Microwave Transmission Methodology On Deteriorated Insulators Detection

As an important insulating component in operation of state grid,insulator is an important part for realizing safe and stable operation of state grid.However,due to the poor environment insulator working in,the insulators in operation are affected by heavy electromagnetic field,intense mechanical stress,external and internal factors,which lead to zero-value and low-value ceramic insulator and make composite insulator ageing,brittle,interface defects and other deterioration.However,methods with poor security and need to power off are still being used.To overcome disadvantages of the methods,this paper proposes a non-destructive detecting method for insulator based on microwave transmission,which make efficiency and safety of insulator detection significantly improved.Microwave has advantages of wide spectrum range,penetrability and anti-interference.Defected structure inside insulator can be detected by penetration of microwave.In chapter two,process of microwave propagation in multilayer medium is analyzed in detail.Feature matrix is used to characterize phase difference and wave impedance of each layer interface.Through the mathematical model,transmission coefficient of microwave transmits through multilayer dielectric plate is obtained,and feasibility of the microwave transmission method is proved.However,considering the requirements of safety,reliability,miniaturization and convenient operation in actual detection,composition and function of microwave transmission detection system are introduced in third chapter.Function of transmitting and receiving signals of antenna is very important.So,a microstrip antenna suitable for microwave transmission detection is designed in the third chapter.It is verified by simulation that it has good performance and is very suitable for defective insulator detection described in this paper.Due to the incomplete defect types of deteriorated insulators in substations,it is difficult to verify various defect types.In order to support the experimental results,in chapter four,the microwave transmission was simulated for XP-160 ceramic insulators by CST.XP-160 ceramic insulator model and its rectangular and annular defective models were established and identifiability of defect defects with water,air gaps and metal inclusions were compared.To verify effect of the method in practice,in the fifth chapter,a microwave experimental platform was built by using vector network analyzer and millimeter wave antenna,and comparing the insulator samples retrieved from the field by the platform.The maximum value of difference of S₂₁ is more than 16dB,indicating high sensitivity.Feasibility of the microwave transmission method for deterioration detection of ceramic insulators is preliminarily proved.Experiments on composite insulator core rods with different defect depths show that the method can determine the position and extent of composite insulator core rod defects.