3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Simulation study of lightning fault waveforms influenced by the arc quenching properties of wooden distribution line poles(2008-05-23T13:08:54Z) Bredenoord, Carl HenkAbstract With an ever increasing emphasis on reliability of supply, improvement in the lightning performance of distribution lines is required. The arc quenching properties of wooden distribution line poles during lightning strikes are an important factor in the reduction of switchgear operation, hence outages. Measurements were conducted on a 22 kV distribution line and it was suspected, in some cases, that direct lightning strikes to the line did not cause switchgear operation. Distribution lines predominantly use wooden poles with a specific configuration which incorporates a 'wooden' spark gap. This paper provides background to the basic configuration of a typical distribution line and the processes which govern the electric arc. A simulation using a dynamic arc model shows that field measured lightning overvoltages on a distribution line are reproducible through system modelling. The simplistic dynamic arc model developed is sufficiently accurate to describe a set of arcs in a larger system such as a distribution line.Item The lightning transient behaviour of a driven rod earth electrode in multi-layer soil(2007-03-07T13:11:44Z) Nixon, Kenneth JohnThe work presented extends and contributes to research in earthing and lightning protection and focuses on the transient behaviour of a driven rod earth electrode. Although previous work in this area has produced practical guidelines and models that may be used for lightning protection system design and analysis purposes, there has not been an investigation into the commonly encountered scenario of multiple layers of di erent soil types, particularly where high current densities cause ionisation to occur in the surrounding soil. In the research presented, the behaviour of a practical driven rod earth electrode subjected to peak impulse currents of up to 30 KA is analysed. Measurements obtained using a large-scale experiment arrangement are compared against results obtained using a time-domain circuit model simulation. It is shown that a single apparent resistivity value calculated from the steady state resistance equation and the measured steady state resistance can be used as a simpli cation for modelling the lightning current transient behaviour of a driven rod earth electrode in multi-layer soil. This represents a unique and valuable contribution to engineers working in the eld of earthing and lightning protection.