Transmission Line Design in Structural Engineering – Ep 078

In this episode, we talk to Cody Forell, Structural Design Engineer at Sunflower Electric Power Corporation,  about transmission line design and what it is like working as a structural engineer at an electrical utility. Engineering Quotes: Here Are Some of the Questions We Ask Cody: What was passing the PE Exam like for you, and what do you hope to accomplish with your PE License? What is your involvement in transmission line design and what kind of transmission line structure configurations do you work with? Which factors need to be considered while designing a transmission system? What are the factors which limit the loading capabilities of transmission lines? What are Phase-to-phase and Phase-to-ground clearances? What is aeolian vibration in transmission lines and how does it affect transmission lines? What roles do substation foundations play in the design process, and how does it affects the clearance requirements? Do you have any advice for young engineers starting in their careers? Here Are Some of the Key Points Discussed About Transmission Line Design in Structural Engineering: The state of Kansas allows engineers to take the PE Exam before they have completed four years of engineering experience. Taking the test early means you will have to complete your four years of engineering experience before you can apply for your PE license. Transmission lines move electric power from one point to another and connect a network of substations and generating facilities. Three-phase alternating current transmission lines have 3 conductors and static wires. The structures are mostly made of wood or steel, but there are other structure material types available. There are 3 main types of transmission line structures namely, tangent structures, angle structures, and dead-end structures. Transmission line structures must be strong enough to support the conductors and static wires. The conductors and static wires also have strength properties. Aluminum Conductor Steel Reinforced (ACSR) conductors have external aluminum strands that carry the electrical current and steel core strands help with the strength. The National Electrical Safety Code (NESC) has limits on a conductor and static wire tensions and sags, which forms a big part of the design and analysis. PLS-CADD and PLS-POLE are the programs used for the modeling and analysis of transmission lines. Phase-to-phase clearance is the clearance that must be maintained between any two conductors on a circuit. Phase-to-ground clearance is the clearance from the conductor to anything besides another conductor. The clearance distances are dependent on the operating voltage of the transmission line. Aeolian vibration is a high-frequency low amplitude oscillation that is caused by a steady wind perpendicular to the wire. Conductors with high tension are most susceptible to experiencing aeolian vibration. Galloping is the opposite conductor movement, which is a low-frequency high amplitude oscillation, that is caused by freezing rain or sleet combined with a steady crosswind on the conductor. The rain or sleet freezes on the conductor in the shape of an airfoil. The wind then lifts the conductor like an airplane wing causing the conductor to gallop. Dampers are used to mitigate the movement of the conductor. The dampers are weights that are strategically placed on the wire to disrupt a range of vibration frequencies. Substation foundations consist of drill piers, slabs on grid, or spread footings depending on the equipment it is supporting. Young engineers should explore intern options to figure out what they like and do not like. Always be prepared and organized so you can take advantage of opportunities that come your way. More Details in This Episode…