ABB REL650 series, Technical Manual

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K
3
I
FA
I
A
Z
L
×
----------------
Z
A
Z
B
+
Z
1
Z
A DD
+
---------------------------
1 +
è ø
æ ö
×
=
EQUATION106 V1 EN
(Equation 111)
and:
• Z
ADD
= Z
A
+ Z
B
for parallel lines.
• I
A
, I
FA
and V
A
are given in the above table.
• K
N
is calculated automatically according to equation 107 .
• Z
A
, Z
B
, Z
L
, Z
0L
and Z
0M
are setting parameters.
For a single line, Z
0M
= 0 and Z
ADD
= 0. Thus, equation 108 applies to both single and
parallel lines.
Equation 108 can be divided into real and imaginary parts:
p
2
p Re K
1
( )
Re K
2
( )
R
F
Re K
3
( )
0 =
×
– +
×
–
EQUATION107 V1 EN
(Equation 112)
p Im K
1
( )
Im K
2
( )
R
F
Im K
3
( )
0 =
× ×
–
×
+
× ×
–
EQUATION108 V1 EN
(Equation 113)
If the imaginary part of K
3
is not zero, R
F
can be solved according to equation 113 , and
then inserted to equation 112 . According to equation 112 , the relative distance to the fault
is solved as the root of a quadratic equation.
Equation 112 gives two different values for the relative distance to the fault as a solution.
A simplified load compensated algorithm, which gives an unequivocal figure for the
relative distance to the fault, is used to establish the value that should be selected.
If the load compensated algorithms according to the above do not give a reliable solution,
a less accurate, non-compensated impedance model is used to calculate the relative
distance to the fault.
14.14.7.3 The non-compensated impedance model
In the non-compensated impedance model, I
A
line current is used instead of I
FA
fault
current:
Section 14
1MRK 506 335-UUS A
Monitoring
670
Technical manual