Innovative insulated cross-arm: Requirements, testing and construction

The first inquiry for new tower designs was launched by Elia (the Belgian TSO) in 2008 in the frame of the need for new 380 kV transmission lines. The requirements of this inquiry included minimum visual effects (similar to the existing 150 kV tower silhouette), low EMF and AN levels under the line and a maximum transport capacity of 3 GVA/circuit. Based on these requirements the innovative compact overhead line with insulated cross-arms made of composite insulators have been designed and installed. This work resulted in a comprehensive project including a number of phases: Development of proper specifications; Evaluation of different designs from maximum E-field point of view; Type testing according to the specification; Development of new test methods and verification of the complete design; Demo and construction. This paper presents the overview of the phases above in relation to the insulated cross-arms. The final design of the tower became similar in height as the existing 150 kV line, however operating at 380 kV. Thus, it was relatively easy to get the public acceptance, and at the same time increase the transfer capacity of energy almost 10 times. This makes Elia's project an excellent example for many European power utilities.