The Simulation Analysis On AC Dielectric Properties Of Linear/Non-linear Composite Insulation

Because of the excellent processing properties and electrical insulationproperties, polymer composite insulating dielectrics have been widely applied inthe electrical stress-controlling plates of the cable terminals and the electricalstress-grading tapes at the winding end of high voltage motors to inhibite coronas.The study of the dielectric properties of linear/non-linear composite insulatingdielectrics under AC field has profound significance both in theoretical andengineering study, for they can suppress the generation of the space charge anduniform the electric field distribution of the insulation structure by self. Thecomposite insulation with polyethylene and nonlinear zinc oxide widely appliedin engineering is regarded as a research object in this dissertation, using a newform to describe the linear/non-linear composite insulation, rather thansimulating composite insulation in the form of adding ellipsoids or small balls tothe polymer matrix in the past. The non-linear characteristics in the broad senseof linear/non-linear composite insulation internal angulation are researched underAC field by quantitative analysis.This dissertation is based on mesoscopic structural unit of linear/non-linearcomposite insulation so as to establish five different types of linear/non-linearcomposite insulation structural unit which angle is from0°to90°. Reference toAC equivalent circuit model of non-linear insulation, AC equivalent circuitmodel of linear/non-linear composite insulation has been established usingsimulation toolbox of Simulink. Our group has successfully developed AC testsystem of non-linear insulating dielectrics to test valve disc of zinc oxide, gettingparameters of non-linear conductance and capacitance under different voltageamplitudes. The time-domain decomposition algorithm of responding current hasbeen developed to decompose the total responding current into the resistive current and capacitive current using MATLAB software as platform, and futhermore characterize dielectric parameters. Through circuit simulation, volumeconcentration, internal angles of composite insulation, the amplitude andfrequency of excitation voltage have been analyzed to prove the influence ondielectric properties of composite insulation, and also the changing law ofinternal electric field amplitude.Simulation results show that the dielectric properties of composite insulationdepend on its volume concentration, internal angles of composite insulation, andthe amplitude and frequency of excitation voltage. The internal electric fieldamplitude of composite insulation is related to the ratio of the linear and non-linear dielectric in the branch, therefore the curves of electric field have leadingor lagging phase shift. Simulation analysis results of AC dielectric properties oflinear/non-linear composite insulation have certain guiding significance insubsequent research and application of composite insulation.