DETERMINING SPACE CHARGE ON INSULATION IN CABLE HVDC BY PEA METHOD: MEASUREMENT AND DECONVOLUTION TECHNIQUE PART 1: APPLICATION ON FLAT MATERIAL SAMPLE
HVDC polymer molded cable design is one of the most challenging problems in the cable industry because the electric field distribution on the insulation thickness is strongly influenced by space charge, which can control the operation of the cable system, especially its reliability and long life. Indeed, when a DC voltage is applied to the polymer dielectric layer, the accumulated space charges depend primarily on the voltage level, the properties of insulating and electrodes. If the space charge density is large enough, the field strength may exceed the strength threshold of dielectric, leading to the insulation failed. There are many methods for determining the space charge distribution in dielectric, with its advantages and disadvantages. However, selected method desired can improve the resolution, constraints and time record information because the obtained space charge distribution depends on time, constraints and the material sample: flat sample or cable model. The Pulsed Electro-Acoustic (PEA) method responds well to measurements of space charge under dynamic constraints. Moreover, the appropriately calibration technique used after measurements is also a very important factor to obtain reliable results. In this paper, the author introduces the deconvolution technique after the space charge measurement of PEA method in a flat material sample.