Space charge measurement for 27mm thick XLPE sample in PEA method

Abstract

Cross linked polyethylene (XLPE) is used in an electric power cable as insulation materials. The maximum thickness of XLPE layer is 27mm in a 500kV class electric power cable. The pulsed electro acoustic (PEA) method is widely used to measure space charge distribution in dielectric materials. When measuring the space charge distribution in dielectric materials by using the normal PEA method, the acoustic wave (PEA signal) obtains the space charge profile detected by the piezoelectric device in the system. Usually the sample thickness is less than 10mm in normal PEA method. When a thicker sample is used as a sample, the space charge measurement is very difficult in the PEA method, because the acoustic wave from the upper electrode strongly decreases with the thickness in comparison with the acoustic wave from lower electrode. By using the remade PEA system, the space charge distributions have been measured in 27mm thick XLPE samples under about 1kV/mm DC electric field. The experimental results show that the remade PEA system can detect the PEA signal form the lower and upper electrodes in samples. The deconvolution technique on the dispersion in the thick sample is also remade.