ABB RELION REX640 - Page 1213

0 2 4 6 8
0
0.5
1
1.5
2
2.5
3
3.5
R (ohm)
X (ohm)
0 2 4 6
8
0
0.5
1
1.5
2
2.5
3
3.5
Fault Distance Error (%)
X (ohm)
PAS150
Swan
Raven
Figure 692: 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).
In Figure 692 the feeder is modelled either with one or three line sections with
parameters given in Table 1155 .
Table 1155: Impedance settings
Parameter Impedance model with one
section
Impedance model with three
sections
R1 line section A 0.660 Ω/pu 0.236 Ω/pu
X1 line section A 0.341 Ω/pu 0.276 Ω/pu
Line Len section A 10.000 pu 4.000 pu
R1 line section B N/A 0.536 Ω/pu
X1 line section B N/A 0.369 Ω/pu
Line Len section B 0.000 pu 3.000 pu
R1 line section C N/A 1.350 Ω/pu
X1 line section C N/A 0.398 Ω/pu
Line Len section C 0.000 pu 3.000 pu
Figure 692 illustrates the error when converting the measured fault loop reactance
into physical fault distance. The fault location is varied from 1 km to 10 km in 1 km
steps (marked with circles). An error of nearly eight per cent at maximum is created
by the conversion procedure when modeling a non-homogenous line with only one
section. By using impedance model with three line sections, there is no error in the
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.
1MRS759142 F
Protection related functions
REX640
Technical Manual
1213