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Overhead transmission line pylons are key components of high voltage powersystems. Traditional steel lattice pylons, which have been designed since 70 yearsago, have a negative visual appearance on landscapes, and for this reason, in recentyears general public oppose against the installation of such pylons for the extensionof power system networks. In order to get public acceptance, a fully composite pylondesign has been proposed in Denmark which has a better visual appearance withrespect to the old ones. The fully composite pylon design is a novel concept andthere is no enough information and practical experience regarding its electrical andmechanical performance. In this book, the electrical performance of fully compositepylon is investigated by using analytical and finite element methods and high voltageexperimental method.The major challenges in the design process of fully composite pylon are addressed.One of the challenges is the electrical dimensioning of the fully compositepylon for which electrical clearances on the pylon should be determined. The electricalair clearances on the pylon must be enough to withstand against power frequency,switching and lightning overvoltages. The air clearances are calculated onthe basis of an extensive insulation coordination study.Another challenge is the selection of the material of the composite cross-armcore. In the book, two kinds of candidate fibre reinforced plastic (FRP) materialsare tested electrically and their important properties, including internal partial discharge(PD) performance, dielectric permittivity and dissipation factor are evaluated.Based on the test results, E-glass reinforced epoxy is recommended as the corematerial of the composite cross-arm. Also, three manufacturing methods for fibrereinforced plastic (FRP) materials are compared and the filament winding methodis recommended to the material supplier. As the fibre reinforced plastic (FRP) coreof the composite cross-arm is always stressed by electrical and mechanical loadingsimultaneously, an electrical-mechanical combined setup that can apply high voltageand dynamic tensile/compression forces to fibre reinforced plastic (FRP) materialssimultaneously is designed. With the combined setup, combined tests are performedon fibre reinforced plastic (FRP) materials and effects of mechanical loadingon their electrical behaviors are investigated. Meanwhile, effects of the electricalstress on the lifetime of fibre reinforced plastic (FRP) materials are studied.Another challenge is the proper design of insulation for the unibody cross-armof fully composite pylon. In this regard, the application of different shed profilesare mentioned and consequently, a small and large shed profile are assigned to theshed housing on the unibody cross-arm. A major challenge in the design of pylon isthe electric field performance of fully composite pylon. Numerous finite elementanalyses of the pylon are carried out to evaluate electric field and potential distributionaround and inside the unibody cross-arm. Two design scenarios of utilizinginternal or external ground connection for the shield wires are examined. Differentconductor clamp designs are considered for the attachment points between phase conductors and the unibody cross-arm. Electric field magnitudes in the differentregions of interest on the fully composite pylon are calculated and compared withthe threshold values.In order to experimentally assess the electric field magnitudes on the unibodycross-arm, a water-induced corona discharge setup is designed, with which a coronatest is performed on an equivalent full-scale composite cross-arm segment in wetconditions. Artificial rain is applied to the cross-arm segment with an equivalentphase-to-ground voltage. During this process, corona discharges from the cross-armsegment are measured and observed. With a stringent corona inception criterion of10 pC, it is found out that corona is triggered from the cross-arm surface undernominal voltage in wet conditions. Thus, it is concluded that corona rings are necessaryfor the fully composite pylon. Therefore, an optimization process is done byusing finite element method to find appropriate dimension and positions for the coronarings at both sides of the conductor clamps to get a design scenario in whichfully composite pylon represents an acceptable electric field performance. Additionally,the suitability of the initially designed unibody cross-arm inclined anglefrom the ground plane is investigated. The water-induced corona discharge test andscale model test are performed with different cross-arm inclined angles. Based ontest results, the initial inclined angle 30° is believed to be satisfactory if the electricfield on the cross-arm surface can be restrained to an acceptable level.The next challenge is the lightning shielding performance of fully composite pylonwhich is calculated and evaluated by different methods. The conventionalmethod of the electro-geometric model (EGM) is modified to be used for the assessmentof effectiveness of lightning shielding system for the fully composite pylon.The feasibility of assigned negative shielding angle for the pylon is investigatedand the outage rate regarding its application is calculated. The protected and unprotectedzones on the fully composite pylon against vertical and possible horizontallightning strikes are visualized for different lightning stroke currents.In order to experimentally evaluation of the lightning protection performance offully composite pylon, a scale model test is performed. It proves experimentally thata shielding failure region exists at the center of the pylon and the experimentalshielding failure rate for an overhead line composed of fully composite pylons issimilar to that predicted by electro-geometric model (EGM). Based on the scalemodel test, it is concluded that the shield wires arrangement in the fully compositepylon is satisfactory.Finally, the environmental aspects of fully composite pylon are calculated basedon analytical and finite element analysis methods. These aspects include radio interferences,audible noises, corona losses and emission of electromagnetic fields atthe right-of-way of the lines. The calculated values are compared with the recommendedthreshold values reported in related standards and literatures. This book presents an innovative concept for designing a 400 kV double circuit composite tower. The major challenges encountered by the authors in the electrical design process of the composite tower are addressed. They concern material selection for the full composite cross-arm core, electrical insulation of the cross-arm, electrical dimensioning of the full composite tower, lightning shielding performance and failure of the full composite tower. The electric field performance of the tower’s insulation has been investigated theoretically by using finite element method and experimentally by testing different fiber reinforced polymers as candidates. The book reports in detail those finite element simulations and tests, together with the authors’ recommendations on the most suitable materials and manufacturing process as well as conductor clamp designs for the cross-arm. Another important issue of the full composite tower, which concerns the environmental aspects of the full composite tower, has also been evaluated. This book offers a timely reference guide on a highly innovative topic, addressing researchers working on power transmission system both in industry and academia.

The main conclusions of electrical aspects of Power Pylons of the Future (PoPyFu) researches are summarized in this chapter and indicate the main findings. Future trends in the electrical design of fully composite pylon are also presented.

The first EHV composite cross-arms have been used since late 1990's in Switzerland. It was the first step to the compaction of towers sizes. Since then, significant advances have been made in composite cross-arms technology while the lattice construction technique has not been seriously challenged until now. For this reason, the next generation of overhead line is introduced to extend the European transmission grid by developing new design pylons that are easier to erect, smaller and better looking than the old ones, which is important to get public acceptance for planning of new lines. The proposed new fully composite pylon has a novel cross-arm in the form of uni-body insulator in order to reduce the tower height. So far, there is no theoretical analysis and technical standards for fully composite pylons. In this paper, two major challenges facing in the design of a fully composite-based pylon are presented, namely the proper design of cross-arm insulation and lightning shielding. The successful electrical design of the pylon depends on resolving these issues; therefore, for better understanding of the requirements and constraints in the electrical design of the pylon, the key advances of EHV composite cross-arms and lightning protection methods are reviewed based on the state of the art review and subsequently some solutions are presented to overcome the two main challenges.