ABB COM600 series User's & Technical Manual page 26

26
COM600 series 5.1
Substation Analytics Technical Manual
Another example of FaultLocator_sc_A is to trig it with generic trip signal update from
the IED.
Fault Location with autoreclosing function
When Fault Location is used with the autoreclosing sequence, the distance estimate from
the first trip is typically the most accurate one. The fault distance estimates from success-
ive trips are possible but accuracy can be degraded due to inaccurate load compensation.
During the autoreclosing cycle dead time, the load condition of the feeder is unsure.
In unearthed networks, the earth-fault magnitude during normal network configuration
is not enough for the accurate fault location estimate. However, the accuracy of the fault
location estimate can be improved by increasing the earthfault current magnitude. This
can be done with the proper switching operations that enlarge the background network
after the tripping of the faulty feeder. The reenergization of the feeder on to the fault
gives an improved estimate about the fault distance. The switching operations that are
needed can also be done during the dead time of the delayed autoreclosing sequence.
The triggering of SCEFRFLO can also be inhibited during the autoreclosing sequence.
This is achieved by connecting the ACTIVE signal from the autoreclosing function which
indicates that the autoreclosing sequence is in progress with the BLOCK input of SCE-
FRFLO. Blocking of the SCEFRFLO triggering is suggested during the autoreclosing
sequence when the load compensation or steady-state asymmetry elimination is based
on the delta quantities. This applies to the short circuit faults for fault loops "AB Fault"
or "BC Fault" or "CA Fault" or "ABC Fault" when the setting Load Com PP loops equals
to "Enabled" or, for earth faults, with the value EF algorithm Sel equal to "Load com-
pensation".
Result validity indicator for earth faults
Fault localization is a challenging task. There are many factors that can deteriorate the
accuracy of the calculated fault distance estimate. The most important factors are:
• Fault resistance. The smaller the fault resistance, the more accurate the result is
likely to be. The accuracy of the fault distance estimation deteriorates if the resistive
part of the fault loop impedance becomes much larger than the reactive part due to
the large fault resistance. The fault resistance is typically quite low during short
circuits. However, it can be the most dominant error source in earth faults.
• Asymmetry. The asymmetry of the line parameters and the loading affects the fault
distance estimation accuracy. If the asymmetry has a very high value, the accuracy
of the fault distance estimation deteriorates.
1MRS758734