{"id":1788,"date":"2026-07-27T10:33:19","date_gmt":"2026-07-27T02:33:19","guid":{"rendered":"https:\/\/jutrion.com\/?page_id=1788"},"modified":"2026-08-07T10:59:47","modified_gmt":"2026-08-07T02:59:47","slug":"calculatrice-pv-spd-ucpv","status":"publish","type":"page","link":"https:\/\/jutrion.com\/fr\/tools\/pv-spd-ucpv-calculator\/","title":{"rendered":"PV SPD Minimum Ucpv Calculator"},"content":{"rendered":"\n<!-- ===== JUTRION PV SPD Minimum Ucpv Calculator \u2014 paste into a WordPress \"Custom HTML\" block ===== -->\n<div class=\"jt-calc\">\n  <p class=\"eyebrow\">Solar &amp; DC<\/p>\n  <h1>PV SPD Minimum U<sub>cpv<\/sub> Calculator<\/h1>\n  <p class=\"tool-lede\">Derive the minimum continuous operating voltage U<sub>cpv<\/sub> a PV surge protective device must have, from the string open-circuit voltage corrected for cold temperature, and screen the SPD type and connection. Under-rating U<sub>cpv<\/sub> lets the array voltage age or fail the SPD; over-rating weakens the protection level.<\/p>\n\n  <div class=\"jt-card\"><div class=\"jt-grid\">\n    <div class=\"jt-inputs\">\n      <div class=\"jt-two\">\n        <div class=\"jt-field\"><label for=\"jt-voc\">String V<sub>oc<\/sub> at STC (V)<\/label><input type=\"number\" id=\"jt-voc\" value=\"900\" min=\"1\" step=\"10\" inputmode=\"numeric\"><\/div>\n        <div class=\"jt-field\"><label for=\"jt-beta\">\u03b2 V<sub>oc<\/sub> (%\/\u00b0C)<\/label><input type=\"number\" id=\"jt-beta\" value=\"-0.27\" max=\"0\" step=\"0.01\" inputmode=\"decimal\"><\/div>\n      <\/div>\n      <div class=\"jt-field\"><label for=\"jt-tmin\">Site min. temperature (\u00b0C)<\/label><input type=\"number\" id=\"jt-tmin\" value=\"-10\" step=\"1\" inputmode=\"numeric\"><\/div>\n      <div class=\"jt-field\"><label for=\"jt-lps\">Lightning exposure<\/label>\n        <select id=\"jt-lps\"><option value=\"2\" selected>No external LPS \u2014 Type 2<\/option><option value=\"1\">External LPS \/ high exposure \u2014 Type 1 (or 1+2)<\/option><\/select>\n      <\/div>\n      <div class=\"jt-note\"><span>\u24d8<\/span><span>Enter the whole string V<sub>oc<\/sub> at STC. The calculator applies the cold-temperature rise and the IEC 61643-31 safety factor.<\/span><\/div>\n    <\/div>\n    <div class=\"jt-readout\">\n      <div><div class=\"jt-rl\">Minimum U<sub>cpv<\/sub><\/div><div class=\"jt-big\"><span id=\"jt-ucpv\">\u2014<\/span> <span>V<\/span><\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">String cold V<sub>oc<\/sub><\/div><div class=\"v\" id=\"jt-cvoc\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">Quick rule 1.2 \u00d7 V<sub>oc,STC<\/sub><\/div><div class=\"v\" id=\"jt-quick\">\u2014<\/div><\/div>\n      <div class=\"jt-rec row\"><div class=\"k\">SPD type &amp; connection<\/div><div class=\"v\" id=\"jt-type\" style=\"font-size:13px\">\u2014<\/div><\/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 U<sub>cpv<\/sub> is derived<\/h2>\n    <div class=\"jt-eq\">V<sub>oc<\/sub>(cold) = V<sub>oc,STC<\/sub> \u00d7 [ 1 + (\u03b2\/100) \u00d7 (T<sub>min<\/sub> \u2212 25) ]\nU<sub>cpv<\/sub> \u2265 V<sub>oc<\/sub>(cold) \u00d7 1.1        (IEC 61643-31)\nQuick rule: U<sub>cpv<\/sub> \u2265 1.2 \u00d7 V<sub>oc,STC<\/sub><\/div>\n    <p>U<sub>cpv<\/sub> is the maximum continuous DC voltage the SPD withstands without conducting. It must sit above the highest voltage the array ever presents \u2014 the cold open-circuit voltage \u2014 with a 1.1 margin so the SPD is not stressed in normal service. The <b>1.2 \u00d7 V<sub>oc,STC<\/sub><\/b> rule of thumb is a quick equivalent that folds temperature and margin into one factor; use the higher of the two results.<\/p>\n\n    <h2>Type and connection<\/h2>\n    <ul>\n      <li><b>Type 2<\/b> \u2014 the usual choice, protecting the array and inverter from induced and switching surges where there is no external lightning protection system.<\/li>\n      <li><b>Type 1 (or 1+2)<\/b> \u2014 required where the building has an external LPS or high direct-strike exposure, to handle partial lightning current.<\/li>\n    <\/ul>\n    <p>PV SPDs commonly use a <b>Y (3+0)<\/b> connection \u2014 each DC pole to earth through a varistor plus a spark gap between the mid-point and earth \u2014 so a single earth fault does not defeat the protection. Follow the SPD maker&#8217;s wiring for the array earthing arrangement.<\/p>\n    <div class=\"jt-note\"><span>\u26a0<\/span><span><b>Match U<sub>cpv<\/sub> to the string, and mind the distance.<\/b> An SPD more than about 10 m of cable from the equipment it protects needs a second SPD nearer the load. Coordinate the SPD with an upstream DC disconnector for safe end-of-life disconnection.<\/span><\/div>\n\n    <h2>Frequently asked questions<\/h2>\n    <div class=\"jt-faq\">\n      <details><summary>Why not just use V<sub>oc<\/sub> at STC?<\/summary><p>Because the array voltage rises in the cold and the SPD needs headroom above the worst case. Sizing U<sub>cpv<\/sub> on the STC value risks continuous stress and premature ageing on cold, sunny days.<\/p><\/details>\n      <details><summary>Where do PV SPDs go?<\/summary><p>At the array\/combiner and at the inverter DC input, with a second device where cable runs exceed roughly 10 m. Both AC and DC sides of a PV system need their own SPDs.<\/p><\/details>\n      <details><summary>Type 1 or Type 2 for my site?<\/summary><p>Type 2 without an external lightning protection system; Type 1 (or a combined Type 1+2) where an LPS is present or the exposure is high. The U<sub>cpv<\/sub> requirement is identical for both.<\/p><\/details>\n    <\/div>\n\n    <div class=\"jt-cta\">\n      <h2>Select the PV SPD<\/h2>\n      <p>Match the U<sub>cpv<\/sub>, type, and connection to a DC surge protective device for the array and inverter.<\/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\/pv-combiner-box\/\">PV combiner box<\/a> \u00b7 <a href=\"https:\/\/jutrion.com\/fuse\/\">Fuse<\/a><\/p>\n    <\/div>\n\n    <div class=\"jt-std\"><strong>Standards referenced<\/strong>IEC 61643-31 (PV SPDs) \u00b7 EN 50539-11 \u00b7 IEC 60364-7-712 (PV systems) \u00b7 IEC 62305 (lightning protection).<\/div>\n    <p class=\"jt-fine\">Estimate for guidance only. The final U<sub>cpv<\/sub>, SPD type, connection, and positions must be confirmed by a qualified person against IEC 61643-31, the array design, and the site lightning risk.<\/p>\n  <\/div>\n<\/div>\n\n<script>\n(function(){\n  var $=function(id){return document.getElementById(id);};\n  var voc=$('jt-voc'),beta=$('jt-beta'),tmin=$('jt-tmin'),lps=$('jt-lps'),\n      ucpvEl=$('jt-ucpv'),cvocEl=$('jt-cvoc'),quickEl=$('jt-quick'),typeEl=$('jt-type');\n  function calc(){\n    var V=parseFloat(voc.value),b=parseFloat(beta.value),T=parseFloat(tmin.value);\n    if(!(V>0)||isNaN(b)||isNaN(T)){ucpvEl.textContent='\u2014';cvocEl.textContent=quickEl.textContent=typeEl.textContent='\u2014';return;}\n    var cv=V*(1+(b\/100)*(T-25));\n    var u1=cv*1.1, u2=1.2*V, u=Math.max(u1,u2);\n    ucpvEl.textContent=Math.ceil(u);\n    cvocEl.textContent=cv.toFixed(0)+' V';\n    quickEl.textContent=Math.ceil(u2)+' V';\n    typeEl.textContent=(lps.value==='1')?'Type 1 (or 1+2), Y connection':'Type 2, Y connection';\n  }\n  [voc,beta,tmin,lps].forEach(function(el){el.addEventListener('input',calc);el.addEventListener('change',calc);});\n  $('jt-copy').addEventListener('click',function(){var b=$('jt-copy');var txt='String Voc(STC): '+voc.value+' V, \u03b2 '+beta.value+' %\/\u00b0C, Tmin '+tmin.value+' \u00b0C\\nString cold Voc: '+cvocEl.textContent+'\\nMinimum Ucpv: '+ucpvEl.textContent+' V\\nSPD: '+typeEl.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>Solar &amp; DC PV SPD Minimum Ucpv Calculator Derive the minimum continuous operating voltage Ucpv a PV surge protective device must have, from the string open-circuit voltage corrected for cold temperature, and screen the SPD type and connection. Under-rating Ucpv lets the array voltage age or fail the SPD; over-rating weakens the protection level. String [&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-1788","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/pages\/1788","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/comments?post=1788"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/pages\/1788\/revisions"}],"predecessor-version":[{"id":1789,"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/pages\/1788\/revisions\/1789"}],"up":[{"embeddable":true,"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/pages\/1778"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/fr\/wp-json\/wp\/v2\/media?parent=1788"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}