Jing Bo Yang

Latest Developments of Materials Used in Transmission Tower Structure

This paper discusses the status quo and development trend of transmission tower materials, points out that there will be higher requirements on the varieties and specifications of transmission tower material alongside the continuous construction of power grids. Tower materials will develop in the environmental-friendly, high-strength and conservation-oriented trend. In the future, the demand for Q420, Q460 high-strength and large-width angle steel will grow enormously; the steel tubular tower will be used in transmission lines more widely due to its excellent carrying capability; new materials like weathering cold-formed steel and composite material will be gradually used in transmission towers.

Turbulence Integral Scale Corrections to Experimental Results of Aeroelastic Models with Large Geometric Scales: Application to Gust Loading Factor of a Transmission Line Tower

Full aeroelastic model tests are often carried out to investigate the buffeting responses and the corresponding gust loading factor (GLF) of flexible structures. The geometric model scale for complicated structures may sometimes be excessively large in comparison with the ratio between turbulence integral scales measured in wind tunnel and in real atmospheric environments. This inconsistency in scale modeling leads to severe distortions of turbulence integral scale similarity whose influence manifests itself by modifications in resonant component of buffeting response and in resulting GLF as well, and numerical correction is needed when these testing results are converted to full-scale. This paper presents a correction procedure in terms of correction factors for experimental GLF obtained from full aeroelastic model tests to account for the inconsistency in scale modeling. The correction is simply made on analyzing the prototype in two air flows with different turbulence integral scales, namely the nominal value in the real atmosphere environment and the full-scale value correspondent to aeroelastic model test. The correction procedure is applied to the full aeroelastic model experiments of a transmission line tower with an unusually large geometric scale of 1/40 in order to examine the effect of turbulence integral scale on GLF. An appreciable effect is observed. It is found that the GLF obtained from wind tunnel experiments tends to be conservative for most structures and becomes unsafe for structures with extremely low modal frequencies when disregarding the correction. Correction factors are then derived to accommodate the inconsistency in modeling turbulence integral lengths. As a first generalization, a set of more general correction factors defined in terms of modal damping ratio and frequency ratio, the ratio between modal frequency and the dominant frequency in wind power spectra, are further developed through parametric analysis. The correction factors decrease with the augment of modal damping ratio and frequency ratio.

Study on TMD Measure to Suppress Wind-Induced Vibration of Power Transmission Steel Tower

Wind-induced vibration can affect the safety of power transmission tower. Vibration suppression of the high-rise tower is of concern in engineering. Vibration of the tower is mostly the first-order bending modal and this vibration can be suppressed by the tuned mass damper (TMD). This paper developed a TMD vibration damping device using eddy current damper constituted by magnetic steel installed in the vibration mass and fixed copper plate. It is characterized by simple structure and easy installation, and is suitable for wind-induced damage prevention of transmission tower. Focusing on a quadruple-circuit on the same steel tube tower, a vibration reduction test on a real-scale tower conducted. The result shows that the damping ratio of the tower after installed with the TMD device will increase about 3%. The actual test result verifies the effectiveness of the eddy current TMD device.

Wind Tunnel Test on Wind-Induced Aerodynamic Force of Transmission Tower

Wind-induced aerodynamic force is the important parameter for transmission tower design. Based on force balance test, the tower and cross arm of typical 500kV power transmission tower have been investigated in wind tunnel using three wind speeds considering Reynolds effect. The test results show that the shape coefficient keeps the same at different wind speed, which means that Reynolds effect on transmission tower can be ignored. Then, the shape coefficients of tower and cross arm are provided.

Investigation on the Wind Pressure Asymmetric Coefficient of Transmission Line

The wind pressure asymmetric coefficient is used to express the variation of wind distribution along the transmission line. In this paper, the value of the wind pressure asymmetric coefficient in some international codes is discussed and compared. It’s shown that the coefficient has no relationship with the span length of transmission only in Chinese code. When the span of the checked transmission line is small, the wind pressure calculated based on Chinese code will be smaller than that based on others.

Construction Methods on Mechanical and Material's Deformation Control during Assembling and Erecting Cup Type Transmission Tower

Take a 1000kV Cup-Type tubular steel test tower as research object, and it is the first one of this type used in heavy ice area. Research on the assembly load’s affect to tower structure was made. The process of assembling tower using suspend guyed pole was analyzed with Finite Element Method. Structures overhanging the tower body, such as cross arms and bracket of earth wire, could be assembled in different ways. The different affect to the built structure corresponding to different assembly method was researched. The objective is to make the deformation of the structure minimum. It was indicated that, reinforce the K-joint by cable and the deformation of structure reduced obviously. The reinforce method is simple and efficient, and ensure the cross arm assembling smoothly. It is avail to improve the assemble quality of the whole structure.

Strengthening Method of Transmission Tower Crossing High-Speed Railway

It is imperative to improve the reliability index of the power transmission line crossing the high-speed railway for the purpose of guaranteeing safe and reliable operation of high-speed railway. Compared with the replacement of all iron towers, the strengthening and reinforcement of original iron towers are an economical and reasonable treatment method. Via the analysis of strengthening methods of iron towers, after different reinforcement measures are taken for different member parts and material forms, the bearing capacity of iron towers may be effectively improved to some extent so as to promote the reliability index of power transmission lines. The strengthening optimization scheme raised on this basis provides references for the strengthening and reinforcement of tower models of the same kind.

Analysis on Wind-Induced Vibration Dynamic Responses of Transmission Tower-Line System

Tower-line system of overhead transmission line are sensitive to wind. Therefore, dynamic effect of wind load should be taken into consideration, for instance, wind-induced vibration coefficient. There might be some errors in the calculation of the coefficient in accordance with ‘Load code for the design of building structures’, for its ignoring the irregular figure, scattered masses and coupling effect of tower-line system. Tower-line system is set up in virtual environment, with tower-line coupling considered, and research wind-induced vibration dynamic responses under Davenport wind speed spectrum. Random vibration theory was applied to calculate the coefficient. Whole tower was divided by hight, and calculated segment’s the wind-induced vibration coefficient seprately. Compare the coefficient from Load Code and random vibration theory, the latter with tower-line coupling effect and tower figure considered, is close to the actual.

Design and Full-Scale Test for Cup-Type Steel Tubular Tower of UHV Transmission Line in Heavy Icing Area

The ZB1 cup-type steel tubular tower is the first single-circuit tower for UHV transmission line in heavy icing area. Except the ground supports, steel tubular are applied in whole tower. The plug-in boards and forging flanges are used in ZB1 tower,and the highest strength of tubular steel is Q345. Through the monographic study on the tower optimizationnode structuretowers Eiffel effect and bending moment at member end et., The design of ZB1 cup-type steel tubular tower is improved. The success of full-scale test verified the reliability in design and manufacture of cup-type steel tubular tower for UHV in heavy icing area. Research results of this paper can be applied in UHV transmission line projects.

Design and Full-Scale Test for Steel Tubular Tower of UHV and EHV Quadruple-Circuit Transmission Line on the same Tower

State Grid Corporation of China has carried out research on key technology of UHV&EHV AC and DC multi-circuit transmission lines, the research on material and structure of transmission tower is the important part. The SSZT2 tower, on which 1000 kV AC double-circuit and 500 kV AC double-circuit are arranged, is the largest power transmission capacity all over the world. Q420 high-strength tubular steel, the plug-in boards and forging flanges are used in SSZT2 tower,and the forging flange with strength classification is applied for the first time. Through the monographic study on the tower structures, wind vibration coefficient, and biaxial bending of steel tube etc. The success of full-scale test verified the reliability in design and manufacture of multi-circuit steel tubular tower for UHV and EHV. Research results of this paper can be applied in UHV transmission line projects.