ABB REO 517 Applications Manual page 345


Fault locator (FLOC)
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The parameters for the fault locator function are set via the local HMI or PST (Param-
eter Setting Tool). Refer to the Technical reference manual for setting parameters and
path in local HMI.
The list of parameters (see the setting parameters in the Technical reference manual) ex-
plains the meaning of the abbreviations. Figure 181 also presents these system param-
eters graphically. Note, that all impedance values relate to their secondary values and
to the total length of the protected line. The conversion procedure follows the same
rules as for the distance-protection function.
R +jX
1A 1A
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For a single-circuit line, the figures for mutual zero-sequence impedance (X
are set at zero.
The source impedance is not constant in the network. However, this has a negligible in-
fluence on the accuracy of the distance-to-fault calculation, because only the phase an-
gle of the distribution factor has an influence on the accuracy. The phase angle of the
distribution factor is normally very low and practically constant, because it is domi-
nated by the positive-sequence line impedance, which has an angle close to 90°. Always
set the source impedance resistance to values other than zero. If the actual values are
not known, the values that correspond to the source impedance characteristic angle of
85° give satisfactory results.
R +jX
0L 0L
R +jX
1L 1L
Z =Z +jX
0m 0m 0m
R +jX
0L 0L
R +jX
1L 1L
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R +jX
1B 1B
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