Ucomp U I Z= - ×
EQUATION1793 V1 EN (Equation 39)
where
U
pol
is the polarizing voltage (memorized UL1 for Phase L1-to- earth fault)
Z
loop
is the loop impedance, which in general terms can be expressed as
( )
1 1Z +ZN 1Z 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 Ucomp and the polarize voltage Upol for a L1-to-earth fault
is
β = − + ⋅
( )
⋅




−
( )
arg argU I KN ZPE Upol
L
L
I1
1
0
3
GUID-A9492CDF-D3B7-4DC5-8E06-6638BEE2540B V2 EN (Equation 40)
where
U
L1
is the phase voltage in faulty phase L1
I
L1
is the phase current in faulty phase L1
3I
0
is the zero-sequence current in faulty phase L1
KN
Z0-Z1
3 Z1×
the setting parameter for the zero sequence
compensation consisting of the magnitude KN and
the angle KNAng .
U
pol
is the 100% of positive sequence memorized voltage
U
L1
1MRK502052-UEN B Section 7
Impedance protection
189
Technical manual