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In this paper, the lightning shielding performance of a newly designed 400-k \textV double-circuit composite tower is investigated. Based on a revised electrogeometric model (EGM) method, traditional shielding failure regions located at both sides of a traditional tower are no longer a big issue for the fully composite tower, due to its unusual ^\prime Y^\prime configuration. Instead, a new unprotected region exists in the tower center. The maximum lightning current that can lead to shielding failure and the shielding failure rate of the new tower are calculated. To verify results from the revised EGM method, a scale model test is conducted. Spatial shielding failure probability around the tower is calculated based on the ratio of discharge paths recorded in the test. Moreover, based on test results, the maximum shielding failure lightning currents are obtained. Analysis and results derived from the revised EGM method and scale model test have a small deviation, verifying the feasibility of these two methods in the lightning performance evaluation of the fully composite tower. Both methods confirm that the unusual negative shielding angle of -\text60^\circ in the newly composite tower provides good lightning shielding performance. The feasibility of the novel composite tower is verified from the lightning protection point of view. [ABSTRACT FROM PUBLISHER]

This paper deal with the electrical performance of a newly proposed fully composite pylon in Denmark, which has a unibody composite cross-arm at 420 kV highest system voltage level. Electric field consideration along the insulations of the novel unibody cross-arm is one of the most important requirements in the design process of a non-traditional pylon. In this paper, ANSYS finite element software is used to calculate the electric field and potential distribution around and inside the fully composite pylon. Electric field criteria related to the design of composite cross-arms are reviewed and applied for interpreting the electrical performance of the unibody cross-arm at power frequency stresses. Three different designs of non-conductive conductor clamp are assumed for the attachment points between phase conductors and the unibody cross-arm. The side effects of conductor clamp are included in 2D modeling in order to determine the minimum required height for phase conductors at the top of the unibody cross-arm. Considering the side effects of phase conductors at both sides of conductor clamp, the application of steel enclosures with an appropriate diameter is introduced to be used around the phase conductors in order to reduce the electric field magnitudes in the region of the conductor clamp. Finally, the feasibility of utilizing steel enclosures for modifying electric stresses inside the conductor clamp and unibody cross-arm is investigated by a 3D finite element analysis. [ABSTRACT FROM AUTHOR]