Partial Discharge Modelling: The Case of High Voltage Insulation Onboard Ship

Abstract

The article deals with partial discharge modeling based on gas inclusion (defect) in high-voltage electrical insulation on board ship. For modeling a sample of insulating material used in ship high-voltage equipment , has been taken. A sample of the insulating material is described by means of three capacitors. Based on the calculated capacitance values, a replacement circuit was constructed, and then a scheme for modeling partial discharges in Matlab / Simulink program was designed. While simulating the most common voltage values applied in ship high-voltage systems have been used. The gas inclusion (defect) of a cylindrical shape, located in the middle of the insulating material, has been taken as reference. Simulation of partial discharges is performed for three gas inclusion versions differing in size. The graphs show partial discharges for which the voltage across the capacitances and the apparent charges for each defect and voltage are calculated using a formula. Dependences of the apparent charge on the area of the defect in the insulation and on the amplitude of the partial discharges are presented for different voltages. Based on these graphs, conclusions are drawn regarding the dependence of partial discharges on the supply voltage and the size of the defect within the insulating material. Spectral analysis of the simulated signals corresponding to the defects considered by the fast Fourier transform method is made and the frequency distribution of the signal depending on its amplitude is presented diagrammatically. Found values of the apparent charge allow to calculate the average value of the current, which makes it possible to estimate the intensity of partial discharges and technical condition of electrical insulation. Another problem with constant monitoring of partial discharges in high-voltage powerequipment is,separating useful signal (partial discharges) from the noise component. This issue needs further detailed study.