ABB RED650, Technical Manual, Page: 600 / 926

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 according to the setting LineLengthUnit. The fault location is
stored as a part of the disturbance report information (ER, DR, IND, TVR and FL)
and managed via the local HMI or PCM600.
15.9.7.1 Measuring Principle
M14983-4 v2
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.
M14983-5 v1
15.9.7.2 Accurate algorithm for measurement of distance to fault
M14983-7 v5
Figure 294 shows a single-line diagram of a single transmission line, that is fed
from both ends with source impedances Z
A
and Z
B
. Assume that the fault occurs at
a distance F from IED A on a line with the length L and impedance Z
L
. The fault
resistance is defined as R
F
. A single-line model is used for better clarification of
the algorithm.
Section 15
1MRK 505 394-UEN A
Monitoring
594 Line differential protection RED650 2.2 IEC
Technical manual