title: Investigation of surge propagation in transient voltage surge suppressors and experimental verification

authors: James, Sisira

subjects: Power quality

abstract: An on-going question in the field of surge protection study is how to predict incipient failure of power electronics in the event of a short time, high voltage, and high energy transient surge propagation. The work presented in this thesis addresses the above question by investigating how a high voltage transient surge, whose duration is in the microseconds range, will propagate through the two-level transient voltage suppressor system that is intended to protect sophisticated electronics situated close to the service entrance of a building. In this work the energy patterns relevant to the individual components of the system are evaluated using numerical methods and some of the results are also compared with those obtained using SPICE simulations. Although several mathematical models for surge protection components are discussed in the literature and some device specific ones are provided by manufacturers, there is no evidence to show that a complete analysis, using any such model, has been performed to predict the energy absorptions and associated time lags between the components in a TVSS.
Numerical simulation techniques using MATLAB are used to estimate the energy absorption and associated time delays in relation to the propagated transient surge, in individual components of a transient voltage surge suppressor. This study develops mathematical models for particular nonlinear transient surge absorbing elements, specifically for the metal oxide varistor and transient voltage suppressor diode, formulates the state equations which are used to numerically simulate several instances of the transient voltage surge suppressor system, and presents simulation results. All results are validated experimentally using a lightning surge simulator. The outcomes established using the two approaches indicate that the theoretical energy calculations are within 10% of the experimental validations for the metal oxide varistor, which is the main energy absorbing element in the system. The remaining energy distributions in the line-filter components and the transient voltage suppressor diode, which are at least 10 times smaller, are all within 20% of the experimental results. The times at which, the metal oxide varistor and the transient voltage suppressor diode switches to heavy conduction mode are also simulated accurately.

text: Investigation of surge propagation in transient voltage surge suppressors and experimental verification An on-going question in the field of surge protection study is how to predict incipient failure of power electronics in the event of a short time, high voltage, and high energy transient surge propagation. The work presented in this thesis addresses the above question by investigating how a high voltage transient surge, whose duration is in the microseconds range, will propagate through the two-level transient voltage suppressor system that is intended to protect sophisticated electronics situated close to the service entrance of a building. In this work the energy patterns relevant to the individual components of the system are evaluated using numerical methods and some of the results are also compared with those obtained using SPICE simulations. Although several mathematical models for surge protection components are discussed in the literature and some device specific ones are provided by manufacturers, there is no evidence to show that a complete analysis, using any such model, has been performed to predict the energy absorptions and associated time lags between the components in a TVSS.
Numerical simulation techniques using MATLAB are used to estimate the energy absorption and associated time delays in relation to the propagated transient surge, in individual components of a transient voltage surge suppressor. This study develops mathematical models for particular nonlinear transient surge absorbing elements, specifically for the metal oxide varistor and transient voltage suppressor diode, formulates the state equations which are used to numerically simulate several instances of the transient voltage surge suppressor system, and presents simulation results. All results are validated experimentally using a lightning surge simulator. The outcomes established using the two approaches indicate that the theoretical energy calculations are within 10% of the experimental validations for the metal oxide varistor, which is the main energy absorbing element in the system. The remaining energy distributions in the line-filter components and the transient voltage suppressor diode, which are at least 10 times smaller, are all within 20% of the experimental results. The times at which, the metal oxide varistor and the transient voltage suppressor diode switches to heavy conduction mode are also simulated accurately.

year: 2014

title: The vulnerability to Online Scamming  in contemporary Tongan Society = Ko e laveangofua ‘i he Ngaue Kākā ‘o e Naluope ‘i he Sosaieti Tonga lolotonga

authors: Laulaupea'alu, Siuta

subjects: Cybersecurity

abstract: This research explores the cybersecurity vulnerabilities of Tongan people to the rapid growth of Information, Communication, and Technology (ICT). A research conducted by Laulaupea‘alu and Keegan in 2016 revealed that Tongan people were vulnerable to the influence of rapid ICT development (Laulaupea‘alu and Keegan, 2016). The cybersecurity vulnerabilities that were identified among the Tongan people in 2016 assisted in informing this research, which is to investigate the current susceptibilities in contemporary Tongan society. The aim of this research is to investigate the reasons why Tongans are vulnerable to ICT development specifically Online Scamming (OS) and find possible solutions to mitigate these susceptibilities. This research is the first to explore and narrow the scope to focus specifically on OS in Tonga. This research also focuses on the technical features of cybersecurity and then extends it to cover the cultural practices that would make Tongan people more susceptible to online scamming. 

Laulaupea‘alu and Keegan (2019) directly conveyed these cybersecurity susceptibilities to the Government of Tonga (GoT) in 2018. This report confirmed that the actual position of cybersecurity in Tonga was that at least 73 percent of the organisations were vulnerable to cybercrime and cyberattacks. These organisations were victims of malicious software, spam, unauthorized access, social engineering, ransomware, data theft/data loss, stolen account, and other types of cybercrimes. This report also provided eleven (11) recommendations and suggested to the GoT to deploy these cybersecurity prevention and awareness features to assist in slowing down the issues of cyberattacks in Tonga. 

One of the modern ICT accomplishments in Tonga was the installation of fibre-optic cable in 2013. Again, Laulaupea'alu and Keegan (2018) warned Tongans about the issue of succeeding in the fast internet speed of fibre-optic cable. The “high speed internet brings opportunities such as jobs and business but it also brings malicious cyber actors who can target victims in the nation” (p. 255).  Drawn by the awareness of ICT issues that may arise and could lead to a stage where is unable to control, this research is undertaken to identify the root cause of these vulnerabilities, further looking for cybersecurity issues that are currently incurred and discovering appropriate defensive tools to counter these vulnerabilities. 

The COVID-19 pandemic disrupted and became a major obstacle to this research. Due to border restrictions, there was no opportunity to travel to Tonga for data collection. To solve these issues, e-fanongonongo tokoto (e-ft) methodology was adopted to challenge the worldwide issues of COVID-19. The implementation of e-ft enabled effective communication from Hamilton to the survey participants in Tonga. E-mail, Facebook, Messenger, and Zoom are the communication methods deployed by e-ft to communicate and collect data from one hundred and thirty-nine (139) participants ranging from 16 to 70 years of age. Participants were selected from government ministries, organisations, boards, businesses and ICT grassroots computer users from all five main regions of Tonga (Tongatapu, Vava‘u, Ha‘apai, ‘Eua and Ongo Niua). Although the e-ft process encountered many obstacles in collecting data from the survey participants, it was able to generate responses and data that have been analysed in this research. 

The findings of this research reveal that Tonga is vulnerable to ICT development, and Tongan people are victims of cyberattacks due to the impact of rapid ICT development. These vulnerabilities relate to cybersecurity technical weaknesses, human behaviours, culture, and the personal beliefs of Tongans. This research also indicated that the people’s vulnerabilities were caused by five main elements: greed, romance/love/empathy, lack of cybersecurity training, lack of ICT knowledge, and unwillingness to report to authorities. These vulnerabilities have resulted in the loss of credential information and the loss of money to cybercriminals from the people of Tonga.
Participants who took part in this research suggested powerful and long-term strategic plans to empower the prevention and awareness of Tongan people toward the impact of rapid ICT development.

text: The vulnerability to Online Scamming  in contemporary Tongan Society = Ko e laveangofua ‘i he Ngaue Kākā ‘o e Naluope ‘i he Sosaieti Tonga lolotonga This research explores the cybersecurity vulnerabilities of Tongan people to the rapid growth of Information, Communication, and Technology (ICT). A research conducted by Laulaupea‘alu and Keegan in 2016 revealed that Tongan people were vulnerable to the influence of rapid ICT development (Laulaupea‘alu and Keegan, 2016). The cybersecurity vulnerabilities that were identified among the Tongan people in 2016 assisted in informing this research, which is to investigate the current susceptibilities in contemporary Tongan society. The aim of this research is to investigate the reasons why Tongans are vulnerable to ICT development specifically Online Scamming (OS) and find possible solutions to mitigate these susceptibilities. This research is the first to explore and narrow the scope to focus specifically on OS in Tonga. This research also focuses on the technical features of cybersecurity and then extends it to cover the cultural practices that would make Tongan people more susceptible to online scamming. 

Laulaupea‘alu and Keegan (2019) directly conveyed these cybersecurity susceptibilities to the Government of Tonga (GoT) in 2018. This report confirmed that the actual position of cybersecurity in Tonga was that at least 73 percent of the organisations were vulnerable to cybercrime and cyberattacks. These organisations were victims of malicious software, spam, unauthorized access, social engineering, ransomware, data theft/data loss, stolen account, and other types of cybercrimes. This report also provided eleven (11) recommendations and suggested to the GoT to deploy these cybersecurity prevention and awareness features to assist in slowing down the issues of cyberattacks in Tonga. 

One of the modern ICT accomplishments in Tonga was the installation of fibre-optic cable in 2013. Again, Laulaupea'alu and Keegan (2018) warned Tongans about the issue of succeeding in the fast internet speed of fibre-optic cable. The “high speed internet brings opportunities such as jobs and business but it also brings malicious cyber actors who can target victims in the nation” (p. 255).  Drawn by the awareness of ICT issues that may arise and could lead to a stage where is unable to control, this research is undertaken to identify the root cause of these vulnerabilities, further looking for cybersecurity issues that are currently incurred and discovering appropriate defensive tools to counter these vulnerabilities. 

The COVID-19 pandemic disrupted and became a major obstacle to this research. Due to border restrictions, there was no opportunity to travel to Tonga for data collection. To solve these issues, e-fanongonongo tokoto (e-ft) methodology was adopted to challenge the worldwide issues of COVID-19. The implementation of e-ft enabled effective communication from Hamilton to the survey participants in Tonga. E-mail, Facebook, Messenger, and Zoom are the communication methods deployed by e-ft to communicate and collect data from one hundred and thirty-nine (139) participants ranging from 16 to 70 years of age. Participants were selected from government ministries, organisations, boards, businesses and ICT grassroots computer users from all five main regions of Tonga (Tongatapu, Vava‘u, Ha‘apai, ‘Eua and Ongo Niua). Although the e-ft process encountered many obstacles in collecting data from the survey participants, it was able to generate responses and data that have been analysed in this research. 

The findings of this research reveal that Tonga is vulnerable to ICT development, and Tongan people are victims of cyberattacks due to the impact of rapid ICT development. These vulnerabilities relate to cybersecurity technical weaknesses, human behaviours, culture, and the personal beliefs of Tongans. This research also indicated that the people’s vulnerabilities were caused by five main elements: greed, romance/love/empathy, lack of cybersecurity training, lack of ICT knowledge, and unwillingness to report to authorities. These vulnerabilities have resulted in the loss of credential information and the loss of money to cybercriminals from the people of Tonga.
Participants who took part in this research suggested powerful and long-term strategic plans to empower the prevention and awareness of Tongan people toward the impact of rapid ICT development.

year: 2022

title: Fanning the divine spark: Gaining understandings of micro-interactions in New Zealand classrooms

authors: Eley, Elizabeth Martha Ann

subjects: micro-interactions

abstract: New Zealand’s Treaty of Waitangi was signed by representatives of Iwi Māori (Indigenous tribal groups) and the British Crown.  Inherent in the heritages of both signatory groups is the ontological positioning that children are born of greatness; carriers of the divine spark from Tama-nui-te-rā (the central sun) and created in the image of God.  Almost all New Zealand children attend school.  For some, their ongoing classroom experiences with educators fans their divine spark and works towards the realisation of their innate potential.  For others, schooling is not a positive experience and their divine spark may be neither recognised nor celebrated.  

This research explores the relationships and pedagogical practices that underpin the classroom micro-interactions experienced by children.  Children’s schooling experience is made up of small interactions in classrooms that are situated in the social, political and legal contexts of schooling.  Therefore, this research applies both a centripetal and a centrifugal examination of the macro and micro contexts of classroom interactions.  

In examining the macro-context, ontological views of the child and the theoretical frameworks that guide pedagogy are considered.  The Education Acts governing New Zealand schooling have successively contained an ontological contradiction that enforces both a factory model as the preferred means of schooling for New Zealand and a requirement to honour the Treaty of Waitangi, including the worldviews of both signatories.  I conclude that educators within the compulsory schooling sector are not provided with specific guidance on how to navigate these contradictory worldviews.  Neither ontological views of how children are perceived within the system, nor theoretical frameworks that could and should inform views of knowledge and how learning occurs, are made explicit for educators.  

At the micro-context level, relationships and pedagogical practices are explored through case studies in three different New Zealand classrooms.  In each case, from video-recordings of classroom interactions, critical incidents were extracted and used to support interviews with participating teachers, students, parents and members of the wider school community.  Employing culturally responsive research methodologies, the interactions with participants were relational and dialogic.  The research found that classroom micro-interactions are pervasive and complex.  All participants, students, teachers and whānau, draw from the knowledge, understandings and positionings of the individual’s own cultural toolkits in classroom interactions.  Their cultural toolkits contain a range of factors to support learning, all of which were necessary and interdependent.  

The thesis calls for all children to receive an education that fans their inherent divine spark.  While this experience is not yet the case for all, there is opportunity in the rhetoric and structures already within New Zealand’s education system for this to occur.  Some schools and communities have begun to successfully challenge and address the prevailing theoretical and pedagogical status quo.  Therefore, there is reason for radical hope for a system-wide fanning of the divine spark in every child.

text: Fanning the divine spark: Gaining understandings of micro-interactions in New Zealand classrooms New Zealand’s Treaty of Waitangi was signed by representatives of Iwi Māori (Indigenous tribal groups) and the British Crown.  Inherent in the heritages of both signatory groups is the ontological positioning that children are born of greatness; carriers of the divine spark from Tama-nui-te-rā (the central sun) and created in the image of God.  Almost all New Zealand children attend school.  For some, their ongoing classroom experiences with educators fans their divine spark and works towards the realisation of their innate potential.  For others, schooling is not a positive experience and their divine spark may be neither recognised nor celebrated.  

This research explores the relationships and pedagogical practices that underpin the classroom micro-interactions experienced by children.  Children’s schooling experience is made up of small interactions in classrooms that are situated in the social, political and legal contexts of schooling.  Therefore, this research applies both a centripetal and a centrifugal examination of the macro and micro contexts of classroom interactions.  

In examining the macro-context, ontological views of the child and the theoretical frameworks that guide pedagogy are considered.  The Education Acts governing New Zealand schooling have successively contained an ontological contradiction that enforces both a factory model as the preferred means of schooling for New Zealand and a requirement to honour the Treaty of Waitangi, including the worldviews of both signatories.  I conclude that educators within the compulsory schooling sector are not provided with specific guidance on how to navigate these contradictory worldviews.  Neither ontological views of how children are perceived within the system, nor theoretical frameworks that could and should inform views of knowledge and how learning occurs, are made explicit for educators.  

At the micro-context level, relationships and pedagogical practices are explored through case studies in three different New Zealand classrooms.  In each case, from video-recordings of classroom interactions, critical incidents were extracted and used to support interviews with participating teachers, students, parents and members of the wider school community.  Employing culturally responsive research methodologies, the interactions with participants were relational and dialogic.  The research found that classroom micro-interactions are pervasive and complex.  All participants, students, teachers and whānau, draw from the knowledge, understandings and positionings of the individual’s own cultural toolkits in classroom interactions.  Their cultural toolkits contain a range of factors to support learning, all of which were necessary and interdependent.  

The thesis calls for all children to receive an education that fans their inherent divine spark.  While this experience is not yet the case for all, there is opportunity in the rhetoric and structures already within New Zealand’s education system for this to occur.  Some schools and communities have begun to successfully challenge and address the prevailing theoretical and pedagogical status quo.  Therefore, there is reason for radical hope for a system-wide fanning of the divine spark in every child.

year: 2020