| In the Hainan area of our country,vacuum circuit breakers are affected by high temperature,high humidity,and high salt spray environments.Sealing deterioration makes the interior damp.and condensation water droplets induce discharge along the surface.Long-term accumulation causes breakdown or even rupture of the circuit breaker,seriously threatening the stability of the power grid.Personal safety of operation and maintenance personnel.In order to reduce accidents and provide guidance for on-site operation and maintenance,this paper uses numerical simulation methods to focus on streamer discharge in a single liquid medium,creeping discharge in a liquid-solid insulation system,and the impact of moisture on the two.Research was carried out on the problem,the internal discharge mechanism of the vacuum circuit breaker was explored,and the acoustic-electric joint detection method was carried out according to the characteristics of the discharge along the surface of the vacuum circuit breaker.The main contents are as follows:(1)In a single liquid medium,the relevant mechanism of carrier generation and recombination is clarified,and the charge continuity equation and Poisson equation are used for mathematical characterization,and the streamer development model in insulating silicone grease is established,and the streamer discharge is obtained.form of development.Based on this,the bulk conductivity is used to model the solid medium,and the surface charge accumulation process is considered to establish a liquid-solid insulation system creeping discharge model.and the influence of polarization on the creeping discharge is explored.The simulation research shows that compared with single liquid medium,the electric field intensity and charge density near the streamer head are higher during the creeping discharge process,indicating that the creeping discharge is more harmful to the insulation performance.(2)Through comparative analysis,it is found that the modeling method including water droplet conductivity and surface charge accumulation is more reasonable.Based on this,the discharge simulation model under different conditions such as water drop stretching,attachment,suspension,and multi-water drop arrangement is established,and the mechanism of the influence of water droplets on discharge is revealed:affected by the external electric field and polarization,the two sides of the water droplets will Positive and negative charges are accumulated separately,and the accumulation of charges causes the distortion of the surrounding electric field.Ionization is prone to occur at high field strength positions,and the ionized charges and background charges are quickly mixed to form a plasma region.With the help of the plasma region,a faster and wider discharge can be generated.In addition,the distortion of the electric field at the three-joint point is more serious when water droplets are attached.When multiple water droplets are arranged,adjacent water droplets will generate discharge,which further expands the plasma area and intensifies the development of discharge along the surface.(3)Build a vacuum circuit breaker failure test platform,verify the feasibility of existing detection methods,and determine the sound-electric joint detection scheme.Analyze the electromagnetic field distribution around the discharge source,discover the sensitivity of the near-field signal to the distance,and determine the electrical signal detection method based on the near-field electromagnetic induction;use the principle of waveguide sound transmission to conduct contact measurement on the circuit breaker to reduce the attenuation of the acoustic signal.The acoustic-electric composite sensor is designed,and the effectiveness of the sensor is verified through experiments. |
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