{"id":5461,"date":"2023-03-23T15:05:26","date_gmt":"2023-03-23T07:05:26","guid":{"rendered":"https:\/\/www.ray-tron.com\/?p=5461"},"modified":"2023-09-01T13:43:17","modified_gmt":"2023-09-01T05:43:17","slug":"ele5139","status":"publish","type":"post","link":"https:\/\/www.ray-tron.com\/en\/ele5139\/","title":{"rendered":"The function and use of shielded wire"},"content":{"rendered":"<p>Shielded cable or screened cable is a cable that has a common conductive layer around its conductors for electromagnetic shielding. This shield is usually covered by the outermost layer of the cable. Common cable shield types can be most widely divided into foil type (hereinafter referred to as: metallized film), wire strands (braided or not) or both. The longitudinal conductors may need to be short-circuited with a dielectric spiral foil for each turn.<\/p><p>The shield acts as a Faraday cage \u2013 a surface that reflects electromagnetic radiation. This both reduces the amount of external noise that can interfere with the signal, and also reduces the signal being radiated and potentially interfering with other equipment (see electromagnetic compatibility). To be effective against electric fields (see also capacitive coupling), the shield must be connected to ground. The shield should be electrically continuous to maximise its effectiveness, including at the joints of any cables. For high frequency signals (over a few MHz), this also extends to the connector and housing, and is also circumferential: The cable shield needs to be circumferentially connected to the housing (if any), either through the connector or cable gland.<\/p><p>Some types of shielded cables use the shield as a return path for the signal. For example, coaxial cable does, while twinaxial cable does not.<\/p><p>High voltage power cables with solid insulation are shielded to protect the cable insulation, personnel and equipment.<\/p><p>The best way to route shielded wire is to ground the shield at both ends of the cable. Traditionally there has been a rule of thumb to only ground the shield at the source end to avoid ground loops. Best practice is to ground at both ends, but ground loops are possible. On aircraft, special cables are used that have both an outer shield to protect against lightning and an inner shield that is grounded at one end to eliminate hum from the 400 Hz power system.<\/p><figure class=\"wp-block-image aligncenter size-full\"><img decoding=\"async\" class=\"wp-image-5462 lazyload\" src=\"data:image\/gif;base64,R0lGODlhAQABAIAAAAAAAP\/\/\/yH5BAEAAAAALAAAAAABAAEAAAIBRAA7\" data-src=\"https:\/\/www.ray-tron.com\/wp-content\/uploads\/2023\/03\/1.png\" alt=\"\" \/><noscript><img fetchpriority=\"high\" decoding=\"async\" width=\"500\" height=\"350\" class=\"wp-image-5462 lazyload\" src=\"https:\/\/www.ray-tron.com\/wp-content\/uploads\/2023\/03\/1.png\" alt=\"\" srcset=\"https:\/\/www.ray-tron.com\/wp-content\/uploads\/2023\/03\/1.png 500w, https:\/\/www.ray-tron.com\/wp-content\/uploads\/2023\/03\/1-300x210.png 300w\" sizes=\"(max-width: 500px) 100vw, 500px\" \/><\/noscript><\/figure><p>application<\/p><p>Using shielded cables in security systems can provide some protection against power frequency and radio frequency interference, reducing false alarms. Best practice is to keep data or signal cables at least 3 inches (75 mm) away from parallel &quot;heavy&quot; power circuits.<\/p><p>Analog signal cables used in professional audio applications are usually shielded twisted pair cables terminated with XLR connectors. The twisted pair cables transmit signals in a balanced audio configuration. The audio multi-core cables from the stage to the mixing console are also shielded.<\/p><p>Consumers use shielded copper wire with a center conductor in an unbalanced configuration.<\/p><p>Power Cable<\/p><p>Medium and high voltage power cables, in circuits over 2000 volts, typically have a shield of copper or aluminum tape or conductive polymer. If an unshielded insulated cable comes into contact with the earth or a grounded object, the electrostatic field around the conductor will concentrate at the point of contact, causing corona discharge and eventually breaking down the insulation. Leakage currents and capacitive currents through the insulation present a shock hazard. Grounding shields balance the electrical stresses around the conductor, diverting any leakage current to ground. Strain relief cones should be applied at both ends of the shield, especially for grounded cables operating above 2kV.<\/p><p>The shield of a power cable can be connected to ground at the end of each shield and at joints to prevent shock, even if induced currents will flow in the shield. This current will generate losses and heat and will reduce the maximum current rating of the circuit. Tests have shown that having an exposed ground conductor next to the insulated wire can conduct fault current to the earth more quickly. In high-current circuits, the shield wire may be connected at only one end. In very long high-voltage circuits, the shield can be divided into several sections because a long shield can rise to a dangerous voltage in the event of a circuit fault. Grounding only one end of the shield poses a shock hazard. IEEE 422 and 525 list cable lengths that limit the shield potential to 25 volts in single-point grounding applications.<\/p><p><\/p>","protected":false},"excerpt":{"rendered":"<p>Shielded cable or screened cable is a cable that has a common conductive layer around its conductors for electromagnetic shielding. This shielding layer is usually covered by the outermost layer of the cable. Common [\u2026]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"default","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"default","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[19],"tags":[253,236],"class_list":["post-5461","post","type-post","status-publish","format-standard","hentry","category-blog","tag-blog","tag-pingbixian"],"_links":{"self":[{"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/posts\/5461","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/comments?post=5461"}],"version-history":[{"count":0,"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/posts\/5461\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/media?parent=5461"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/categories?post=5461"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ray-tron.com\/en\/wp-json\/wp\/v2\/tags?post=5461"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}