| Intelligent high voltage equipment is the basic unit of intelligent substation.It has technical characteristics of measurement digitalization,control networking,state visualization,functional integration and information interaction.It consists of high voltage equipment body,sensors and intelligent components.The intelligent components of intelligent substation need to be located near the host equipment of the intelligent high voltage equipment,which puts forward more stringent requirements for the safe and reliable operation of the intelligent components.The reliability of intelligent components directly affects the safe operation of intelligent high-voltage equipment.The electromagnetic disturbance such as transient ground potential rise in substation has an obvious impact on Intelligent components.Transformer is the most critical equipment in substation,and its intelligent components have a higher probability of failure in the process of lightning impulse and switching operation.It has not only the instantaneous failure of some IED functions,but also the breakdown damage of electrical interface and even the internal circuit board.It shows the lack of overvoltage protection measures in the process of integration design of intelligent components and host equipment.Moreover,transformer intelligent components need to carry out type tests with transformers in body.Through field tests at several transformer factory experimental stations,it is found that the damage of intelligent components in the tests mainly focuses on the damage of power supply.Therefore,this thesis focuses on the electromagnetic disturbance of Switching Power Supply for Intelligent Components.The switching action of semiconductor devices in switching power supply will produce serious electromagnetic interference,which will be transmitted to electromagnetic noise sensitive equipment through the power grid and will hinder its normal operation.On the other hand,because intelligent components need to carry out type tests together with transformer body,transient ground potential rise caused by lightning full wave and intercept shock test also threatens the safe operation of DC power supply for intelligent components.Therefore,this thesis mainly studies the time-frequency characteristics,propagation paths and suppression methods of electromagnetic interference and reveals the electromagnetic interference mechanism of DC power supply for intelligent components then puts forward corresponding protection measures.The main work of this thesis is as follows:(1)Considering that it is difficult to analyze the electromagnetic interference inside the switching power supply precisely by using the traditional method.In this method,only switching power supply is considered as a macromodel with certain input and output characteristics.Therefore,this thesis is based on the working principle of fly-back switching power supply.Through the selection of switching tube,diode,filter capacitor and the design of feedback circuit,control circuit and buffer circuit,a fly-back switching power supply has been manufactured and its correctness has been verified by its on-load operation.(2)The high-frequency model of active and passive components in fly-back switching power supply is established by means of electromagnetic field simulation and experimental test,and the complete simulation circuit of switching power supply is established based on Pspice.Based on this model,the time-frequency characteristics of electromagnetic disturbance produced by switching power supply are analyzed.Finally,the corresponding suppression measures are proposed for the generation mechanism and propagation path of electromagnetic interference,and the effectiveness of the suppression measures is verified by simulation.(3)The electromagnetic interference model of switching power supply caused by transient ground potential rise in high voltage experimental hall is established.By establishing the simulation model,the damage mechanism of switching power supply caused by transient ground potential rise is analyzed,and the reason why the rectifier diode inside the power supply is easily damaged in the test is revealed.On the basis of the above analysis,effective protective measures are put forward,and the effectiveness of protective measures is verified by experiments. |
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