ABB RELION Series, Technical Manual

Page: 503 / 804

allows the modeling of the line impedance variation in protection relay with three line
sections with independent impedance settings. This improves the accuracy of physical
fault distance conversion done in the protection relay, especially in cases where the
line impedance non-homogeneity is severe. Each section is enabled by entering a
section length, which differs from zero, to settings
Line Len section A , 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
Figure 258
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 258 .
1MRS758755 A
Section 5
Protection related functions
REC615 and RER615 497
Technical Manual