{"id":1830,"date":"2026-07-27T10:31:39","date_gmt":"2026-07-27T02:31:39","guid":{"rendered":"https:\/\/jutrion.com\/?page_id=1830"},"modified":"2026-07-27T10:38:48","modified_gmt":"2026-07-27T02:38:48","slug":"%e1%9e%a7%e1%9e%94%e1%9e%80%e1%9e%9a%e1%9e%8e%e1%9f%8d%e1%9e%87%e1%9f%92%e1%9e%9a%e1%9e%be%e1%9e%9f%e1%9e%9a%e1%9e%be%e1%9e%9f-spd","status":"publish","type":"page","link":"https:\/\/jutrion.com\/km\/tools\/spd-selector\/","title":{"rendered":"\u17a7\u1794\u1780\u179a\u178e\u17cd\u1787\u17d2\u179a\u17be\u179f\u179a\u17be\u179f spd"},"content":{"rendered":"\n<!-- ===== JUTRION SPD Selector \u2014 paste into a WordPress \"Custom HTML\" block ===== -->\n<div class=\"jt-calc\">\n  <p class=\"eyebrow\">Surge &amp; voltage<\/p>\n  <h1>Surge Protective Device (SPD) Selector<\/h1>\n  <p class=\"tool-lede\">Get the SPD type, minimum U<sub>c<\/sub>, target U<sub>p<\/sub>, and discharge rating for a low-voltage installation from the system earthing and the point of installation, to IEC 61643-11 \/ IEC 60364-5-534. Confirm the final device against the equipment withstand voltage and the manufacturer&#8217;s data.<\/p>\n\n  <div class=\"jt-card\"><div class=\"jt-grid\">\n    <div class=\"jt-inputs\">\n      <div class=\"jt-field\"><label for=\"jt-earth\">System earthing<\/label>\n        <select id=\"jt-earth\"><option value=\"TN\">TN-S \/ TN-C-S<\/option><option value=\"TT\">TT<\/option><option value=\"IT\">IT<\/option><\/select>\n      <\/div>\n      <div class=\"jt-field\"><label>Supply<\/label>\n        <div class=\"jt-seg\" id=\"jt-phase\"><button type=\"button\" data-ph=\"3\" aria-pressed=\"true\">Three-phase 400 V<\/button><button type=\"button\" data-ph=\"1\" aria-pressed=\"false\">Single-phase 230 V<\/button><\/div>\n      <\/div>\n      <div class=\"jt-field\"><label for=\"jt-loc\">Point of installation<\/label>\n        <select id=\"jt-loc\">\n          <option value=\"origin\">Origin \u2014 lightning risk \/ overhead line \/ LPS present<\/option>\n          <option value=\"board\" selected>Main or sub distribution board<\/option>\n          <option value=\"equip\">At \/ near sensitive equipment<\/option>\n        <\/select>\n      <\/div>\n      <div class=\"jt-note\"><span>\u24d8<\/span><span>Type 1 protects against direct lightning at the origin; Type 2 is the common board device; Type 3 gives fine protection at sensitive loads and needs a Type 2 upstream.<\/span><\/div>\n    <\/div>\n    <div class=\"jt-readout\">\n      <div><div class=\"jt-rl\">Recommended SPD type<\/div><div class=\"jt-type\" id=\"jt-typev\">\u2014<\/div><\/div>\n      <div class=\"jt-stage\"><div id=\"st1\">T1<\/div><div id=\"st2\">T2<\/div><div id=\"st3\">T3<\/div><\/div>\n      <div class=\"jt-rec row\"><span class=\"k\">Minimum U<sub>c<\/sub><\/span><span class=\"v\" id=\"jt-uc\">\u2014<\/span><\/div>\n      <div class=\"jt-rec row\"><span class=\"k\">Target U<sub>p<\/sub><\/span><span class=\"v\" id=\"jt-up\">\u2014<\/span><\/div>\n      <div class=\"jt-rec row\"><span class=\"k\">Discharge rating<\/span><span class=\"v\" id=\"jt-id\">\u2014<\/span><\/div>\n      <div class=\"jt-rec row\"><span class=\"k\">Connection mode<\/span><span class=\"v\" id=\"jt-conn\">\u2014<\/span><\/div>\n      <button type=\"button\" class=\"jt-copy\" id=\"jt-copy\">Copy result<\/button>\n    <\/div>\n  <\/div><\/div>\n\n  <div class=\"jt-content\">\n    <h2>How the SPD is selected<\/h2>\n    <p>Four properties define the device. The <b>type<\/b> follows the point of installation and the lightning exposure. The <b>U<sub>c<\/sub><\/b> (maximum continuous operating voltage) must sit above the system voltage in the relevant connection mode: at least 275 V for line-to-neutral modes on 230\/400 V systems, and 440 V for line-to-line modes such as IT. The <b>U<sub>p<\/sub><\/b> (voltage protection level) must be below the impulse withstand of the protected equipment \u2014 2.5 kV for standard category II equipment, 1.5 kV for sensitive category I. The <b>discharge rating<\/b> is I<sub>imp<\/sub> for Type 1 and I<sub>n<\/sub> \/ I<sub>max<\/sub> for Type 2.<\/p>\n    <div class=\"jt-note\"><span>\u26a0<\/span><span><b>Types must be coordinated.<\/b> A Type 1 alone does not protect category II equipment; pair it with a Type 2 downstream. A Type 3 always needs a Type 2 upstream.<\/span><\/div>\n\n    <h2>Frequently asked questions<\/h2>\n    <div class=\"jt-faq\">\n      <details><summary>Type 1, 2 or 3 \u2014 which do I need?<\/summary><p>Type 1 at the origin where direct lightning is a risk (external LPS, overhead lines); Type 2 at main and sub-distribution boards for most installations; Type 3 at sensitive equipment for fine protection, always with a Type 2 upstream.<\/p><\/details>\n      <details><summary>How is Uc chosen?<\/summary><p>From the system earthing and connection mode. For 230\/400 V TN and TT, line-to-neutral Uc is at least 275 V; IT and line-to-line modes need at least 440 V. Always confirm against the manufacturer&#8217;s rated Uc.<\/p><\/details>\n      <details><summary>Does the SPD need a backup fuse?<\/summary><p>Yes \u2014 an SPD needs an overcurrent disconnector (fuse or breaker) sized per the manufacturer&#8217;s data, unless one is integrated. Keep connecting leads short to keep the effective Up low.<\/p><\/details>\n    <\/div>\n\n    <div class=\"jt-cta\">\n      <h2>Specify the SPD<\/h2>\n      <p>Match the type, U<sub>c<\/sub>, U<sub>p<\/sub>, and discharge rating to a device, and add the correct backup protection.<\/p>\n      <div class=\"jt-cta-btns\">\n        <a class=\"jt-btn\" href=\"https:\/\/jutrion.com\/spd\/\">Explore JUTRION SPDs<\/a>\n        <a class=\"jt-btn ghost\" href=\"https:\/\/jutrion.com\/contact\/\">Get a free quote<\/a>\n      <\/div>\n      <p class=\"jt-related\">Related products: <a href=\"https:\/\/jutrion.com\/spd\/\">SPD<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/products\/\">All products<\/a><\/p>\n    <\/div>\n\n    <div class=\"jt-std\"><strong>Standards referenced<\/strong>IEC 61643-11 (SPD product) \u00b7 IEC 60364-5-534 (selection &amp; installation) \u00b7 IEC 60664 \/ 60364-4-443 (equipment withstand categories).<\/div>\n    <p class=\"jt-fine\">Guidance for a starting specification only. Final selection, coordination, backup protection, and installation must be verified by a qualified person against the equipment withstand voltage and the manufacturer&#8217;s datasheet.<\/p>\n  <\/div>\n<\/div>\n\n<script>\n(function(){\n  var $=function(id){return document.getElementById(id);};\n  var earth=$('jt-earth'),loc=$('jt-loc'),typev=$('jt-typev'),uc=$('jt-uc'),up=$('jt-up'),idr=$('jt-id'),conn=$('jt-conn');\n  var st1=$('st1'),st2=$('st2'),st3=$('st3'),phase=3;\n  document.querySelectorAll('#jt-phase button').forEach(function(b){b.addEventListener('click',function(){phase=parseInt(b.dataset.ph,10);document.querySelectorAll('#jt-phase button').forEach(function(x){x.setAttribute('aria-pressed',x===b?'true':'false');});calc();});});\n  function calc(){\n    var e=earth.value,l=loc.value;st1.className='';st2.className='';st3.className='';\n    if(l==='origin'){typev.textContent='Type 1 (+ 2)';idr.textContent='Iimp \u2265 12.5 kA (10\/350)';st1.className='on';st2.className='up';up.textContent='\u2264 2.5 kV (Cat II)';}\n    else if(l==='board'){typev.textContent='Type 2';idr.textContent='In 20 kA \/ Imax 40 kA (8\/20)';st2.className='on';up.textContent='\u2264 2.5 kV (Cat II)';}\n    else{typev.textContent='Type 3 (+ 2 upstream)';idr.textContent='Uoc rated, coordinated';st3.className='on';st2.className='up';up.textContent='\u2264 1.5 kV (Cat I)';}\n    if(e==='IT'){uc.textContent='\u2265 440 V (L-L)';conn.textContent='per system, L-PE';}\n    else if(e==='TT'){uc.textContent='\u2265 275 V L-N \u00b7 N-PE \u2265 230 V';conn.textContent='3+1 (L-N + N-PE)';}\n    else{uc.textContent='\u2265 275 V (L-N \/ L-PE)';conn.textContent='4+0 or 3+1';}\n  }\n  [earth,loc].forEach(function(el){el.addEventListener('input',calc);el.addEventListener('change',calc);});\n  $('jt-copy').addEventListener('click',function(){var b=$('jt-copy');var txt='System: '+earth.value+', '+(phase===3?'3-phase 400V':'1-phase 230V')+'\\nSPD type: '+typev.textContent+'\\nMin Uc: '+uc.textContent+'\\nTarget Up: '+up.textContent+'\\nDischarge: '+idr.textContent+'\\nConnection: '+conn.textContent;navigator.clipboard.writeText(txt).then(function(){var o=b.textContent;b.textContent='Copied \u2713';setTimeout(function(){b.textContent=o;},1500);}).catch(function(){b.textContent='Press Ctrl+C';});});\n  calc();\n})();\n<\/script>\n<!-- ===== end block ===== -->\n\n","protected":false},"excerpt":{"rendered":"<p>Surge &amp; voltage Surge Protective Device (SPD) Selector Get the SPD type, minimum Uc, target Up, and discharge rating for a low-voltage installation from the system earthing and the point of installation, to IEC 61643-11 \/ IEC 60364-5-534. Confirm the final device against the equipment withstand voltage and the manufacturer&#8217;s data. System earthing TN-S \/ [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1778,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1830","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/pages\/1830","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/comments?post=1830"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/pages\/1830\/revisions"}],"predecessor-version":[{"id":1831,"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/pages\/1830\/revisions\/1831"}],"up":[{"embeddable":true,"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/pages\/1778"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/km\/wp-json\/wp\/v2\/media?parent=1830"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}