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Abstract

The shape of current transients in solid and liquid insulants obtained by "time of flight" measurements, are often not in accordance with simple theories of the charge transport mechanism. This work is concerned with the application of the techniques of current transient analysis to the problem,

The thesis contains a study of the fundamental relationships between the motion of charge and the resulting current at the electrodes, including the transition from low level to space charge perturbed (S.C.P.) currents. The case involving static space charge is given special study for this has often resulted ie the use of fallacious expressions in the past.

An iterative computer simulation of the process has been developed, using a computer in real time,to further aid the analysis of transients. This model can simulate the motion of two carriers of differing mobilities and can allow the possibility of either, or both, of the carriers being converted (or "trapped") into the other. Such a model can be easily used to represent a whole range of conditions and transport mechanisms; examples of which are given. One important application is the use of the model in an adaptive mode to produce the charge injection necessary for a given current transient.

The ionic charge transport mechanism in the liquid hydrocarbon n-hexane is studied in depth. For this, a fresh look at earlier work and results is taken from a current transient analysis point of view. This work includes experimental work undertaken, using U.V. photoinjection, to produce the best possible current transients for various conditions for analysis. To this end, a lot of attention is paid to test cell design and use has been made of "state of the art" picoammeter techniques to achieve the best possible performance in terms of noise, risetime and sensitivity.

The experimental results allow an investigation of the linearity of, and the effects of temperature, current level, U.V. filtering, ageing etc. on the shape of the current transients. The results are compatible with earlier work and suggest that the “long tail" effect in the transients is due to impurities producing an effective range of carrier mobilities. The transients also apparently give an indication of current levels necessary for the onset of liquid motion.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses

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