The role of space charge in modern dielectrics and its measurement with PEA system

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Cselkó Richárd
Department of Electric Power Engineering

Plastics have become dominant in many fields of modern electrical insulation technology. Unlike in oil-paper insulations the mobility of charge carriers in plastics are minor, hence the possibility of space charge accumulation is more likely.

When space charge is present in electrical insulations under high voltage the electric field can be highly distorted compared to the distribution defined by the electrodes. Hence, even in normal operation the electric stress within the dielectric material can be locally multiple times higher than the nominal value. The pulsed electroacoustic measurement method has been developed to examine space charge distributions. The basic result of the measurement is the one-dimensional distribution of charges in the insulating material. The physical basis of the detection is as follows. The dielectric is put between two electrodes and a fast voltage impulse is applied on it. Force will act on free charges and mechanical waves will be initiated. There is a piezoelectric film placed on the back of the ground electrode that is able to convert the pressure waves to electric signals.

In my Thesis I introduce the applications of modern dielectrics, the physics of space charges, the theory of the measurement method, the design, the simulation and the implementation of the measurement device, the principle of the signal processing software, and further development possibilities.


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