{"id":4523,"date":"2026-09-15T15:13:10","date_gmt":"2026-09-15T07:13:10","guid":{"rendered":"https:\/\/cnkuangya.com\/?p=4523"},"modified":"2026-09-15T15:13:26","modified_gmt":"2026-09-15T07:13:26","slug":"spd-backup-fuse","status":"publish","type":"post","link":"https:\/\/cnkuangya.com\/fr\/blog\/spd-backup-fuse\/","title":{"rendered":"Un parafoudre a-t-il besoin d'un fusible ou d'un disjoncteur de protection ? Guide pratique de s\u00e9lection"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Un parafoudre prot\u00e8ge les \u00e9quipements \u00e9lectriques contre les surtensions transitoires, mais qu'est-ce qui prot\u00e8ge le parafoudre en cas de d\u00e9faut interne ou de court-circuit ?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">C'est l\u00e0 que le <strong>fusible ou disjoncteur de protection de secours du parafoudre<\/strong> devient important.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cependant, il n'existe pas de r\u00e8gle universelle telle que :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c Chaque parafoudre de type 2 n\u00e9cessite un fusible de 125 A. \u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">ou :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c Un parafoudre de 40 kA doit utiliser un disjoncteur de 40 A. \u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Les deux affirmations peuvent \u00eatre fausses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Correct <strong>Fusible de protection du parafoudre<\/strong> La s\u00e9lection d\u00e9pend du mod\u00e8le exact de parafoudre, de la protection contre les surintensit\u00e9s en amont, du courant de court-circuit pr\u00e9sum\u00e9, de la section des conducteurs, de la configuration du syst\u00e8me et des instructions du fabricant.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Certains parafoudres peuvent utiliser le fusible ou le disjoncteur amont existant. D'autres n\u00e9cessitent une protection de secours s\u00e9par\u00e9e. Certains produits int\u00e8grent m\u00eame la protection de secours directement dans le parafoudre.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">La r\u00e8gle la plus importante est donc simple :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Do not select an SPD backup fuse only from the SPD&#8217;s In, Imax or Type classification. Always check the manufacturer&#8217;s declared backup protection and the actual installation conditions.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">R\u00e9ponse rapide : Un parafoudre a-t-il besoin d'un fusible de protection ?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Un parafoudre peut n\u00e9cessiter un fusible ou un disjoncteur de protection, mais chaque installation n'en requiert pas n\u00e9cessairement un s\u00e9par\u00e9.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the existing upstream overcurrent protective device already satisfies the SPD manufacturer&#8217;s permitted protection arrangement, an additional backup fuse may not be required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the upstream protective device exceeds the manufacturer&#8217;s permitted value, or if the SPD instructions specify dedicated branch protection, an additional <strong>fusible ou disjoncteur de protection de secours du parafoudre<\/strong> peut \u00eatre n\u00e9cessaire.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cela signifie que la bonne question n'est pas simplement :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c Quelle taille de fusible dois-je installer ? \u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Posez plut\u00f4t la question suivante :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>\u201cLa protection amont existante satisfait-elle d\u00e9j\u00e0 aux exigences sp\u00e9cifiques de ce parafoudre ?\u201d<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Principaux enseignements<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Un parafoudre et un fusible ou un disjoncteur assurent des fonctions de protection diff\u00e9rentes.<\/li>\n\n\n\n<li>An SPD&#8217;s internal thermal disconnector does not automatically replace external short-circuit or overcurrent protection.<\/li>\n\n\n\n<li>Tous les parafoudres ne n\u00e9cessitent pas un fusible de secours s\u00e9par\u00e9.<\/li>\n\n\n\n<li>The upstream protective device must be compared with the SPD manufacturer&#8217;s declared limits.<\/li>\n\n\n\n<li>Un fusible plus gros n'est pas automatiquement meilleur.<\/li>\n\n\n\n<li>Un fusible plus petit n'est pas automatiquement plus s\u00fbr, car un dimensionnement inappropri\u00e9 peut entra\u00eener un d\u00e9clenchement intempestif.<\/li>\n\n\n\n<li>Les calibres en amp\u00e8res des fusibles et des disjoncteurs ne doivent pas \u00eatre consid\u00e9r\u00e9s comme directement interchangeables.<\/li>\n\n\n\n<li>Les exigences relatives aux parafoudres CA et aux parafoudres CC PV doivent \u00eatre \u00e9valu\u00e9es s\u00e9par\u00e9ment.<\/li>\n\n\n\n<li>Le courant de court-circuit pr\u00e9sum\u00e9 au point d'installation est important.<\/li>\n\n\n\n<li>La section des conducteurs et la longueur des c\u00e2bles de raccordement du parafoudre doivent \u00e9galement \u00eatre prises en compte.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Quel est le r\u00f4le r\u00e9el d'un fusible de protection pour parafoudre ?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Un parafoudre et un dispositif de protection contre les surintensit\u00e9s r\u00e9solvent des probl\u00e8mes \u00e9lectriques diff\u00e9rents.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Un parafoudre de puissance typique est connect\u00e9 en parall\u00e8le avec le circuit.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">En fonctionnement normal, il ne transporte que peu ou pas de courant de charge. Lorsqu'une surtension transitoire survient, le parafoudre devient conducteur et d\u00e9vie le courant de choc \u00e0 travers son chemin de protection con\u00e7u \u00e0 cet effet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Un fusible ou un disjoncteur a une fonction diff\u00e9rente.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Sa fonction principale est d'interrompre les surintensit\u00e9s prolong\u00e9es ou les courants de d\u00e9faut.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Dispositif<\/th><th>Fonction principale<\/th><th>Con\u00e7u principalement pour<\/th><\/tr><\/thead><tbody><tr><td>DOCUP<\/td><td>Limite les surtensions transitoires et d\u00e9vie les courants de foudre<\/td><td>Ph\u00e9nom\u00e8nes transitoires de foudre et de commutation<\/td><\/tr><tr><td>Fusible<\/td><td>Interrompt les courants excessifs<\/td><td>Surcharge et court-circuit<\/td><\/tr><tr><td>Disjoncteur<\/td><td>Interrompt les courants excessifs et assure l'isolation\/la commutation<\/td><td>Surcharge et court-circuit<\/td><\/tr><tr><td>D\u00e9connecteur interne de parafoudre<\/td><td>D\u00e9connecte un \u00e9l\u00e9ment de protection d\u00e9faillant ou en surchauffe<\/td><td>Fin de vie du parafoudre ou condition interne anormale<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Par cons\u00e9quent :<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Un parafoudre n'est pas un fusible<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">et :<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Un fusible n'est pas un parafoudre<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ils offrent une protection compl\u00e9mentaire.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-1024x576.jpg\" alt=\"SPD fuse and circuit breaker protection device comparison\" class=\"wp-image-4525\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-fuse-circuit-breaker-comparison.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Un parafoudre limite les surtensions transitoires, tandis que les fusibles et les disjoncteurs sont principalement utilis\u00e9s pour la protection contre les surintensit\u00e9s et les d\u00e9fauts.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Pourquoi un parafoudre peut-il n\u00e9cessiter une protection de secours ?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">De nombreux parafoudres \u00e0 limitation de tension utilisent des composants non lin\u00e9aires tels que des varistances \u00e0 oxyde m\u00e9tallique.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">En tension nominale du syst\u00e8me, l'\u00e9l\u00e9ment de protection reste \u00e0 haute imp\u00e9dance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Lors d'une surtension, son comportement \u00e9lectrique change rapidement et il conduit le courant de surtension.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Cependant, les composants de protection contre les surtensions peuvent finir par atteindre leur fin de vie ou \u00eatre endommag\u00e9s en raison de :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>contraintes de surtension r\u00e9p\u00e9t\u00e9es,<\/li>\n\n\n\n<li>\u00e9v\u00e9nements de surtension s\u00e9v\u00e8res,<\/li>\n\n\n\n<li>surtensions temporaires,<\/li>\n\n\n\n<li>tension syst\u00e8me incorrecte,<\/li>\n\n\n\n<li>conditions de d\u00e9faut anormales,<\/li>\n\n\n\n<li>ou d\u00e9gradation interne.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Si un \u00e9l\u00e9ment de protection d\u00e9veloppe un d\u00e9faut \u00e0 faible imp\u00e9dance, l'installation doit \u00eatre capable de d\u00e9connecter en toute s\u00e9curit\u00e9 le courant de d\u00e9faut \u00e0 fr\u00e9quence industrielle ou le courant continu r\u00e9sultant.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">C'est pourquoi les fiches techniques des parafoudres peuvent inclure des param\u00e8tres tels que :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>fusible de protection maximal,<\/li>\n\n\n\n<li>protection maximale contre les surintensit\u00e9s c\u00f4t\u00e9 r\u00e9seau,<\/li>\n\n\n\n<li>protection de secours,<\/li>\n\n\n\n<li>courant de court-circuit nominal,<\/li>\n\n\n\n<li>Isccr,<\/li>\n\n\n\n<li>SCCR,<\/li>\n\n\n\n<li>ou dispositif de protection recommand\u00e9.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Pour les parafoudres basse tension CA, la norme internationale actuelle est <strong>IEC 61643-11:2025<\/strong>, qui couvre les exigences et les m\u00e9thodes d'essai pour les parafoudres connect\u00e9s aux circuits CA jusqu'\u00e0 1 000 V RMS.<br><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-11:2025 \u2014 page officielle de l'IEC<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">D\u00e9connecteur interne de parafoudre vs fusible de protection externe<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Une question courante est :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c Si mon parafoudre poss\u00e8de d\u00e9j\u00e0 un d\u00e9connecteur interne, pourquoi aurait-il besoin d'un autre fusible ? \u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Parce qu'ils n'assurent pas n\u00e9cessairement la m\u00eame fonction.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">D\u00e9connecteur interne de parafoudre<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Le d\u00e9connecteur interne est g\u00e9n\u00e9ralement associ\u00e9 au composant de protection contre les surtensions \u00e0 l'int\u00e9rieur du parafoudre.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Par exemple, lorsqu'une varistance (MOV) atteint une condition thermique dangereuse, le m\u00e9canisme interne peut d\u00e9connecter l'\u00e9l\u00e9ment d\u00e9faillant.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Sur de nombreux parafoudres modulaires, cette condition est li\u00e9e m\u00e9caniquement \u00e0 un indicateur d'\u00e9tat.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The window may change from green to red, depending on the manufacturer&#8217;s design.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Protection de secours externe<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The external fuse or circuit breaker is part of the installation&#8217;s fault-current protection and coordination.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Selon le parafoudre (SPD), il peut aider \u00e0 :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>interrompre le courant de court-circuit dans la branche du parafoudre,<\/li>\n\n\n\n<li>prot\u00e9ger les conducteurs associ\u00e9s,<\/li>\n\n\n\n<li>permettre une isolation en toute s\u00e9curit\u00e9,<\/li>\n\n\n\n<li>and keep the installation within the SPD manufacturer&#8217;s tested fault conditions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Par cons\u00e9quent :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Un d\u00e9connecteur thermique interne ne doit pas \u00eatre automatiquement consid\u00e9r\u00e9 comme un remplacement pour un fusible de protection externe du parafoudre.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">La documentation du produit doit toujours \u00eatre v\u00e9rifi\u00e9e.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Chaque parafoudre n\u00e9cessite-t-il un fusible de protection s\u00e9par\u00e9 ?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Non.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Il existe trois situations courantes.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Condition d'installation<\/th><th>Protection de secours s\u00e9par\u00e9e<\/th><\/tr><\/thead><tbody><tr><td>Existing upstream device is within the SPD manufacturer&#8217;s permitted conditions<\/td><td>Souvent non requis<\/td><\/tr><tr><td>Existing upstream device exceeds the manufacturer&#8217;s permitted limit<\/td><td>Une protection d\u00e9di\u00e9e peut \u00eatre n\u00e9cessaire<\/td><\/tr><tr><td>Le parafoudre dispose d'une protection de secours int\u00e9gr\u00e9e test\u00e9e<\/td><td>Un dispositif de secours suppl\u00e9mentaire peut ne pas \u00eatre requis sous certaines conditions sp\u00e9cifi\u00e9es<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Il s'agit de l'un des points les plus importants dans <strong>Protection de secours pour parafoudre<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Vous ne pouvez pas prendre la d\u00e9cision en utilisant uniquement :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Type 1,<\/li>\n\n\n\n<li>Type 2,<\/li>\n\n\n\n<li>Type 1+2,<\/li>\n\n\n\n<li>In,<\/li>\n\n\n\n<li>Imax,<\/li>\n\n\n\n<li>Uc,<\/li>\n\n\n\n<li>Ucpv.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Deux parafoudres de type 2 ayant des tensions et des courants Imax similaires peuvent avoir des exigences de protection de secours diff\u00e9rentes.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">F1 et F2 : Comprendre la protection de secours des parafoudres<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Les sch\u00e9mas d'installation des parafoudres utilisent souvent deux d\u00e9signations :<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = dispositif de protection du syst\u00e8me en amont<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F2 = dispositif de protection de secours d\u00e9di\u00e9 au parafoudre<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Un agencement simplifi\u00e9 peut ressembler \u00e0 ceci :<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Alimentation \u2192 F1 \u2192 Syst\u00e8me de distribution<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">avec le parafoudre connect\u00e9 en parall\u00e8le via <strong>F2<\/strong> l\u00e0 o\u00f9 une protection F2 d\u00e9di\u00e9e est requise.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Lors de la s\u00e9lection d'un <strong>Fusible de protection du parafoudre<\/strong>, la premi\u00e8re question ne devrait donc pas \u00eatre :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c Quelle taille de fusible dois-je acheter ? \u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Demandez plut\u00f4t :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c Le dispositif F1 existant peut-il d\u00e9j\u00e0 assurer la protection requise par ce parafoudre ? \u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">If F1 meets the manufacturer&#8217;s conditions, F2 may not be necessary.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Si F1 est sup\u00e9rieur \u00e0 la valeur autoris\u00e9e, un dispositif F2 d\u00e9di\u00e9 peut \u00eatre n\u00e9cessaire.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-1024x576.jpg\" alt=\"F1 and F2 SPD backup protection diagram\" class=\"wp-image-4526\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-f1-f2-diagram.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">F1 est le dispositif de protection du syst\u00e8me en amont, tandis que F2 est un dispositif de protection d\u00e9di\u00e9 au parafoudre (SPD) lorsque cela est requis.<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">This principle is demonstrated clearly in several manufacturer&#8217;s published installation guides, which we will examine later.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">7 r\u00e8gles pour une s\u00e9lection correcte du fusible de protection du parafoudre<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">R\u00e8gle 1 : Commencez par la fiche technique exacte du parafoudre<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Il n'existe pas de taille <strong>Fusible de protection du parafoudre<\/strong> universelle.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Always start with the exact manufacturer&#8217;s datasheet or installation instructions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Recherchez des formulations telles que :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Fusible de protection maximale<\/li>\n\n\n\n<li>Protection contre les surintensit\u00e9s c\u00f4t\u00e9 r\u00e9seau max.<\/li>\n\n\n\n<li>Fusible de protection<\/li>\n\n\n\n<li>Protection de secours<\/li>\n\n\n\n<li>Dispositif de protection recommand\u00e9<\/li>\n\n\n\n<li>Fusible amont maximal<\/li>\n\n\n\n<li>Courant de court-circuit assign\u00e9<\/li>\n\n\n\n<li>Isccr<\/li>\n\n\n\n<li>SCCR<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Ne prenez pas la valeur d'un fusible d'un autre parafoudre simplement parce que les deux appareils sont de type 2 ou ont tous deux un Imax = 40 kA.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Product construction and tested coordination can be different.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-1024x576.jpg\" alt=\"Checking SPD datasheet before selecting backup fuse\" class=\"wp-image-4528\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/check-spd-datasheet-before-backup-fuse-selection.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Backup protection should be selected from the exact SPD datasheet rather than from a universal fuse value.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 2: Check the Existing Upstream Protection First<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Suppose an SPD manufacturer allows:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximum upstream protection = 125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and the system already has:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = 63 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If all other manufacturer requirements are satisfied, the existing upstream fuse may already provide the necessary protection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Installing another 125 A fuse does not automatically make the installation safer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Now consider:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = 250 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the SPD is only approved with a maximum 125 A gG backup arrangement, the existing 250 A protection may no longer satisfy the SPD requirements.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A dedicated <strong>Fusible de protection du parafoudre<\/strong> may then be necessary.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is why F1 must be checked before adding F2.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 3: Check the Prospective Short-Circuit Current<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Fuse ampere rating alone is not enough.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">You must also consider the available fault current at the installation point.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The same SPD can face very different fault conditions depending on where it is installed.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Par exemple :<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A small downstream distribution board may have relatively low prospective short-circuit current.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A main industrial panel close to a transformer can have significantly higher available fault current.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore, always evaluate the combination of:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>SPD + backup protection + available short-circuit current<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ceci est particuli\u00e8rement important dans :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>industrial distribution boards,<\/li>\n\n\n\n<li>large commercial buildings,<\/li>\n\n\n\n<li>transformer secondary panels,<\/li>\n\n\n\n<li>large PV installations,<\/li>\n\n\n\n<li>energy storage systems,<\/li>\n\n\n\n<li>and high-current electrical systems.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 4: Never Size an SPD Backup Fuse From Imax<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a Type 2 SPD marked:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>In = 20 kA<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Imax = 40 kA<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A very common mistake is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cThe SPD is 40 kA, so it should use a 40 A fuse.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">That is incorrect.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Imax = 40 kA<\/strong> describes a surge-current characteristic associated with the relevant impulse waveform.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A <strong>40 A fuse<\/strong> is an overcurrent protective device rating.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These values describe different electrical phenomena.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Par cons\u00e9quent :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>The SPD backup fuse rating cannot be calculated directly from the SPD&#8217;s Imax value.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-1024x683.jpg\" alt=\"40 kA SPD Imax is not equal to a 40 A backup fuse\" class=\"wp-image-4527\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-1024x683.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-300x200.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-768x512.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-18x12.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating-600x400.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-imax-vs-backup-fuse-rating.jpg 1536w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">SPD surge-current ratings such as Imax cannot be directly converted into a backup-fuse ampere rating.<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">If you are unsure about the difference between In, Imax, Up and Iscpv, see our <a href=\"https:\/\/cnkuangya.com\/fr\/blog\/dc-spd-specifications\/\" target=\"_blank\" rel=\"noreferrer noopener\">guide des sp\u00e9cifications des parafoudres CC<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Understanding these parameters prevents one of the most common SPD selection errors.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 5: Check the Conductor Size<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The manufacturer&#8217;s maximum backup-fuse value does not mean that the largest permitted fuse should always be installed.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The protective device must also coordinate with:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>cable cross-sectional area,<\/li>\n\n\n\n<li>conductor insulation,<\/li>\n\n\n\n<li>terminal capacity,<\/li>\n\n\n\n<li>wiring method,<\/li>\n\n\n\n<li>installation temperature,<\/li>\n\n\n\n<li>enclosure conditions,<\/li>\n\n\n\n<li>and local electrical requirements.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For example, if an SPD permits a maximum backup fuse of 125 A, that does not automatically mean every installation should use a 125 A fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximum<\/strong> is a limit, not always a recommendation.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 6: Do Not Assume a Fuse and Circuit Breaker Are Equivalent<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">A fuse and a circuit breaker can both provide overcurrent protection, but their operating characteristics are different.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Facteur<\/th><th>Fusible<\/th><th>Disjoncteur<\/th><\/tr><\/thead><tbody><tr><td>Replacement after operation<\/td><td>Must normally be replaced<\/td><td>Can normally be reset after investigation<\/td><\/tr><tr><td>Time-current behavior<\/td><td>Depends on fuse class and rating<\/td><td>Depends on breaker type and trip curve<\/td><\/tr><tr><td>Short-circuit capability<\/td><td>Can be very high<\/td><td>Depends on breaker breaking capacity<\/td><\/tr><tr><td>Surge impulse behavior<\/td><td>Depends on fuse characteristics<\/td><td>Depends on breaker characteristics<\/td><\/tr><tr><td>Isolation<\/td><td>Requires suitable holder\/switching arrangement<\/td><td>Often convenient<\/td><\/tr><tr><td>Coordination<\/td><td>Must match SPD data<\/td><td>Must match SPD data<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Par cons\u00e9quent :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Do not assume that a 125 A gG fuse can automatically be replaced by a 125 A circuit breaker.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Manufacturers can specify different protective-device combinations.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, Schneider Electric publishes coordination tables pairing particular SPD models with specific protective-device ratings rather than applying one universal breaker value.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Rule 7: Separate AC and PV DC Requirements<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Do not copy an AC SPD backup-protection rule directly into a photovoltaic DC system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">PV systems have different:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>voltage characteristics,<\/li>\n\n\n\n<li>fault-current behavior,<\/li>\n\n\n\n<li>source characteristics,<\/li>\n\n\n\n<li>protection devices,<\/li>\n\n\n\n<li>and disconnection requirements.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">SPDs designed specifically for the DC side of photovoltaic installations are covered by <strong>IEC 61643-31:2018<\/strong>, which applies to PV DC SPDs up to 1,500 V DC.<br><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/26931\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-31:2018 \u2014 official IEC page<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is why an AC SPD backup-fuse example should never automatically be applied to a 1,000 V or 1,500 V PV system.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Real Manufacturer SPD Backup Fuse Examples<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">The following <strong>SPD backup fuse examples<\/strong> come from published manufacturer technical information.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They are useful because they demonstrate that backup-protection requirements vary significantly between products.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Do not copy these values to another SPD without checking its own datasheet.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Manufacturer Example<\/th><th>Published Information<\/th><th>What It Demonstrates<\/th><\/tr><\/thead><tbody><tr><td>Schneider Electric Resi MAX<\/td><td>Backup fuse only required if not already provided in mains; published table shows no F2 required in one F1 \u2264125 A \/ Isc &lt;50 kA arrangement<\/td><td>Existing upstream protection may sometimes provide the required backup protection<\/td><\/tr><tr><td>Phoenix Contact VAL-SEC<\/td><td>Published guidance allows installation without additional F2 up to specified upstream conditions; if dedicated F2 is used, 125 A gG is recommended in the example<\/td><td>F2 is not automatically required<\/td><\/tr><tr><td>DEHNguard SE CI<\/td><td>Integrated backup fuse; manufacturer states no additional backup fuse required up to its specified 25 kArms short-circuit condition<\/td><td>Backup protection can be integrated into the SPD<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">Let&#8217;s look at these examples more closely.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example 1: Schneider Electric \u2014 Existing F1 Can Sometimes Replace F2<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Schneider Electric&#8217;s Resi MAX installation instructions provide an especially useful example.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For the documented SPD arrangement, Schneider states that the backup fuse is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">required only if suitable protection is not already provided in the mains.<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The document lists <strong>\u2264125 A gL\/gG<\/strong> backup protection and shows a case where:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 \u2264125 A<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">et :<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Isc &lt;50 kA<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">can result in:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>No need for F2<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">under the manufacturer&#8217;s stated conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/download.schneider-electric.com\/files?filename=Instruction+sheet&amp;p_Doc_Ref=CLPDOC_W0001675\" target=\"_blank\" rel=\"noreferrer noopener\">Schneider Electric Resi MAX SPD installation instructions<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is an excellent example of why installing an additional fuse automatically is not always correct.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example 2: Phoenix Contact \u2014 Too Small Is Not Automatically Better<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Phoenix Contact provides a useful Type 2 SPD backup-fuse example for its VAL-SEC range.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Its published technical guidance explains that the device can be installed in the branch line without an additional F2 under specified upstream protection conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Where a dedicated F2 is nevertheless required or desired, the document gives:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">as an appropriate value for the example.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">More importantly, Phoenix Contact also warns against selecting certain smaller backup fuses below <strong>80 A gG<\/strong> in that specific arrangement because their impulse withstand may result in unwanted operation during surge events.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/assets.phoenixcontact.com\/file\/e01e5152-d450-43c3-aaa4-1a68dcc61f14\/media\/original?EN_Info_Vorsicherung_LoRes.pdf\" target=\"_blank\" rel=\"noreferrer noopener\">Phoenix Contact \u2014 The Right Backup Fuse for Surge Protective Devices<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Ceci fait <strong>pas<\/strong> mean that every Type 2 SPD needs an 80 A or 125 A fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It demonstrates something more important:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>An SPD backup fuse must be coordinated with the specific SPD. Choosing the smallest possible fuse is not automatically the safest option.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example 3: DEHN \u2014 Integrated Backup Protection<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Not every SPD requires an external backup fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">DEHN&#8217;s <strong>DEHNguard SE CI<\/strong> Type 2 SPD includes an integrated backup fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">DEHN states that no additional backup fuse is required for installations within the product&#8217;s specified maximum short-circuit current of <strong>25 kArms<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.dehn-international.com\/store\/p\/en-DE\/F1869543\/dehnguard-se-ci-with-integrated-backup-fuse?locale=en\" target=\"_blank\" rel=\"noreferrer noopener\">DEHNguard SE CI with integrated backup fuse<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This example shows why the statement:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201cEvery SPD must have a separate external fuse.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">is incorrect.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The correct arrangement depends on the tested product design.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can an SPD Backup Fuse Be Too Small?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Oui.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A smaller fuse is not automatically safer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The protective device must be capable of remaining intact during the surge conditions that the SPD is intended to handle while still interrupting a sustained fault when required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If an undersized fuse operates unnecessarily during a surge, the SPD can become disconnected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The electrical installation may then continue operating normally while surge protection has been lost.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This can be particularly difficult to notice in a parallel-connected SPD.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Phoenix Contact&#8217;s published example illustrates this issue by warning against certain undersized gG backup fuses in the specific Type 2 SPD arrangement described above.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Again:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>This is a product-specific example, not a universal minimum fuse value.<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can an SPD Backup Fuse Be Too Large?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Oui.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the external protective device exceeds the maximum value permitted by the SPD manufacturer, the SPD may no longer be operating within the tested fault-protection arrangement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, if a product states:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">Maximum backup fuse: 125 A gG<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">this should not be interpreted as:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\">\u201c125 A must always be installed.\u201d<\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Instead it means that the protection arrangement should not exceed the manufacturer&#8217;s stated limit unless another approved configuration is provided.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The actual selection must still consider:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>upstream protection,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>short-circuit current,<\/li>\n\n\n\n<li>SPD instructions,<\/li>\n\n\n\n<li>and installation design.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example: Small Commercial Distribution Board<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a Type 2 SPD in a small commercial distribution board.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Assume:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Main upstream fuse F1 = 63 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">and the selected SPD permits:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximum upstream protection = 125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the available short-circuit current is within the SPD&#8217;s declared capability,<\/li>\n\n\n\n<li>the wiring is suitable,<\/li>\n\n\n\n<li>and the manufacturer permits the arrangement,<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">then the existing 63 A upstream device may already provide the required backup protection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Adding a second 125 A fuse would not automatically improve the system.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Example: Industrial Main Distribution Board<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Now consider a larger industrial panel.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Assume:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>F1 = 400 A<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">while the SPD permits:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximum backup protection = 125 A gG<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The upstream protection now exceeds the manufacturer&#8217;s stated limit.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A dedicated F2 may therefore be required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The simplified arrangement may become:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>400 A upstream protection \u2192 SPD branch \u2192 approved F2 \u2192 SPD<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, the designer must still verify:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>prospective short-circuit current,<\/li>\n\n\n\n<li>breaking capacity,<\/li>\n\n\n\n<li>conductor cross-section,<\/li>\n\n\n\n<li>SPD short-circuit rating,<\/li>\n\n\n\n<li>fuse class,<\/li>\n\n\n\n<li>and manufacturer instructions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This is why a backup-protection arrangement that works in a small distribution board cannot simply be copied into an industrial main panel.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-1024x576.jpg\" alt=\"SPD backup protection in small and industrial electrical panels\" class=\"wp-image-4529\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-protection-small-vs-industrial-panel.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">SPD backup protection must be coordinated with the actual upstream protection and short-circuit conditions of the installation.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">How Does SPD Backup Protection Work in a PV DC System?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Photovoltaic DC systems require additional care.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A PV DC SPD must be suitable for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the maximum PV system voltage,<\/li>\n\n\n\n<li>Ucpv,<\/li>\n\n\n\n<li>PV fault-current conditions,<\/li>\n\n\n\n<li>the relevant system topology,<\/li>\n\n\n\n<li>and the manufacturer&#8217;s specified disconnection arrangement.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The exact <strong>Fusible de protection du parafoudre<\/strong> arrangement can depend on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>maximum PV short-circuit current,<\/li>\n\n\n\n<li>number of parallel strings,<\/li>\n\n\n\n<li>existing string protection,<\/li>\n\n\n\n<li>array protection,<\/li>\n\n\n\n<li>SPD Iscpv,<\/li>\n\n\n\n<li>gPV fuse characteristics,<\/li>\n\n\n\n<li>and system voltage.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Before choosing backup protection, the SPD voltage itself must also be correct.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For more detail, see our <a href=\"https:\/\/cnkuangya.com\/fr\/blog\/dc-spd-selection-guide\/\" target=\"_blank\" rel=\"noreferrer noopener\">DC SPD voltage selection guide for solar PV systems<\/a>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Should a PV SPD Always Use a gPV Fuse?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Non.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A gPV fuse is specifically designed for photovoltaic applications, but this does <strong>pas<\/strong> mean every PV SPD requires a separate gPV backup fuse.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The manufacturer&#8217;s instructions must be checked first.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Depending on the system design, existing PV overcurrent protection may already form part of the approved protection arrangement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If a gPV fuse is required, it must also be suitable for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>DC voltage,<\/li>\n\n\n\n<li>current,<\/li>\n\n\n\n<li>breaking capacity,<\/li>\n\n\n\n<li>PV application,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>and environmental conditions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For examples of PV-rated fuse links and holders, see KUANGYA&#8217;s <a href=\"https:\/\/cnkuangya.com\/fr\/dc-fuse\/\" target=\"_blank\" rel=\"noreferrer noopener\">DC gPV fuse range<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The product page is useful for understanding available PV fuse formats, but final SPD coordination must still follow the SPD manufacturer&#8217;s technical data.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Where Should the SPD Backup Fuse Be Installed?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Where dedicated backup protection is required, it is normally positioned in the SPD branch so that fault current flowing to the SPD can be interrupted.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A simplified concept is:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Busbar \/ Supply \u2192 F2 \u2192 SPD \u2192 required protection path<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, the exact wiring depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>TN-S,<\/li>\n\n\n\n<li>TN-C,<\/li>\n\n\n\n<li>TN-C-S,<\/li>\n\n\n\n<li>TT,<\/li>\n\n\n\n<li>IT,<\/li>\n\n\n\n<li>single-phase,<\/li>\n\n\n\n<li>three-phase,<\/li>\n\n\n\n<li>PV DC configuration,<\/li>\n\n\n\n<li>SPD protection modes.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Always follow the wiring diagram for the exact SPD.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Do Not Forget SPD Lead Length<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Adding a fuse or breaker should not result in unnecessarily long SPD connections.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">SPD connection conductors have inductance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">During a fast-rising surge current, additional lead length can increase the voltage appearing across the protected equipment.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This means backup protection should be coordinated while keeping the SPD connection path short and direct.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For PV systems, there is also another distance issue: the distance between the SPD location and the inverter.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These two distances should not be confused.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a detailed explanation, see our guide to <a href=\"https:\/\/cnkuangya.com\/fr\/blog\/spd-distance-from-inverter\/\" target=\"_blank\" rel=\"noreferrer noopener\">SPD distance from inverter and SPD connection lead length<\/a>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Can One Breaker Protect Both the Load and the SPD?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Sometimes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The existing protective device may be acceptable if:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the SPD manufacturer allows it,<\/li>\n\n\n\n<li>its rating is within the required limit,<\/li>\n\n\n\n<li>the short-circuit conditions are acceptable,<\/li>\n\n\n\n<li>conductor protection is maintained,<\/li>\n\n\n\n<li>and the installation arrangement satisfies applicable requirements.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">However, a dedicated SPD breaker can also provide practical advantages such as easier isolation and maintenance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Le point important est le suivant :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Dedicated protection does not automatically mean correctly coordinated protection.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The device must still match the SPD manufacturer&#8217;s requirements.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">What Happens If the SPD Backup Fuse Opens?<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Because many power SPDs are connected in parallel, the main electrical load can continue operating even after the SPD branch is disconnected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">That means:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Power ON does not necessarily mean surge protection ON.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the backup fuse opens, the cause should be investigated rather than simply replacing the fuse and re-energizing the system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Les causes possibles sont les suivantes :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>an SPD internal fault,<\/li>\n\n\n\n<li>severe surge stress,<\/li>\n\n\n\n<li>surtensions temporaires,<\/li>\n\n\n\n<li>incorrect SPD selection,<\/li>\n\n\n\n<li>inappropriate backup protection,<\/li>\n\n\n\n<li>wiring faults,<\/li>\n\n\n\n<li>or abnormal system conditions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">If you suspect the SPD itself has failed, see our guide on <a href=\"https:\/\/cnkuangya.com\/fr\/blog\/how-to-know-if-an-spd-is-bad\/\" target=\"_blank\" rel=\"noreferrer noopener\">comment savoir si un parafoudre est d\u00e9fectueux<\/a>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Common SPD Backup Protection Mistakes<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Erreur<\/th><th>Why It Is Wrong<\/th><\/tr><\/thead><tbody><tr><td>40 kA SPD = 40 A fuse<\/td><td>Imax and fuse current rating describe completely different electrical quantities<\/td><\/tr><tr><td>Every Type 2 SPD needs 125 A<\/td><td>Backup protection is manufacturer-specific<\/td><\/tr><tr><td>Smaller fuse is always safer<\/td><td>It may disconnect unnecessarily during surge events<\/td><\/tr><tr><td>Internal SPD disconnector means no external protection is ever required<\/td><td>Internal and external protective functions are not necessarily identical<\/td><\/tr><tr><td>125 A fuse = 125 A breaker<\/td><td>Fuse and breaker operating characteristics differ<\/td><\/tr><tr><td>F2 must always be installed<\/td><td>Existing F1 may already meet the SPD requirement<\/td><\/tr><tr><td>Ignore prospective short-circuit current<\/td><td>SPD protection must be coordinated with available fault current<\/td><\/tr><tr><td>Use AC examples for PV DC SPD<\/td><td>AC and PV DC systems have different requirements<\/td><\/tr><tr><td>Choose only by Imax<\/td><td>Imax does not determine backup-fuse rating<\/td><\/tr><tr><td>Use maximum permitted fuse automatically<\/td><td>\u201cMaximum\u201d is a limit, not necessarily the ideal rating<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">SPD Backup Fuse Selection Checklist<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Before selecting an <strong>fusible ou disjoncteur de protection de secours du parafoudre<\/strong>, check the following:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>V\u00e9rifier<\/th><th>Question<\/th><\/tr><\/thead><tbody><tr><td>Exact SPD<\/td><td>What manufacturer and model is installed?<\/td><\/tr><tr><td>Application<\/td><td>AC or photovoltaic DC?<\/td><\/tr><tr><td>Type de DOCUP<\/td><td>Type 1, Type 1+2 or Type 2?<\/td><\/tr><tr><td>Tension<\/td><td>Are Uc\/Ucpv suitable for the system?<\/td><\/tr><tr><td>Upstream device<\/td><td>What is F1?<\/td><\/tr><tr><td>Manufacturer limit<\/td><td>What maximum backup protection is specified?<\/td><\/tr><tr><td>Dedicated F2<\/td><td>Is it actually required?<\/td><\/tr><tr><td>Fault current<\/td><td>What is the prospective short-circuit current?<\/td><\/tr><tr><td>Fuse class<\/td><td>gG, gPV or another specified type?<\/td><\/tr><tr><td>Disjoncteur<\/td><td>What curve and breaking capacity are required?<\/td><\/tr><tr><td>Conductors<\/td><td>Is the conductor cross-section suitable?<\/td><\/tr><tr><td>Terminaux<\/td><td>Can the SPD terminals accept the selected conductors?<\/td><\/tr><tr><td>Lead length<\/td><td>Are SPD connection leads short and direct?<\/td><\/tr><tr><td>Earthing<\/td><td>Is the protection path correctly connected?<\/td><\/tr><tr><td>Indication<\/td><td>Can failure or disconnection be detected?<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">If several of these answers are unknown, selecting a backup fuse by guesswork is not appropriate.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-1024x576.jpg\" alt=\"SPD backup fuse selection checklist for electrical installation\" class=\"wp-image-4531\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/spd-backup-fuse-selection-checklist.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Check the SPD model, upstream protection, short-circuit conditions, conductors and manufacturer requirements before selecting backup protection.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Relevant Standards to Check<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">IEC 61643-11:2025<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IEC 61643-11 covers SPDs intended for connection to AC low-voltage power circuits and specifies performance and safety requirements, tests and ratings.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-11:2025<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">IEC 61643-31:2018<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IEC 61643-31 applies specifically to SPDs intended for the DC side of photovoltaic installations up to <strong>1 500 V CC<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/26931\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 61643-31:2018<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">IEC 60364-5-53<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">IEC 60364-5-53 covers the selection and erection of electrical equipment for protection, isolation, switching, control and monitoring.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The current IEC consolidated version includes the 2019 base publication plus amendments from 2020 and 2024.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/104394\" target=\"_blank\" rel=\"noreferrer noopener\">IEC 60364-5-53:2019+A1:2020+A2:2024<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Applicable national standards, installation rules and manufacturer instructions must also be followed.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Questions fr\u00e9quemment pos\u00e9es<\/h1>\n\n\n\n<h2 class=\"wp-block-heading\">Does Every SPD Need a Backup Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Non.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A separate <strong>Fusible de protection du parafoudre<\/strong> is not always necessary.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the existing upstream protective device already satisfies the manufacturer&#8217;s permitted backup-protection conditions, another fuse may not be required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Some SPDs also include integrated backup protection.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">What Size Fuse Should I Use for an SPD?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">There is no universal fuse size for an SPD.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Use the exact SPD datasheet and check:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>maximum backup protection,<\/li>\n\n\n\n<li>existing F1,<\/li>\n\n\n\n<li>prospective short-circuit current,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>and manufacturer instructions.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Do not calculate the fuse size from Imax alone.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Does a Type 2 SPD Always Need a 125 A Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Non.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">125 A appears in several manufacturer examples, but it is not a universal Type 2 SPD value.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Published examples show SPDs with different arrangements, including:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>existing upstream protection,<\/li>\n\n\n\n<li>dedicated backup fuse,<\/li>\n\n\n\n<li>integrated backup fuse,<\/li>\n\n\n\n<li>or other specified protection.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Can I Use a Circuit Breaker Instead of a Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Sometimes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But the circuit breaker&#8217;s:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>current rating,<\/li>\n\n\n\n<li>trip characteristic,<\/li>\n\n\n\n<li>breaking capacity,<\/li>\n\n\n\n<li>surge behavior,<\/li>\n\n\n\n<li>and manufacturer-approved coordination<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">must be suitable.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Do not replace a specified fuse with a breaker simply because both devices have the same ampere rating.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Does an SPD&#8217;s Red Indicator Mean Its Backup Fuse Has Blown?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Pas n\u00e9cessairement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A red status indicator commonly relates to the condition of the SPD&#8217;s internal protection module or disconnection mechanism.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An external backup fuse is a separate protective device.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore, both the SPD status and the upstream or branch protection should be inspected.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Can the Electrical System Keep Working After the SPD Fuse Opens?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Oui.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Because many power SPDs are connected in parallel, the protected load may remain energized even if the SPD has been disconnected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This means surge protection can be lost while the equipment appears to operate normally.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Does a PV DC SPD Always Need a gPV Backup Fuse?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Non.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The requirement depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the exact SPD,<\/li>\n\n\n\n<li>its Iscpv or short-circuit data,<\/li>\n\n\n\n<li>manufacturer instructions,<\/li>\n\n\n\n<li>PV array design,<\/li>\n\n\n\n<li>available fault current,<\/li>\n\n\n\n<li>and existing overcurrent protection.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Never assume every PV SPD needs the same gPV fuse.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-1024x576.jpg\" alt=\"PV DC SPD and gPV fuse backup protection\" class=\"wp-image-4530\" srcset=\"https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-1024x576.jpg 1024w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-300x169.jpg 300w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-768x432.jpg 768w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-1536x864.jpg 1536w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-18x10.jpg 18w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection-600x338.jpg 600w, https:\/\/cnkuangya.com\/wp-content\/uploads\/2026\/09\/pv-dc-spd-gpv-backup-fuse-protection.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">PV DC SPD backup protection depends on the SPD data, PV system design, fault current and existing overcurrent protection.<\/figcaption><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Is SPD Backup Fuse Rating Related to Imax?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Not directly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Imax represents a surge-discharge current characteristic.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Fuse current rating relates to overcurrent protection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A 40 kA Imax rating does not mean a 40 A backup fuse is required.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Conclusion<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">So, does an SPD need a backup fuse or circuit breaker?<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Sometimes yes\u2014but not always as a separate device.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Correct <strong>SPD backup fuse selection<\/strong> starts with the manufacturer&#8217;s technical data rather than a universal ampere rating.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The correct decision depends on the relationship between:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>SPD \u2192 F1 \u2192 F2 \u2192 available fault current \u2192 conductors \u2192 electrical system<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Before installing additional backup protection, first check whether the existing upstream device already satisfies the SPD manufacturer&#8217;s requirements.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If dedicated protection is required, verify:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>fuse class or breaker characteristic,<\/li>\n\n\n\n<li>maximum permitted rating,<\/li>\n\n\n\n<li>short-circuit capability,<\/li>\n\n\n\n<li>conductor size,<\/li>\n\n\n\n<li>system voltage,<\/li>\n\n\n\n<li>and installation arrangement.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Most importantly:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Never select an SPD backup fuse only from Type 1 \/ Type 2, In or Imax. Use the exact manufacturer&#8217;s backup-protection requirements and the actual system conditions.<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">For photovoltaic applications, you can also review KUANGYA&#8217;s <a href=\"https:\/\/cnkuangya.com\/fr\/dc-spd\/\" target=\"_blank\" rel=\"noreferrer noopener\">DC surge protective devices for solar PV systems<\/a> when comparing Type 2 and Type 1+2 DC SPD options.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>","protected":false},"excerpt":{"rendered":"<p>A surge protective device protects electrical equipment from transient overvoltage, but what protects the SPD if an internal fault or short circuit occurs? This is where the SPD backup fuse or circuit breaker becomes important. However, there is no universal rule such as: \u201cEvery Type 2 SPD needs a 125 A fuse.\u201d or: \u201cA 40 [&hellip;]<\/p>\n","protected":false},"author":7,"featured_media":4524,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[35],"tags":[],"class_list":["post-4523","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/posts\/4523","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/comments?post=4523"}],"version-history":[{"count":1,"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/posts\/4523\/revisions"}],"predecessor-version":[{"id":4532,"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/posts\/4523\/revisions\/4532"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/media\/4524"}],"wp:attachment":[{"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/media?parent=4523"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/categories?post=4523"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cnkuangya.com\/fr\/wp-json\/wp\/v2\/tags?post=4523"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}