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 Thames miners’ union

authors: Hart, Philip

abstract: More of a friendly society than a class conscious workers’ movement, the Thames Miners’ Union was formed in 1890 as a branch of the Amalgamated Miners’ Association of Australasia. The state of mining at this time in Australia and New Zealand discouraged militancy, and although the inaugural meeting agreed that miners must stand together to protect their rights, it was hoped to avoid strike action. Because of its focus on ‘practical sympathy’, meaning providing financial assistance to members in need, the new union had wide public support, as illustrated by non-miners joining as honorary members.
From the start, the union wished to assist its members by regulating hours and wages, and was willing to look beyond its confines to assist other unions’ struggles. Accepting that capitalists were needed if mining was to develop, it would in time seek legislation to benefit the industry. Mini-biographies of the leading members of the new union and of some of its branches in outlying mining districts (including at Te Aroha) illustrate the moderate nature of these men. Some were mine managers, most were active within the wider community, and all were thoroughly respectable. Examples are included of harmonious relationships between miners and their managers.
Accident and health benefit payments were devised, and public concerts were held for the union’s ‘benevolvent fund’. Miners’ Union Demonstrations, held annually to mark the union’s founding, included parades and sports meetings involving members’ families. Miners’ halls became the social centres of mining communities. Involvement in national politics commenced when a labour candidate, a clergyman, stood for the Thames electorate.
In the Te Aroha district, the first association was an accident relief fund, which involved non-miners. A branch of the union had only a brief life because of the rapid decline of mining there.
By the twentieth century there were demands for more militancy, especially at Waihi, where the policies of the Waihi Company provoked resistance amongst the workers. By then Hauraki miners were experiencing increased unemployment, with companies under-manning or not working some of their ground, all causes for complaint. In 1903 the Waihi branch would break away from the parent union, which steadily declined as mining declined. The Thames Miners’ Union, which exalted the ‘dignity of honest labour’, gently faded away without ever calling a strike.

text: The Thames miners’ union More of a friendly society than a class conscious workers’ movement, the Thames Miners’ Union was formed in 1890 as a branch of the Amalgamated Miners’ Association of Australasia. The state of mining at this time in Australia and New Zealand discouraged militancy, and although the inaugural meeting agreed that miners must stand together to protect their rights, it was hoped to avoid strike action. Because of its focus on ‘practical sympathy’, meaning providing financial assistance to members in need, the new union had wide public support, as illustrated by non-miners joining as honorary members.
From the start, the union wished to assist its members by regulating hours and wages, and was willing to look beyond its confines to assist other unions’ struggles. Accepting that capitalists were needed if mining was to develop, it would in time seek legislation to benefit the industry. Mini-biographies of the leading members of the new union and of some of its branches in outlying mining districts (including at Te Aroha) illustrate the moderate nature of these men. Some were mine managers, most were active within the wider community, and all were thoroughly respectable. Examples are included of harmonious relationships between miners and their managers.
Accident and health benefit payments were devised, and public concerts were held for the union’s ‘benevolvent fund’. Miners’ Union Demonstrations, held annually to mark the union’s founding, included parades and sports meetings involving members’ families. Miners’ halls became the social centres of mining communities. Involvement in national politics commenced when a labour candidate, a clergyman, stood for the Thames electorate.
In the Te Aroha district, the first association was an accident relief fund, which involved non-miners. A branch of the union had only a brief life because of the rapid decline of mining there.
By the twentieth century there were demands for more militancy, especially at Waihi, where the policies of the Waihi Company provoked resistance amongst the workers. By then Hauraki miners were experiencing increased unemployment, with companies under-manning or not working some of their ground, all causes for complaint. In 1903 the Waihi branch would break away from the parent union, which steadily declined as mining declined. The Thames Miners’ Union, which exalted the ‘dignity of honest labour’, gently faded away without ever calling a strike.

year: 2016

title: Kia reo Māori anahe te reo karanga

authors: Puke, Haupai

subjects: Karanga

abstract: Mā taku karanga o runga ake nei tēnei tuhinga e wāwāhi. Ahakoa he aha te ahurea ōna tikanga me ōna kawa, kua hurihia i roto i ngā rautau. Ko ngētehi kei te pupuruhia tonutia hāunga anō he hou ōna āhuatanga. Ko te kaupapa rangahau o tēnei tuhinga ko te karanga me ngētehi āhuatanga ōna hei tautoko i te whakahau kia noho reo Māori anahe te reo karanga. He aha e pēnei na ai te whakaaro mō tēnei o ngā tikanga o te ao Māori? I runga anō i ngā āhuatanga hou, i ngā whakarerekētanga tikanga o te karanga i roto i tēnei ao hurihuri kāore e tautāwhina te take. Ko ngā kōrero, ngā whakaaro hoki e whai ake nei e wānangahia ai hei tautoko i tēnei whakapae āku.

text: Kia reo Māori anahe te reo karanga Mā taku karanga o runga ake nei tēnei tuhinga e wāwāhi. Ahakoa he aha te ahurea ōna tikanga me ōna kawa, kua hurihia i roto i ngā rautau. Ko ngētehi kei te pupuruhia tonutia hāunga anō he hou ōna āhuatanga. Ko te kaupapa rangahau o tēnei tuhinga ko te karanga me ngētehi āhuatanga ōna hei tautoko i te whakahau kia noho reo Māori anahe te reo karanga. He aha e pēnei na ai te whakaaro mō tēnei o ngā tikanga o te ao Māori? I runga anō i ngā āhuatanga hou, i ngā whakarerekētanga tikanga o te karanga i roto i tēnei ao hurihuri kāore e tautāwhina te take. Ko ngā kōrero, ngā whakaaro hoki e whai ake nei e wānangahia ai hei tautoko i tēnei whakapae āku.

year: 2012-05