Research On Signal Propagation Characteristics And Fault Location Of Power Cable Based On Fractional Circuit Model

With the rapid development of China's power industry,power cables are important transmission equipment after the overhead lines.The development of UHV and long-distance transmission projects has put forward higher requirements for the safe operation,fault location and maintenance of power cables.When the transient high frequency signal is transmitting in cross-linked polyethylene(XLPE)cables,the skin effect of conductor and the frequency change effect of semi-conductive layer are the main causes of the attenuation and dispersion of the high frequency signal.In the past,the model of cables often ignored the frequency effect of the inner and outer semiconducting layers,which affected the accuracy of the transient analysis.Therefore,the establishment of a cable fractional broadband model is important for the analysis of high frequency signals.Secondly,power cables are often laid underground or under the sea.After failure,it will bring inconvenience to operation and maintenance.Based on the various fault location theories proposed by the predecessors,it is necessary to propose a fault location method with high positioning accuracy and high positioning speed.In this paper,the relative complex permittivity of the semi-conductive layer is measured first.After fitting the data with the Cole-Cole,the fractional admittance parameters of the inner and outer semi conductive layers of the power cable are derived by using the fitting model and the cylindrical capacitance formula.According to the radial cable model proposed by Boogs,a fractional order cable model,which both considers the skin effect and the frequency change effect of the semi conductive layers is set up.The model is solved in the frequency domain,and the experimental platform is built to verify the accuracy of the model.Based on this model,the propagation characteristic of the high frequency signal in the cable is analyzed.Finally,based on the time reversal focusing principle combined with the fractional model of power cable,the common cable faults such as short circuit fault,partial discharge fault and electromagnetic interference source are located.The superiority of using the fractional cable model to locate the faults is verified compared with the traditional cable models.