ABB RELION REX640, Техническое руководство, Страница: 1212 / 1960

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.
The 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.
The 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.
The impedance model with three line sections is enabled by setting
Line Len section
A, Line Len section B and Line Len section C 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, 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 on the conversion of fault loop
reactance into physical fault distance is demonstrated in the example shown in
Figure 692
with a 10-km-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 692
.
Protection related functions 1MRS759142 F
1212 REX640
Technical Manual