Research On Arc Motion Between Arcing Horns Of Grounding Electrode Line In HVDC Project

HVDC transmission system can be divided into unipolar earth loop mode,unipolar metal loop mode and bipolar operation mode,etc.No matter which mode,the HVDC transmission system needs to have an earthing pole.The function of the DC grounding pole line is to form the backflow when the converter station is in bipolar non-equilibrium operation or unipolar ground operation.The location of grounding pole is usually tens or hundreds of kilometers away from the converter station.Because the voltage drop on the grounding electrode line is generated by the valve side current line,the insulating strength of the line design is relatively low,not exceeding 10 kV.Generally,two or three insulators are adopted.In case of lightning strike or operating overvoltage,it is easy to set up an arc on the insulator string of the grounding pole line.In order to keep the arc from burning the insulator,the method of parallel arcing horn is usually adopted at both ends of the insulator string.At present,the configuration of arcing horn on the DC grounding electrode line is determined by operating experience,lacking theoretical basis.There is no research on the DC arc motion process and arc quenching time and it is difficult to conduct the DC arc experiment.For a long time,the simulation research on the arc motion process has adopted the chain arc model,which discretizes the arc into a series of current elements,and regards the current elements as rigid bodies.The effects of magnetic field force,thermal buoyancy and air resistance on the current element are considered,but the adhesive force between the sections of the adjacent current element is not considered.At present,there is no research on the influence of intersectional adhesive force of current elements on the arc motion between arcing horns.The arc is essentially a hot gas(fluid),and there is adhesive force between the flow layers,when the viscous fluid is flowing.In this paper,based on the chain arc model,the force in arc motion is considered comprehensively,and a DC arc motion model is established.The main contents and conclusions of this paper are as follows:(1)The conditions and mechanism of arc starting,arc resuming and arc quenching on DC grounding line are studied;(2)The motion model of the arc between arcing horns of the DC grounding electrode line is established,and a simulation algorithm based on the position coordinates of the current element stored by the variable dimension matrix is proposed.Taking four common arc horns as examples,and the simulation analysis is carried out in MATLAB.It is found that the arc horns’ quenching processes of different structures are different,and the arc shape is different in the process of motion.(3)The main factors affecting the quenching of arc horns are studied.It is found that the arc current,gap voltage,the angle between the plane of the arcing horn and the line of the grounding electrode,the distance between the fault arc point and the grounding electrode have great influence on the quenching of arcing horn,but the influence of the arcing horn’s opening angle is small;(4)The force and velocity changes in arc motion are studied,it is found that thermal buoyancy and magnetic field force are the main factors affecting arc motion,while air resistance and adhesive force between sections of current elements have little influence on arc motion.Based on Mayer’s arc model,the variation of arc’s dissipated power in the process of arcing horn’s quenching is also studied.It is found that the variation of dissipated power is consistent with the trend of arc length variation,which leads to the variation of arc dissipated power,and the variation of dissipated power leads to the upward shift of arc steady-state voltammetry characteristic curve.The simulation model established in this paper is consistent with the simulation model established in the comparative literature.Through simulation experiments,the influence of arc current and the opening angle of arc horn on arc quenching process and arc quenching time is analyzed.By comparing the results of simulation and experiment,it is found that the time and position of arc’s quenching are roughly the same,which verifies the correctness and validity of the DC arc motion model established in this paper.In this paper,through the study and simulation of the motion model between the arc horns of the ground pole line,the law of arc motion between the arc horns is studied,the main factors affecting the arc quenching of the arc horns are analyzed,and the mechanism of arc quenching of the ground pole line is studied.When the actual experiment cannot be carried out due to the limited conditions in the laboratory,the research results in this paper can provide significant reference for the design and installation of the arcing horns of the grounding electrode line.