Technical description
3 Supporting functions
3.15 Short circuit fault location
VM259.EN007
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179
3.15.
Short circuit fault location
VS_SCD
The device includes a stand-alone fault location algorithm. The
algorithm can locate a short circuit in radial operated
networks. The fault location is given as in reactance (ohms) and
kilometres. Fault value can then be exported, for example, with
event to a DMS (Distribution Management System). The
system can then localize the fault. If a DMS is not available,
the distance to the fault is displayed as kilometres, as well as a
reactance value. However, the distance value is valid only if the
line reactance is set correctly. Furthermore, the line should be
homogenous, that is, the wire type of the line should be the
same for the whole length. If there are several wire types on
the same line, an average line reactance value can be used to
get an approximate distance value to the fault (examples of line
reactance values: Overhead wire Sparrow: 0.408 ohms/km and
Raven: 0.378 ohms/km).
The fault location is normally used in the incoming bay of the
substation. Therefore, the fault location is obtained for the
whole network with just one device. This is very cost-effective
upgrade of an existing system.
The algorithm functions in the following order:
1.
The needed measurements (phase currents and voltages)
are continuously available.
2.
The fault distance calculation can be triggered in two ways:
by opening a feeder circuit-breaker due to a fault and
sudden increase in phase currents (∆I + DI). Other option is
to use only the sudden increase in the phase currents (∆I).
3.
Phase currents and voltages are registered in three stages:
before the fault, during the fault and after the faulty feeder
circuit-breaker was opened.
4.
The fault distance quantities are calculated.
5.
Two phases with the biggest fault current are selected.
6.
The load currents are compensated.
7.
The faulty line length reactance is calculated.