Arcing horns - Video Learning - WizScience.com

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• published: 10 Sep 2015
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"Arcing horns" are projecting conductors used to protect insulators on high voltage electric power transmission systems from damage during flashover. Overvoltages on transmission lines, due to atmospheric electricity, lightning strikes, or electrical faults, can cause arcs across insulators that can damage them. The horns encourage the flashover to occur between themselves rather than across of the surface of the insulator they protect. Horns are normally paired on either side of the insulator, one connected to the high voltage part and the other to ground. They are frequently to be seen on insulator strings on overhead lines, or protecting transformer bushings. The horns can take various forms, such as simple cylindrical rods, circular guard rings, or contoured curves, sometimes known as 'stirrups'. High voltage equipment, particularly that which is installed outside, such as overhead power lines, is commonly subject to transient overvoltages, which may be caused by phenomena such as lightning strikes, faults on other equipment, or switching surges during circuit re-energisation. Overvoltage events such as these are unpredictable, and in general cannot be completely prevented. Line terminations, at which a transmission line connects to a busbar or transformer bushing, are at greatest risk to overvoltage due to the change in characteristic impedance at this point. An electrical insulator serves to provide physical separation of conducting parts, and under normal operating conditions is continuously subject to a high electric field which occupies the air surrounding the equipment. Overvoltage events may cause the electric field to exceed the dielectric strength of air and result in the formation of an arc between the conducting parts and over the surface of the insulator. This is called flashover. Contamination of the surface of the insulator reduces the breakdown strength and increases the tendency to flash over. On an electrical transmission system, protective relays are expected to detect the formation of the arc and automatically open circuit breakers to discharge the circuit and extinguish the arc. Under a worst case, this process may take as long as several seconds, during which time the insulator surface would be in close contact with the highly energetic plasma of the arc. This is very damaging to an insulator, and may shatter brittle glass or ceramic disks, resulting in its complete failure. Wiz Science™ is "the" learning channel for children and all ages. SUBSCRIBE TODAY Disclaimer: This video is for your information only. The author or publisher does not guarantee the accuracy of the content presented in this video. USE AT YOUR OWN RISK. Background Music: "The Place Inside" by Silent Partner (royalty-free) from YouTube Audio Library. This video uses material/images from https://en.wikipedia.org/wiki/Arcing+horns, which is released under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . This video is licensed under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . To reuse/adapt the content in your own work, you must comply with the license terms. Wiz Science™ is "the" learning channel for children and all ages. SUBSCRIBE TODAY Disclaimer: This video is for your information only. The author or publisher does not guarantee the accuracy of the content presented in this video. USE AT YOUR OWN RISK. Background Music: "The Place Inside" by Silent Partner (royalty-free) from YouTube Audio Library. This video uses material/images from https://en.wikipedia.org/wiki/Arcing+horns, which is released under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . This video is licensed under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . To reuse/adapt the content in your own work, you must comply with the license terms.