Modelling and performance evaluation of a three-phase capacitive voltage sensor topology
Date
2006-12
Authors
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Journal ISSN
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Publisher
Stellenbosch : University of Stellenbosch
Abstract
This research project investigates the design, modelling and application of an open-air capacitive
voltage sensor assembly for the measurement of wideband High Voltage signals on three-phase
transmission lines. The advantages and disadvantages of conventional methods used to measure
these voltages are reviewed and the advantages of the open-air capacitive sensor are established.
The main research objective of this project involves extending the application of previously
developed single-phase capacitive sensor topologies to three-phase applications. A three-phase
set of mobile, compact and relatively inexpensive capacitive voltage sensors for open-air
application under overhead transmission lines are designed and constructed, including a data
acquisition triggering system for the measurement of transient waveforms. Equivalent circuit
models, using a Thévenin equivalent approach, are developed for the three-phase sensor topology
and the associated three-phase transmission line configuration. A number of different methods
for simplifying the associated Thévenin equivalent impedance and voltage equations are
evaluated.
The decoupling of the voltage waveforms measured by the individual sensors for a three-phase
transmission line configuration is subsequently examined with the view to derive mathematical
relationships for determining the phase conductor voltages from the measured sensor voltages.
The performance of the sensor assembly is experimentally evaluated under laboratory conditions
as well as field conditions. An outdoor HV test facility, representing a scaled three-phase flat
transmission line structure, is developed for evaluation of the three-phase sensor topology in a
controlled environment. The methodology for decoupling the phase voltages and reconstructing
the phase conductor voltages from the voltages induced on the sensors is evaluated using
measured data obtained with this HV test facility. It is shown that the three-phase capacitive
voltage sensor topology as applied in the test facility delivers good results for the measurement of
three-phase transient voltage waveforms.
Description
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006.
Keywords
Dissertations -- Electrical and electronic engineering, Theses -- Electrical and electronic engineering, Voltmeters