Research On The Effect Of Insulator Arrangement On Secondary Arc Motion And Heat Dissipation Characteristics Under Rainfall

Recently,with the rapid development of economy and the rapid increase of power demand in China,UHV transmission meets the requirements of long-distance and large capacity power transmission.Due to the large distance between UHV transmission lines and the high probability of single-phase grounding faults,the problem of secondary arc is more prominent,while the rainfall environment will greatly increase the probability of insulator string flashover and is easy to cause the secondary arc burning.Based on different insulator string arrangements,this paper uses the chain arc model to simulate the motion characteristics of the secondary arc,extracts the motion characteristics of the secondary arc image,and explores the energy transfer process of the secondary arc under the rainfall environment.Firstly,concentrating on the horizontal insulator string arrangement,a secondary arc dynamics model based on electromagnetic force,thermal buoyancy force and air resistance is established.The results show that the morphology of the secondary arc shows the characteristics of left high and right low,both sides high and middle low,left back and right front.Electromagnetic force is mainly caused by the current flowing through the arc itself,the arc on the other side of the transmission line and jumper,and the electromagnetic force by arc itself is dominant gradually.The arcing force is greater in the case of the right-hand power configuration,while the left-hand power configuration will cause the phenomenon of adhering insulator strings.The arc morphology develops along the insulator spiral as the vertical angle increases,and changes the force characteristics in y direction.Compared with the suspension insulator string arc,the horizontal arc in the y direction is less force.Secondly,based on the arc image skeleton extraction,the motion characteristics of the secondary arc are studied.Using the characteristics of RGB arc image,image denoising and image segmentation are carried out.The image processing results of the secondary arc shows that the movement direction of the arc is mainly away from the insulator string and vertical upward direction,the arc column by the arc itself electromagnetic force,more likely to occur short circuit phenomenon.There are random fluctuations in the arc extinguishing length of the secondary arc,but it is consistent with the positive correlation between the current value and the arc extinguishing length.The arc diameter varies with the instantaneous value of the current,but there is a hysteresis.Each part of the arc current element movement speed fluctuates roughly in a certain range,the direction of basic movement in the z-axis positive direction,but there is part of the current elements in the y-axis negative direction of movement.In addition,in the rainfall environment,considering conduction heat dissipation,convection heat dissipation,radiation heat dissipation and rain heat dissipation,the secondary arc energy balance equation is established,in which the energy transfer process of rain heat dissipation is divided into liquid raindrop warming process,raindrop liquid-gas conversion process and water vapor warming process.Without rainfall conditions,the input and output energy of the arc shows a step-up,the arc mainly accumulates energy in the short-circuit arc stage but consumes energy in the secondary arc stage.The arc energy is mainly dissipated by convection,conduction heat dissipation and radiation heat dissipation accounted for a relatively small.Rain heat dissipation increases with increasing rain rate,and after a certain point,the arc is extinguished in the short-circuit phase.Comparing the effects of rainfall types,it is found that the rainfall heat dissipation under convective rainfall is always greater than that under stratiform rainfall,and the arc burning time under convective rainfall is less than that under stratiform rainfall.