Research On Lightning Current Acquisition Method And Design Of Lightning Current Acquisition System Based On Lightning Rod

Lightning disaster is a serious natural disaster.Lightning protection technology still needs further development.The lightning current acquisition system provides raw data for the study of natural lightning by collecting and storing the lightning current data,which plays a key role in improving the lightning protection technology.Therefore,it is of great significance to study lightning current acquisition methods and design acquisition systems.However,at the current stage,the detection and collection of lightning currents generally have problems such as erroneous acquisition,leaky acquisition,incomplete acquisition of waveform data,and poor accuracy of the acquired data.These problems bring trouble to the improvement of lightning protection technology,analysis of lightning accidents,and troubleshooting of equipment.Therefore,it is necessary to study the method of collecting lightning current and design the system of collecting lightning current.In this paper,the lightning current acquisition system is the research object.Based on the characteristics of lightning current and the current measurement principle of Rogowski coil,the scheme and performance index of the system are established.This paper presents an algorithm of lightning current discrimination,which is used to detect and extract lightning current,improve the shortcomings of existing lightning current acquisition system,and improve the quality of acquisition data.According to the system scheme and performance index requirements,the hardware circuit is designed,the software of the lower computer and the upper computer is compiled,the design of the lightning current acquisition system is completed,the whole machine is tested and the error is calibrated.The basic function of collecting lightning current is realized.The specific work is as follows:(1)Five kinds of common lightning current models are analyzed systematically.The relationship between each function model,their advantages and disadvantages,and the application scope of each model are pointed out.Using 10 / 350 us waveform as standard lightning wave,the spectrum and energy of lightning current waveform are studied by using Fourier transform and paswar's theorem.The steepness of the lightning current model is analyzed,the parameters of each model are given,and the comparative analysis is carried out to provide theoretical basis for the design of the lightning current acquisition system.The characteristics of the structure of the Rogowski coil and the basic principle of measuring current are analyzed,and the amplitude frequency response and phase frequency response are analyzed by using the lumped parameter equivalent circuit model of the Rogowski coil.Through simulation,the error of measuring lightning current is about 2% under ideal condition,which meets the requirements of lightning current acquisition.(2)Aiming at the problems of missing trigger,false trigger and waveform data integrity existing in the lightning current acquisition system,this paper analyzes the shortcomings of hardware trigger and software trigger as well as the advantages and disadvantages of standard deviation as the criterion,and puts forward a lightning current discrimination algorithm based on the sum of square residuals,which is used to detect and extract lightning current and improve the data quality problems caused by false trigger.The trigger threshold can be reduced by using the lightning current discrimination algorithm,so as to improve the leakage trigger and data integrity.Based on the double exponential function model,seven common waveforms are used as reference to generate standard points.The residual square sum of standard points is calculated for the collected data set,and whether the data set is lightning current data is judged according to the calculation results.Through the simulation analysis and experimental test,the lightning current discrimination algorithm has obvious effect and practical value.(3)In the lower computer,the signal conditioning circuit is designed to solve the problem that the output range of the lightning current sensor does not match the input range of the analog-to-digital converter;combined with the data buffer technology,a high-speed acquisition module with FPGA as the core is designed.In order to enable the lower computer to upload data in the field environment,the wireless communication module is designed;considering the poor coverage of the field network,the storage system of the lower computer is designed to improve the fault tolerance.The communication protocol is designed with error detection function to ensure the correct transmission of data.The host computer has completed the functions of communication,data storage,parameter extraction and display with the acquisition node.Two ways of serial communication and network communication are designed for data transmission;the method of classified storage is used to design a unified storage format;the program design of lightning current discrimination algorithm is completed,and the function of waveform drawing is realized.(4)The lightning current pulse generated by the lightning current generator is used to test the functions,overall performance and acquisition accuracy of the system.Then,the least square method is used to fit the error curve to calibrate the system.Theoretical analysis and test results show that the overall error of the system is about 3%,the measurement range of lightning current is between-100 k A and 100 k A,the acquisition rate can reach 50 MSPS,the lightning current data can be uploaded and stored stably,all functions operate well and meet the requirements of lightning current acquisition as a whole.