Since space charge plays a significant role in long-term electrical degradation of polymeric insulation in high voltage cables, there is growing interest in the measurement of the energy dissipation of mobile and trapped charges in the dielectric molecules. The dissipation process is associated with the emission of visible photons, a process known as electroluminescence (EL) and can be used, potentially, as an indicator for the inhibition of electrical ageing of insulation. This thesis is based on an investigation into the occurrence of EL in dielectric materials as a result of applying high ac stresses. The phenomenon has been observed and analyzed for different types of thin polymeric films using a charge coupled device (CCD) detection system. This unique experimental setup enables a range of measurements to be performed including the imaging of EL, its temporal behaviour, spectral analysis and phase-resolved measurements using the same detector. The effects of several factors such as the types of material under study and local gas environment have been assessed based on the results obtained. Previously, different research groups have monitored the occurrence of EL under ac conditions by applying a sinusoidal electric field across the polymer but in this project, the emission is also examined under the influence of triangular and square voltage waveforms, together with their asymmetrical counterparts. In addition to this, a dynamic bipolar charge recombination model has been developed in order to simulate studies of EL under an alternating field. By comparing experimental results with the stimulation, the theories relating to the processes responsible for the occurrence of EL have been evaluated and a good agreement was found between the simulation and experimental results.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:494683 |
| Date | January 2008 |
| Creators | Ariffin, Azrul Mohd |
| Publisher | University of Southampton |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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