Application of diagnostic measurements of high voltage insulations

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Cselkó Richárd
Department of Electric Power Engineering

This thesis work is based on the application of diagnostic tests and insulation resistance measurements on high voltage apparatus (such as oil insulated capacitors and transformers) in order to assess the insulation condition of the apparatus. Deterioration of these apparatus needs to be avoided through replacement of parts of the apparatus or regular observation to detect any problem in its primitive stage for maintenance, and enhancing safety and reliability.

Insulators are made up of dielectric materials (which have the ability to store energy when an external electric field is applied). The paper review the relevant literature related to dielectric measurement applied to high voltage insulations. These include how dielectric polarization, dielectric response function, polarization and depolarization currents affect the dielectric materials.

Dielectric loss and capacitance measurement expresses the characterization of the insulation materials in frequency domain. These can be achieved through the use of different types of methods from less sensitive such as Schering-bridge to a more sensitive one’s like current comparator bridges. Basic literature of partial discharges including its causes, forms, measurement, and detection are also highlighted.

In general, the work is based on non-destructive tests that provide us with necessary information about the insulation of high voltage equipment.

I divided the work in to three chapters, one of which I discuss dielectric properties and the time and frequency domain analysis (discussing more about the time domain). The second chapter is about Partial discharges and the last chapter is about the measurements I performed on the impulse generator and the transformers.

I used DIA software and Paint to make the circuits and the schematic diagrams. I used excel to make histograms of the measured data from which I make my observations. I then make the conclusion after which I put all my result of the measurements I performed under the annex.


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