ABB RELION Series, Technical Manual

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GUID-AEA0E874-C871-4C90-82ED-3AFE41D28145 V2 EN
Figure 258: 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 258 the feeder is modelled either with one or three line sections with
parameters given in Table 518 .
Table 518: 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 10000 pu 4000 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 3000 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 3000 pu
Figure 258 illustrates the conversion error from 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.
Taps or spurs in the feeder
If the protected feeder consists of taps or spurs, the measured fault impedance
corresponds to several physical fault locations (For example, A or B in
Figure 259 ).
The actual fault location must be identified using additional information, for example,
short circuit current indicators placed on tapping points.
Section 5
1MRS758755 A
Protection related functions
498 REC615 and RER615
Technical Manual