Line Len section B or Line Len section C in the order section A-> section B-> section
C.
Impedance model with one line section is enabled by setting
Line Len section A
to differ from zero. In this case the impedance settings
R1 line section A, X1 line
section A, R0 line section A and X0 line section A are used for the fault distance
calculation and for conversion from reactance to physical fault distance. This option
should be used only in the case of a homogeneous line, that is, when the protected
feeder consists of only one conductor type.
Impedance model with two line sections is enabled by setting both
Line Len section
A and Line Len section B to differ from zero. In this case the impedance settings
R1 line section A, X1 line section A, R0 line section A, X0 line section A, R1 line
section B, X1 line section B, R0 line section B and X0 line section B are used for
the fault distance calculation and for conversion from reactance to physical fault
distance. This option should be used in the case of a non-homogeneous line when
the protected feeder consists of two types of conductors.
Impedance model with three line sections is enabled by setting
Line Len section
A, Line Len section B and Line Len section C all differ from zero. In this case the
impedance settings
R1 line section A, X1 line section A, R0 line section A, X0 line
section A, R1 line section B, X1 line section B, R0 line section B, X0 line section B,
R1 line section C, X1 line section C, R0 line section C and X0 line section C are used
for the fault distance calculation and for conversion from reactance to physical fault
distance. This option should be used in the case of a non-homogeneous line 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 demonstrated in example shown in
with 10 kilometer long feeder with three line types. The total line impedance
for the 10 km line is R1 = 6.602 Ω (0.660 Ω/km) and X1 = 3.405 Ω (0.341 Ω/km),
consisting of the following sections and impedance values.
• 4 km of PAS 150 (R1 = 0.236 Ω/km, X1 = 0.276 Ω/km)
• 3 km of Al/Fe 54/9 Raven (R1 = 0.536 Ω/km, X1 = 0.369 Ω/km)
• 3 km of Al/Fe 21/4 Swan (R1 = 1.350 Ω/km, X1 = 0.398 Ω/km)
The non-homogeneity of feeder impedance can be illustrated by drawing the
protected feeder in RX-diagram (in the impedance plane), as shown in
.
Figure 452: Example impedance diagram of an electrically non-homogeneous feeder
(left), and the resulting error in fault distance if the measured fault loop reactance
is converted into physical fault distance by using only one line section parameters
(right).
Protection related functions
1MRS757644 H
850
620 series
Technical Manual
