Research On Single Conductor Transmmission Lines

Single-conductor transmission lines?SCTLs?are single-metal open-waveguide transmission lines proposed in the early days.Electromagnetic waves can transmit along the outer space of the SCTLs.Georg Goubau found that as the increase of the microwave frequency,its radial transmission space range along the single-metal lines will gradually shrink.The research of the Georg Goubau indicated that SCTLs show potential application value in engineering applications such as communication,imaging,field emission microscope and nondestructive testing.At present,there are still many problems in the research methods of the SCTLs,and the experimental results and theoretical prediction are not completely consistent.In order to promote the development of the SCTLs technology,this thesis attempts to explore and study this subject.This thesis focus on the practical applications of the electromagnetic transmission along the overhead power lines,and the key to solving this problem is to grasp the propagation characteristics of electromagnetic waves along the SCTLs.Therefore,it is necessary to make a quantitative analysis of the transmission modes and characteristics of the SCTLs through theoretical research and then guide the research of mode exciter technology and experimental research of the overhead power lines transmission through theoretical research.Therefore,this thesis studies the SCTLs through theoretical analysis,simulation optimization and experimental verification.The main research contents include the following four aspects:1.Analysis of the transmission modes on the SCTLs.Based on the basic theory of surface wave on plane structure,the analytical expressions of the transmission modes of the Sommerfeld lines with circular cross-section is derived and concluded;2.Theoretical analysis of theTM₀₁ mode on the Sommerfeld lines.When theTM₀₁ mode transmits on the Sommerfeld lines,the effect of conductivity on the surface wave radial electrical field and radial energy distribution was analysed,and the loss of the transmission lines was also analyzed.The problem of model imperfection is also pointed out when the conventional electromagnetic simulation software calculates the single conductor transmission.Moreover,the effective method to improve the calculation accuracy is given.3.Research on the technology of the mode exciter of the SCTLs.Under the guidance of the above theoretical methods,two kinds of compact,noninvasive and ultra widebandTM₀₁ mode exciters with frequency in the range of 0.5-4GHz are researched.The final designs are also given.4.The experimental research of TMTM₀₁ mode transmitting along the long power lines.Using the designed mode exciter,an experimental platform was built,and the transmission characteristic of the power linesTM₀₁ mode is measured and analysed.The test results show that,when the length of the power lines is 10m,the maximum transmission efficiency of the power lines with a cross-sectional radius of 9.5mm reach up to 99.26%in frequency ranges of 0.5-1.3GHz and 1.5-4GHz.The maximum transmission efficiency deviation between the theoretical analysis and the experimental measure reaches 2.8%when the length of the power lines is 1m.