Abstract
The report discusses post fault transient analysis for
single phase to ground
fault distance estimation in
electrical distribution networks. The networks are
assumed to be radially
operated, and the neutral either
isolated or compensated.
The composition of ground fault transients, i.e. charge,
discharge and
interline compensating com
ponents, is first discussed. For transient analysis, a
new two frequency model
is introduced, which takes
into account the interdependence of charge and discharge
components. According
to the theory, the
charge transient, which is primarily due to the voltage
rise of the two fault
free phases, is most suitable
for fault location, since it is the lowest in frequency
and in most cases also
the largest in amplitude.
Of the various factors affecting the transients, fault
resistance and loads
were found to be the most
important ones. When the magnitude of these is increased,
the transients become
damped, which makes
their parameter identification difficult. Load impedances
can also cause large
errors to the distance
estimates, although the parameters were identified
accurately. Of significance
also is the fault moment. If
the instantaneous voltage is zero, the transient
amplitudes are smaller than
that of the uncompensated
fundamental frequency fault current.
Also errors of measurement transformers are discussed,
and models proposed for
the analysis of their
transient response. From the other error sources, the
effect of fault arc
nonlinearity was studied using a
simulation model.
Of crucial importance are the methods, by which the
transient parameters are
identified from the
measured signals. In the prototype system developed,
other signal components,
except the charge
transient, are first filtered out numerically. The
transient parameters are
then estimated using a least
squares modification of Prony's method.
Three methods were developed for fault location. The
first one is based on the
correlation of transient
frequency and fault distance. Unfortunately the method is
in practice too
sensitive to variation of ground
capacitances and impedances of low voltage loads.
The other two methods are based on the transient line
terminal impedance. The
measurements needed are
from the phase voltages and phase currents of the faulty
line. The location
accuracy is, according to the
field tests, about one kilometer. However, only the
faults with resistances
lower than about 50 ohms can
be located reliably.
Finally other transient based methods,
differentialequation algorithms and
frequency domain methods,
are discussed for comparison.
Original language  English 

Qualification  Doctor Degree 
Awarding Institution 

Supervisors/Advisors 

Award date  16 Nov 1992 
Place of Publication  Espoo 
Publisher  
Print ISBNs  9513842339 
Publication status  Published  1992 
MoE publication type  G4 Doctoral dissertation (monograph) 
Keywords
 electric power distribution
 power distribution lines
 circuits
 ground fault
 fault analysis
 transient analysis
 distance
 position (location)
 theses
Fingerprint Dive into the research topics of 'Transient analysis for ground fault distance estimation in electrical distribution networks: Dissertation'. Together they form a unique fingerprint.
Cite this
Lehtonen, M. (1992). Transient analysis for ground fault distance estimation in electrical distribution networks: Dissertation. VTT Technical Research Centre of Finland.