Research On Model And Parameter Measurement Method Of Transmission Line Grounding System

High-voltage transmission lines have a high probability of tripping accidents due to lightning strikes.Protecting transmission lines from lightning strikes under severe weather conditions so that electrical energy can be safely and efficiently transmitted to all parts of the country is a key issue of concern to the national power department.The lightning protection grounding system of the transmission line is an important power facility to prevent lightning disasters.It is composed of overhead lightning protection lines,transmission towers,grounding down conductors,and grounding devices.The impedance parameter of the grounding system is a measure of the lightning resistance level of the transmission line Main Specifications.The current relevant specifications require regular measurements of the grounding resistance parameters of the grounding device to ensure that the value of the impedance parameter is within a reasonable range as required by the specification,early detection of hidden dangers and specific fault locations,and effective completion of the transmission line grounding device Inspection and maintenance work to reduce the economic losses caused by lightning accidents and ensure the safe operation of transmission lines.At present,the research on the relevant parameters of the lightning protection grounding system of the transmission line mainly focuses on the measurement of the grounding resistance of the grounding body.In the actual field implementation,the three-pole method,the loop method and the high-frequency parallel method are often used.However,there are still some issues that have not been studied in depth in the modeling and measurement of the parameters of the transmission line grounding system.The traditional measurement method has the disadvantages of difficult operation and unsuitable on-site,while the measurement accuracy of the loop method and the high-frequency parallel method are both Relying on the electrical model of the transmission line grounding system,the modeling and measurement of the transmission line grounding system parameters are of great significance for determining the measurement accuracy of the loop method and the high-frequency parallel method.The related theoretical derivation of the problems in the grounding system model of the transmission line is carried out.Based on the simplified model of the grounding system,a loop measurement method using multi-frequency current injection is proposed.The physical model of the grounding system is established by ATPDraw electromagnetic transient design software,including lightning current,towers,grounding devices,etc.,to simulate the circuit characteristics of the back strike when the transmission line is struck by lightning.Taking the35 k V transmission line lightning protection standard as a reference,the reliability of the equivalent model of the grounding system built is verified,the influence of the parameter change of the ground impedance on the lightning protection level of the transmission line is analyzed,and the inductance component of the grounding device and the lightning protection line is studied.The effect of frequency changes.It provides a theoretical basis for the lightning protection prediction and analysis of the line,and has important guiding significance for the further improvement of the ground impedance detection algorithm.Through the research on the measurement method of the grounding system parameters of the transmission line,the embedded development technology and the frequency conversion measurement method are integrated with each other,so as to realize the measurement of the impedance parameters of the grounding device under different frequency conditions.First,the overall plan of the measuring instrument system is completed in combination with the application environment on the spot,and then each module is individually designed according to the functional requirements of the hardware circuit,and a ground impedance parameter measuring instrument that can realize variable frequency measurement is developed.The measuring instrument uses voltage transformer and current transformer clamp to measure on the same grounding wire,and is responsible for collecting voltage and current data respectively.The MSP430 single-chip microcomputer is used as the core processor.The sinusoidal AC signal is generated by the sinusoidal excitation source module,and the frequency of the output AC signal is changed according to the measurement requirements.After the signal passes through the two-stage amplifying circuit,the voltage transformer is induced to the loop of the grounding system.The current transformer collects the induced current signal,and completes the real-time data storage,analysis and processing work through the band-pass filter module,the signal amplification module and the analog-to-digital conversion module.The time-domain data is processed according to the Fourier transform method,combined with the transmission line parameter model design equation to complete the parameter solution,so as to realize the comprehensive solution of the parameters of the transmission line grounding system,and to efficiently and accurately evaluate the lightning protection capability of the transmission line Provide technical support.