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
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