Faculty of Health, Engineering & Sciences

Vibroacoustic Transformer Condition Monitoring

A dissertation submitted by

Dean Mark Starkey

Student ID: 0061038897

in fulfilment of the requirement of

ENG4112 Research Project Part 2

towards the degree of

Bachelor of Engineering (Honours)

Major Power Engineering

October 2016

Dean Starkey | 0061038897 i

ABSTRACT

Throughout the life of a transformer the effects of mechanical shocks, insulation

aging, thermal processes and short circuit forces will cause deformations in the

winding. This deformation can lead to vibration in the transformer and mechanical

fatigue of the solid insulation. Defects which form in a transformers structure can

cause faults such as partial discharge, hot spots and arcing. These faults generate

combustible gases which can be analysed for condition assessment of the transformer.

The development of a suitable and cost effective vibration measurement system forms

a key part of this research project. A monitoring system is developed for real-time

vibration analysis. An embedded capacitive accelerometer is used in conjunction with

an Arduino microcontroller to record vibrations. The sensor platform is designed to

communicate wirelessly via XBee radios to a terminal computer. A software program

and user interface is designed as a tool for analysis.

The outcomes and benefits of these works are primarily based on determining the

condition of transformer insulation through measurements of vibration. Following a

working measurement system, suitable transformer sites are monitored. Spectral

analysis is performed in the frequency domain to determine a correlation with gas

analysis results. The validity of vibroacoustic measurement as a predictive

maintenance tool is subsequently evaluated.

Six transformers are chosen for vibration monitoring with analysis of the vibration

signatures correlated to the dissolved gas analysis reports at each site. The vibration

signatures at each location are analysed using the Short Time Fourier Transform and

frequency peaks compared for the different sites. It was noted that sensor location does

not have a large impact on vibration magnitudes and identifying the frequency

components present in the signal. However, from the signatures obtained there is not

enough variation in magnitude or frequency components to suggest that this method

can identify the type of fault present.

Dean Starkey | 0061038897 ii

LIMITATIONS OF USE

The Council of the University of Southern Queensland, its Faculty of Health,

Engineering & Sciences, and the staff of the University of Southern Queensland, do

not accept any responsibility for the truth, accuracy or completeness of material

contained within or associated with this dissertation.

Persons using all or any part of this material do so at their own risk, and not at the risk

of the Council of the University of Southern Queensland, its Faculty of Health,

Engineering & Sciences or the staff of the University of Southern Queensland.

This dissertation reports an educational exercise and has no purpose or validity beyond

this exercise. The sole purpose of the course pair entitled “Research Project” is to

contribute to the overall education within the student’s chosen degree program. This

document, the associated hardware, software, drawings, and other material set out in

the associated appendices should not be used for any other purpose: if they are so used,

it is entirely at the risk of the user.

Dean Starkey | 0061038897 iii

CERTIFICATION

I certify that the ideas, designs and experimental work, results, analyses and

conclusions set out in this dissertation are entirely my own effort, except where

otherwise indicated and acknowledged.

I further certify that the work is original and has not been previously submitted for

assessment in any other course or institution, except where specifically stated.

Dean Starkey

Student Number 0061038897

Signature

Date

Dean Starkey | 0061038897 iv

ACKNOWLEDGEMENTS

I would like to thank my supervisors Mr Andreas Helwig and Dr Narottam Das for

their guidance, feedback and support during this project.

I would also like to thank my work colleague Matthew Gibson for providing the DGA

information and reports needed. I would like to thank my parents for their continued

support and encouragement throughout this journey. Above all I would like to thank

my wife Yasmin Starkey for patiently supporting me in my studies over the past five

years.

Dean Starkey | 0061038897 v

ABSTRACT ................................................................................................................. i

LIMITATIONS OF USE ........................................................................................... ii

CERTIFICATION .................................................................................................... iii

ACKNOWLEDGEMENTS ...................................................................................... iv

LIST OF FIGURES .................................................................................................. ix

LIST OF TABLES .................................................................................................. xiii

............................................................................................................. 15

INTRODUCTION .................................................................................................... 15

1.1 Project Aim ................................................................................................ 16

1.2 Project Objectives ...................................................................................... 17

1.3 Ethical Considerations ............................................................................... 18

............................................................................................................. 20

BACKGROUND AND LITERATURE ................................................................. 20

2.1 Magnetostriction ........................................................................................ 20

2.2 Acoustic Signals ......................................................................................... 22

2.3 Traditional Condition Monitoring .............................................................. 23

Chemical Detection ................................................................................ 24

Acoustic Detection ................................................................................. 26

Source location of partial discharge ....................................................... 26

2.4 Vibroacoustic Condition Monitoring ......................................................... 28

2.5 Signal Processing ....................................................................................... 29

Dean Starkey | 0061038897 vi

Shannon Nyquist Sampling Theorem .................................................... 29

Fast Fourier Transform (FFT) ................................................................ 30

Window Function ................................................................................... 30

Power Spectral Density (PSD) ............................................................... 31

2.6 Review of Information ............................................................................... 32

............................................................................................................. 33

METHODOLOGY ................................................................................................... 33

3.1 Measurement System Hardware ................................................................ 33

Sensor Selection ..................................................................................... 34

Microcontroller ...................................................................................... 38

Resource Analysis .................................................................................. 40

3.2 Measurement System Software .................................................................. 42

3.3 Controlled Experiment ............................................................................... 44

3.4 Field Testing .............................................................................................. 46

Condition Analysis ................................................................................. 46

Site Selection .......................................................................................... 47

3.5 Risk Assessment ........................................................................................ 50

.....................................................................