Space charge measurement in thick dielectric materials by pulsed electroacoustic method

Abstract

The new application of pulsed electroacoustic (PEA) method to measure space charge profiles in several millimeters thick polymers such as power transmission cable was proposed. In this method, space charge profiles are detected as acoustic wave signals that are generated by the space charge profiles existing in the sample under stimulation of an electric pulse. In most polymer samples, such as cross-linked polyethylene (XLPE) widely used in XLPE cable (CV cable), however, the acoustic wave form is obviously distorted as it propagates through the thick polymer. The acoustic wave distortion cannot be negligible when applying this method directly to very thick samples (several millimeters thick). To recover the wave form and obtain the accurate space charge profiles, it is necessary to study the attenuation and dispersion characteristics of the sample and remove their effects to the propagating acoustic wave. So-called ‘‘deconvolution processing’’ using ‘‘Jacobi method’’ was employed in this report to obtain the undistorted wave form. The principle of the data processing method is introduced and some examples for recovering the wave form are given to verify the effectiveness of the data processing method.