| The problem of insulator icing is not conducive to the safe operation of transmission lines.The existing insulator deicing methods have the disadvantages of large safety risk,damage to insulator and low efficiency.Hot water jet has large convective heat transfer coefficient and specific heat capacity and good insulation performance.The damage to insulator can be avoided easily using water jet,which is a deicing method suitable for insulator.In order to know the method of insulator deicing using hot water,the two stages during the hot water deicing process were studied,which are that water jet sprays and that the ice layer melts and falls off under the combination of heat and water jet impact.Finally,the safety distance of hot water deicing for live insulator was discussed.The main results of the thesis are:(1)In the aspect of injection and temperature spatial distribution characteristics of water jet during the insulator hot water deicing process,the overall and local flow states of water jet are observed by high-speed photograph.The effective length of water jet under different nozzle diameters and outlet pressures is approximately calculated.The numerical calculation model for the water jet flow field is established and validated by the experiment of water jet temperature distribution at Xuefeng Mountain Natural Icing Test Base.The spatial distribution of water jet temperature is simulated and obtained under different different initial temperature of hot water,jet distance,outlet pressure,ambient temperature and wind speed,nozzle diameter.The influencing laws of above factors are analyzed.(2)In the aspect of insulator deicing characteristics and efficiency optimization,calculation model of hot water deicing time for insulators is established and the cubic heat balance integral method is employed to solve the internal temperature of ice layer and the position of melting interface by stages.At the same time,the influence of the proportion of ice layer shedding under the impact force of water jet is taken into consideration.The hot water deicing time for insulator is calculated and the test verification is carried out at Xuefeng Mountain Natural Icing Test Base.The calculation process of hot water deicing for insulator is proposed.The influence of the initial temperature of hot water,outlet pressure and ice weight on the deicing time is calculated and analyzed.With the deicing efficiency as the goal,an optimized objective function is constructed to optimize the the initial water temperature and outlet pressure to obtain the optimal combination of hot water temperature and outlet pressure.Meanwhile,for the complex factors such as deicing method and shed grouping,the influence of them on the insulator deicing time is experimentally studied.In addition,in order to obtain the proportion of ice shedding under the impact force,the impact force test of water jet is carried out and the influence rules of nozzle diameter,distance,outlet pressure and angle on impact force are obtained.(3)In the aspect of the safety distance of hot water deicing for live insulator,the insulation characteristics of water column during hot water deicing for operating insulator in 110 k V system are carried out.The leakage current of water jet under different combinations of jet distance,hot water conductivity,outlet pressure and nozzle diameter is tested and the influence of the above factors on the leakage current is analyzed.According to the experiment value of leakage current,the minimum deicing distance under different outlet pressure and hot water conductivity is calculated.Finally,by comparing with the safety distance in regulation of hot washing for electric power apparatus,the safety distance which is applicable to hot water deicing for live insulator in 110 kV system is obtained. |
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