ABB REC650 ANSI - The Non-Compensated Impedance Model

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 71)
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
67.
• 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 68 applies to both single and
parallel lines.
Equation
68 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 72)
p Im K
1
( ) Im K
2
( ) R
F
Im K
3
( ) 0=× ×–×+× ×–
EQUATION108 V1 EN (Equation 73)
If the imaginary part of K
3
is not zero, R
F
can be solved according to equation 73, and then
inserted to equation 72. According to equation 72, the relative distance to the fault is
solved as the root of a quadratic equation.
Equation 72 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.
12.14.7.3 The non-compensated impedance model
In the non-compensated impedance model, I
A
line current is used instead of I
FA
fault
current:
Section 12 1MRK 511 287-UUS A
Monitoring
514
Technical manual