Mr. Bell holds a Bachelor of Applied Science ME degree from the University of Toronto and works as part of the engineering and development team devoted to new composite insulator and interphase spacer designs and applications. Among his current goals is further improving insulator performance through research and product testing. He is active in IEEE/PES, including NEMA and ANSI C29 Insulator Working Groups and participates in current IEEE e-field sensitivity studies and Guide updates.
1. Framing for overhead transmission lines has conventionally relied on designs based on pole-top cross-arms or davit arms. More recently, however, composite line post insulators, which are more flexible and handle dynamic mechanical loads better than porcelain, are being used for this framing function, also allowing reduced structure costs and right-of-way widths. This presentation explains how line post insulator selection should consider combined in-service vertical and longitudinal cantilever loads as well as transverse compression and tension loads from wind and line angle. Combined Load Curves then correlate combined OHL design loads to a 50% value of the insulator’s specified cantilever load to prevent damage.
2. Conductors are flexible structures with almost no self-damping and are therefore susceptible to aeroelastic instabilities. For example, wind passing over an overhead power line with either single or bundled conductors can cause Aeolian vibration or galloping. Bundled conductors are also susceptible to wake-induced oscillation, caused by aerodynamic shielding of leeward-lying conductors by the windward conductors. Flashovers can result if galloping phase conductors are momentarily too close to one another or to overhead ground wires while conductors, insulators and structures are also at risk of damage. This presentation explains how composite interphase spacers are an effective countermeasure to galloping while Stockbridge dampers mitigate Aeolian vibration.