Study On Temperature Rise And Corrosion Characteristics Of High-voltage And High-power DC Water Resistance

DC de-icer technology of transmission lines is an important technology to defense ice disaster in power grids,which makes up for the deficiency of power capacity limit of AC de-icer method.As the use of DC de-icer device is obviously seasonal,it needs to be tested before activation.Simulation load of DC de-icer device used in load test should meets the characteristics of low resistance,high power and good reliability.Currently,there is no ready-made load device which meets the requirements,and the water resistance is an ideal selection of simulation load for the load test of DC de-icer device.In the present work,some corresponding parameters of simulation load for a three parallel 10MW DC de-icer device are designed.The main work is as follows:By studying the operating parameters of the DC de-icer device,the design specifications of the high-power DC de-icer device are proposed,including the resistance value,the load power,the flow time and the allowable temperature rise,etc.According to the design specifications,the load structure size,electrical parameters and cooling method of high-power DC water resistance are investigated.Based on the computational fluid mechanics and heat transfer theory,the mathematical model of water resistance device is established for the fluid field motion and temperature rise in the operating process of water resistance,which provides the theoretical basis for the coupling simulation calculation of electric field-fluid field and temperature field.According to the design ideas of the parameters of the water resistance load device,a scaled model of water resistance load device is designed with 1/100 power multiplier,and the temperature rise of the water resistance is compared by means of simulation calculation and experiment analysis.Considering the heat convection of the device,a calculation model coupling the electric field-fluid field and temperature field is established,and the fluid field and the temperature distribution are calculated by the finite element method.The flow rates of the device are 2.2m3/h and 8.8m3/h,and the maximum temperature rise meets the design specification.The results show that the experimental data are in good agreement with the simulation ones for temperature rise.The validity of the design of the water resistance and the rationality of the calculation method are verified by the analysis results of the scaled model.Due to the electrolytic corrosion of metal electrode found in the experiments for scaled model of water resistance,a small-size model of water resistance is designed.A single electrolysis experiment with different corrosion conditions and repeated electrolysis experiments with a fixed corrosion condition are carried out.The results show that the iron anodes are oxidized to ferrous iron in the electrolysis reaction and then rapidly to ferric hydroxide colloids.After each electrolysis reaction,the corrosion of the plate surface is serious and the corrosion products are attached.The iron ions in the water combine with the hydroxide ions,which reduce the concentration of solution and change the pH value and increase the equivalent resistance of the water resistance further.Based on the verification of the design of high power DC water resistance and the correctness of the calculation method,and combined with the key problems in the calculations and experiments of the scaled model,the structural size,electrical parameters and the cooling method of the high-power DC water resistance load are designed according to the specification of actual power load.The fluid and temperature distribution of water resistance are calculated.Hard graphite plates are selected as the electrode plates of the high-power DC water resistance,and a 20-foot flat-bottomed and open-top container is selected as the volume constraint.The equivalent resistance is 1.86Ω,which meets the design requirements of 2Ω.Forced convection is used as the cooling method in water resistance device,where the inlet flow rate is 35m3/h.In 30min,the maximum temperature rise reaches 62.31 ℃,which meets the design requirements.