The Non-Compensated Impedance Model - ABB REC650 Technical Manual

1MRK 511 287-UEN A
12.14.7.3
Technical manual
and:
• Z = Z + Z for parallel lines.
ADD A B
• I , I and U are given in the above table.
A FA A
• K is calculated automatically according to equation 67.
N
• Z , Z , Z , Z and Z
A B L 0L
For a single line, Z = 0 and Z
0M
parallel lines.
Equation 68 can be divided into real and imaginary parts:
2
× ( ) ( ) R
p – p Re K + Re K
1 2
EQUATION107 V1 EN
× × ( ) × ( ) R
p Im K Im K
– + –
1 2
EQUATION108 V1 EN
If the imaginary part of K
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.

The non-compensated impedance model

In the non-compensated impedance model, I
current:
× × ×
U = p Z I + R I
A 1 L A F A
EQUATION109 V1 EN
Where:
I is according to table 411.
A
The accuracy of the distance-to-fault calculation, using the non-compensated
impedance model, is influenced by the pre-fault load current. So, this method is only
used if the load compensated models do not function.
are setting parameters.
0M
= 0. Thus, equation
ADD
× ( )
– Re K = 0
F 3
× × ( )
Im K 0
=
F 3
is not zero, R can be solved according to equation 73, and
3 F
line current is used instead of I
A
Section 12
Monitoring
68 applies to both single and
(Equation 72)
(Equation 73)
FA
(Equation 74)
fault
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