Study On Signal Propagation Characteristics In Single Core Crosslinking Polyethylene Power Cable

With the continuous development of urbanization,the electricity consumption of the city has risen sharply,then the power cable as the main artery of urban transmission has been used widely.In recent years,countless fire accidents were caused by the insulation degradation of power cable,which has serious influence on the stable and secure operation of power system and production and living of residents,thus the correct evaluation of power cable insulation performance is extremely urgent.Partial discharge detection is the main evaluation method of power cable insulation property,however,the detection sensitivity is not very satisfactory as its relatively rough recognition of the propagation law of internal signals and its imperfect equivalent circuit model of power cable.Therefore,it is of great theoretical significance and engineering value to study the transmission mechanism of power cable in actual operation.In this work,we embark from the actual operation of power cable.Firstly,we establish actual operation high frequency circuit model of power cable and obtain the mathematical expressions of voltage and current of center 'conductor and metal shielding layer via a series of solving.The power cable distributed parameters of two kinds of single core XLPE metal shielded power cables with different structural types are calculated.Then,we analyze the propagation rules of AC steady state high frequency signal in the two types power cable,and the characteristic parameters of them' are obtained.Accordingly,the correctness of our proposed model is verified by compared with the characteristic parameters of classical transmission line model.Sequentially,the approximate model of power cable is established to analyze the attenuating contribution to AC steady state high frequency signal from each layer structure of power cable.It turned out that the attenuation caused by metal shielding layer is accounted for about 40%of the conductance attenuation,indicating the necessity of considering longitudinal electrical resistance of metal shielding layer in the central parameter circuit model.Finally,using the finite difference time domain method,the propagation law of AC stable UHF signal in power cable is analyzed,and the two-dimensional finite difference equation of the power cable in the rotating symmetric coordinate system is derived,and the simulation analysis is carried out in the time domain finite difference software XFDTD,and the AC steady state UHF signal propagation law is obtained.