Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: The objective of this project is to develop an electromagnetic model that can be used to
accurately calculate the voltage distribution in a transformer winding structure when excited
with standard impulse excitation waves. This voltage distribution is required during the
design stage of a power transformer to ensure that the insulation is capable of withstanding
the occurring electric field stresses during these tests. This study focuses on the modelling
of a single disk-type power transformer winding without the presence of an iron-core.
Methods of calculating self- and mutual-inductances of transformer windings are presented
and validated by means of finite element method software simulations. The same is done for
the calculation methods used for calculating the capacitances in and around the winding
structure. The calculated and FEM-simulated results are compared to measured values as a
final stage of validation. The methods used to calculate the various model parameters seem
to produce results that agrees well with measured values. The non-linear frequency
dependant dissipative nature of transformer windings is also investigated and a methodology
to take this into account is proposed and implemented. The complete modelling
methodology proposed in this thesis, which includes the calculation of the model
parameters, model synthesis and solver algorithm, are applied to an actual case study. The
case study is performed on an air-core reactor manufactured using a disk-type power
transformer winding. The reactor is excited with standard lightning impulse waves and the
voltages along the winding are measured. The calculated and measured voltage wave
forms are compared in both the frequency and time-domain. From the comparison it is
found that the model accurately represents the actual transient voltage response of the testunit
for the frequency range of interest during standard factory acceptance tests. / AFRIKAANSE OPSOMMING: Die doel van hierdie projek is om 'n elektromagnetiese model te ontwikkel wat gebruik kan
word om die spanningsverspreiding in 'n transformatorwindingstruktuur te bereken as
standaard weerligimpulstoetse toegedien word. Hierdie spanningsverspreiding word vereis
tydens die ontwerpstadium van ‘n kragtransformator om te verseker dat die isolasie in staat
is om die elektriese veldsterkte tydens hierdie toetse te weerstaan. Hierdie studie fokus op
die modelering van 'n enkele skyftipe-kragtransformatorwinding sonder die teenwoordigheid
van 'n ysterkern. Metodes van berekening van self- n wedersydse-induktansie van
transformatorwindings word aangebied en getoets deur middel van Eindige-Element-Metode
(EEM) simulasies. Dieselfde word gedoen vir die metodes wat gebruik word vir die
berekening van die kapasitansies in en rondom die windingstruktuur. Die berekende en
EEM-gesimuleerde resultate word vergelyk met die gemeete waardes as 'n finale vlak van
bekragtiging. Die metodes wat gebruik word om die verskillende modelparameters te
bereken vergelyk goed met gemete waardes. Die nie-lineêre frekwensie-afhanklike verliese
van transformatorwindings word ook ondersoek en 'n metode om hierdie in ag te neem is
voorgestel en geïmplementeer. Die volledige voorgestelde modeleringsmetodiek in hierdie
tesis, wat die berekening van die modelparameters, modelsintese en oplosingsalgoritme
insluit word toegepas op 'n werklike gevallestudie. Die gevallestudie is uitgevoer op 'n
lugkern-reaktor wat 'n skyftipe-kragtransformatorwinding. Die reaktor word onderwerp aan
die standaard weerligimpuls golwe en die spanning al langs die winding word gemeet. Die
berekende en gemete spanning golf vorms word met mekaar vergelyk in beide die
frekwensie- en tyd-vlak. Uit die vergelyking blyk dit dat die model die werklike
oorgangspanningsweergawe van die toetseenheid akkuraat verteenwoordig vir die
frekwensie reeks van belang tydens standaard fabriekaanvaardingstoetse.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/85823 |
| Date | 12 1900 |
| Creators | Van Jaarsveld, Barend Jacobus |
| Contributors | Vermeulen, H. J., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xviii, 127 p. : ill. |
| Rights | Stellenbosch University |
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