Effect Of Electrode Material Modification On Space Charge In Low Density Polyethylene

High voltage direct current(HVDC)cables have the advantages of long-distance and high-capacity transmission,which can effectively solve the problem of unbalanced distribution of energy supply and demand in China.Compared to alternating current(AC)cables,space charge is more likely to accumulate in the insulation layer of HVDC cables,which may cause partial discharge or aging even failure of insulation layer.Suppression of space charge accumulation in the insulating layer is one of the difficulties in the development of HVDC cables.In this paper,the composition of HVDC cable is simulated,and the effect of electrode modification on space charge injection of insulation layer is studied from the conductive copper core and semiconducting layer.In this paper,thin films of titanium and wolfram were deposited on pure copper by plasma chemical vapor deposition,and thin film of aurum was deposited on pure copper by ion sputtering.The coated copper sheets were used as electrodes,and arsenicdoped silicon wafers with different concentrations were used as semi-conductive layer.Using the methods of PEA and TSC,space charge injected from the electrode the insulating layer of LDPE under different field strengths was investigated.It was found that the surface of the coated copper sheets was densely packed with spherical particles of uniform size by SEM and AFM observation.According to EDS analysis,the atomic percentage of coating metal is within 10%.XPS results showed that the surface of the copper sheets were partially oxidized except gold plating.The work function test results showed that the surface work function increased after coating.The results of PEA showed that in the absence of a semiconducting layer,the amount of charge in insulating layer from pure copper electrode was the least;In the presence of a semiconducting layer,the titanium plated electrode has suppressed effect on the charge injection in the insulating layer,In other cases,the amount of charge injected into the insulating layer by electrode tungsten plating was the least.The semi-conductive layer could inhibit injection of charge into the LDPE,and the silicon wafer with resistivity of 0.013 ?·cm had a significant suppression effect on charge injection into the LDPE.In the case of titanium-plated copper and aurum-plated copper as electrodes,the silicon wafer with a resistivity of 6 ?·cm also had a certain effect on inhibiting the injection of charges into the insulating layer.In addition,with the increasing of field strength,the amount of charge in LDPE was increase.The results of TSC showed that when pure copper and gold-plated copper sheet were used as electrodes,less charges could be measured through thermal stimulation;Adding a semiconducting layer helped reduce the injection of charges from the electrode into LDPE;The amount of charge in LDPE increased with the increase of field strength.