Research On Electromagnetic Radiation Of Pantograph-catenary Arc Based On Hilbert Curve Fractal Antenna

The pantograph arcing is becoming more and more frequent as the running speed of the locomotive continues to increase.With the characteristics of high temperature and energy,the pantograph arcing not only seriously ablates the contact wire and the pantograph strip,increases the wear amount,affecting the service life,but also generates inevitable high frequency electromagnetic radiation interference,which has serious influence on the reliable use of the vehicle equipment,the normal operation of the communication system along the railway line and the normal transmission of the radio signal,posing a potential threat to the safe operation of locomotives.Therefore,studying the pantograph arcing and its electromagnetic radiation characteristics is of great significance for evaluating the performance of the pantograph-catenary system and improving the service performance of electrified railways and urban traffic.Firstly,from the theoretical point of view,the components,formation principle of pantograph arcing and the generation and transmission mechanism of electromagnetic radiation are studied comprehensively.Furthermore,based on the theory of fractal geometry and the basic principle of receiving antenna,a small-sized,wide-band,light-weight,portable,low-cost Hilbert curve fractal antenna for detecting pantograph arcing electromagnetic radiation is proposed.The antenna simulation model is built by the 3D electromagnetic simulation software ANSOFT HFSS software,and the design parameters of the antenna are optimized by its own optimization function.The effects of antenna wire width,dielectric substrate thickness,and feed point position on antenna performance are studied.Finally,the antenna parameters are determined to produce a physical PCB antenna.Secondly,a pantograph arcing electromagnetic radiation test device is constructed.Using a voltage probe and a self-made Hilbert curve fractal antenna to simultaneously acquire the pantograph arcing voltage and electromagnetic radiation signals.The studies analyze the relationship between the changes of the electromagnetic radiation signal and the changes of the voltage.The frequency domain characteristics of arcing electromagnetic radiation are analyzed by means of FFT.The spectrum distribution range,typical frequency interval and characteristic frequency value of the arcing electromagnetic radiation at different voltage mutation moments,different currents and different electrode gaps are discussed in depth.Furthermore,the STFT method is used to study the evolution law of the power spectrum of the arcing electromagnetic radiation with time.And not only the frequency characteristics of the electromagnetic radiation signal,but also the accurate arcing moment,extinguished time,arcing duration and the arcing radiation intensity can be obtained intuitively.Therefore,a non-contact arcing detection method based on electromagnetic radiation is proposed in this paper.With the detection method,the electromagnetic interference of pantograph arcing can be analyzed qualitatively and quantitatively,providing a theoretical basis for suppressing the arcing electromagnetic interference.Additionally,the locomotiv off-line rate and the current-collecting performance can also be effectively evaluated based on the results of the arcing electromagnetic signal analysis.