Characteristics of pantograph‐catenary arc under low air pressure and strong airflow

Pantograph‐catenary arc fault is the primary factor threatening the stability of the power transmission for high‐speed railway.The motion characteristics of the pantograph‐catenary arc under low air pressure and strong airflow is significantly different from the case under atmospheric pressure.In this paper,an experimental platform of panto-graph‐catenary arc was built to investigate arc root position‐time and arc column lon-gitudinal drift height‐time characteristic curves under different air pressures and airflow velocites.Via analysing the corresponding results,it can be found that there are different arc root-arc column traction mechanisms at different stages of arc development.The arcing time and arc root stagnation time under low air pressure are significantly longer than the case under atmospheric pressure,resulting in more serious electrode ablation.The arc column longitudinal drift velocity and height are greater with the increase of airflow velocity.Two typical irregular arc motion phenomena-arc root jumping and arc reignition are observed.To clarify the internal mechanism of the above phenomenon,a magnetohydrodynamics(MHD)model of the pantograph‐catenary arc was lauched,the influence mechanism of the pantograph‐catenary arc temperature and voltage are studied,and the physical process of arc temperature oscillation is analysed.The research results provide theoretical support for arc protection in high‐altitude areas.

Study on the erosion characteristics of copper-carbon electrode pairs by DC air arc

As common electric contact materials,copper-carbon electrode pairs are widely used in the field of electric contact such as in high-speed railways,motor collector rings and grounding brushes.They play a key role in energy transmission in the above-mentioned systems.Arc erosion has become a key issue threatening system safety.In this work,a dedicated arc erosion platform was built to study the polarity effect of copper-carbon electrode pairs.It was found that arc dynamics and electrodes erosion behaviours were significantly different under different polarities,which could be understood from the mechanism of heat transfer,cooling and electron emission of the electrode.Then,when the carbon material was used as an anode,the arc caused carbon transfer:the carbon material sublimated quickly due to electron condensation and thermal conduction and quickly condensed on the low-temperature metal electrode,while the carbon material transfer could partly inhibit the oxidation of the cathode metal electrode.In addition,the rapid sublimation of the carbon material produced high-temperature airflow,which would make the arc impedance fluctuate and cause the arc voltage to jump.Finally,the anode heat transfer and cathode cooling mechanism directly affected the material state,and the erosion of the anode material was more serious。