{"id":29971,"date":"2026-07-10T13:09:00","date_gmt":"2026-07-10T05:09:00","guid":{"rendered":"https:\/\/www.cnspd.com\/?p=29971"},"modified":"2026-07-10T13:09:17","modified_gmt":"2026-07-10T05:09:17","slug":"common-causes-of-spd-failure-why-spds-fail-and-fail-again","status":"publish","type":"post","link":"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/","title":{"rendered":"Common Causes of SPD Failure: Why SPDs Fail and Fail Again"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"29971\" class=\"elementor elementor-29971\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-1e6eb9c e-flex e-con-boxed e-con e-parent\" data-id=\"1e6eb9c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-3ef0ef2 elementor-widget elementor-widget-html\" data-id=\"3ef0ef2\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"html.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<style>\r\n  \/* =========================================================\r\n     LEEYEE \/ CNSPD B2B Technical Article\r\n     Page: Common Causes of SPD Failure\r\n     URL: \/spd-failure-causes\/\r\n     Brand color: #004898\r\n     ========================================================= *\/\r\n\r\n  .leeyee-spdfail-article,\r\n  .leeyee-spdfail-article * {\r\n    box-sizing: border-box;\r\n  }\r\n\r\n  .leeyee-spdfail-article {\r\n    --leeyee-blue: #004898;\r\n    --leeyee-blue-dark: #00366f;\r\n    --leeyee-blue-soft: #f7fbff;\r\n    --leeyee-blue-light: #eef6ff;\r\n    --leeyee-heading: #152235;\r\n    --leeyee-text: #253243;\r\n    --leeyee-muted: #607086;\r\n    --leeyee-border: #dce6f0;\r\n    --leeyee-warning: #a85800;\r\n    --leeyee-warning-bg: #fff8ec;\r\n    --leeyee-danger: #a43b35;\r\n    --leeyee-danger-bg: #fff4f3;\r\n    --leeyee-success: #277447;\r\n    --leeyee-success-bg: #f2fbf6;\r\n\r\n    width: 100%;\r\n    margin: 0;\r\n    padding: 0 20px 70px;\r\n    color: var(--leeyee-text);\r\n    background: #ffffff;\r\n    font-family: Arial, Helvetica, sans-serif;\r\n    font-size: 17px;\r\n    line-height: 1.72;\r\n    overflow-wrap: anywhere;\r\n  }\r\n\r\n  .leeyee-spdfail-inner {\r\n    width: 100%;\r\n    max-width: 860px;\r\n    margin: 0 auto;\r\n  }\r\n\r\n  .leeyee-spdfail-article p {\r\n    margin: 0 0 20px;\r\n  }\r\n\r\n  .leeyee-spdfail-article a {\r\n    color: var(--leeyee-blue);\r\n    text-decoration: underline;\r\n    text-decoration-thickness: 1px;\r\n    text-underline-offset: 3px;\r\n  }\r\n\r\n  .leeyee-spdfail-article a:hover,\r\n  .leeyee-spdfail-article a:focus {\r\n    color: var(--leeyee-blue-dark);\r\n  }\r\n\r\n  .leeyee-spdfail-article strong {\r\n    color: var(--leeyee-heading);\r\n  }\r\n\r\n  .leeyee-spdfail-article h2 {\r\n    margin: 54px 0 20px;\r\n    color: 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 .leeyee-spdfail-scope-note p {\r\n    margin: 0;\r\n  }\r\n\r\n  .leeyee-spdfail-quick {\r\n    margin: 30px 0 38px;\r\n    padding: 26px 28px;\r\n    border: 1px solid #cfe0f2;\r\n    border-radius: 12px;\r\n    background: var(--leeyee-blue-soft);\r\n    box-shadow: 0 8px 24px rgba(22, 55, 88, 0.06);\r\n  }\r\n\r\n  .leeyee-spdfail-kicker {\r\n    display: inline-block;\r\n    margin-bottom: 10px;\r\n    color: var(--leeyee-blue);\r\n    font-size: 13px;\r\n    line-height: 1.2;\r\n    font-weight: 700;\r\n    letter-spacing: 0.08em;\r\n    text-transform: uppercase;\r\n  }\r\n\r\n  .leeyee-spdfail-quick h2 {\r\n    margin: 0 0 14px;\r\n    font-size: 27px;\r\n  }\r\n\r\n  .leeyee-spdfail-quick p:last-child {\r\n    margin-bottom: 0;\r\n  }\r\n\r\n  \/* Images *\/\r\n\r\n  .leeyee-spdfail-figure {\r\n    width: 100%;\r\n    margin: 32px 0 42px;\r\n  }\r\n\r\n  .leeyee-spdfail-image-link {\r\n    display: block;\r\n    width: 100%;\r\n    overflow: hidden;\r\n    border: 1px solid var(--leeyee-border);\r\n    border-radius: 12px;\r\n    background: #f7faff;\r\n    box-shadow: 0 9px 28px rgba(22, 55, 88, 0.08);\r\n    text-decoration: none !important;\r\n  }\r\n\r\n  .leeyee-spdfail-image-link:hover,\r\n  .leeyee-spdfail-image-link:focus {\r\n    border-color: #b9cee4;\r\n    box-shadow: 0 12px 32px rgba(22, 55, 88, 0.12);\r\n  }\r\n\r\n  .leeyee-spdfail-figure img {\r\n    display: block !important;\r\n    width: 100% !important;\r\n    max-width: 100% !important;\r\n    height: auto !important;\r\n    margin: 0 !important;\r\n    border: 0 !important;\r\n    border-radius: 0 !important;\r\n    object-fit: contain !important;\r\n    background: #ffffff;\r\n  }\r\n\r\n  .leeyee-spdfail-figure figcaption {\r\n    margin: 12px auto 0;\r\n    padding: 0 10px;\r\n    color: var(--leeyee-muted);\r\n    font-size: 14px;\r\n    line-height: 1.55;\r\n    text-align: center;\r\n  }\r\n\r\n  .leeyee-spdfail-figure figcaption strong {\r\n    color: #42546a;\r\n  }\r\n\r\n  \/* Tables *\/\r\n\r\n  .leeyee-spdfail-table-wrap {\r\n    width: 100%;\r\n    margin: 24px 0 34px;\r\n    overflow-x: auto;\r\n    border: 1px solid var(--leeyee-border);\r\n    border-radius: 10px;\r\n    background: #ffffff;\r\n    -webkit-overflow-scrolling: touch;\r\n  }\r\n\r\n  .leeyee-spdfail-table {\r\n    width: 100%;\r\n    min-width: 760px;\r\n    border-collapse: collapse;\r\n    table-layout: fixed;\r\n    font-size: 15.5px;\r\n    line-height: 1.55;\r\n  }\r\n\r\n  .leeyee-spdfail-table th,\r\n  .leeyee-spdfail-table td {\r\n    padding: 15px 16px;\r\n    border-right: 1px solid var(--leeyee-border);\r\n    border-bottom: 1px solid var(--leeyee-border);\r\n    vertical-align: top;\r\n    text-align: left;\r\n  }\r\n\r\n  .leeyee-spdfail-table th:last-child,\r\n  .leeyee-spdfail-table td:last-child {\r\n    border-right: 0;\r\n  }\r\n\r\n  .leeyee-spdfail-table tr:last-child td {\r\n    border-bottom: 0;\r\n  }\r\n\r\n  .leeyee-spdfail-table thead th {\r\n    color: #ffffff;\r\n    background: var(--leeyee-blue);\r\n    font-weight: 700;\r\n  }\r\n\r\n  .leeyee-spdfail-table tbody tr:nth-child(even) {\r\n    background: #f9fbfd;\r\n  }\r\n\r\n  .leeyee-spdfail-table tbody tr:hover {\r\n    background: #f2f7fc;\r\n  }\r\n\r\n  .leeyee-spdfail-table .leeyee-col-cause {\r\n    width: 23%;\r\n  }\r\n\r\n  .leeyee-spdfail-table .leeyee-col-effect {\r\n    width: 34%;\r\n  }\r\n\r\n  .leeyee-spdfail-table .leeyee-col-check {\r\n    width: 43%;\r\n  }\r\n\r\n  .leeyee-spdfail-four-column {\r\n    min-width: 820px;\r\n  }\r\n\r\n  .leeyee-spdfail-four-column th:nth-child(1),\r\n  .leeyee-spdfail-four-column td:nth-child(1) {\r\n    width: 22%;\r\n  }\r\n\r\n  .leeyee-spdfail-four-column th:nth-child(2),\r\n  .leeyee-spdfail-four-column td:nth-child(2) {\r\n    width: 29%;\r\n  }\r\n\r\n  .leeyee-spdfail-four-column th:nth-child(3),\r\n  .leeyee-spdfail-four-column td:nth-child(3) {\r\n    width: 25%;\r\n  }\r\n\r\n  .leeyee-spdfail-four-column th:nth-child(4),\r\n  .leeyee-spdfail-four-column td:nth-child(4) {\r\n    width: 24%;\r\n  }\r\n\r\n  \/* Callouts *\/\r\n\r\n  .leeyee-spdfail-callout {\r\n    margin: 25px 0 32px;\r\n    padding: 20px 22px;\r\n    border-radius: 10px;\r\n  }\r\n\r\n  .leeyee-spdfail-callout h3,\r\n  .leeyee-spdfail-callout h4 {\r\n    margin-top: 0;\r\n  }\r\n\r\n  .leeyee-spdfail-callout p:last-child,\r\n  .leeyee-spdfail-callout ul:last-child {\r\n    margin-bottom: 0;\r\n  }\r\n\r\n  .leeyee-spdfail-warning {\r\n    border: 1px solid #f0d6aa;\r\n    border-left: 5px solid var(--leeyee-warning);\r\n    background: var(--leeyee-warning-bg);\r\n  }\r\n\r\n  .leeyee-spdfail-danger {\r\n    border: 1px solid #edcecb;\r\n    border-left: 5px solid var(--leeyee-danger);\r\n    background: var(--leeyee-danger-bg);\r\n  }\r\n\r\n  .leeyee-spdfail-note {\r\n    border: 1px solid #cfe0f2;\r\n    border-left: 5px solid var(--leeyee-blue);\r\n    background: var(--leeyee-blue-soft);\r\n  }\r\n\r\n  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h2 {\r\n    margin: 0 0 12px;\r\n    font-size: 27px;\r\n  }\r\n\r\n  .leeyee-spdfail-cta p {\r\n    max-width: 690px;\r\n    margin-bottom: 20px;\r\n  }\r\n\r\n  .leeyee-spdfail-btn-row {\r\n    display: flex;\r\n    flex-wrap: wrap;\r\n    gap: 12px;\r\n    align-items: center;\r\n  }\r\n\r\n  .leeyee-spdfail-btn,\r\n  .leeyee-spdfail-btn:link,\r\n  .leeyee-spdfail-btn:visited,\r\n  .leeyee-spdfail-btn:hover,\r\n  .leeyee-spdfail-btn:focus,\r\n  .leeyee-spdfail-btn:active,\r\n  button.leeyee-spdfail-btn {\r\n    display: inline-flex !important;\r\n    align-items: center !important;\r\n    justify-content: center !important;\r\n    min-width: 210px;\r\n    min-height: 48px;\r\n    padding: 12px 20px !important;\r\n    border: 2px solid var(--leeyee-blue) !important;\r\n    border-radius: 6px !important;\r\n    color: #ffffff !important;\r\n    background: var(--leeyee-blue) !important;\r\n    box-shadow: none !important;\r\n    font-family: Arial, Helvetica, sans-serif !important;\r\n    font-size: 15px !important;\r\n    line-height: 20px !important;\r\n    font-weight: 700 !important;\r\n    text-align: center !important;\r\n    text-decoration: none !important;\r\n    white-space: normal !important;\r\n    cursor: pointer !important;\r\n    appearance: none !important;\r\n    opacity: 1 !important;\r\n    visibility: visible !important;\r\n  }\r\n\r\n  .leeyee-spdfail-btn:hover,\r\n  .leeyee-spdfail-btn:focus,\r\n  button.leeyee-spdfail-btn:hover,\r\n  button.leeyee-spdfail-btn:focus {\r\n    color: #ffffff !important;\r\n    background: var(--leeyee-blue-dark) !important;\r\n    border-color: var(--leeyee-blue-dark) !important;\r\n  }\r\n\r\n  .leeyee-spdfail-btn span,\r\n  .leeyee-spdfail-btn .w-btn-label,\r\n  button.leeyee-spdfail-btn span,\r\n  button.leeyee-spdfail-btn .w-btn-label {\r\n    display: inline-block !important;\r\n    position: static !important;\r\n    width: auto !important;\r\n    height: auto !important;\r\n    margin: 0 !important;\r\n    padding: 0 !important;\r\n    color: #ffffff !important;\r\n    background: transparent !important;\r\n    font-family: inherit !important;\r\n    font-size: inherit !important;\r\n    line-height: 20px !important;\r\n    font-weight: 700 !important;\r\n    text-align: center !important;\r\n    text-indent: 0 !important;\r\n    white-space: normal !important;\r\n    opacity: 1 !important;\r\n    visibility: visible !important;\r\n    overflow: visible !important;\r\n    clip: auto !important;\r\n    transform: none !important;\r\n  }\r\n\r\n  .leeyee-spdfail-btn-secondary,\r\n  .leeyee-spdfail-btn-secondary:link,\r\n  .leeyee-spdfail-btn-secondary:visited {\r\n    color: var(--leeyee-blue) !important;\r\n    background: #ffffff !important;\r\n  }\r\n\r\n  .leeyee-spdfail-btn-secondary span {\r\n    color: var(--leeyee-blue) !important;\r\n  }\r\n\r\n  .leeyee-spdfail-btn-secondary:hover,\r\n  .leeyee-spdfail-btn-secondary:focus {\r\n    color: #ffffff !important;\r\n    background: var(--leeyee-blue) !important;\r\n  }\r\n\r\n  .leeyee-spdfail-btn-secondary:hover span,\r\n  .leeyee-spdfail-btn-secondary:focus span {\r\n    color: #ffffff !important;\r\n  }\r\n\r\n  \/* FAQ *\/\r\n\r\n  .leeyee-spdfail-faq {\r\n    margin: 23px 0 40px;\r\n  }\r\n\r\n  .leeyee-spdfail-faq details {\r\n    margin: 0 0 12px;\r\n    border: 1px solid var(--leeyee-border);\r\n    border-radius: 8px;\r\n    background: #ffffff;\r\n    overflow: hidden;\r\n  }\r\n\r\n  .leeyee-spdfail-faq summary {\r\n    position: relative;\r\n    padding: 17px 48px 17px 18px;\r\n    color: var(--leeyee-heading);\r\n    font-weight: 700;\r\n    line-height: 1.45;\r\n    cursor: pointer;\r\n    list-style: none;\r\n  }\r\n\r\n  .leeyee-spdfail-faq summary::-webkit-details-marker {\r\n    display: none;\r\n  }\r\n\r\n  .leeyee-spdfail-faq summary::after {\r\n    content: \"+\";\r\n    position: absolute;\r\n    top: 50%;\r\n    right: 18px;\r\n    color: var(--leeyee-blue);\r\n    font-size: 24px;\r\n    line-height: 1;\r\n    transform: translateY(-50%);\r\n  }\r\n\r\n  .leeyee-spdfail-faq details[open] summary::after {\r\n    content: \"\u2212\";\r\n  }\r\n\r\n  .leeyee-spdfail-faq-answer {\r\n    padding: 0 18px 18px;\r\n  }\r\n\r\n  .leeyee-spdfail-faq-answer p:last-child {\r\n    margin-bottom: 0;\r\n  }\r\n\r\n  \/* References and related links *\/\r\n\r\n  .leeyee-spdfail-references {\r\n    margin: 44px 0 10px;\r\n    padding: 25px 26px;\r\n    border: 1px solid var(--leeyee-border);\r\n    border-radius: 10px;\r\n    background: #fafcfe;\r\n  }\r\n\r\n  .leeyee-spdfail-references h2 {\r\n    margin: 0 0 15px;\r\n    font-size: 25px;\r\n  }\r\n\r\n  .leeyee-spdfail-references ul {\r\n    margin: 0;\r\n    padding-left: 21px;\r\n  }\r\n\r\n  .leeyee-spdfail-references li {\r\n    margin: 8px 0;\r\n  }\r\n\r\n  .leeyee-spdfail-related {\r\n    margin: 45px 0 10px;\r\n    padding-top: 30px;\r\n    border-top: 1px solid var(--leeyee-border);\r\n  }\r\n\r\n  .leeyee-spdfail-related h2 {\r\n    margin-top: 0;\r\n  }\r\n\r\n  .leeyee-spdfail-related-links {\r\n    display: grid;\r\n    grid-template-columns: 1fr 1fr;\r\n    gap: 12px 22px;\r\n  }\r\n\r\n  .leeyee-spdfail-related-link {\r\n    display: block;\r\n    padding: 12px 0;\r\n    border-bottom: 1px solid #e7edf3;\r\n    font-weight: 700;\r\n    text-decoration: none !important;\r\n  }\r\n\r\n  .leeyee-spdfail-related-link::after {\r\n    content: \" \u2192\";\r\n  }\r\n\r\n  .leeyee-spdfail-footnote {\r\n    margin-top: 36px;\r\n    padding-top: 18px;\r\n    border-top: 1px solid var(--leeyee-border);\r\n    color: var(--leeyee-muted);\r\n    font-size: 13.5px;\r\n    line-height: 1.6;\r\n  }\r\n\r\n  \/* =========================================================\r\n     Responsive CSS \u2014 common screen sizes\r\n     ========================================================= *\/\r\n\r\n  \/* Desktop 1440px and above *\/\r\n  @media (min-width: 1440px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 24px;\r\n      padding-right: 24px;\r\n    }\r\n\r\n    .leeyee-spdfail-inner {\r\n      max-width: 860px;\r\n    }\r\n  }\r\n\r\n  \/* Desktop 1366px *\/\r\n  @media (max-width: 1366px) {\r\n    .leeyee-spdfail-inner {\r\n      max-width: 850px;\r\n    }\r\n  }\r\n\r\n  \/* Desktop 1280px *\/\r\n  @media (max-width: 1280px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 22px;\r\n      padding-right: 22px;\r\n    }\r\n\r\n    .leeyee-spdfail-inner {\r\n      max-width: 840px;\r\n    }\r\n  }\r\n\r\n  \/* Tablet landscape 1024px *\/\r\n  @media (max-width: 1024px) {\r\n    .leeyee-spdfail-article {\r\n      padding: 0 28px 64px;\r\n    }\r\n\r\n    .leeyee-spdfail-inner {\r\n      max-width: 820px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h2 {\r\n      font-size: 30px;\r\n    }\r\n  }\r\n\r\n  \/* Tablet 912px *\/\r\n  @media (max-width: 912px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 26px;\r\n      padding-right: 26px;\r\n    }\r\n\r\n    .leeyee-spdfail-figure {\r\n      margin-top: 29px;\r\n      margin-bottom: 38px;\r\n    }\r\n  }\r\n\r\n  \/* Tablet 820px *\/\r\n  @media (max-width: 820px) {\r\n    .leeyee-spdfail-article {\r\n      padding: 0 24px 60px;\r\n      font-size: 16.5px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h2 {\r\n      margin-top: 47px;\r\n      font-size: 29px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h3 {\r\n      font-size: 22px;\r\n    }\r\n\r\n    .leeyee-spdfail-decision-row {\r\n      grid-template-columns: 165px 1fr;\r\n    }\r\n  }\r\n\r\n  \/* Tablet portrait 768px *\/\r\n  @media (max-width: 768px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 22px;\r\n      padding-right: 22px;\r\n    }\r\n\r\n    .leeyee-spdfail-lead {\r\n      font-size: 18px;\r\n    }\r\n\r\n    .leeyee-spdfail-quick {\r\n      padding: 23px;\r\n    }\r\n\r\n    .leeyee-spdfail-table {\r\n      min-width: 720px;\r\n    }\r\n\r\n    .leeyee-spdfail-four-column {\r\n      min-width: 790px;\r\n    }\r\n\r\n    .leeyee-spdfail-check-grid {\r\n      grid-template-columns: 1fr;\r\n    }\r\n\r\n    .leeyee-spdfail-related-links {\r\n      grid-template-columns: 1fr;\r\n      gap: 0;\r\n    }\r\n\r\n    .leeyee-spdfail-image-link {\r\n      border-radius: 10px;\r\n    }\r\n  }\r\n\r\n  \/* Small tablet \/ large mobile 600px *\/\r\n  @media (max-width: 600px) {\r\n    .leeyee-spdfail-article {\r\n      padding: 0 20px 54px;\r\n      font-size: 16px;\r\n      line-height: 1.7;\r\n    }\r\n\r\n    .leeyee-spdfail-article h2 {\r\n      margin-top: 42px;\r\n      font-size: 27px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h3 {\r\n      margin-top: 30px;\r\n      font-size: 21px;\r\n    }\r\n\r\n    .leeyee-spdfail-quick {\r\n      margin-top: 25px;\r\n      padding: 21px;\r\n    }\r\n\r\n    .leeyee-spdfail-quick h2 {\r\n      font-size: 24px;\r\n    }\r\n\r\n    .leeyee-spdfail-decision-row {\r\n      display: block;\r\n    }\r\n\r\n    .leeyee-spdfail-decision-label,\r\n    .leeyee-spdfail-decision-text {\r\n      padding: 14px 16px;\r\n    }\r\n\r\n    .leeyee-spdfail-decision-label {\r\n      border-bottom: 1px solid var(--leeyee-border);\r\n    }\r\n\r\n    .leeyee-spdfail-cta {\r\n      padding: 23px 21px;\r\n    }\r\n\r\n    .leeyee-spdfail-btn-row {\r\n      display: block;\r\n    }\r\n\r\n    .leeyee-spdfail-btn,\r\n    button.leeyee-spdfail-btn {\r\n      width: 100% !important;\r\n      min-width: 0 !important;\r\n      margin: 0 0 11px !important;\r\n    }\r\n\r\n    .leeyee-spdfail-figure {\r\n      margin: 26px 0 34px;\r\n    }\r\n\r\n    .leeyee-spdfail-figure figcaption {\r\n      padding: 0 4px;\r\n      font-size: 13.5px;\r\n    }\r\n\r\n    .leeyee-spdfail-references {\r\n      padding: 21px 20px;\r\n    }\r\n  }\r\n\r\n  \/* Mobile 540px *\/\r\n  @media (max-width: 540px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 18px;\r\n      padding-right: 18px;\r\n    }\r\n\r\n    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.leeyee-spdfail-article {\r\n      padding-left: 16px;\r\n      padding-right: 16px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h2 {\r\n      font-size: 25px;\r\n      line-height: 1.28;\r\n    }\r\n\r\n    .leeyee-spdfail-article h3 {\r\n      font-size: 20px;\r\n    }\r\n\r\n    .leeyee-spdfail-cta h2 {\r\n      font-size: 24px;\r\n    }\r\n\r\n    .leeyee-spdfail-faq summary {\r\n      padding-left: 16px;\r\n      font-size: 15.5px;\r\n    }\r\n\r\n    .leeyee-spdfail-references h2 {\r\n      font-size: 23px;\r\n    }\r\n  }\r\n\r\n  \/* Mobile 414px *\/\r\n  @media (max-width: 414px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 15px;\r\n      padding-right: 15px;\r\n    }\r\n\r\n    .leeyee-spdfail-callout,\r\n    .leeyee-spdfail-check-card {\r\n      padding: 17px;\r\n    }\r\n  }\r\n\r\n  \/* Mobile 390px *\/\r\n  @media (max-width: 390px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 14px;\r\n      padding-right: 14px;\r\n      font-size: 15.8px;\r\n    }\r\n\r\n    .leeyee-spdfail-quick {\r\n      padding: 18px 16px;\r\n    }\r\n\r\n    .leeyee-spdfail-cta {\r\n      padding: 21px 17px;\r\n    }\r\n\r\n    .leeyee-spdfail-btn,\r\n    button.leeyee-spdfail-btn {\r\n      padding-left: 14px !important;\r\n      padding-right: 14px !important;\r\n      font-size: 14.5px !important;\r\n    }\r\n\r\n    .leeyee-spdfail-figure figcaption {\r\n      font-size: 13px;\r\n    }\r\n\r\n    .leeyee-spdfail-references {\r\n      padding: 19px 17px;\r\n    }\r\n  }\r\n\r\n  \/* Mobile 375px *\/\r\n  @media (max-width: 375px) {\r\n    .leeyee-spdfail-article h2 {\r\n      font-size: 24px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h3 {\r\n      font-size: 19.5px;\r\n    }\r\n\r\n    .leeyee-spdfail-table {\r\n      min-width: 660px;\r\n    }\r\n\r\n    .leeyee-spdfail-four-column {\r\n      min-width: 730px;\r\n    }\r\n  }\r\n\r\n  \/* Mobile 360px *\/\r\n  @media (max-width: 360px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 13px;\r\n      padding-right: 13px;\r\n    }\r\n\r\n    .leeyee-spdfail-lead {\r\n      font-size: 16.5px;\r\n    }\r\n\r\n    .leeyee-spdfail-callout,\r\n    .leeyee-spdfail-check-card {\r\n      padding: 16px 15px;\r\n    }\r\n  }\r\n\r\n  \/* Mobile 320px *\/\r\n  @media (max-width: 320px) {\r\n    .leeyee-spdfail-article {\r\n      padding-left: 11px;\r\n      padding-right: 11px;\r\n      font-size: 15.5px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h2 {\r\n      font-size: 23px;\r\n    }\r\n\r\n    .leeyee-spdfail-article h3 {\r\n      font-size: 19px;\r\n    }\r\n\r\n    .leeyee-spdfail-quick,\r\n    .leeyee-spdfail-cta {\r\n      padding: 17px 14px;\r\n    }\r\n\r\n    .leeyee-spdfail-table {\r\n      min-width: 630px;\r\n      font-size: 14px;\r\n    }\r\n\r\n    .leeyee-spdfail-four-column {\r\n      min-width: 700px;\r\n    }\r\n\r\n    .leeyee-spdfail-btn,\r\n    button.leeyee-spdfail-btn {\r\n      min-height: 46px;\r\n      font-size: 14px !important;\r\n    }\r\n\r\n    .leeyee-spdfail-figure {\r\n      margin-top: 23px;\r\n      margin-bottom: 30px;\r\n    }\r\n  }\r\n<\/style>\r\n\r\n<article class=\"leeyee-spdfail-article\">\r\n  <div class=\"leeyee-spdfail-inner\">\r\n\r\n    <section class=\"leeyee-spdfail-intro\" aria-label=\"Article introduction\">\r\n      <p class=\"leeyee-spdfail-lead\">\r\n        The most common causes of SPD failure are repeated surge stress, temporary\r\n        overvoltage, incorrect Uc or Ucpv selection, wiring errors, unsuitable backup\r\n        protection, excessive temperature, moisture, and the use of the wrong surge\r\n        protective device for the system.\r\n      <\/p>\r\n\r\n      <p>\r\n        Lightning is only one possible cause. A surge protective device may also fail\r\n        prematurely because the real operating voltage is higher than expected, a neutral\r\n        fault creates abnormal voltage, a PV array exceeds the selected Ucpv, or the SPD\r\n        is installed under unsuitable electrical or environmental conditions.\r\n      <\/p>\r\n\r\n      <p>\r\n        For maintenance teams, the important question is not only\r\n        <strong>\u201cHas the SPD failed?\u201d<\/strong> It is also\r\n        <strong>\u201cWhy did it fail, and will the replacement SPD fail again?\u201d<\/strong>\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-scope-note\">\r\n        <p>\r\n          <strong>Scope of this guide:<\/strong> This page explains why SPDs fail and why\r\n          replacement modules sometimes fail again. For step-by-step inspection procedures,\r\n          see\r\n          <a href=\"https:\/\/www.cnspd.com\/check-spd-failure\/\">\r\n            How to Check SPD Failure\r\n          <\/a>.\r\n          For plug-in cartridge replacement, use the related replacement guide.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section class=\"leeyee-spdfail-quick\" aria-labelledby=\"leeyee-spdfail-quick-answer\">\r\n      <span class=\"leeyee-spdfail-kicker\">Quick Answer<\/span>\r\n\r\n      <div id=\"ez-toc-container\" class=\"ez-toc-v2_0_85 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#what-causes-an-spd-to-fail\" >What causes an SPD to fail?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#cause-failure-mechanism-and-visible-result-are-not-the-same\" >Cause, failure mechanism and visible result are not the same<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#1-repeated-surges-gradually-age-the-spd\" >1. Repeated surges gradually age the SPD<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#2-one-surge-can-exceed-the-spds-discharge-capability\" >2. One surge can exceed the SPD\u2019s discharge capability<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#3-temporary-overvoltage-is-not-the-same-as-a-lightning-surge\" >3. Temporary overvoltage is not the same as a lightning surge<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#4-uc-or-ucpv-was-selected-below-the-real-operating-voltage\" >4. Uc or Ucpv was selected below the real operating voltage<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#5-incorrect-wiring-changes-the-intended-protection-path\" >5. Incorrect wiring changes the intended protection path<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#6-the-backup-fuse-or-mcb-is-missing-or-incorrectly-coordinated\" >6. The backup fuse or MCB is missing or incorrectly coordinated<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#7-long-leads-and-poor-bonding-mainly-reduce-protection-performance\" >7. Long leads and poor bonding mainly reduce protection performance<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#8-high-enclosure-temperature-accelerates-spd-ageing\" >8. High enclosure temperature accelerates SPD ageing<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#9-solar-and-dc-spd-failures-need-a-separate-review\" >9. Solar and DC SPD failures need a separate review<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#10-product-quality-or-manufacturing-defects-are-also-possible\" >10. Product quality or manufacturing defects are also possible<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#11-why-does-the-replacement-spd-fail-again\" >11. Why does the replacement SPD fail again?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#12-when-should-several-spd-modules-be-checked-or-replaced\" >12. When should several SPD modules be checked or replaced?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#13-root-cause-checklist-before-ordering-replacement-spds\" >13. Root-cause checklist before ordering replacement SPDs<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#not-sure-why-several-spds-failed\" >Not sure why several SPDs failed?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#frequently-asked-questions\" >Frequently Asked Questions<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#technical-basis-and-application-notes\" >Technical Basis and Application Notes<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/#related-spd-maintenance-guides\" >Related SPD Maintenance Guides<\/a><\/li><\/ul><\/nav><\/div>\n<h2 id=\"leeyee-spdfail-quick-answer\"><span class=\"ez-toc-section\" id=\"what-causes-an-spd-to-fail\"><\/span>\r\n        What causes an SPD to fail?\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        An SPD can fail after accumulated surge exposure, one event above its discharge\r\n        capability, a temporary overvoltage or another sustained abnormal voltage condition,\r\n        Uc or Ucpv selected below the real system voltage, incorrect wiring, unsuitable\r\n        fault-current backup protection, high enclosure temperature, moisture, or an\r\n        incorrect AC or PV DC application.\r\n      <\/p>\r\n\r\n      <p>\r\n        If a new replacement SPD fails again, do not continue changing cartridges without\r\n        investigating the system. Measure the actual voltage, verify the SPD label and\r\n        application, check the neutral and wiring, inspect the backup fuse or MCB, and\r\n        examine the base, terminals and enclosure conditions.\r\n      <\/p>\r\n    <\/section>\r\n\r\n    <div\r\n      class=\"leeyee-spdfail-table-wrap\"\r\n      role=\"region\"\r\n      aria-label=\"Common causes of SPD failure\"\r\n      tabindex=\"0\">\r\n\r\n      <table class=\"leeyee-spdfail-table\">\r\n        <thead>\r\n          <tr>\r\n            <th class=\"leeyee-col-cause\">Possible cause<\/th>\r\n            <th class=\"leeyee-col-effect\">What may happen<\/th>\r\n            <th class=\"leeyee-col-check\">What maintenance teams should verify<\/th>\r\n          <\/tr>\r\n        <\/thead>\r\n\r\n        <tbody>\r\n          <tr>\r\n            <td>Repeated surge exposure<\/td>\r\n            <td>\r\n              MOV components gradually age after accumulated electrical and thermal stress.\r\n            <\/td>\r\n            <td>\r\n              Lightning exposure, switching events, surge history and replacement records.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>Surge above SPD capability<\/td>\r\n            <td>\r\n              A severe event can cause immediate degradation or operate the internal\r\n              disconnector.\r\n            <\/td>\r\n            <td>\r\n              SPD type, In, Imax or Iimp, installation position and lightning protection\r\n              concept.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>Temporary or abnormal overvoltage<\/td>\r\n            <td>\r\n              The SPD may conduct for too long, generate heat and disconnect.\r\n            <\/td>\r\n            <td>\r\n              L-N, L-PE, N-PE or DC voltage, neutral condition, transformer, generator\r\n              and grid abnormalities.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>Uc or Ucpv too low<\/td>\r\n            <td>\r\n              Normal operating voltage or expected variation can accelerate varistor ageing.\r\n            <\/td>\r\n            <td>\r\n              Maximum continuous voltage, earthing arrangement, PV Voc and low-temperature\r\n              correction.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>Incorrect wiring or application<\/td>\r\n            <td>\r\n              One protection mode may carry abnormal voltage or the intended protection\r\n              path may not operate correctly.\r\n            <\/td>\r\n            <td>\r\n              Terminal assignment, polarity, pole configuration, N-PE arrangement and AC\r\n              versus PV DC application.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>Incorrect backup protection<\/td>\r\n            <td>\r\n              A power-frequency fault may not be cleared correctly, or the upstream device\r\n              may trip unnecessarily.\r\n            <\/td>\r\n            <td>\r\n              Fuse or MCB rating, breaking capacity, short-circuit current and manufacturer\r\n              requirements.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>Long leads or poor bonding<\/td>\r\n            <td>\r\n              Protection performance may be reduced and the equipment may see a higher\r\n              effective residual voltage.\r\n            <\/td>\r\n            <td>\r\n              PE continuity, equipotential bonding, conductor length, routing and terminal\r\n              tightness.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>High temperature or moisture<\/td>\r\n            <td>\r\n              Thermal ageing, corrosion, insulation deterioration and terminal heating may\r\n              be accelerated.\r\n            <\/td>\r\n            <td>\r\n              Enclosure temperature, ventilation, sunlight, condensation, IP protection\r\n              and loose terminals.\r\n            <\/td>\r\n          <\/tr>\r\n\r\n          <tr>\r\n            <td>Product or batch problem<\/td>\r\n            <td>\r\n              Components, connections or disconnection mechanisms may not perform as declared.\r\n            <\/td>\r\n            <td>\r\n              Whether similar failures appear in one production batch or under verified\r\n              normal conditions in different installations.\r\n            <\/td>\r\n          <\/tr>\r\n        <\/tbody>\r\n      <\/table>\r\n    <\/div>\r\n\r\n    <figure class=\"leeyee-spdfail-figure\">\r\n      <a\r\n        class=\"leeyee-spdfail-image-link\"\r\n        href=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/common-causes-of-spd-failure-overview-scaled.webp\"\r\n        target=\"_blank\"\r\n        rel=\"noopener\">\r\n\r\n        <img loading=\"lazy\"\r\n          src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/common-causes-of-spd-failure-overview-scaled.webp\"\r\n          alt=\"Common causes of SPD failure including repeated surges, temporary overvoltage, incorrect Uc, wiring errors, backup protection and overheating\"\r\n          width=\"1600\"\r\n          height=\"1000\"\r\n          loading=\"lazy\"\r\n          decoding=\"async\">\r\n      <\/a>\r\n\r\n      <figcaption>\r\n        <strong>Common causes of SPD failure:<\/strong>\r\n        the failed module may be the result of surge exposure, abnormal voltage,\r\n        incorrect selection, installation conditions or environmental stress.\r\n      <\/figcaption>\r\n    <\/figure>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"cause-failure-mechanism-and-visible-result-are-not-the-same\"><\/span>\r\n        Cause, failure mechanism and visible result are not the same\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        A useful SPD root-cause investigation separates four different levels. The visible\r\n        red indicator is usually the final result, not the original cause.\r\n      <\/p>\r\n\r\n      <div\r\n        class=\"leeyee-spdfail-table-wrap\"\r\n        role=\"region\"\r\n        aria-label=\"SPD root cause and failure mechanism example\"\r\n        tabindex=\"0\">\r\n\r\n        <table class=\"leeyee-spdfail-table leeyee-spdfail-four-column\">\r\n          <thead>\r\n            <tr>\r\n              <th>Root cause<\/th>\r\n              <th>Failure mechanism<\/th>\r\n              <th>Protective response<\/th>\r\n              <th>Visible result<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n\r\n          <tbody>\r\n            <tr>\r\n              <td>Disconnected or unstable neutral<\/td>\r\n              <td>\r\n                The applied voltage exceeds the normal operating range and the MOV conducts\r\n                for too long.\r\n              <\/td>\r\n              <td>\r\n                Internal temperature rises and the thermal disconnector opens.\r\n              <\/td>\r\n              <td>\r\n                The status window changes, the remote contact changes state, or the SPD\r\n                becomes disconnected.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>Repeated surge exposure<\/td>\r\n              <td>\r\n                MOV characteristics gradually change after accumulated electrical and thermal\r\n                stress.\r\n              <\/td>\r\n              <td>\r\n                Leakage and heating increase until the protection element is isolated.\r\n              <\/td>\r\n              <td>\r\n                End-of-life indication appears after a later event or during operation.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>One event above the SPD capability<\/td>\r\n              <td>\r\n                The protection component experiences excessive impulse energy.\r\n              <\/td>\r\n              <td>\r\n                The disconnector operates or upstream fault protection clears the circuit.\r\n              <\/td>\r\n              <td>\r\n                Immediate indication, tripped protection or visible damage may occur.\r\n              <\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n\r\n      <div class=\"leeyee-spdfail-note leeyee-spdfail-callout\">\r\n        <h3>A red indicator identifies the SPD condition, not the root cause<\/h3>\r\n\r\n        <p>\r\n          Maintenance personnel still need to determine whether the original cause was normal\r\n          accumulated surge ageing, abnormal system voltage, incorrect selection, installation\r\n          conditions or a possible product problem.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"1-repeated-surges-gradually-age-the-spd\"><\/span>1. Repeated surges gradually age the SPD<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        Many voltage-limiting SPDs use metal oxide varistors. During a surge, the varistor\r\n        changes from a high-impedance state to a conductive state and limits the transient\r\n        voltage across the protected circuit.\r\n      <\/p>\r\n\r\n      <p>\r\n        Every significant operation creates electrical and thermal stress. A small event may\r\n        have little measurable effect, while repeated or higher-energy events can gradually\r\n        change the MOV characteristics, increase leakage current and reduce the remaining\r\n        operating margin.\r\n      <\/p>\r\n\r\n      <p>\r\n        Eventually, the internal thermal disconnector may isolate the protection component\r\n        and the visual indicator or remote contact may change state.\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-warning leeyee-spdfail-callout\">\r\n        <h3>There is no universal number of lightning strikes for an SPD<\/h3>\r\n\r\n        <p>\r\n          SPD service life cannot be predicted by counting lightning events alone. A low-energy\r\n          switching transient and a high-energy lightning current do not place the same stress\r\n          on the device. Waveform, amplitude, duration, current distribution, SPD rating,\r\n          installation position and previous degradation all affect the result.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <p>\r\n        A relatively new SPD can fail during one severe event. An older SPD may remain\r\n        operational after many smaller events. A surge counter therefore cannot provide an\r\n        exact percentage of remaining SPD life.\r\n      <\/p>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"2-one-surge-can-exceed-the-spds-discharge-capability\"><\/span>2. One surge can exceed the SPD\u2019s discharge capability<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        An SPD is not an unlimited energy absorber. Its declared current ratings describe\r\n        performance under specified test waveforms and conditions.\r\n      <\/p>\r\n\r\n      <p>\r\n        Type 2 SPDs commonly declare nominal discharge current\r\n        <strong>In<\/strong> and maximum discharge current <strong>Imax<\/strong>.\r\n        Type 1 SPDs declare impulse current <strong>Iimp<\/strong>.\r\n      <\/p>\r\n\r\n      <p>\r\n        If an actual event is more severe than the device, installation position or protection\r\n        concept can manage, the SPD may disconnect immediately, suffer internal degradation\r\n        or lose protection without dramatic external damage.\r\n      <\/p>\r\n\r\n      <p>\r\n        A Type 2 SPD that fails near the service entrance is not automatically defective.\r\n        The project may have required a Type 1 or Type 1+2 SPD, a different current rating,\r\n        shorter conductors or better coordination with other protection stages.\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-note leeyee-spdfail-callout\">\r\n        <h3>Do not diagnose surge capacity from Imax alone<\/h3>\r\n\r\n        <p>\r\n          The correct SPD type and rating depend on installation position, lightning exposure,\r\n          the presence of an external lightning protection system, incoming service type and\r\n          coordination with downstream SPDs. See the\r\n          <a href=\"https:\/\/www.cnspd.com\/spd-imax-selection\/\">\r\n            SPD Imax Selection Guide\r\n          <\/a>.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"3-temporary-overvoltage-is-not-the-same-as-a-lightning-surge\"><\/span>\r\n        3. Temporary overvoltage is not the same as a lightning surge\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        Many premature or repeated SPD failures are blamed on lightning when the actual cause\r\n        is a temporary overvoltage, or another abnormal voltage condition that remains present\r\n        for much longer than a transient surge.\r\n      <\/p>\r\n\r\n      <figure class=\"leeyee-spdfail-figure\">\r\n        <a\r\n          class=\"leeyee-spdfail-image-link\"\r\n          href=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/surge-vs-tov-spd-failure-comparison-scaled.webp\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\">\r\n\r\n          <img loading=\"lazy\"\r\n            src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/surge-vs-tov-spd-failure-comparison-scaled.webp\"\r\n            alt=\"Surge versus temporary overvoltage comparison showing why abnormal voltage duration can cause SPD overheating\"\r\n            width=\"1600\"\r\n            height=\"1000\"\r\n            loading=\"lazy\"\r\n            decoding=\"async\">\r\n        <\/a>\r\n\r\n        <figcaption>\r\n          <strong>Surge vs temporary overvoltage:<\/strong>\r\n          a transient surge is extremely short, while an abnormal voltage that remains above\r\n          the SPD operating range can create sustained thermal stress.\r\n        <\/figcaption>\r\n      <\/figure>\r\n\r\n      <p>\r\n        A transient surge may have a very high peak but last only microseconds. A temporary\r\n        overvoltage usually has a lower peak than a lightning impulse, but it remains present\r\n        for a much longer time.\r\n      <\/p>\r\n\r\n      <p>\r\n        A surge protective device is designed to limit short transient overvoltages. It is\r\n        not intended to operate continuously as a voltage regulator.\r\n      <\/p>\r\n\r\n      <p>\r\n        If the applied voltage remains above the SPD\u2019s continuous operating range, the\r\n        voltage-limiting component may conduct for too long, produce heat and activate its\r\n        thermal disconnector.\r\n      <\/p>\r\n\r\n      <p>\r\n        A compliant SPD should have a defined response to specified temporary overvoltage\r\n        conditions. Depending on the declared design, it may withstand the condition or reach\r\n        a controlled end-of-life state. This does not mean that it can safely clamp every\r\n        sustained abnormal voltage indefinitely.\r\n      <\/p>\r\n\r\n      <h3>Possible sources of abnormal voltage<\/h3>\r\n\r\n      <ul class=\"leeyee-spdfail-list\">\r\n        <li>Loose, damaged or disconnected neutral conductor.<\/li>\r\n        <li>Incorrect transformer tap setting.<\/li>\r\n        <li>Generator voltage-regulation problem.<\/li>\r\n        <li>Phase imbalance or another network fault.<\/li>\r\n        <li>Incorrect line, neutral or protective-conductor connection.<\/li>\r\n        <li>PV earth fault, insulation fault or unexpected conductor-to-earth voltage.<\/li>\r\n        <li>System voltage consistently higher than assumed during SPD selection.<\/li>\r\n      <\/ul>\r\n\r\n      <div class=\"leeyee-spdfail-danger leeyee-spdfail-callout\">\r\n        <h3>Replacing the cartridge does not remove abnormal voltage<\/h3>\r\n\r\n        <p>\r\n          If the original failure was caused by a neutral problem, TOV or another sustained\r\n          abnormal voltage condition, a replacement cartridge with the same rating may also\r\n          overheat and disconnect. Measure and correct the system condition before repeatedly\r\n          installing new cartridges.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"4-uc-or-ucpv-was-selected-below-the-real-operating-voltage\"><\/span>\r\n        4. Uc or Ucpv was selected below the real operating voltage\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        <strong>Uc<\/strong> is the maximum continuous operating voltage declared for an AC SPD.\r\n        For photovoltaic SPDs, the corresponding DC parameter is commonly shown as\r\n        <strong>Ucpv<\/strong>.\r\n      <\/p>\r\n\r\n      <p>\r\n        When Uc or Ucpv is too low, normal voltage variation or an expected operating condition\r\n        may repeatedly bring the protection component closer to conduction.\r\n      <\/p>\r\n\r\n      <p>\r\n        The result can be higher leakage current, additional heating, accelerated MOV ageing\r\n        and premature operation of the internal thermal disconnector.\r\n      <\/p>\r\n\r\n      <p>\r\n        Selecting the lowest available Uc does not automatically provide the best protection.\r\n        The continuous voltage rating must first be high enough for the actual system voltage,\r\n        expected variation and earthing arrangement.\r\n      <\/p>\r\n\r\n      <h3>AC distribution systems<\/h3>\r\n\r\n      <p>\r\n        Do not choose Uc only from the nominal line-to-line voltage. Confirm which conductors\r\n        each protection mode is connected between. TN, TT and IT systems can create different\r\n        voltage conditions across the SPD protection modes.\r\n      <\/p>\r\n\r\n      <p>\r\n        For the complete AC selection process, see the\r\n        <a href=\"https:\/\/www.cnspd.com\/spd-uc-selection-guide\/\">\r\n          SPD Uc Selection Guide\r\n        <\/a>.\r\n      <\/p>\r\n\r\n      <h3>Solar PV DC systems<\/h3>\r\n\r\n      <p>\r\n        The open-circuit voltage of a PV module rises at low temperature. String length,\r\n        module data and the lowest expected site temperature must therefore be considered\r\n        when calculating the maximum array voltage.\r\n      <\/p>\r\n\r\n      <p>\r\n        The SPD must also match the PV topology and maximum voltage from each active conductor\r\n        to earth. For the separate PV calculation process, see the\r\n        <a href=\"https:\/\/www.cnspd.com\/dc-spd-ucpv-selection\/\">\r\n          DC SPD Ucpv Selection Guide\r\n        <\/a>.\r\n      <\/p>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"5-incorrect-wiring-changes-the-intended-protection-path\"><\/span>\r\n        5. Incorrect wiring changes the intended protection path\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        An SPD can show a green indicator while still being installed incorrectly. The\r\n        indicator normally reports the condition of a monitored internal protection component.\r\n        It does not verify every external conductor, terminal and protection mode.\r\n      <\/p>\r\n\r\n      <h3>Typical wiring and application problems include:<\/h3>\r\n\r\n      <ul class=\"leeyee-spdfail-list\">\r\n        <li>Line, neutral or PE connected to the wrong terminal.<\/li>\r\n        <li>Incorrect 1P+N, 2P, 3P+N or 4P configuration for the network.<\/li>\r\n        <li>Incorrect N-PE protection arrangement in a TT system.<\/li>\r\n        <li>Loose terminals creating resistance heating.<\/li>\r\n        <li>Connection conductors routed in a large loop.<\/li>\r\n        <li>Very long line and PE conductors.<\/li>\r\n        <li>DC positive, negative and PE protection paths connected incorrectly.<\/li>\r\n        <li>An AC SPD installed on the PV DC side.<\/li>\r\n        <li>A cartridge installed in an incompatible base.<\/li>\r\n      <\/ul>\r\n\r\n      <p>\r\n        Incorrect wiring does not always destroy the SPD immediately. In some installations,\r\n        the more direct result is poor equipment protection. In other cases, one protection\r\n        mode can be exposed to a voltage or fault condition outside its intended application.\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-note leeyee-spdfail-callout\">\r\n        <h3>Need a wiring reference?<\/h3>\r\n\r\n        <p>\r\n          Use the\r\n          <a href=\"https:\/\/www.cnspd.com\/three-phase-spd-wiring-diagram\/\">\r\n            Three-Phase SPD Wiring Diagram Guide\r\n          <\/a>\r\n          or the\r\n          <a href=\"https:\/\/www.cnspd.com\/single-phase-spd-wiring-diagram\/\">\r\n            Single-Phase SPD Wiring Diagram Guide\r\n          <\/a>.\r\n          Installation and voltage measurement must be performed by qualified electrical\r\n          personnel.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"6-the-backup-fuse-or-mcb-is-missing-or-incorrectly-coordinated\"><\/span>\r\n        6. The backup fuse or MCB is missing or incorrectly coordinated\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        The upstream fuse or circuit breaker does not normally limit a microsecond surge.\r\n        Its main role in the SPD branch is to clear power-frequency fault current if the SPD\r\n        or its connection develops a fault.\r\n      <\/p>\r\n\r\n      <p>\r\n        Correct coordination should consider the SPD manufacturer\u2019s declared maximum backup\r\n        protection, the conductor, the upstream device, the prospective short-circuit current\r\n        and the required breaking capacity.\r\n      <\/p>\r\n\r\n      <h3>If the protective device is unsuitable:<\/h3>\r\n\r\n      <ul class=\"leeyee-spdfail-list\">\r\n        <li>An internal SPD fault may not be disconnected safely or quickly enough.<\/li>\r\n        <li>An undersized fuse or unsuitable MCB may operate during expected surge events.<\/li>\r\n        <li>The SPD branch may remain disconnected without being noticed.<\/li>\r\n        <li>The interrupting capacity may be insufficient for the panel fault level.<\/li>\r\n        <li>Replacing the SPD alone may leave the original coordination problem unchanged.<\/li>\r\n      <\/ul>\r\n\r\n      <div class=\"leeyee-spdfail-warning leeyee-spdfail-callout\">\r\n        <h3>Do not copy a backup fuse rating from another SPD<\/h3>\r\n\r\n        <p>\r\n          Two SPDs with similar Uc, In or Imax values may have different backup protection\r\n          requirements. Confirm the documentation for the exact model and the actual\r\n          short-circuit conditions of the panel.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"7-long-leads-and-poor-bonding-mainly-reduce-protection-performance\"><\/span>\r\n        7. Long leads and poor bonding mainly reduce protection performance\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        During a fast surge, conductor inductance matters. A long connection conductor can\r\n        develop additional voltage while surge current is flowing.\r\n      <\/p>\r\n\r\n      <p>\r\n        This voltage is added to the SPD\u2019s own protection voltage and can increase the voltage\r\n        experienced by downstream equipment.\r\n      <\/p>\r\n\r\n      <p>\r\n        Loose PE connections, poor equipotential bonding, corrosion and unnecessarily long\r\n        conductors can therefore make the complete protection system less effective.\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-warning leeyee-spdfail-callout\">\r\n        <h3>Long conductors do not automatically mean the SPD itself will fail<\/h3>\r\n\r\n        <p>\r\n          The most direct effect of excessive connection length or poor bonding is usually\r\n          reduced protection performance and a higher effective voltage at the equipment.\r\n          These conditions may contribute to abnormal current distribution or additional\r\n          stress, but they should not be described as an automatic direct cause of SPD failure.\r\n        <\/p>\r\n      <\/div>\r\n\r\n      <h3>Check the complete connection path<\/h3>\r\n\r\n      <ul class=\"leeyee-spdfail-list\">\r\n        <li>Line or neutral connection from the busbar to the SPD.<\/li>\r\n        <li>Connection from the SPD to PE, PEN or the equipotential bonding bar.<\/li>\r\n        <li>Total conductor length, not only one side of the connection.<\/li>\r\n        <li>Loops and separation between incoming and protected conductors.<\/li>\r\n        <li>Terminal torque, corrosion and conductor cross-section.<\/li>\r\n        <li>Coordination with upstream and downstream SPDs.<\/li>\r\n      <\/ul>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"8-high-enclosure-temperature-accelerates-spd-ageing\"><\/span>8. High enclosure temperature accelerates SPD ageing<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        SPD components already experience thermal stress during surge operation and abnormal\r\n        voltage conditions. High ambient temperature reduces the available thermal margin\r\n        and can accelerate ageing of varistors, insulation, terminals and disconnection\r\n        components.\r\n      <\/p>\r\n\r\n      <h3>Common high-temperature situations<\/h3>\r\n\r\n      <ul class=\"leeyee-spdfail-list\">\r\n        <li>Outdoor solar combiner boxes exposed to direct sunlight.<\/li>\r\n        <li>Sealed cabinets with limited ventilation.<\/li>\r\n        <li>SPDs installed close to contactors, power supplies or other heat sources.<\/li>\r\n        <li>Loose terminals producing local resistance heating.<\/li>\r\n        <li>High-current conductors heating the same enclosure.<\/li>\r\n        <li>Ambient temperature outside the product\u2019s declared operating range.<\/li>\r\n      <\/ul>\r\n\r\n      <p>\r\n        Moisture and condensation can cause corrosion, contamination and insulation\r\n        deterioration. For outdoor PV, telecom and industrial installations, inspect cable\r\n        glands, enclosure sealing, drainage and condensation control\u2014not only the plug-in\r\n        module.\r\n      <\/p>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"9-solar-and-dc-spd-failures-need-a-separate-review\"><\/span>9. Solar and DC SPD failures need a separate review<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        A PV DC system is not simply an AC distribution board with a different voltage label.\r\n        Long string cables, voltage rise at low temperature, conductor-to-earth voltage,\r\n        insulation monitoring and DC fault interruption all affect SPD selection.\r\n      <\/p>\r\n\r\n      <div\r\n        class=\"leeyee-spdfail-table-wrap\"\r\n        role=\"region\"\r\n        aria-label=\"Common solar and DC SPD failure causes\"\r\n        tabindex=\"0\">\r\n\r\n        <table class=\"leeyee-spdfail-table\">\r\n          <thead>\r\n            <tr>\r\n              <th>DC-specific issue<\/th>\r\n              <th>Why it matters<\/th>\r\n              <th>What to confirm<\/th>\r\n            <\/tr>\r\n          <\/thead>\r\n\r\n          <tbody>\r\n            <tr>\r\n              <td>Ucpv below maximum array voltage<\/td>\r\n              <td>\r\n                The SPD can remain exposed to excessive DC voltage instead of seeing only\r\n                short transient events.\r\n              <\/td>\r\n              <td>\r\n                Maximum corrected string Voc at the lowest expected site temperature.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>AC SPD used on the DC side<\/td>\r\n              <td>\r\n                The device may not have the required DC voltage, disconnection or arc-handling\r\n                design.\r\n              <\/td>\r\n              <td>\r\n                PV DC declaration, product application and relevant IEC 61643-31 requirements.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>Wrong PV topology assumption<\/td>\r\n              <td>\r\n                Positive or negative conductor-to-earth voltage may differ from the value\r\n                assumed during selection.\r\n              <\/td>\r\n              <td>\r\n                Floating, earthed or other PV system arrangement.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>Incorrect protection mode<\/td>\r\n              <td>\r\n                One internal protection mode may carry voltage or surge stress outside its\r\n                intended design.\r\n              <\/td>\r\n              <td>\r\n                Positive-to-PE, negative-to-PE and positive-to-negative configuration.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>Outdoor thermal stress<\/td>\r\n              <td>\r\n                High combiner-box temperature reduces thermal margin and accelerates ageing.\r\n              <\/td>\r\n              <td>\r\n                Direct sunlight, internal temperature, ventilation and installation spacing.\r\n              <\/td>\r\n            <\/tr>\r\n\r\n            <tr>\r\n              <td>Long DC cable routes<\/td>\r\n              <td>\r\n                Surges may enter from different points and require coordinated protection\r\n                near arrays, combiner boxes and inverter inputs.\r\n              <\/td>\r\n              <td>\r\n                Cable route, SPD locations and coordination between protection stages.\r\n              <\/td>\r\n            <\/tr>\r\n          <\/tbody>\r\n        <\/table>\r\n      <\/div>\r\n\r\n      <div class=\"leeyee-spdfail-danger leeyee-spdfail-callout\">\r\n        <h3>Do not apply one polarity rule to every DC SPD<\/h3>\r\n\r\n        <p>\r\n          DC SPD internal protection circuits differ. Some products use symmetrical protection\r\n          arrangements, while others have defined terminal or polarity requirements. Follow\r\n          the diagram for the exact model rather than applying a general rule from another\r\n          product.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"10-product-quality-or-manufacturing-defects-are-also-possible\"><\/span>\r\n        10. Product quality or manufacturing defects are also possible\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        System voltage, selection and installation should be investigated carefully,\r\n        especially when replacement SPDs repeatedly fail in the same location. However,\r\n        product quality problems cannot be excluded automatically.\r\n      <\/p>\r\n\r\n      <p>\r\n        Possible product-related causes include inconsistent MOV characteristics, unsuitable\r\n        thermal disconnection, weak internal connections, poor terminal contact, incorrect\r\n        materials, inadequate sealing, incorrect labels or insufficient batch consistency.\r\n      <\/p>\r\n\r\n      <h3>A product or batch issue becomes more likely when:<\/h3>\r\n\r\n      <ul class=\"leeyee-spdfail-list\">\r\n        <li>Similar failures concentrate in the same production batch.<\/li>\r\n        <li>Units fail under verified normal voltage and temperature conditions.<\/li>\r\n        <li>The same unusual damage pattern appears in unrelated installations.<\/li>\r\n        <li>Wiring, protection coordination and system voltage have been independently verified.<\/li>\r\n        <li>Failure occurs much earlier than comparable units under similar conditions.<\/li>\r\n        <li>The label or supplied replacement cartridge does not match the approved specification.<\/li>\r\n      <\/ul>\r\n\r\n      <div class=\"leeyee-spdfail-success leeyee-spdfail-callout\">\r\n        <h3>A balanced root-cause investigation protects both buyer and supplier<\/h3>\r\n\r\n        <p>\r\n          Not every failed SPD is defective, but not every failure should be blamed on the\r\n          installation. Recording product labels, batch information, operating conditions,\r\n          wiring and damage patterns makes the conclusion more reliable.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"11-why-does-the-replacement-spd-fail-again\"><\/span>11. Why does the replacement SPD fail again?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        Repeated failure shortly after replacement is a strong sign that the original cause\r\n        may still be present. Installing another cartridge restores protection only when the\r\n        base, wiring and system conditions remain suitable.\r\n      <\/p>\r\n\r\n      <figure class=\"leeyee-spdfail-figure\">\r\n        <a\r\n          class=\"leeyee-spdfail-image-link\"\r\n          href=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/repeated-spd-failure-root-cause-checklist-scaled.webp\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\">\r\n\r\n          <img loading=\"lazy\"\r\n            src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/repeated-spd-failure-root-cause-checklist-scaled.webp\"\r\n            alt=\"Repeated SPD failure root cause checklist covering system voltage, Uc, wiring, backup protection, grounding and temperature\"\r\n            width=\"1600\"\r\n            height=\"1000\"\r\n            loading=\"lazy\"\r\n            decoding=\"async\">\r\n        <\/a>\r\n\r\n        <figcaption>\r\n          <strong>Repeated SPD failure process:<\/strong>\r\n          verify the voltage, SPD label, wiring, backup protection, bonding, environment and\r\n          plug-in base before fitting another replacement cartridge.\r\n        <\/figcaption>\r\n      <\/figure>\r\n\r\n      <h3>Frequent causes of repeated SPD failure<\/h3>\r\n\r\n      <ul class=\"leeyee-spdfail-list\">\r\n        <li>The replacement has the same unsuitable Uc or Ucpv as the original.<\/li>\r\n        <li>A neutral fault or abnormal system voltage was not corrected.<\/li>\r\n        <li>The cartridge was replaced but the base or terminal was heat-damaged.<\/li>\r\n        <li>The backup fuse or MCB remains incorrectly selected.<\/li>\r\n        <li>Loose wiring continues to produce local heating.<\/li>\r\n        <li>The enclosure remains too hot or contains condensation.<\/li>\r\n        <li>A Type 2 SPD is exposed to a duty requiring Type 1 protection.<\/li>\r\n        <li>The PV array voltage exceeds the original design assumption.<\/li>\r\n        <li>Only one pole was replaced although all modules experienced the same event.<\/li>\r\n        <li>An incompatible replacement cartridge was installed in the existing base.<\/li>\r\n      <\/ul>\r\n\r\n      <div class=\"leeyee-spdfail-danger leeyee-spdfail-callout\">\r\n        <h3>Do not continue replacing cartridges without measuring the system<\/h3>\r\n\r\n        <p>\r\n          A second failure should trigger a root-cause review. Continuing to install the same\r\n          SPD specification without checking the operating voltage, neutral, PV Voc, wiring,\r\n          base and enclosure can reproduce the same failure.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"12-when-should-several-spd-modules-be-checked-or-replaced\"><\/span>\r\n        12. When should several SPD modules be checked or replaced?\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        One failed cartridge does not automatically mean that every SPD in the facility must\r\n        be replaced. The decision should be based on the event, installation history, common\r\n        exposure, system criticality and whether the remaining protection condition can be\r\n        verified.\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-decision\">\r\n        <div class=\"leeyee-spdfail-decision-row\">\r\n          <div class=\"leeyee-spdfail-decision-label\">\r\n            Replace one cartridge\r\n          <\/div>\r\n\r\n          <div class=\"leeyee-spdfail-decision-text\">\r\n            Consider this when one compatible plug-in module has reached end of life, the\r\n            base is undamaged, the other poles remain normal and no system abnormality is found.\r\n          <\/div>\r\n        <\/div>\r\n\r\n        <div class=\"leeyee-spdfail-decision-row\">\r\n          <div class=\"leeyee-spdfail-decision-label\">\r\n            Inspect the complete SPD\r\n          <\/div>\r\n\r\n          <div class=\"leeyee-spdfail-decision-text\">\r\n            Inspect every pole, the base, terminals, backup protection and wiring after\r\n            overheating, visible damage, a severe event or repeated indicator changes.\r\n          <\/div>\r\n        <\/div>\r\n\r\n        <div class=\"leeyee-spdfail-decision-row\">\r\n          <div class=\"leeyee-spdfail-decision-label\">\r\n            Inspect the panel group\r\n          <\/div>\r\n\r\n          <div class=\"leeyee-spdfail-decision-text\">\r\n            Extend the inspection when several boards share the same supply, neutral problem,\r\n            lightning event, enclosure condition or SPD batch.\r\n          <\/div>\r\n        <\/div>\r\n\r\n        <div class=\"leeyee-spdfail-decision-row\">\r\n          <div class=\"leeyee-spdfail-decision-label\">\r\n            Consider batch replacement\r\n          <\/div>\r\n\r\n          <div class=\"leeyee-spdfail-decision-text\">\r\n            Planned replacement may be appropriate when several units of the same age or batch\r\n            show similar deterioration, the remaining condition cannot be verified, or critical\r\n            equipment cannot accept uncertain protection.\r\n          <\/div>\r\n        <\/div>\r\n      <\/div>\r\n\r\n      <div class=\"leeyee-spdfail-warning leeyee-spdfail-callout\">\r\n        <h3>Correct the common cause before replacing a full batch<\/h3>\r\n\r\n        <p>\r\n          Batch replacement without correcting abnormal voltage, unsuitable Uc or Ucpv,\r\n          incorrect wiring, heat or moisture can reproduce the same failure across the new\r\n          modules.\r\n        <\/p>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"13-root-cause-checklist-before-ordering-replacement-spds\"><\/span>\r\n        13. Root-cause checklist before ordering replacement SPDs\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        The following information helps maintenance teams and suppliers distinguish normal\r\n        end-of-life replacement from a system, selection, installation or possible batch problem.\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-check-grid\">\r\n        <div class=\"leeyee-spdfail-check-card\">\r\n          <h3>Product information<\/h3>\r\n\r\n          <ul>\r\n            <li>Full SPD model and clear label photo.<\/li>\r\n            <li>Type 1, Type 2 or Type 1+2.<\/li>\r\n            <li>Uc or Ucpv.<\/li>\r\n            <li>In, Imax or Iimp.<\/li>\r\n            <li>Up and pole configuration.<\/li>\r\n            <li>Plug-in cartridge and base model.<\/li>\r\n            <li>Production batch and installation date.<\/li>\r\n          <\/ul>\r\n        <\/div>\r\n\r\n        <div class=\"leeyee-spdfail-check-card\">\r\n          <h3>System information<\/h3>\r\n\r\n          <ul>\r\n            <li>Nominal and measured operating voltage.<\/li>\r\n            <li>AC earthing system or PV topology.<\/li>\r\n            <li>Maximum corrected PV string Voc.<\/li>\r\n            <li>Backup fuse or MCB model and rating.<\/li>\r\n            <li>Prospective short-circuit current if available.<\/li>\r\n            <li>Installation position in the protection system.<\/li>\r\n            <li>Upstream and downstream SPD arrangement.<\/li>\r\n          <\/ul>\r\n        <\/div>\r\n\r\n        <div class=\"leeyee-spdfail-check-card\">\r\n          <h3>Failure evidence<\/h3>\r\n\r\n          <ul>\r\n            <li>Indicator and remote-contact status.<\/li>\r\n            <li>Cracking, discoloration or burning.<\/li>\r\n            <li>Base or terminal heat damage.<\/li>\r\n            <li>Number of failed units.<\/li>\r\n            <li>Failure date and operating condition.<\/li>\r\n            <li>Recent lightning, outage or grid event.<\/li>\r\n            <li>Whether a replacement also failed.<\/li>\r\n          <\/ul>\r\n        <\/div>\r\n\r\n        <div class=\"leeyee-spdfail-check-card\">\r\n          <h3>Installation environment<\/h3>\r\n\r\n          <ul>\r\n            <li>Panel and wiring photos.<\/li>\r\n            <li>Approximate SPD conductor length.<\/li>\r\n            <li>PE and equipotential-bonding arrangement.<\/li>\r\n            <li>Ambient and internal enclosure temperature.<\/li>\r\n            <li>Direct sunlight, moisture or condensation.<\/li>\r\n            <li>Nearby heat-producing equipment.<\/li>\r\n            <li>Enclosure type and ingress protection.<\/li>\r\n          <\/ul>\r\n        <\/div>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section class=\"leeyee-spdfail-cta\" aria-labelledby=\"leeyee-spdfail-cta-title\">\r\n      <h2 id=\"leeyee-spdfail-cta-title\"><span class=\"ez-toc-section\" id=\"not-sure-why-several-spds-failed\"><\/span>\r\n        Not sure why several SPDs failed?\r\n      <span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        Send us the SPD label, measured system voltage, panel wiring photo, backup protection,\r\n        failure quantity and base condition. LEEYEE can help compare the failed model with the\r\n        real application and recommend a suitable replacement specification for maintenance,\r\n        panel-building or OEM orders.\r\n      <\/p>\r\n\r\n      <div class=\"leeyee-spdfail-btn-row\">\r\n        <button\r\n          type=\"button\"\r\n          class=\"leeyee-spdfail-btn leeyee-site-popup-btn\"\r\n          aria-label=\"Request SPD failure analysis\">\r\n\r\n          <span class=\"w-btn-label\">\r\n            Request SPD Failure Analysis\r\n          <\/span>\r\n        <\/button>\r\n\r\n        <a\r\n          class=\"leeyee-spdfail-btn leeyee-spdfail-btn-secondary\"\r\n          href=\"https:\/\/www.cnspd.com\/contact\/\"\r\n          target=\"_blank\"\r\n          rel=\"noopener\">\r\n\r\n          <span>\r\n            Send Replacement Details\r\n          <\/span>\r\n        <\/a>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section>\r\n      <h2><span class=\"ez-toc-section\" id=\"frequently-asked-questions\"><\/span>Frequently Asked Questions<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <div class=\"leeyee-spdfail-faq\">\r\n\r\n        <details>\r\n          <summary>\r\n            What is the most common cause of SPD failure?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              There is no single cause for every installation. Repeated surge stress and\r\n              abnormal system voltage are common electrical causes. Incorrect Uc or Ucpv,\r\n              wiring errors, unsuitable backup protection, high temperature and incorrect\r\n              application often explain premature or repeated SPD failure.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Is SPD failure always caused by lightning?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              No. Lightning is only one possible cause. A disconnected neutral, temporary\r\n              overvoltage, incorrect voltage rating, wiring error, overheating, moisture,\r\n              unsuitable system configuration or a possible product defect can also cause\r\n              an SPD to disconnect or fail prematurely.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Why does an SPD keep failing after replacement?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Repeated failure usually means the original cause remains. Possible causes\r\n              include abnormal system voltage, Uc or Ucpv selected too low, incorrect wiring,\r\n              unsuitable backup protection, a damaged plug-in base, high temperature or an\r\n              incompatible replacement cartridge.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Can repeated lightning surges wear out an SPD?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Yes. Repeated surge current creates electrical and thermal stress in the\r\n              protection components. The degradation rate depends on event energy, waveform,\r\n              SPD rating, installation conditions and previous ageing. There is no fixed\r\n              number of lightning events that applies to every SPD.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Can high mains voltage damage an SPD?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Yes. If the voltage remains above the SPD\u2019s continuous operating range, the\r\n              voltage-limiting component may conduct for too long, generate heat and activate\r\n              its thermal disconnector.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            What happens if SPD Uc is too low?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Normal operating voltage or expected voltage variation may repeatedly stress\r\n              the SPD. This can increase leakage current, heating and MOV ageing and lead to\r\n              premature disconnection.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Can poor grounding cause SPD failure?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Poor bonding, loose PE connections and long conductors mainly reduce overall\r\n              protection performance and increase the effective voltage at the equipment.\r\n              They may contribute to abnormal stress, but they should not be treated as an\r\n              automatic direct cause of SPD failure.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Does an SPD need a backup fuse or MCB?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              The requirement depends on the SPD, upstream protective device and installation.\r\n              When required, backup protection clears power-frequency fault current in the\r\n              SPD branch. Its rating and breaking capacity must follow the exact product\r\n              documentation and the panel fault level.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Why does a solar DC SPD fail repeatedly?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Common causes include Ucpv below the corrected maximum array Voc, use of an AC\r\n              SPD on the DC side, incorrect PV topology, unsuitable protection modes, high\r\n              combiner-box temperature, moisture or unresolved insulation and earth faults.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Should all SPD modules be replaced when one module fails?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Not automatically. Inspect the remaining poles, base, terminals, event history\r\n              and system condition. Broader replacement may be appropriate after a common\r\n              severe event, repeated failures or when the remaining condition cannot be\r\n              verified.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Can I replace only the plug-in SPD cartridge?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              Yes, when the replacement cartridge is exactly compatible and the base, contacts,\r\n              terminals and wiring are undamaged. Replace or further inspect the complete unit\r\n              when there is melting, discoloration, cracking, loose contacts or repeated failure.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n        <details>\r\n          <summary>\r\n            Does a green indicator prove that the SPD is correctly installed?\r\n          <\/summary>\r\n\r\n          <div class=\"leeyee-spdfail-faq-answer\">\r\n            <p>\r\n              No. A green indicator normally reports the condition of a monitored internal\r\n              component. It does not confirm correct wiring, suitable Uc or Ucpv, correct\r\n              backup protection, short conductors or effective bonding.\r\n            <\/p>\r\n          <\/div>\r\n        <\/details>\r\n\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <section class=\"leeyee-spdfail-references\">\r\n      <h2><span class=\"ez-toc-section\" id=\"technical-basis-and-application-notes\"><\/span>Technical Basis and Application Notes<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <p>\r\n        SPD failure analysis should be based on the exact product documentation, system\r\n        measurements and the applicable installation requirements. The following standards\r\n        are particularly relevant to the topics discussed in this guide:\r\n      <\/p>\r\n\r\n      <ul>\r\n        <li>\r\n          <strong>IEC 61643-11:<\/strong>\r\n          requirements and test methods for SPDs connected to low-voltage AC power systems.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>IEC 61643-31:<\/strong>\r\n          requirements and test methods for SPDs used in photovoltaic installations.\r\n        <\/li>\r\n\r\n        <li>\r\n          <strong>IEC 60364-5-53:<\/strong>\r\n          selection and erection requirements for isolation, switching, control and surge\r\n          protective devices in low-voltage installations.\r\n        <\/li>\r\n\r\n        <li>\r\n          The manufacturer\u2019s declared Uc or Ucpv, TOV behaviour, backup protection,\r\n          short-circuit withstand information and installation instructions for the exact\r\n          SPD model.\r\n        <\/li>\r\n      <\/ul>\r\n\r\n      <p>\r\n        Standards and local installation rules may be revised. Project engineers should\r\n        confirm the edition and regional requirements applicable to the specific installation.\r\n      <\/p>\r\n    <\/section>\r\n\r\n    <section class=\"leeyee-spdfail-related\">\r\n      <h2><span class=\"ez-toc-section\" id=\"related-spd-maintenance-guides\"><\/span>Related SPD Maintenance Guides<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n      <div class=\"leeyee-spdfail-related-links\">\r\n        <a\r\n          class=\"leeyee-spdfail-related-link\"\r\n          href=\"https:\/\/www.cnspd.com\/check-spd-failure\/\">\r\n          How to Check SPD Failure\r\n        <\/a>\r\n\r\n        <a\r\n          class=\"leeyee-spdfail-related-link\"\r\n          href=\"https:\/\/www.cnspd.com\/spd-failure-indicator-replacement\/\">\r\n          SPD Failure Indicator and Replacement\r\n        <\/a>\r\n\r\n        <a\r\n          class=\"leeyee-spdfail-related-link\"\r\n          href=\"https:\/\/www.cnspd.com\/spd-cartridge-replacement\/\">\r\n          SPD Cartridge Replacement Guide\r\n        <\/a>\r\n\r\n        <a\r\n          class=\"leeyee-spdfail-related-link\"\r\n          href=\"https:\/\/www.cnspd.com\/spd-uc-selection-guide\/\">\r\n          SPD Uc Selection Guide\r\n        <\/a>\r\n\r\n        <a\r\n          class=\"leeyee-spdfail-related-link\"\r\n          href=\"https:\/\/www.cnspd.com\/dc-spd-ucpv-selection\/\">\r\n          DC SPD Ucpv Selection Guide\r\n        <\/a>\r\n\r\n        <a\r\n          class=\"leeyee-spdfail-related-link\"\r\n          href=\"https:\/\/www.cnspd.com\/spd-imax-selection\/\">\r\n          SPD Imax Selection Guide\r\n        <\/a>\r\n      <\/div>\r\n    <\/section>\r\n\r\n    <p class=\"leeyee-spdfail-footnote\">\r\n      Safety note: SPD inspection, live-voltage measurement and replacement must be performed\r\n      by qualified electrical personnel using appropriate isolation, verification and personal\r\n      protective procedures. Product ratings and replacement decisions should be confirmed\r\n      against the documentation of the exact SPD model and the applicable installation rules.\r\n    <\/p>\r\n\r\n  <\/div>\r\n<\/article>\r\n\r\n<script>\r\n  document.addEventListener('DOMContentLoaded', function () {\r\n    var aboutPopupButtons = document.querySelectorAll('.leeyee-site-popup-btn');\r\n\r\n    aboutPopupButtons.forEach(function (button) {\r\n      button.addEventListener('click', function () {\r\n        var realPopupTrigger = document.querySelector(\r\n          '.w-popup.ush_popup_1 .w-popup-trigger'\r\n        );\r\n\r\n        if (realPopupTrigger) {\r\n          realPopupTrigger.click();\r\n        } else {\r\n          window.open(\r\n            'https:\/\/www.cnspd.com\/contact\/',\r\n            '_blank',\r\n            'noopener'\r\n          );\r\n        }\r\n      });\r\n    });\r\n  });\r\n<\/script>\r\n\r\n<script type=\"application\/ld+json\">\r\n{\r\n  \"@context\": \"https:\/\/schema.org\",\r\n  \"@type\": \"FAQPage\",\r\n  \"mainEntity\": [\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"What is the most common cause of SPD failure?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"There is no single cause for every installation. Repeated surge stress and abnormal system voltage are common electrical causes. Incorrect Uc or Ucpv, wiring errors, unsuitable backup protection, high temperature and incorrect application often explain premature or repeated SPD failure.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Is SPD failure always caused by lightning?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"No. Lightning is only one possible cause. A disconnected neutral, temporary overvoltage, incorrect voltage rating, wiring error, overheating, moisture, unsuitable system configuration or a possible product defect can also cause an SPD to fail prematurely.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Why does an SPD keep failing after replacement?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Repeated failure usually means the original cause remains. Possible causes include abnormal system voltage, Uc or Ucpv selected too low, incorrect wiring, unsuitable backup protection, a damaged plug-in base, high temperature or an incompatible replacement cartridge.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Can repeated lightning surges wear out an SPD?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Yes. Repeated surge current creates electrical and thermal stress. The degradation rate depends on event energy, waveform, SPD rating, installation conditions and previous ageing.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Can high mains voltage damage an SPD?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Yes. If voltage remains above the SPD continuous operating range, the voltage-limiting component may conduct for too long, generate heat and activate its thermal disconnector.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"What happens if SPD Uc is too low?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Normal operating voltage or expected voltage variation may repeatedly stress the SPD. This can increase leakage current, heating and MOV ageing and lead to premature disconnection.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Can poor grounding cause SPD failure?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Poor bonding, loose PE connections and long conductors mainly reduce overall protection performance and increase the effective voltage at the equipment. They may contribute to abnormal stress but are not an automatic direct cause of SPD failure.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Does an SPD need a backup fuse or MCB?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"The requirement depends on the SPD, upstream protective device and installation. When required, backup protection clears power-frequency fault current in the SPD branch.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Why does a solar DC SPD fail repeatedly?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Common causes include Ucpv below corrected maximum array voltage, use of an AC SPD on the DC side, incorrect PV topology, unsuitable protection modes, high temperature, moisture or unresolved system faults.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Should all SPD modules be replaced when one module fails?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Not automatically. Inspect the remaining poles, base, terminals, event history and system condition before deciding whether broader replacement is necessary.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Can I replace only the plug-in SPD cartridge?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Yes, when the replacement cartridge is exactly compatible and the base, contacts, terminals and wiring are undamaged.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Does a green indicator prove that the SPD is correctly installed?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"No. A green indicator does not confirm correct external wiring, suitable voltage rating, correct backup protection, short conductors or effective bonding.\"\r\n      }\r\n    }\r\n  ]\r\n}\r\n<\/script>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>The most common causes of SPD failure are repeated surge stress, temporary overvoltage, incorrect Uc or Ucpv selection, wiring errors, unsuitable backup protection, excessive temperature, moisture, and the use of the wrong surge protective device for the system. Lightning is only one possible cause. A surge protective device may also fail prematurely because the real&#8230;<\/p>","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-29971","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Common Causes of SPD Failure: Why SPDs Fail Again | LEEYEE<\/title>\n<meta name=\"description\" content=\"Learn why SPDs fail from repeated surges, TOV, wrong Uc or Ucpv, wiring errors, backup protection and overheating\u2014and what to check before replacement.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Common Causes of SPD Failure: Why SPDs Fail Again | LEEYEE\" \/>\n<meta property=\"og:description\" content=\"Learn why SPDs fail from repeated surges, TOV, wrong Uc or Ucpv, wiring errors, backup protection and overheating\u2014and what to check before replacement.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.cnspd.com\/fr\/spd-failure-causes\/\" \/>\n<meta property=\"og:site_name\" content=\"Surge Protector, Surge Arrestor, Isolating Switch - LEEYEE\" \/>\n<meta property=\"article:published_time\" content=\"2026-07-10T05:09:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-07-10T05:09:17+00:00\" \/>\n<meta name=\"author\" content=\"Devin Ling\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"Devin Ling\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"19 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/\"},\"author\":{\"name\":\"Devin Ling\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#\\\/schema\\\/person\\\/f49dbafe62c5b47100ad2d9f88af92d3\"},\"headline\":\"Common Causes of SPD Failure: Why SPDs Fail and Fail Again\",\"datePublished\":\"2026-07-10T05:09:00+00:00\",\"dateModified\":\"2026-07-10T05:09:17+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/\"},\"wordCount\":4014,\"articleSection\":[\"News\"],\"inLanguage\":\"fr-FR\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/\",\"url\":\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/\",\"name\":\"Common Causes of SPD Failure: Why SPDs Fail Again | LEEYEE\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#website\"},\"datePublished\":\"2026-07-10T05:09:00+00:00\",\"dateModified\":\"2026-07-10T05:09:17+00:00\",\"author\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#\\\/schema\\\/person\\\/f49dbafe62c5b47100ad2d9f88af92d3\"},\"description\":\"Learn why SPDs fail from repeated surges, TOV, wrong Uc or Ucpv, wiring errors, backup protection and overheating\u2014and what to check before replacement.\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/#breadcrumb\"},\"inLanguage\":\"fr-FR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/spd-failure-causes\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.cnspd.com\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Common Causes of SPD Failure: Why SPDs Fail and Fail Again\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/www.cnspd.com\\\/#website\",\"url\":\"https:\\\/\\\/www.cnspd.com\\\/\",\"name\":\"Surge Protector, Surge Arrestor, Isolating Switch - 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