Comparison of space charge distribution measurements among planar sample, HVDC Cable on external layer and from inner conductor by Laser PWP method

For the real HVDC cable, because of the limitation of technical level and experimental conditions, the measurement of space charge distribution is a difficult problem. The suitable method may be Laser PWP method which use a powerful laser to generate a pressure wave. In this paper, space charge of planar sample, HVDC Cable on external layer and from inner conductor are respectively measured. All the tests are kept in the same condition which includes the energy of laser, temperature, high voltage applied and so on. In order to reduce the spatial noise and improve the signal-noise ratio, the cable sample is set in a iron box with only one hole for the laser. Comparing the test results above, the amplitude and area of the current signal in the three tests are in correspondence with each other theoretically. The experiment results presented demonstrate the validity of the measurement system which picks signal from external layer, and also provide a good foundation of theory and experiment method for the measurement of real full-size HVDC cable.