A State of the Art Overview: EHV Composite Cross-Arms and Composite-Based Pylons

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.