ABB COM600 series User's & Technical Manual page 35

1MRS758734 COM600 series 5.1
Substation Analytics Technical Manual
B, R0 line section B, X0 line section B, R1 line section C, X1 line section C, R0 line
section C, X0 line section C and the parameters Line Len section A, Line Len section
B, Line Len section C are enabled for the conversion of the electrical fault distance into
a physical distance. This option should be used in the case of a non-homogenous line,
for example, when the protected feeder consists of more than two types of conductors.
The effect of line impedance non-homogeneity in the conversion of fault loop reactance
into physical fault distance is shown with an example of a 10-kilometer long feeder with
three line types.
• 4 km of PAS 150 (R1 = 0.236 ohm/km, X1 = 0.276 ohm/km)
•
3 km of Al/Fe 54/9 Raven (R1 = 0.536 ohm/km, X1 = 0.369 ohm/km)
•
3 km of Al/Fe 21/4 Swan (R1 = 1.350 ohm/km, X1 = 0.398 ohm/km)
The total line impedance for the 10 km line is R1 = 6.602 ohm (0.660 ohm/km) and X1
= 3.405 ohm (0.341 ohm/km).
Figure 4.3-33 shows an example impedance diagram of the protected feeder when the
line is modeled either with one or three impedance settings. The model with one
impedance setting assumes homogeneous line while the model with three impedance
settings gives accurate non-homogeneous line with three sections. These parameters are
given in Table 4.3-1.
Table 4.3-1 Impedance diagram model parameters
Parameter
R1 line section A
X1 line section A
Line Len section A
X1 line section B
Line Len section B
R1 line section C
X1 line section C
Line Len section C
Figure 4.3-33 illustrates the conversion error as a function of physical fault location.
An error of at maximum nearly eight per cent is created by the conversion procedure
when modeling non-homogenous line with only one section parameter.
The fault location is varied from 1 km to 10 km in 1 km steps (marked with circles). As
a result of a more accurate modelling, that is, with all three different line sections modeled,
there is no error in conversion.
The previous example assumed a short circuit fault and thus, only positive sequence
impedance settings were used. The results, however, also apply for earth faults.
One impedance setting
0.660 Ω/pu
0.341 Ω/pu
10.000 pu
N/A
0.000 pu (default)
N/A
N/A
0.000 pu (default)
Three impedance setting
0.236 Ω/pu
0.276 Ω/pu
4.000 pu
0.369 Ω/pu
3.000 pu
1.350 Ω/pu
0.398 Ω/pu
3.000 pu
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