Measuring Principle - ABB REL650 series Technical Manual

Section 14
Monitoring
14.14.7.1
14.14.7.2
666
R +jX
1A 1A
DRPRDRE
LMBRFLO
ANSI09000726 V1 EN
Figure 306: Simplified network configuration with network data, required for settings
of the fault location-measuring function
If source impedance in the near and far end of the protected line have changed in a
significant manner relative to the set values at fault location calculation time (due to
exceptional switching state in the immediate network, power generation out of order, and
so on), new values can be entered via the local HMI and a recalculation of the distance to
the fault can be ordered using the algorithm described below. It's also possible to change
fault loop. In this way, a more accurate location of the fault can be achieved.
The function indicates the distance to the fault as a percentage of the line length, in
kilometers or miles as selected on the local HMI. LineLengthUnit setting is used to select
the unit of length either, in kilometer or miles for the distance to fault. Line length unit can
also be configured using PCM600. The fault location is stored as a part of the disturbance
report information and managed via the LHMI or PCM600.

Measuring Principle

For transmission lines with voltage sources at both line ends, the effect of double-end
infeed and additional fault resistance must be considered when calculating the distance to
the fault from the currents and voltages at one line end. If this is not done, the accuracy of
the calculated figure will vary with the load flow and the amount of additional fault
resistance.
The calculation algorithm used in the fault locator in compensates for the effect of double-
end infeed, additional fault resistance and load current.
Accurate algorithm for measurement of distance to fault
Figure 307 shows a single-line diagram of a single transmission line, that is fed from both
ends with source impedances Z
IED A on a line with the length L and impedance Z
A single-line model is used for better clarification of the algorithm.
R +jX
1B 1B
R +jX
0L 0L
R +jX
1L 1L
ANSI09000726-1-en.vsd
and Z . Assume that the fault occurs at a distance F from
A B
. The fault resistance is defined as R
L
1MRK 506 335-UUS A
.
F
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