A strain insulator is an electrical insulator that is designed to work in mechanical tension (strain), to withstand the pull of a suspended electrical wire or cable. They are used in overhead electrical wiring, to support radioantennas and overhead power lines. A strain insulator may be inserted between two lengths of wire to isolate them electrically from each other while maintaining a mechanical connection, or where a wire attaches to a pole or tower, to transmit the pull of the wire to the support while insulating it electrically. Strain insulators were first used in telegraph systems in the mid 19th century.
A typical strain insulator is a piece of glass, porcelain, or fiberglass that is shaped to accommodate two cables or a cable shoe and the supporting hardware on the support structure (hook eye, or eyelet on a steel pole/tower). The shape of the insulator maximizes the distance between the cables while also maximizing the load-bearing transfer capacity of the insulator. In practice, for radio antennas, guy-wires, overhead power lines and most other loads, the strain insulator is usually in physical tension.[1]
When the line voltage requires more insulation than a single insulator can supply, strain insulators are used in series: A set of insulators are connected to each other using special hardware. The series can support the same strain as a single insulator, but the series provides a much higher effective insulation.[2]
If one string is insufficient for the strain, a heavy steel plate effectively bundles several insulator strings mechanically. One plate is on the "hot" end and another is located at the support structure. This setup is almost universally used on long spans, such as when a power line crosses a river, canyon, lake, or other terrain requiring a longer than nominal span.[3]
Strain insulators are typically used outdoors in overhead wiring. In this environment they are exposed to rain and, in urban settings, pollution. As a practical matter, the shape of the insulator becomes critically important, since a wetted path from one cable to the other can create a low-resistance electrical path.
Strain insulators intended for horizontal mounting (often referred to as "dead ends") therefore incorporate flanges to shed water, and strain insulators intended for vertical mounting (referred to as "suspension insulators") are often bell-shaped.[1]
Low-voltage "egg"-type strain insulator, used in utility-pole guy cables to prevent any voltage on the guy caused by an electrical fault on the pole from reaching the lower sections accessible to the public
High-voltage strain insulators used on 66 kV, 230 kV and 115 kV AC lines. The number of insulator skirts varies with voltage and atmospheric conditions.
Pyrex-glass strain insulator used for radio antennas
Other than their industrial use for which they are produced, strain insulators can be collectables, especially antique ones.[4][5][6]
References
^ abTuran Gonen (19 April 2016). Modern Power System Analysis. CRC Press. pp. 186–. ISBN978-1-4665-9932-1.
^U.A.Bakshi; M.V.Bakshi (2009). Generation, Transmission And Distribution. Technical Publications. pp. 4–. ISBN978-81-8431-567-7.
^Whapham, R.; Robinson, J.A. (2006). "Use of Factory-Formed Dead-Ends on High Temperature Conductors". 2005/2006 IEEE/PES Transmission and Distribution Conference and Exhibition. pp. 1134–1138. doi:10.1109/TDC.2006.1668662. ISBN0-7803-9194-2.
^Zsiray, John (June 8, 2017). "Glass insulator collector talks about hobby, upcoming swap meet". The Herald Journal. Retrieved 15 December 2019.
^Michael Bruner (November 1999). The Definitive Guide to Colorful Insulators. Schiffer Publishing, Limited. ISBN978-0-7643-1045-4.
External links
US collectors club for glass insulators
August 21, 2023
strain, insulator, strain, insulator, electrical, insulator, that, designed, work, mechanical, tension, strain, withstand, pull, suspended, electrical, wire, cable, they, used, overhead, electrical, wiring, support, radio, antennas, overhead, power, lines, str. A strain insulator is an electrical insulator that is designed to work in mechanical tension strain to withstand the pull of a suspended electrical wire or cable They are used in overhead electrical wiring to support radio antennas and overhead power lines A strain insulator may be inserted between two lengths of wire to isolate them electrically from each other while maintaining a mechanical connection or where a wire attaches to a pole or tower to transmit the pull of the wire to the support while insulating it electrically Strain insulators were first used in telegraph systems in the mid 19th century Strain insulators on high voltage power lines Contents 1 Description and use 2 Collectors 3 References 4 External linksDescription and use EditA typical strain insulator is a piece of glass porcelain or fiberglass that is shaped to accommodate two cables or a cable shoe and the supporting hardware on the support structure hook eye or eyelet on a steel pole tower The shape of the insulator maximizes the distance between the cables while also maximizing the load bearing transfer capacity of the insulator In practice for radio antennas guy wires overhead power lines and most other loads the strain insulator is usually in physical tension 1 When the line voltage requires more insulation than a single insulator can supply strain insulators are used in series A set of insulators are connected to each other using special hardware The series can support the same strain as a single insulator but the series provides a much higher effective insulation 2 If one string is insufficient for the strain a heavy steel plate effectively bundles several insulator strings mechanically One plate is on the hot end and another is located at the support structure This setup is almost universally used on long spans such as when a power line crosses a river canyon lake or other terrain requiring a longer than nominal span 3 Strain insulators are typically used outdoors in overhead wiring In this environment they are exposed to rain and in urban settings pollution As a practical matter the shape of the insulator becomes critically important since a wetted path from one cable to the other can create a low resistance electrical path Strain insulators intended for horizontal mounting often referred to as dead ends therefore incorporate flanges to shed water and strain insulators intended for vertical mounting referred to as suspension insulators are often bell shaped 1 Low voltage egg type strain insulator used in utility pole guy cables to prevent any voltage on the guy caused by an electrical fault on the pole from reaching the lower sections accessible to the public High voltage strain insulators used on 66 kV 230 kV and 115 kV AC lines The number of insulator skirts varies with voltage and atmospheric conditions Pyrex glass strain insulator used for radio antennas horizontal lines and strain insulators inclined lines at Hoover DamCollectors EditOther than their industrial use for which they are produced strain insulators can be collectables especially antique ones 4 5 6 References Edit a b Turan Gonen 19 April 2016 Modern Power System Analysis CRC Press pp 186 ISBN 978 1 4665 9932 1 U A Bakshi M V Bakshi 2009 Generation Transmission And Distribution Technical Publications pp 4 ISBN 978 81 8431 567 7 Whapham R Robinson J A 2006 Use of Factory Formed Dead Ends on High Temperature Conductors 2005 2006 IEEE PES Transmission and Distribution Conference and Exhibition pp 1134 1138 doi 10 1109 TDC 2006 1668662 ISBN 0 7803 9194 2 Zsiray John June 8 2017 Glass insulator collector talks about hobby upcoming swap meet The Herald Journal Retrieved 15 December 2019 Rayburn Rosalie June 9 2017 Colorful glass insulators fascinate hobbyists Albuquerque Journal Retrieved 15 December 2019 Michael Bruner November 1999 The Definitive Guide to Colorful Insulators Schiffer Publishing Limited ISBN 978 0 7643 1045 4 External links EditUS collectors club for glass insulators Retrieved from https en wikipedia org w index php title Strain insulator amp oldid 1155713247, wikipedia, wiki, book, books, library,
