Purpose -The purpose of the paper was to design an anti-corrosion system that combined conductive coatings with cathodic protection for a 500-kV substation ground grid, and provide a basis for the anti-corrosion construction of the installation. Design/methodology/approach -The study took the Shaoguan 500-kV substation grounding grid as the research object. The anti-corrosion performance of KV conductive coatings on grounding metal was researched. In parallel, the alkalinity of substation soil was evaluated according to the German DIN50929 Standard, and the combined protection system comprising conductive coatings and impressed current cathodic protection was designed. Findings -KV conductive coatings, that have resistance to acids, alkalis and salts, can effectively slow down the corrosion rate of the grounding grid. The investigation also provided the outline design, installation, construction requirements and monitoring methods for the 500-kV substation grounding grid. Originality/value -This report contains some guiding significance for anti-corrosion engineering of 500-kV substation grounding grids.
As one of the most common inorganic ions in daily food and ecological environment, nitrate (NO3−) is potentially harmful to both environment and humans. Therefore, the detection of nitrate concentration is quite important. Chemical sensors, as analytical measurement tools, usually demonstrate high selectivity, fast analysis speed, simple structure, convenient operation, and low cost and are considered to be a promising method for ion identification and detection. In this paper, a miniaturized electrochemical electrode is fabricated based on the microfabrication technology, and an electrochemical sensor for the detection of nitrate concentration in water is developed by combining the deposition technology of nanometal particles with electrochemical analysis technique. The developed electrochemical sensor utilizes electrochemical deposition to prepare a copper (Cu) granular sensitive film with a branch-cluster structure on the surface of a circular working electrode (Pt). Using copper’s characteristics of electrocatalytic reduction of NO3− in the acid solution environment (pH = 2), the concentration of NO3− in the water sample was calculated by measuring the reduction current on the working electrode when the electrocatalytic reduction reaction of NO3− occurred on the surface of the copper-sensitive membrane. The sensitive film is characterized and detected both with the scanning electron microscope (SEM) and X-ray diffraction analysis (XRD) technique; and the microsensor is used to detect nitrate standard samples; a high detection sensitivity (24.9 μA/mmol·L−1) is achieved in the concentration range of 0.0 to 3.0 mmol/L. At the same time, a MEMS three-electrode sensor without gold wire bonding and insulating glue packaging is designed, and an automatic detection system is constructed with a STM32f103 microcontroller as the controller to realize the automated detecting process for nitrate ions. At the same time, a distributed system is constructed, which can describe the nitrate concentration in every position of the water area and realize the monitoring of the whole water area. The detection system can meet the working environment under most conditions and has practical significance.
Land settlement produced by groundwater exploitation may cause larger deformation of the high-speed subgrade. To meet the settlement control requirements after construction of the high standard of high-speed railway subgrade, Pile-Slab composite foundation treatment technology keeps developing and applying in high-speed railway construction. However, the settlement deformation calculation theory of Pile-Slab composite foundation is not mature, in particular, the research for Pile-Slab composite foundation deformation caused by groundwater exploitation is seldom, which is far behind the requirements of engineering practice. To study the effect of exploiting groundwater near the highspeed railway on Pile-Slab composite foundation deformation, in this paper, we establish 3D fluid-solid coupling model using ABAQUS, analyze the effect of different groundwater exploiting quantities on high-speed railway subgrade when CFG piles are used to strengthen the foundation, and compare to the result with no CFG piles. The analysis shows that in the condition of pumping water, CFG Pile-Slab composite foundation has a significant effect on decreasing subgrade lateral deformation and settlement which are reduced by 70%.
To allow the hoisting motor drive system of a crane to track a load torque quickly, a linearization method was used to transform a motor nominal dynamics model into two decoupled linear rotor speed and flux linkage subsystems. The method based on the theory of differential geometry was a precise feedback method. Two active disturbance rejection controllers (ADRCs) with identical structures were designed for the rotor speed and flux linkage subsystems. The extended state observer of the ADRC could estimate the unmodeled dynamics of the motor, the variation of motor parameters due to heating, and the unknown disturbances of the motor system to determine the total disturbances of the system. A closed-loop system with ADRC and an open-loop system were compared. The motor's full-load starting time was reduced by about 50%. When the motor operated smoothly at different load rates and the rated load was suddenly applied, the electromagnetic torque fluctuation range did not exceed 20 N• m. The rotor flux was always stable at the reference value. The motor speed decreased, but the amount of decrease did not exceed 7 rad/s. The closed-loop system had a significant energy-saving effect during the motor's starting process. The power saving rate was about 55%-59% if the motor started with a light load. The power saving rate could reach 71% if the motor started with a heavy load. The ADRC system could accurately estimate the unknown model of the rotor speed and flux linkage subsystems, and adapt to parameter variations of the motor stator and rotor resistance in the range of ±10%. Motor: Te, TL Electromagnetic and load torques. TN Nominal torque. ET Electromagnetic torque tracking error. np Motor's pole logarithm. Je Rotational inertia of the rotor. n Rotor speed. ω Electric angular velocity. ωr Mechanical angular velocity. α, β Static two-phase coordinate axis.
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