Research On Vacuum Arcing Chamber With Quick Action Mechanism For Protecting 10kV Potential Transformer

The potential transformers are important electrical equipment to connect primary system.They are installed in each node of power grid to provide the voltage information for monitoring the operation of primary system.The front part of potential transformers often connect fuses for the protection in the 10 kV switchgear system.However,the fuses for the protection of potential transformers often occur without action or fuse blown phenomenons and they even lead to the potential transformers burned.Therefore they will bring a great threat on the system of reliable economic operation.Especially,for the industrial and mining industries,the probability of fault is quite higher.Although the structure of fuse is simple,the problems of a single fuse caused by the frequent replacement will cause varying degrees of power outages,and the fuse replacement is very troublesome,most of the domestic fuses are expensive and imported from foreign.Besides,breaking process likely to affect the environment and even explode.Hence it doesn’t benefit from safe,reliable,stable and economic operation of the distribution power grid,and be quickly in need of improvement.Based on the defect of fuse protection,using the methods of combining theoretical analysis,numerical simulations and experiment was explored to design a kind of protection device that consists of a vacuum arcing chamber,a electromagnetic mechanism and a tripping mechanism taking the place of fuse protection.It will realize the open circuit protection of the fault current of potential transformers primary side for advantages of using many times,reusable performance,simple structure,low cost,wide scope of protection.In addition,opening circuit process has no impacts on the environment.The details are show as follows.Firstly,the working principle,fault types and fuse protection under different fault characteristics of potential transformer are analyzed,and it is concluded that the protection demand characteristics of potential transformer including the fault current range of opening circuit,opening spring force of vacuum arcing chamber.So it will provide theoretical basis for analysis of tripping mechanism.Secondly,using SOLIDWORKS modeling software to design the four schemes of tripping mechanism,and using ADAMS software to simulate its mechanical dynamic characteristics respectively.In the end,the fourth scheme is optimal solution,which has the highest ratio of tripping torque magnification.Meanwhile,it can use small force to take off the larger opening spring force.When it comes to take off tripping device,rotating electromagnet need to provide at least 7.6 electromagnet striking force,and straight acting electromagnet need to offer at least 9.5 electromagnet striking force,which provide the theoretical reference for selection and design of electromagnetic mechanism.Thirdly,11 electromagnetic mechanisms were designed by SOLIEWORKS software,including 9 kinds of electromagnetic mechanisms,1 kind of permanent magnetic mechanism and 1 kind of electromagnetic repulsion mechanism.Besides,making use of the electromagnetic field model of COMSOL5.1 software to simulate static characteristics of total 9 modules.The ninth scheme of electromagnetic mechanism output the largest electromagnetic force.Meanwhile,it further be optimized and calculate size parameters of the coil,etc.Using the electromagnetic field of ANSYS ANSOFT MAXWELL software to simulate and analyze dynamic characteristics of ninth scheme,which draws the curve of electromagnetic force with the change of time under a closed process.Fourthly,determine the final total scheme of 10 kV PT protection with vacuum arcing chamber matching quick action.A vacuum arcing chamber,ninth scheme of tripping mechanism and fourth scheme of electromagnetic mechanism are established and matched.In addition,using the ADAMS software to simulate and analyze protect mechanical dynamic characters of overall model,and regard the curve of electromagnetic force with the change of time as a power source imported into the ADAMS software.Through the simulation analysis to evaluate the mechanical properties of a suit of protection device.The current and temperature field models of COMSOL5.1 software are adopted to simulate and analyze the dynamic characteristics and thermal characteristics of primary winding and loop wire of potential transformer under the condition of fault.The simulation results meet the designed requirements.Fifth,drawing the 2-dimension engineering drawings and making the prototype of model.Changing the initial elongation of latch spring and the dead center position to conclude the values of minimum tripping force and torque amplification factors.Changing the air gaps of collision position,the spring initial elongation of electromagnetic mechanism,and pre-stressed spring length of break-brake spring to conclude the value of magnetic potential,which compares with the result of simulation.Finally through the experiment of break-brake mechanical properties of vacuum arcing chamber,drawing the characteristics of coil current,the relation between stroke and time,break-brake average velocity.It is concluded that new protection device in protecting potential transformer is more reliable than fuse protection.Although a certain gap between results of simulation and experiment,it’s advantages are that the range of protection is more wider.Meanwhile,it has the very good market prospects and high value of engineering research.