Pulsed electroacoustic (PEA) method is a very popular method for measurement of charge in dielectrics. In this method, an acoustic wave proportional to charge is generated by a pulsed HV. The acoustic wave traverses several material layers before being sensed and converted to electrical signal by a piezoelectric transducer. Due to multiple reflections in its path, a direct analysis of traveling acoustic wave would be complex. In this paper, we have proposed simulation of the physical model of the PEA method consisting of electrical and acoustic circuits. Using PSpice model of the method, authors have tried to address some design-related issues, which appear to have not been reported in earlier works. The acoustic circuit has been realized using analogy between acoustic wave and wave propagation in electric transmission line. The piezoelectric transducer is also modeled as a transmission line as in modified Leach's transducer model, except that, in the present case the transducer absorbs acoustic signal instead of generating. Approximate theoretical equations have been used to compare with simulations, wherever a comparison is possible, and found to match well in those cases.Index Terms-Charge measurement, PSpice model, pulsed electroacoustic (PEA) method.

The space charge phenomenon in PE (polyethylene) particularly in LDPE (low density polyethylene) is being widely researched for more than two decades. Despite various theories proposed by researchers, the charge dynamics in general and charge packets in particular, inside the polymeric insulation are yet to be completely known. The authors have investigated the dependence of charge dynamics on electric field using PEA (pulsed electroacoustic) technique. The experiments were carried out at 25 ºC on 100 µm LDPE film samples under applied electric fields of 100-150 kV/mm. External current measurements were also performed under similar conditions. The analysis of charge profiles and external currents shows that apart from other factors, charge formation and polarity of charge also depend on history of electric field application.Interesting observations were made on the consequence of such results. Experiments were performed repeatedly on virgin samples, taken from same lot, and the results were found to be almost same. It is believed that the effect of history of voltage application on charge formation, presented in the paper, is useful for understanding practical behavior of LDPE which, if used in power cables, is expected to serve as a dielectric for several years -accumulating a lot of history of voltage application.

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Space charge accumulation in dielectrics is a hot topic among dielectric research group for more than a decade.The charge accumulation has been observed to be of various types like homo, hetero and packet charge, etc. Volume resistivity and its non-uniform distribution has been suspected for formation of space charge. The author has recently shown that apart from volume resistivity, diffusion coefficient plays a significant role on the type of charge formation. Several issues still remain unaddressed. In the current paper, the author investigates the role of internal properties like volume resistivity and diffusion and external parameters like boundary conditions or condition of electrodes on the formation of space charge more clearly. It has been shown that manipulation in any of the parameters can alter the type of charge formation. It shows a direction for investigation of new insulation materials with suitable material properties and suitable boundaries for minimizing space charge effects. Interesting results have been presented that seem to have not been presented earlier.

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