Long Distance Exploding Wires
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Electrical arcs are usually created with the breakdown of air, requiring an average electric field (AEF) of at least 100 kV/m in long spark gaps. This thesis explores a novel method of creating long electrical arcs using exploding wires (EWs). Arcs up to 60 m long have been produced with AEFs of just 4.5 kV/m. Extensive observations of the EW process are presented, which demonstrate that the arcs, which are a type of ‘restrike', form via the seldom-reported ‘plasma bead' restrike mechanism. Beads of plasma appear to form at sites of wire fragmentation, and can expand and coalesce into a continuous plasma column.
There are strict conditions under which the plasma beads, and hence restrike channels, are produced. A restrike prediction model has been developed to provide a reliable method of producing restrike. The model was derived from the improved understanding of the restrike mechanism, and uses the wire's length and the energy supply voltage and characteristics as inputs. Capability diagrams are then constructed, which allow researchers to easily design experiments that will produce restrike.
Extensive descriptions are provided of the experimental environments that were designed and constructed to facilitate long distance EW experiments. Experiments have been performed inside a high voltage laboratory, in the laboratory's outdoor compound, off the laboratory's earth grid and completely off-site. The off-site location allowed vertical experiments, suspended by a weather balloon, to be performed. This led to a theory on artificially triggered lightning, which is one of many exciting future applications that are suggested. It is also predicted that other research groups will be able to create arcs of several hundred metres long.