Investigation of electrical properties of field grading materials based ZnO microvaristors

Ahmad, Hafisoh 2017. Investigation of electrical properties of field grading materials based ZnO microvaristors. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Field grading material based microvaristors are widely used to minimise the localised field enhancement which could trigger corona and partial discharges in high voltage equipment. In this research, two different microvaristor powders, A and B are composed of silicone rubber matrix at certain filler concentration. The fabrication process of this composite is done by mixing the insulating matrix with filler using high shear mixer, follow by degassing and curing. The additional procedure, heat treatment, is introduced to avoid the agglomeration risk. Such challenges during running this process are well discussed. The composites are subjected to three high voltage tests, alternating current (AC), direct current (DC) and impulse. The non-linearity behaviour of these composite is characterised as dependent on the microvaristor loading, material properties and voltage application. The microscopic evaluations are conducted to examine the effect of material properties toward the electrical properties of composites. An 11 kV polymeric insulator has been modelled and simulated in COMSOL® platform. The performance of this insulator is assessed under a number of simulation scenarios. The potential voltage and field profile of this insulator are identified. Such improvement of field distribution along the insulator is required, therefore the electrical properties of field grading material is adopted into numerical simulation. The introduction of microvaristor material with an appropriate switching characteristic has led to a substantial improvement in the electric field and heat distributions along the insulator profile.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Engineering
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Uncontrolled Keywords:	Materials; Microvaristors; Field Grading Materials; ZNO Varistors; Electrical Field Control; Polymeric Outdoor Insulator.
Date of First Compliant Deposit:	24 January 2017
Last Modified:	20 Apr 2021 09:23
URI:	https://orca.cardiff.ac.uk/id/eprint/97711

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