Space charge measurement for a 27-mm-thick cross-linked polyethylene sample using the pulsed electroacoustic method

摘要

Cross-linked polyethylene (XLPE) is used in electric power cables as insulation. The maximum thickness of an XLPE layer is 27 mm in a 500 kV class electric power cable. The pulsed electroacoustic (PEA) method is widely used to measure the space charge distribution in dielectric materials. When measuring the space charge distribution in dielectric materials using the normal PEA method, the acoustic wave (PEA signal) from which the space charge profile is obtained is detected by a piezoelectric device in the system. Usually, the sample thickness is less than 10 mm in a normal PEA system. When a thicker sample is used, the space charge measurement is very difficult to obtain with a normal PEA system, because the amplitude of the acoustic wave from the upper electrode decreases with thickness compared with that of the acoustic wave from the lower electrode. Using a redesigned PEA system, space charge distributions have been measured in the 27-mm-thick XLPE sample in a 1 kV/mm DC electric field. The experimental results show that the redesigned PEA system can detect a PEA signal from the lower and upper electrodes in the 27-mm-thick XLPE sample. The deconvolution technique applied to the dispersion in the thick XLPE sample has also been improved.%PEA method; Polymer insulating material; Space charge; Thick sample; XLPE