{"id":30077,"date":"2026-07-15T13:43:51","date_gmt":"2026-07-15T05:43:51","guid":{"rendered":"https:\/\/www.cnspd.com\/?p=30077"},"modified":"2026-07-15T15:15:01","modified_gmt":"2026-07-15T07:15:01","slug":"spd-grounding-resistance-does-high-earth-resistance-reduce-protection","status":"publish","type":"post","link":"https:\/\/www.cnspd.com\/it\/spd-grounding-resistance\/","title":{"rendered":"SPD Grounding Resistance: Does High Earth Resistance Reduce Protection?"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"30077\" class=\"elementor elementor-30077\" data-elementor-post-type=\"post\">\n\t\t\t\t<div class=\"elementor-element elementor-element-779eb86 e-flex e-con-boxed e-con e-parent\" data-id=\"779eb86\" 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-f349e3b elementor-widget elementor-widget-html\" data-id=\"f349e3b\" 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 \u2014 SPD Grounding Resistance Guide\r\n   Page scope: #leeyee-gr36\r\n   No H1 included: WordPress page title supplies the H1.\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 {\r\n  --gr-primary: #004898;\r\n  --gr-primary-dark: #00366f;\r\n  --gr-primary-soft: #edf5fd;\r\n  --gr-blue-50: #f7faff;\r\n  --gr-blue-100: #e5effa;\r\n  --gr-green: #16784a;\r\n  --gr-green-soft: #edf8f2;\r\n  --gr-amber: #915800;\r\n  --gr-amber-soft: #fff7e8;\r\n  --gr-red: #a33b3b;\r\n  --gr-red-soft: #fff2f2;\r\n  --gr-text: #202a35;\r\n  --gr-muted: #5b6877;\r\n  --gr-line: #dbe4ed;\r\n  --gr-white: #ffffff;\r\n  --gr-shadow: 0 12px 34px rgba(14, 43, 74, 0.08);\r\n\r\n  width: 100%;\r\n  max-width: 100%;\r\n  margin: 0;\r\n  padding: 0;\r\n  color: var(--gr-text);\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-gr36 *,\r\n#leeyee-gr36 *::before,\r\n#leeyee-gr36 *::after {\r\n  box-sizing: border-box;\r\n}\r\n\r\n#leeyee-gr36 .gr-container {\r\n  width: min(1180px, calc(100% - 48px));\r\n  margin: 0 auto;\r\n}\r\n\r\n#leeyee-gr36 .gr-article {\r\n  padding: 18px 0 70px;\r\n}\r\n\r\n#leeyee-gr36 section[id] {\r\n  scroll-margin-top: 110px;\r\n}\r\n\r\n#leeyee-gr36 p {\r\n  margin: 0 0 18px;\r\n}\r\n\r\n#leeyee-gr36 strong {\r\n  color: #172433;\r\n}\r\n\r\n#leeyee-gr36 a {\r\n  color: var(--gr-primary);\r\n  text-decoration: underline;\r\n  text-decoration-thickness: 1px;\r\n  text-underline-offset: 3px;\r\n}\r\n\r\n#leeyee-gr36 a:hover,\r\n#leeyee-gr36 a:focus {\r\n  color: var(--gr-primary-dark);\r\n}\r\n\r\n#leeyee-gr36 img {\r\n  display: block;\r\n  max-width: 100%;\r\n  height: auto;\r\n}\r\n\r\n#leeyee-gr36 h2,\r\n#leeyee-gr36 h3 {\r\n  color: #172433;\r\n  line-height: 1.28;\r\n  letter-spacing: -0.015em;\r\n}\r\n\r\n#leeyee-gr36 h2 {\r\n  margin: 58px 0 20px;\r\n  padding-bottom: 12px;\r\n  border-bottom: 2px solid var(--gr-blue-100);\r\n  font-size: 32px;\r\n}\r\n\r\n#leeyee-gr36 h3 {\r\n  margin: 30px 0 12px;\r\n  font-size: 23px;\r\n}\r\n\r\n#leeyee-gr36 ul,\r\n#leeyee-gr36 ol {\r\n  margin: 0 0 20px;\r\n  padding-left: 24px;\r\n}\r\n\r\n#leeyee-gr36 li {\r\n  margin: 8px 0;\r\n}\r\n\r\n\/* =========================================================\r\n   Article introduction\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-intro {\r\n  margin-bottom: 28px;\r\n  padding: 30px 34px;\r\n  border: 1px solid var(--gr-line);\r\n  border-left: 5px solid var(--gr-primary);\r\n  border-radius: 12px;\r\n  background: var(--gr-white);\r\n  box-shadow: var(--gr-shadow);\r\n}\r\n\r\n#leeyee-gr36 .gr-eyebrow {\r\n  margin: 0 0 10px;\r\n  color: var(--gr-primary);\r\n  font-size: 14px;\r\n  font-weight: 700;\r\n  letter-spacing: 0.09em;\r\n  text-transform: uppercase;\r\n}\r\n\r\n#leeyee-gr36 .gr-intro-text {\r\n  margin: 0;\r\n  color: #344354;\r\n  font-size: 21px;\r\n  line-height: 1.6;\r\n}\r\n\r\n#leeyee-gr36 .gr-tag-row {\r\n  display: flex;\r\n  flex-wrap: wrap;\r\n  gap: 9px;\r\n  margin-top: 20px;\r\n}\r\n\r\n#leeyee-gr36 .gr-tag {\r\n  display: inline-flex;\r\n  align-items: center;\r\n  min-height: 32px;\r\n  padding: 6px 11px;\r\n  border: 1px solid #cbdcf0;\r\n  border-radius: 999px;\r\n  background: var(--gr-blue-50);\r\n  color: var(--gr-primary-dark);\r\n  font-size: 13px;\r\n  font-weight: 700;\r\n  line-height: 1.2;\r\n}\r\n\r\n\/* =========================================================\r\n   Quick answer\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-quick-answer {\r\n  margin: 28px 0;\r\n  padding: 30px 34px;\r\n  border-radius: 14px;\r\n  background: var(--gr-primary);\r\n  color: var(--gr-white);\r\n  box-shadow: 0 14px 36px rgba(0, 72, 152, 0.18);\r\n}\r\n\r\n#leeyee-gr36 .gr-quick-answer h2 {\r\n  margin: 0 0 14px;\r\n  padding: 0;\r\n  border: 0;\r\n  color: var(--gr-white);\r\n  font-size: 27px;\r\n}\r\n\r\n#leeyee-gr36 .gr-quick-answer p,\r\n#leeyee-gr36 .gr-quick-answer strong {\r\n  color: var(--gr-white);\r\n}\r\n\r\n#leeyee-gr36 .gr-quick-answer p:first-of-type {\r\n  font-size: 18px;\r\n  line-height: 1.65;\r\n}\r\n\r\n#leeyee-gr36 .gr-quick-answer p:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n#leeyee-gr36 .gr-keyline {\r\n  display: block;\r\n  margin-top: 16px;\r\n  padding: 14px 17px;\r\n  border: 1px solid rgba(255, 255, 255, 0.24);\r\n  border-radius: 9px;\r\n  background: rgba(255, 255, 255, 0.1);\r\n  font-weight: 700;\r\n}\r\n\r\n\/* =========================================================\r\n   Figures\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-figure {\r\n  margin: 32px 0;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 14px;\r\n  background: var(--gr-white);\r\n  box-shadow: var(--gr-shadow);\r\n  overflow: hidden;\r\n}\r\n\r\n#leeyee-gr36 .gr-figure-image {\r\n  width: 100%;\r\n  height: auto;\r\n  aspect-ratio: 16 \/ 10;\r\n  background: #f4f8fc;\r\n  object-fit: contain;\r\n}\r\n\r\n#leeyee-gr36 .gr-figure-content {\r\n  padding: 18px 22px 20px;\r\n  border-top: 1px solid var(--gr-line);\r\n}\r\n\r\n#leeyee-gr36 .gr-figure-title {\r\n  display: block;\r\n  margin-bottom: 5px;\r\n  color: #172433;\r\n  font-size: 16px;\r\n  font-weight: 700;\r\n  line-height: 1.45;\r\n}\r\n\r\n#leeyee-gr36 .gr-figure figcaption {\r\n  margin: 0;\r\n  color: var(--gr-muted);\r\n  font-size: 14px;\r\n  line-height: 1.6;\r\n}\r\n\r\n\/* =========================================================\r\n   Grids and cards\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-grid {\r\n  display: grid;\r\n  gap: 20px;\r\n  margin: 24px 0;\r\n}\r\n\r\n#leeyee-gr36 .gr-grid-2 {\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n}\r\n\r\n#leeyee-gr36 .gr-grid-3 {\r\n  grid-template-columns: repeat(3, minmax(0, 1fr));\r\n}\r\n\r\n#leeyee-gr36 .gr-grid-4 {\r\n  grid-template-columns: repeat(4, minmax(0, 1fr));\r\n}\r\n\r\n#leeyee-gr36 .gr-card {\r\n  height: 100%;\r\n  padding: 23px;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 12px;\r\n  background: var(--gr-white);\r\n  box-shadow: 0 8px 24px rgba(26, 55, 86, 0.055);\r\n}\r\n\r\n#leeyee-gr36 .gr-card h3 {\r\n  margin-top: 0;\r\n  font-size: 20px;\r\n}\r\n\r\n#leeyee-gr36 .gr-card p:last-child,\r\n#leeyee-gr36 .gr-card ul:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n#leeyee-gr36 .gr-card-number {\r\n  display: inline-flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  width: 35px;\r\n  height: 35px;\r\n  margin-bottom: 14px;\r\n  border-radius: 50%;\r\n  background: var(--gr-primary);\r\n  color: var(--gr-white);\r\n  font-size: 15px;\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-gr36 .gr-definition {\r\n  border-top: 4px solid var(--gr-primary);\r\n}\r\n\r\n#leeyee-gr36 .gr-definition:nth-child(2) {\r\n  border-top-color: #267aa8;\r\n}\r\n\r\n#leeyee-gr36 .gr-definition:nth-child(3) {\r\n  border-top-color: #4371a8;\r\n}\r\n\r\n#leeyee-gr36 .gr-definition:nth-child(4) {\r\n  border-top-color: var(--gr-green);\r\n}\r\n\r\n\/* =========================================================\r\n   Notes\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-note,\r\n#leeyee-gr36 .gr-warning,\r\n#leeyee-gr36 .gr-success,\r\n#leeyee-gr36 .gr-danger {\r\n  margin: 24px 0;\r\n  padding: 22px 24px;\r\n  border-radius: 11px;\r\n}\r\n\r\n#leeyee-gr36 .gr-note {\r\n  border: 1px solid #bfd5ed;\r\n  background: var(--gr-primary-soft);\r\n}\r\n\r\n#leeyee-gr36 .gr-warning {\r\n  border: 1px solid #e8c87d;\r\n  background: var(--gr-amber-soft);\r\n}\r\n\r\n#leeyee-gr36 .gr-success {\r\n  border: 1px solid #b8dfca;\r\n  background: var(--gr-green-soft);\r\n}\r\n\r\n#leeyee-gr36 .gr-danger {\r\n  border: 1px solid #e4bcbc;\r\n  background: var(--gr-red-soft);\r\n}\r\n\r\n#leeyee-gr36 .gr-note-title,\r\n#leeyee-gr36 .gr-warning-title,\r\n#leeyee-gr36 .gr-success-title,\r\n#leeyee-gr36 .gr-danger-title {\r\n  display: block;\r\n  margin-bottom: 8px;\r\n  color: #172433;\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-gr36 .gr-note p:last-child,\r\n#leeyee-gr36 .gr-warning p:last-child,\r\n#leeyee-gr36 .gr-success p:last-child,\r\n#leeyee-gr36 .gr-danger p:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n\/* =========================================================\r\n   Equations\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-equation {\r\n  margin: 28px 0;\r\n  padding: 28px;\r\n  border: 1px solid #c8d9eb;\r\n  border-radius: 13px;\r\n  background: linear-gradient(135deg, #f8fbff 0%, #edf5fd 100%);\r\n  text-align: center;\r\n}\r\n\r\n#leeyee-gr36 .gr-equation-main {\r\n  display: block;\r\n  color: var(--gr-primary-dark);\r\n  font-family: \"Courier New\", Courier, monospace;\r\n  font-size: 25px;\r\n  font-weight: 700;\r\n  line-height: 1.45;\r\n}\r\n\r\n#leeyee-gr36 .gr-equation-caption {\r\n  display: block;\r\n  max-width: 830px;\r\n  margin: 13px auto 0;\r\n  color: var(--gr-muted);\r\n  font-size: 14px;\r\n  line-height: 1.55;\r\n}\r\n\r\n\/* =========================================================\r\n   Protection flow\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-mode-flow {\r\n  display: grid;\r\n  grid-template-columns: 1fr auto 1fr auto 1fr;\r\n  align-items: stretch;\r\n  gap: 12px;\r\n  margin: 28px 0;\r\n}\r\n\r\n#leeyee-gr36 .gr-mode-box {\r\n  display: flex;\r\n  flex-direction: column;\r\n  justify-content: center;\r\n  min-height: 140px;\r\n  padding: 21px;\r\n  border: 1px solid #cadaec;\r\n  border-radius: 11px;\r\n  background: var(--gr-white);\r\n  text-align: center;\r\n}\r\n\r\n#leeyee-gr36 .gr-mode-box strong {\r\n  display: block;\r\n  margin-bottom: 8px;\r\n  color: var(--gr-primary-dark);\r\n  font-size: 18px;\r\n}\r\n\r\n#leeyee-gr36 .gr-mode-arrow {\r\n  display: flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  color: var(--gr-primary);\r\n  font-size: 28px;\r\n  font-weight: 700;\r\n}\r\n\r\n\/* =========================================================\r\n   Tables\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-table-wrap {\r\n  width: 100%;\r\n  margin: 25px 0;\r\n  overflow-x: auto;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 12px;\r\n  background: var(--gr-white);\r\n  box-shadow: 0 8px 24px rgba(26, 55, 86, 0.045);\r\n}\r\n\r\n#leeyee-gr36 table {\r\n  width: 100%;\r\n  min-width: 760px;\r\n  margin: 0;\r\n  border-collapse: collapse;\r\n  table-layout: fixed;\r\n}\r\n\r\n#leeyee-gr36 th,\r\n#leeyee-gr36 td {\r\n  padding: 16px 17px;\r\n  border-right: 1px solid var(--gr-line);\r\n  border-bottom: 1px solid var(--gr-line);\r\n  vertical-align: top;\r\n  text-align: left;\r\n}\r\n\r\n#leeyee-gr36 th:last-child,\r\n#leeyee-gr36 td:last-child {\r\n  border-right: 0;\r\n}\r\n\r\n#leeyee-gr36 tr:last-child td {\r\n  border-bottom: 0;\r\n}\r\n\r\n#leeyee-gr36 th {\r\n  background: var(--gr-primary);\r\n  color: var(--gr-white);\r\n  font-size: 15px;\r\n  font-weight: 700;\r\n  line-height: 1.4;\r\n}\r\n\r\n#leeyee-gr36 td {\r\n  color: #344354;\r\n  font-size: 15px;\r\n  line-height: 1.55;\r\n}\r\n\r\n#leeyee-gr36 tbody tr:nth-child(even) {\r\n  background: #fafcff;\r\n}\r\n\r\n\/* =========================================================\r\n   Steps\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-steps {\r\n  counter-reset: gr-step;\r\n  display: grid;\r\n  gap: 17px;\r\n  margin: 25px 0;\r\n}\r\n\r\n#leeyee-gr36 .gr-step {\r\n  position: relative;\r\n  padding: 22px 24px 22px 76px;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 11px;\r\n  background: var(--gr-white);\r\n}\r\n\r\n#leeyee-gr36 .gr-step::before {\r\n  counter-increment: gr-step;\r\n  content: counter(gr-step);\r\n  position: absolute;\r\n  top: 22px;\r\n  left: 22px;\r\n  display: flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  width: 37px;\r\n  height: 37px;\r\n  border-radius: 50%;\r\n  background: var(--gr-primary);\r\n  color: var(--gr-white);\r\n  font-size: 16px;\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-gr36 .gr-step h3 {\r\n  margin: 0 0 8px;\r\n  font-size: 20px;\r\n}\r\n\r\n#leeyee-gr36 .gr-step p:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n\/* =========================================================\r\n   Checklists\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-checklist {\r\n  display: grid;\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  gap: 11px 20px;\r\n  margin: 22px 0;\r\n  padding: 0;\r\n  list-style: none;\r\n}\r\n\r\n#leeyee-gr36 .gr-checklist li {\r\n  position: relative;\r\n  margin: 0;\r\n  padding: 13px 15px 13px 43px;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 9px;\r\n  background: #fbfdff;\r\n}\r\n\r\n#leeyee-gr36 .gr-checklist li::before {\r\n  content: \"\u2713\";\r\n  position: absolute;\r\n  top: 12px;\r\n  left: 15px;\r\n  color: var(--gr-green);\r\n  font-size: 18px;\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-gr36 .gr-action-list {\r\n  display: grid;\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  gap: 16px;\r\n  margin: 25px 0;\r\n  padding: 0;\r\n  list-style: none;\r\n}\r\n\r\n#leeyee-gr36 .gr-action-list li {\r\n  position: relative;\r\n  min-height: 100%;\r\n  margin: 0;\r\n  padding: 20px 19px 20px 54px;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 10px;\r\n  background: var(--gr-white);\r\n}\r\n\r\n#leeyee-gr36 .gr-action-list li::before {\r\n  content: attr(data-number);\r\n  position: absolute;\r\n  top: 19px;\r\n  left: 17px;\r\n  display: flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  width: 27px;\r\n  height: 27px;\r\n  border-radius: 50%;\r\n  background: var(--gr-primary);\r\n  color: var(--gr-white);\r\n  font-size: 13px;\r\n  font-weight: 700;\r\n}\r\n\r\n#leeyee-gr36 .gr-action-list strong {\r\n  display: block;\r\n  margin-bottom: 5px;\r\n}\r\n\r\n\/* =========================================================\r\n   FAQ\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-faq {\r\n  margin-top: 24px;\r\n}\r\n\r\n#leeyee-gr36 .gr-faq-item {\r\n  margin-bottom: 13px;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 10px;\r\n  background: var(--gr-white);\r\n  overflow: hidden;\r\n}\r\n\r\n#leeyee-gr36 .gr-faq-item details {\r\n  padding: 0;\r\n}\r\n\r\n#leeyee-gr36 .gr-faq-item summary {\r\n  position: relative;\r\n  padding: 19px 52px 19px 21px;\r\n  color: #172433;\r\n  font-size: 17px;\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-gr36 .gr-faq-item summary::-webkit-details-marker {\r\n  display: none;\r\n}\r\n\r\n#leeyee-gr36 .gr-faq-item summary::after {\r\n  content: \"+\";\r\n  position: absolute;\r\n  top: 50%;\r\n  right: 21px;\r\n  transform: translateY(-50%);\r\n  color: var(--gr-primary);\r\n  font-size: 25px;\r\n  font-weight: 400;\r\n}\r\n\r\n#leeyee-gr36 .gr-faq-item details[open] summary::after {\r\n  content: \"\u2212\";\r\n}\r\n\r\n#leeyee-gr36 .gr-faq-answer {\r\n  padding: 0 21px 20px;\r\n  color: #465567;\r\n}\r\n\r\n#leeyee-gr36 .gr-faq-answer p:last-child {\r\n  margin-bottom: 0;\r\n}\r\n\r\n\/* =========================================================\r\n   CTA\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-cta {\r\n  margin: 52px 0 34px;\r\n  padding: 38px;\r\n  border-radius: 15px;\r\n  background: linear-gradient(135deg, #003d82 0%, #0057ad 100%);\r\n  color: var(--gr-white);\r\n  text-align: center;\r\n  box-shadow: 0 16px 40px rgba(0, 64, 137, 0.2);\r\n}\r\n\r\n#leeyee-gr36 .gr-cta h2 {\r\n  margin: 0 0 13px;\r\n  padding: 0;\r\n  border: 0;\r\n  color: var(--gr-white);\r\n  font-size: 30px;\r\n}\r\n\r\n#leeyee-gr36 .gr-cta p {\r\n  max-width: 830px;\r\n  margin: 0 auto 22px;\r\n  color: var(--gr-white);\r\n}\r\n\r\n#leeyee-gr36 .gr-btn-row {\r\n  display: flex;\r\n  flex-wrap: wrap;\r\n  justify-content: center;\r\n  gap: 12px;\r\n}\r\n\r\n#leeyee-gr36 .gr-btn {\r\n  display: inline-flex;\r\n  align-items: center;\r\n  justify-content: center;\r\n  min-height: 48px;\r\n  padding: 12px 22px;\r\n  border: 2px solid var(--gr-white);\r\n  border-radius: 7px;\r\n  background: var(--gr-white);\r\n  color: var(--gr-primary-dark);\r\n  font-size: 15px;\r\n  font-weight: 700;\r\n  line-height: 1.2;\r\n  text-decoration: none;\r\n  cursor: pointer;\r\n  transition:\r\n    transform 0.2s ease,\r\n    background 0.2s ease;\r\n}\r\n\r\n#leeyee-gr36 .gr-btn:hover,\r\n#leeyee-gr36 .gr-btn:focus {\r\n  transform: translateY(-1px);\r\n  background: #eaf3fd;\r\n  color: var(--gr-primary-dark);\r\n  text-decoration: none;\r\n}\r\n\r\n#leeyee-gr36 a.gr-btn.gr-btn-secondary {\r\n  border-color: #ffffff !important;\r\n  background: transparent !important;\r\n  color: #ffffff !important;\r\n  -webkit-text-fill-color: #ffffff !important;\r\n}\r\n\r\n#leeyee-gr36 a.gr-btn.gr-btn-secondary span {\r\n  color: #ffffff !important;\r\n  -webkit-text-fill-color: #ffffff !important;\r\n  opacity: 1 !important;\r\n}\r\n\r\n#leeyee-gr36 a.gr-btn.gr-btn-secondary:hover,\r\n#leeyee-gr36 a.gr-btn.gr-btn-secondary:focus {\r\n  border-color: #ffffff !important;\r\n  background: #ffffff !important;\r\n  color: #004898 !important;\r\n  -webkit-text-fill-color: #004898 !important;\r\n  text-decoration: none !important;\r\n}\r\n\r\n#leeyee-gr36 a.gr-btn.gr-btn-secondary:hover span,\r\n#leeyee-gr36 a.gr-btn.gr-btn-secondary:focus span {\r\n  color: #004898 !important;\r\n  -webkit-text-fill-color: #004898 !important;\r\n}\r\n\r\n\/* =========================================================\r\n   Related guides\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-related {\r\n  margin: 34px 0;\r\n  padding: 28px;\r\n  border: 1px solid var(--gr-line);\r\n  border-radius: 12px;\r\n  background: var(--gr-blue-50);\r\n}\r\n\r\n#leeyee-gr36 .gr-related h2 {\r\n  margin-top: 0;\r\n  font-size: 25px;\r\n}\r\n\r\n#leeyee-gr36 .gr-related-grid {\r\n  display: grid;\r\n  grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  gap: 15px;\r\n}\r\n\r\n#leeyee-gr36 .gr-related-link {\r\n  display: block;\r\n  min-height: 100%;\r\n  padding: 17px;\r\n  border: 1px solid #cfdeee;\r\n  border-radius: 9px;\r\n  background: var(--gr-white);\r\n  color: #24435f;\r\n  font-weight: 700;\r\n  line-height: 1.45;\r\n  text-decoration: none;\r\n}\r\n\r\n#leeyee-gr36 .gr-related-link:hover,\r\n#leeyee-gr36 .gr-related-link:focus {\r\n  border-color: var(--gr-primary);\r\n  color: var(--gr-primary);\r\n  text-decoration: none;\r\n}\r\n\r\n\/* =========================================================\r\n   References and disclaimer\r\n   ========================================================= *\/\r\n\r\n#leeyee-gr36 .gr-references {\r\n  margin-top: 48px;\r\n  padding-top: 4px;\r\n}\r\n\r\n#leeyee-gr36 .gr-references ol {\r\n  padding-left: 22px;\r\n}\r\n\r\n#leeyee-gr36 .gr-references li {\r\n  margin-bottom: 12px;\r\n  color: var(--gr-muted);\r\n  font-size: 14px;\r\n  line-height: 1.58;\r\n}\r\n\r\n#leeyee-gr36 .gr-disclaimer {\r\n  margin-top: 28px;\r\n  padding: 18px 20px;\r\n  border-top: 1px solid var(--gr-line);\r\n  border-bottom: 1px solid var(--gr-line);\r\n  color: var(--gr-muted);\r\n  font-size: 13px;\r\n  line-height: 1.6;\r\n}\r\n\r\n\/* =========================================================\r\n   Desktop 1440\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 1440px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: min(1140px, calc(100% - 48px));\r\n  }\r\n\r\n  #leeyee-gr36 h2 {\r\n    font-size: 31px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Desktop 1366\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 1366px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: min(1100px, calc(100% - 44px));\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro,\r\n  #leeyee-gr36 .gr-quick-answer {\r\n    padding: 28px 31px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Desktop 1280\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 1280px) {\r\n  #leeyee-gr36 {\r\n    font-size: 16.5px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-container {\r\n    width: min(1040px, calc(100% - 42px));\r\n  }\r\n\r\n  #leeyee-gr36 .gr-grid-4 {\r\n    grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Tablet 1024\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 1024px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 38px);\r\n  }\r\n\r\n  #leeyee-gr36 h2 {\r\n    margin-top: 50px;\r\n    font-size: 29px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-grid-3 {\r\n    grid-template-columns: repeat(2, minmax(0, 1fr));\r\n  }\r\n\r\n  #leeyee-gr36 .gr-mode-flow {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-mode-arrow {\r\n    min-height: 28px;\r\n    transform: rotate(90deg);\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Tablet 912\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 912px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 34px);\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro-text {\r\n    font-size: 20px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-equation-main {\r\n    font-size: 23px;\r\n  }\r\n\r\n  #leeyee-gr36 th,\r\n  #leeyee-gr36 td {\r\n    padding: 14px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Tablet 820\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 820px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 30px);\r\n  }\r\n\r\n  #leeyee-gr36 .gr-grid-2,\r\n  #leeyee-gr36 .gr-grid-3 {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-checklist,\r\n  #leeyee-gr36 .gr-action-list {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-cta {\r\n    padding: 34px 27px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Tablet 768\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 768px) {\r\n  #leeyee-gr36 {\r\n    font-size: 16px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-article {\r\n    padding-top: 10px;\r\n  }\r\n\r\n  #leeyee-gr36 h2 {\r\n    margin-top: 44px;\r\n    font-size: 27px;\r\n  }\r\n\r\n  #leeyee-gr36 h3 {\r\n    font-size: 21px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro,\r\n  #leeyee-gr36 .gr-quick-answer {\r\n    padding: 25px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-grid-4 {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-related-grid {\r\n    grid-template-columns: 1fr;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-figure-content {\r\n    padding: 16px 18px 18px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 600\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 600px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 24px);\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro,\r\n  #leeyee-gr36 .gr-quick-answer,\r\n  #leeyee-gr36 .gr-card,\r\n  #leeyee-gr36 .gr-related,\r\n  #leeyee-gr36 .gr-figure {\r\n    border-radius: 9px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro-text {\r\n    font-size: 18px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-figure {\r\n    margin: 25px 0;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-figure-image {\r\n    aspect-ratio: auto;\r\n    width: 100%;\r\n    height: auto;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-figure-title {\r\n    font-size: 15px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-figure figcaption {\r\n    font-size: 13px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-table-wrap {\r\n    overflow: visible;\r\n    border: 0;\r\n    border-radius: 0;\r\n    box-shadow: none;\r\n    background: transparent;\r\n  }\r\n\r\n  #leeyee-gr36 table,\r\n  #leeyee-gr36 thead,\r\n  #leeyee-gr36 tbody,\r\n  #leeyee-gr36 tr,\r\n  #leeyee-gr36 th,\r\n  #leeyee-gr36 td {\r\n    display: block;\r\n    width: 100%;\r\n    min-width: 0;\r\n  }\r\n\r\n  #leeyee-gr36 thead {\r\n    position: absolute;\r\n    width: 1px;\r\n    height: 1px;\r\n    overflow: hidden;\r\n    clip: rect(0 0 0 0);\r\n  }\r\n\r\n  #leeyee-gr36 tbody tr {\r\n    margin-bottom: 14px;\r\n    border: 1px solid var(--gr-line);\r\n    border-radius: 9px;\r\n    background: var(--gr-white);\r\n    overflow: hidden;\r\n  }\r\n\r\n  #leeyee-gr36 td {\r\n    position: relative;\r\n    min-height: 48px;\r\n    padding: 13px 14px 13px 43%;\r\n    border: 0;\r\n    border-bottom: 1px solid var(--gr-line);\r\n  }\r\n\r\n  #leeyee-gr36 td:last-child {\r\n    border-bottom: 0;\r\n  }\r\n\r\n  #leeyee-gr36 td::before {\r\n    content: attr(data-label);\r\n    position: absolute;\r\n    top: 13px;\r\n    left: 14px;\r\n    width: 36%;\r\n    color: #1b3855;\r\n    font-size: 13px;\r\n    font-weight: 700;\r\n    line-height: 1.4;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-equation {\r\n    padding: 22px 16px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-equation-main {\r\n    font-size: 19px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-btn-row {\r\n    flex-direction: column;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-btn {\r\n    width: 100%;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 540\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 540px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 22px);\r\n  }\r\n\r\n  #leeyee-gr36 h2 {\r\n    font-size: 25px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-quick-answer h2 {\r\n    font-size: 24px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-step {\r\n    padding: 68px 19px 20px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-step::before {\r\n    top: 18px;\r\n    left: 19px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 480\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 480px) {\r\n  #leeyee-gr36 .gr-intro,\r\n  #leeyee-gr36 .gr-quick-answer,\r\n  #leeyee-gr36 .gr-card,\r\n  #leeyee-gr36 .gr-related {\r\n    padding: 21px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-tag-row {\r\n    gap: 7px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-tag {\r\n    font-size: 12px;\r\n  }\r\n\r\n  #leeyee-gr36 td {\r\n    padding-left: 41%;\r\n  }\r\n\r\n  #leeyee-gr36 td::before {\r\n    width: 34%;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-cta {\r\n    padding: 29px 20px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-cta h2 {\r\n    font-size: 25px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 430\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 430px) {\r\n  #leeyee-gr36 {\r\n    font-size: 15.5px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 20px);\r\n  }\r\n\r\n  #leeyee-gr36 h2 {\r\n    font-size: 24px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro-text {\r\n    font-size: 17px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-figure-content {\r\n    padding: 14px 15px 16px;\r\n  }\r\n\r\n  #leeyee-gr36 td {\r\n    padding: 43px 13px 13px;\r\n  }\r\n\r\n  #leeyee-gr36 td::before {\r\n    top: 12px;\r\n    left: 13px;\r\n    width: calc(100% - 26px);\r\n  }\r\n\r\n  #leeyee-gr36 .gr-action-list li {\r\n    padding-right: 15px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 414\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 414px) {\r\n  #leeyee-gr36 .gr-intro,\r\n  #leeyee-gr36 .gr-quick-answer,\r\n  #leeyee-gr36 .gr-card {\r\n    padding: 19px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-equation-main {\r\n    font-size: 17px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-faq-item summary {\r\n    padding-left: 17px;\r\n    font-size: 16px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-faq-answer {\r\n    padding-right: 17px;\r\n    padding-left: 17px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 390\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 390px) {\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 18px);\r\n  }\r\n\r\n  #leeyee-gr36 h2 {\r\n    font-size: 23px;\r\n  }\r\n\r\n  #leeyee-gr36 h3 {\r\n    font-size: 19px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-quick-answer h2 {\r\n    font-size: 22px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-mode-box {\r\n    min-height: 0;\r\n    padding: 18px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 375\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 375px) {\r\n  #leeyee-gr36 .gr-tag {\r\n    width: 100%;\r\n    justify-content: center;\r\n    text-align: center;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-note,\r\n  #leeyee-gr36 .gr-warning,\r\n  #leeyee-gr36 .gr-success,\r\n  #leeyee-gr36 .gr-danger {\r\n    padding: 18px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-checklist li {\r\n    padding-right: 12px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 360\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 360px) {\r\n  #leeyee-gr36 {\r\n    font-size: 15px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-container {\r\n    width: calc(100% - 16px);\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro,\r\n  #leeyee-gr36 .gr-quick-answer,\r\n  #leeyee-gr36 .gr-card,\r\n  #leeyee-gr36 .gr-related {\r\n    padding: 17px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-cta {\r\n    padding: 25px 17px;\r\n  }\r\n}\r\n\r\n\/* =========================================================\r\n   Mobile 320\r\n   ========================================================= *\/\r\n\r\n@media (max-width: 320px) {\r\n  #leeyee-gr36 h2 {\r\n    font-size: 21px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-intro-text {\r\n    font-size: 16px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-equation {\r\n    padding: 18px 11px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-equation-main {\r\n    font-size: 15px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-faq-item summary {\r\n    padding-right: 42px;\r\n    font-size: 15px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-btn {\r\n    padding-right: 14px;\r\n    padding-left: 14px;\r\n    font-size: 14px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-action-list li {\r\n    padding: 54px 14px 17px;\r\n  }\r\n\r\n  #leeyee-gr36 .gr-action-list li::before {\r\n    top: 16px;\r\n    left: 14px;\r\n  }\r\n}\r\n<\/style>\r\n\r\n<article id=\"leeyee-gr36\">\r\n  <div class=\"gr-container\">\r\n    <div class=\"gr-article\">\r\n\r\n      <section class=\"gr-intro\" aria-label=\"Article introduction\">\r\n        <p class=\"gr-eyebrow\">\r\n          SPD Engineering, Site Inspection and OEM Selection Guide\r\n        <\/p>\r\n\r\n        <p class=\"gr-intro-text\">\r\n          A low earth-resistance reading is helpful, but it does not by itself\r\n          prove that an SPD has an effective surge-current path. Engineers must\r\n          also check PE continuity, transient impedance, equipotential bonding,\r\n          earthing-system type and the relationship between the SPD and the\r\n          protected equipment.\r\n        <\/p>\r\n\r\n        <div class=\"gr-tag-row\" aria-label=\"Applicable project types\">\r\n          <span class=\"gr-tag\">Solar PV<\/span>\r\n          <span class=\"gr-tag\">Telecom Sites<\/span>\r\n          <span class=\"gr-tag\">Industrial Panels<\/span>\r\n          <span class=\"gr-tag\">Outdoor Cabinets<\/span>\r\n          <span class=\"gr-tag\">EPC Projects<\/span>\r\n          <span class=\"gr-tag\">OEM Distribution Boards<\/span>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section class=\"gr-quick-answer\" aria-labelledby=\"gr-quick-answer-title\">\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\/it\/spd-grounding-resistance\/#quick-answer\" >Quick Answer<\/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\/it\/spd-grounding-resistance\/#can-an-spd-work-without-grounding\" >Can an SPD Work Without Grounding?<\/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\/it\/spd-grounding-resistance\/#why-does-grounding-matter-to-an-spd\" >Why Does Grounding Matter to an 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\/it\/spd-grounding-resistance\/#four-grounding-terms-that-must-not-be-treated-as-the-same-thing\" >Four Grounding Terms That Must Not Be Treated as the Same Thing<\/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\/it\/spd-grounding-resistance\/#what-happens-when-grounding-resistance-or-path-impedance-is-too-high\" >What Happens When Grounding Resistance or Path Impedance Is Too High?<\/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\/it\/spd-grounding-resistance\/#grounding-resistance-vs-surge-path-impedance\" >Grounding Resistance vs Surge-Path Impedance<\/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\/it\/spd-grounding-resistance\/#does-an-spd-require-1%ce%a9-5%ce%a9-or-10%ce%a9-grounding-resistance\" >Does an SPD Require 1\u03a9, 5\u03a9 or 10\u03a9 Grounding Resistance?<\/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\/it\/spd-grounding-resistance\/#how-should-spd-grounding-resistance-be-measured\" >How Should SPD Grounding Resistance Be Measured?<\/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\/it\/spd-grounding-resistance\/#what-should-be-done-if-grounding-resistance-is-too-high\" >What Should Be Done If Grounding Resistance Is Too High?<\/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\/it\/spd-grounding-resistance\/#how-earthing-system-type-changes-the-spd-assessment\" >How Earthing-System Type Changes the SPD Assessment<\/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\/it\/spd-grounding-resistance\/#grounding-checks-for-solar-telecom-and-industrial-projects\" >Grounding Checks for Solar, Telecom and Industrial Projects<\/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\/it\/spd-grounding-resistance\/#information-buyers-should-provide-before-ordering-an-spd\" >Information Buyers Should Provide Before Ordering an SPD<\/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\/it\/spd-grounding-resistance\/#common-spd-grounding-mistakes\" >Common SPD Grounding Mistakes<\/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\/it\/spd-grounding-resistance\/#how-is-this-different-from-the-spd-05m-connection-length-rule\" >How Is This Different from the SPD 0.5m Connection-Length Rule?<\/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\/it\/spd-grounding-resistance\/#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-16\" href=\"#\" data-href=\"https:\/\/www.cnspd.com\/it\/spd-grounding-resistance\/#confirm-the-spd-and-grounding-path-before-bulk-ordering\" >Confirm the SPD and Grounding Path Before Bulk Ordering<\/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\/it\/spd-grounding-resistance\/#related-technical-guides\" >Related Technical Guides<\/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\/it\/spd-grounding-resistance\/#authoritative-references\" >Authoritative References<\/a><\/li><\/ul><\/nav><\/div>\n<h2 id=\"gr-quick-answer-title\"><span class=\"ez-toc-section\" id=\"quick-answer\"><\/span>Quick Answer<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          <strong>\r\n            High grounding resistance can reduce the installed protection\r\n            performance of an SPD\r\n          <\/strong>\r\n          by increasing transient voltage along the earth, PE and bonding path.\r\n          However, there is no universal 1\u03a9, 5\u03a9 or 10\u03a9 requirement for every\r\n          SPD installation. The applicable project standard, earthing system,\r\n          equipotential bonding and complete surge-current path must all be checked.\r\n        <\/p>\r\n\r\n        <p>\r\n          The SPD may operate normally while the protected equipment still experiences\r\n          excessive voltage caused by conductor impedance or a transient potential\r\n          difference between separate grounding references.\r\n        <\/p>\r\n\r\n        <span class=\"gr-keyline\">\r\n          Good SPD protection requires a coordinated, short and low-impedance\r\n          current path\u2014not only a low reading on an earth-resistance tester.\r\n        <\/span>\r\n      <\/section>\r\n\r\n      <figure class=\"gr-figure\">\r\n        <img fetchpriority=\"high\"\r\n          class=\"gr-figure-image\"\r\n          src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/spd-grounding-resistance-effective-protection-voltage.webp\"\r\n          alt=\"How grounding resistance and surge path impedance affect the effective voltage at protected equipment\"\r\n          width=\"1600\"\r\n          height=\"1000\"\r\n          loading=\"eager\"\r\n          decoding=\"async\"\r\n        >\r\n\r\n        <div class=\"gr-figure-content\">\r\n          <span class=\"gr-figure-title\">\r\n            The SPD nameplate Up is only one part of the installed protection result\r\n          <\/span>\r\n\r\n          <figcaption>\r\n            The voltage experienced by the equipment can also include voltage\r\n            developed along the SPD connection and a transient potential difference\r\n            between the SPD reference point and the equipment grounding reference.\r\n          <\/figcaption>\r\n        <\/div>\r\n      <\/figure>\r\n\r\n      <section id=\"can-an-spd-work-without-grounding\">\r\n        <h2><span class=\"ez-toc-section\" id=\"can-an-spd-work-without-grounding\"><\/span>Can an SPD Work Without Grounding?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          The technically correct answer is:\r\n          <strong>it depends on the SPD protection mode and the system design.<\/strong>\r\n        <\/p>\r\n\r\n        <p>\r\n          An SPD limits voltage between the conductors connected to its terminals.\r\n          A protection mode between line and neutral can limit a differential-mode\r\n          surge without using a local earth electrode as the direct current path.\r\n          By contrast, L\u2013PE, N\u2013PE, positive\u2013PE, negative\u2013PE and many signal-to-earth\r\n          protection modes depend strongly on a correct PE or equipotential-bonding\r\n          connection.\r\n        <\/p>\r\n\r\n        <div class=\"gr-table-wrap\">\r\n          <table>\r\n            <thead>\r\n              <tr>\r\n                <th style=\"width:24%;\">Protection Mode<\/th>\r\n                <th style=\"width:34%;\">Dependence on PE or Earth<\/th>\r\n                <th style=\"width:42%;\">Engineering Meaning<\/th>\r\n              <\/tr>\r\n            <\/thead>\r\n\r\n            <tbody>\r\n              <tr>\r\n                <td data-label=\"Protection Mode\">\r\n                  <strong>L\u2013N or pole-to-pole<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"PE or Earth Dependence\">\r\n                  May limit differential-mode voltage between the two connected\r\n                  current-carrying conductors.\r\n                <\/td>\r\n\r\n                <td data-label=\"Engineering Meaning\">\r\n                  This does not prove that common-mode protection or the complete\r\n                  installation is safe without PE.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Protection Mode\">\r\n                  <strong>L\u2013PE or pole-to-PE<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"PE or Earth Dependence\">\r\n                  Requires a suitable protective-earth or equipotential-bonding path.\r\n                <\/td>\r\n\r\n                <td data-label=\"Engineering Meaning\">\r\n                  A missing, loose or high-impedance PE connection can seriously\r\n                  reduce the installed protection result.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Protection Mode\">\r\n                  <strong>N\u2013PE<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"PE or Earth Dependence\">\r\n                  Depends on the neutral-to-earth protection path defined by the\r\n                  earthing system and SPD topology.\r\n                <\/td>\r\n\r\n                <td data-label=\"Engineering Meaning\">\r\n                  Particularly important in many TT-system 1+1 and 3+1 arrangements.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Protection Mode\">\r\n                  <strong>Signal-to-earth or shield<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"PE or Earth Dependence\">\r\n                  Requires coordinated reference bonding between the signal SPD,\r\n                  equipment and cable screen.\r\n                <\/td>\r\n\r\n                <td data-label=\"Engineering Meaning\">\r\n                  Separate earth references can force current through communication\r\n                  ports or equipment insulation.\r\n                <\/td>\r\n              <\/tr>\r\n            <\/tbody>\r\n          <\/table>\r\n        <\/div>\r\n\r\n        <div class=\"gr-warning\">\r\n          <span class=\"gr-warning-title\">\r\n            Do not describe an ungrounded installation as fully protected\r\n          <\/span>\r\n\r\n          <p>\r\n            Even where one differential protection mode can conduct, the installation\r\n            may still lack safe common-mode protection, protective bonding or the\r\n            connection required by the SPD manufacturer. Always follow the wiring\r\n            diagram and the applicable electrical design.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"why-grounding-matters\">\r\n        <h2><span class=\"ez-toc-section\" id=\"why-does-grounding-matter-to-an-spd\"><\/span>Why Does Grounding Matter to an SPD?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          When a transient exceeds the SPD operating threshold, the SPD changes to\r\n          a conductive state and creates a lower-impedance path between its connected\r\n          terminals. Surge current then follows the electrical system path through\r\n          live conductors, neutral, PE, bonding conductors, cable screens, structural\r\n          metal or the earth-termination system.\r\n        <\/p>\r\n\r\n        <div class=\"gr-mode-flow\" aria-label=\"Simplified SPD protection process\">\r\n          <div class=\"gr-mode-box\">\r\n            <strong>Transient Arrives<\/strong>\r\n            Lightning-induced or switching overvoltage appears between conductors.\r\n          <\/div>\r\n\r\n          <div class=\"gr-mode-arrow\" aria-hidden=\"true\">\u2192<\/div>\r\n\r\n          <div class=\"gr-mode-box\">\r\n            <strong>SPD Conducts<\/strong>\r\n            The SPD limits voltage between the conductors connected to its terminals.\r\n          <\/div>\r\n\r\n          <div class=\"gr-mode-arrow\" aria-hidden=\"true\">\u2192<\/div>\r\n\r\n          <div class=\"gr-mode-box\">\r\n            <strong>Current Uses the System Path<\/strong>\r\n            Current flows through the coordinated neutral, PE, bonding or earth network.\r\n          <\/div>\r\n        <\/div>\r\n\r\n        <p>\r\n          The purpose is not simply to \u201csend all surge energy into the soil.\u201d\r\n          The more important objective is to keep connected equipment and conductive\r\n          systems at controlled relative potentials during the surge event.\r\n        <\/p>\r\n      <\/section>\r\n\r\n      <section id=\"grounding-terms\">\r\n        <h2><span class=\"ez-toc-section\" id=\"four-grounding-terms-that-must-not-be-treated-as-the-same-thing\"><\/span>Four Grounding Terms That Must Not Be Treated as the Same Thing<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <div class=\"gr-grid gr-grid-4\">\r\n          <div class=\"gr-card gr-definition\">\r\n            <h3>Earth Electrode Resistance<\/h3>\r\n\r\n            <p>\r\n              The measured resistance between an earth-electrode system and the\r\n              surrounding soil under the selected test method.\r\n            <\/p>\r\n          <\/div>\r\n\r\n          <div class=\"gr-card gr-definition\">\r\n            <h3>PE Continuity<\/h3>\r\n\r\n            <p>\r\n              Whether the SPD earth terminal, cabinet, PE bar and main earthing\r\n              terminal have a continuous and mechanically reliable metallic connection.\r\n            <\/p>\r\n          <\/div>\r\n\r\n          <div class=\"gr-card gr-definition\">\r\n            <h3>Surge-Path Impedance<\/h3>\r\n\r\n            <p>\r\n              The transient opposition created by resistance, inductance, conductor\r\n              geometry, joints, routing and the wider bonding network.\r\n            <\/p>\r\n          <\/div>\r\n\r\n          <div class=\"gr-card gr-definition\">\r\n            <h3>Equipotential Bonding<\/h3>\r\n\r\n            <p>\r\n              The coordinated connection of conductive systems to reduce dangerous\r\n              voltage differences during fault, lightning and surge events.\r\n            <\/p>\r\n          <\/div>\r\n        <\/div>\r\n\r\n        <p>\r\n          A site can show a relatively low earth-electrode resistance but still have\r\n          poor SPD performance because of a long PE route, corroded joint, isolated\r\n          earth network or large separation between the SPD reference point and the\r\n          protected equipment.\r\n        <\/p>\r\n\r\n        <figure class=\"gr-figure\">\r\n          <img loading=\"lazy\"\r\n            class=\"gr-figure-image\"\r\n            src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/spd-equipotential-bonding-vs-isolated-earth-rod.webp\"\r\n            alt=\"Correct SPD equipotential bonding compared with an incorrect isolated earth rod connection\"\r\n            width=\"1600\"\r\n            height=\"1000\"\r\n            loading=\"lazy\"\r\n            decoding=\"async\"\r\n          >\r\n\r\n          <div class=\"gr-figure-content\">\r\n            <span class=\"gr-figure-title\">\r\n              Common equipotential bonding versus an uncoordinated isolated SPD earth\r\n            <\/span>\r\n\r\n            <figcaption>\r\n              Connecting the SPD, protected equipment, cabinet and signal protection\r\n              to a coordinated bonding network reduces transient potential differences.\r\n              A separate unbonded SPD earth can force current through communication\r\n              cables, shields or equipment interfaces.\r\n            <\/figcaption>\r\n          <\/div>\r\n        <\/figure>\r\n      <\/section>\r\n\r\n      <section id=\"effects-of-high-grounding-resistance\">\r\n        <h2><span class=\"ez-toc-section\" id=\"what-happens-when-grounding-resistance-or-path-impedance-is-too-high\"><\/span>What Happens When Grounding Resistance or Path Impedance Is Too High?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <div class=\"gr-table-wrap\">\r\n          <table>\r\n            <thead>\r\n              <tr>\r\n                <th style=\"width:23%;\">Potential Problem<\/th>\r\n                <th style=\"width:35%;\">What Happens During a Surge<\/th>\r\n                <th style=\"width:42%;\">Possible Project Consequence<\/th>\r\n              <\/tr>\r\n            <\/thead>\r\n\r\n            <tbody>\r\n              <tr>\r\n                <td data-label=\"Potential Problem\">\r\n                  <strong>Higher path voltage<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"What Happens\">\r\n                  Surge current passing through resistance and inductance creates\r\n                  additional transient voltage along the current path.\r\n                <\/td>\r\n\r\n                <td data-label=\"Project Consequence\">\r\n                  Equipment may experience a voltage higher than the SPD\u2019s declared\r\n                  Up alone would suggest.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Potential Problem\">\r\n                  <strong>Ground-potential rise<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"What Happens\">\r\n                  Current entering an earth-termination system raises its local\r\n                  potential relative to other reference points.\r\n                <\/td>\r\n\r\n                <td data-label=\"Project Consequence\">\r\n                  Current may flow through data cables, screens, pipes or another\r\n                  structure\u2019s grounding network.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Potential Problem\">\r\n                  <strong>Different equipment references<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"What Happens\">\r\n                  The SPD and protected equipment do not rise to the same transient\r\n                  potential at the same time.\r\n                <\/td>\r\n\r\n                <td data-label=\"Project Consequence\">\r\n                  Damaging voltage can appear across equipment terminals,\r\n                  communication ports or insulation.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Potential Problem\">\r\n                  <strong>Unintended current path<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"What Happens\">\r\n                  The surge uses a parallel path with lower transient impedance than\r\n                  the intended bonding route.\r\n                <\/td>\r\n\r\n                <td data-label=\"Project Consequence\">\r\n                  Cable shields, PLC I\/O, RS485, Ethernet or inverter communication\r\n                  ports may carry part of the current.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Potential Problem\">\r\n                  <strong>Protection coordination failure<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"What Happens\">\r\n                  Power and signal SPDs reference different earth or bonding points.\r\n                <\/td>\r\n\r\n                <td data-label=\"Project Consequence\">\r\n                  Different circuits connected to the same device can be clamped to\r\n                  different transient potentials.\r\n                <\/td>\r\n              <\/tr>\r\n            <\/tbody>\r\n          <\/table>\r\n        <\/div>\r\n\r\n        <div class=\"gr-warning\">\r\n          <span class=\"gr-warning-title\">\r\n            Poor grounding does not necessarily slow the MOV or GDT\r\n          <\/span>\r\n\r\n          <p>\r\n            The main problem is normally not slower internal SPD operation. The\r\n            problem is additional voltage outside the SPD, along the conductors and\r\n            between different grounding references.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"resistance-vs-surge-impedance\">\r\n        <h2><span class=\"ez-toc-section\" id=\"grounding-resistance-vs-surge-path-impedance\"><\/span>Grounding Resistance vs Surge-Path Impedance<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          A normal earth-resistance test provides useful information about the\r\n          earth-electrode system under the selected test conditions. Lightning and\r\n          surge currents, however, can rise very quickly. During these transient\r\n          events, conductor inductance, bends, loops, spacing and bonding geometry\r\n          can become major parts of the current-path impedance.\r\n        <\/p>\r\n\r\n        <div\r\n          class=\"gr-equation\"\r\n          aria-label=\"Conceptual effective equipment voltage equation\"\r\n        >\r\n          <span class=\"gr-equation-main\">\r\n            U<sub>effective<\/sub> \u2248 U<sub>p<\/sub> +\r\n            \u0394U<sub>connection<\/sub> + \u0394U<sub>bonding<\/sub>\r\n          <\/span>\r\n\r\n          <span class=\"gr-equation-caption\">\r\n            Up is the SPD voltage-protection level under its specified test conditions.\r\n            The installed result can also include voltage along the connection path\r\n            and transient potential difference between the SPD and equipment references.\r\n          <\/span>\r\n        <\/div>\r\n\r\n        <div\r\n          class=\"gr-equation\"\r\n          aria-label=\"Simplified conductor transient voltage equation\"\r\n        >\r\n          <span class=\"gr-equation-main\">\r\n            \u0394U \u2248 I \u00d7 R + L \u00d7 di\/dt\r\n          <\/span>\r\n\r\n          <span class=\"gr-equation-caption\">\r\n            The equation is a simplified engineering explanation. Fast current rise\r\n            makes the inductive term important, which is why short and direct SPD\r\n            connections remain necessary even when DC continuity is satisfactory.\r\n          <\/span>\r\n        <\/div>\r\n\r\n        <div class=\"gr-success\">\r\n          <span class=\"gr-success-title\">Practical project objective<\/span>\r\n\r\n          <p>\r\n            Keep the surge-current loop compact, use the intended equipotential\r\n            bonding point, avoid uncoordinated reference systems and protect all\r\n            conductive services entering the protected zone.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"required-grounding-resistance\">\r\n        <h2><span class=\"ez-toc-section\" id=\"does-an-spd-require-1%ce%a9-5%ce%a9-or-10%ce%a9-grounding-resistance\"><\/span>Does an SPD Require 1\u03a9, 5\u03a9 or 10\u03a9 Grounding Resistance?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          <strong>\r\n            There is no universal SPD-only resistance limit that applies to every\r\n            installation.\r\n          <\/strong>\r\n          A numerical requirement may come from a national electrical code,\r\n          lightning-protection design, utility rule, telecom operator specification,\r\n          project owner, insurer or equipment manufacturer.\r\n        <\/p>\r\n\r\n        <p>\r\n          The measured result must therefore be compared with a clearly identified\r\n          governing document\u2014not copied from a generic online article.\r\n        <\/p>\r\n\r\n        <div class=\"gr-table-wrap\">\r\n          <table>\r\n            <thead>\r\n              <tr>\r\n                <th style=\"width:24%;\">Project Situation<\/th>\r\n                <th style=\"width:34%;\">How to Treat the Ohm Value<\/th>\r\n                <th style=\"width:42%;\">What Must Also Be Verified<\/th>\r\n              <\/tr>\r\n            <\/thead>\r\n\r\n            <tbody>\r\n              <tr>\r\n                <td data-label=\"Project Situation\">\r\n                  <strong>General LV building<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Ohm Value\">\r\n                  Follow local electrical-safety and earthing requirements. Do not\r\n                  invent a separate SPD limit without a defined basis.\r\n                <\/td>\r\n\r\n                <td data-label=\"Also Verify\">\r\n                  Main earthing terminal, PE continuity, bonding, SPD location,\r\n                  protection mode and conductor routing.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Project Situation\">\r\n                  <strong>Free-field PV plant<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Ohm Value\">\r\n                  Use the project\u2019s PV and lightning-protection design, including its\r\n                  specified earth-grid acceptance criteria.\r\n                <\/td>\r\n\r\n                <td data-label=\"Also Verify\">\r\n                  Meshed earth network, interconnected structures, inverter stations,\r\n                  cable routes, corrosion and seasonal conditions.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Project Situation\">\r\n                  <strong>Telecom or tower site<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Ohm Value\">\r\n                  Use the operator\u2019s earthing specification and the site\r\n                  lightning-protection design.\r\n                <\/td>\r\n\r\n                <td data-label=\"Also Verify\">\r\n                  Tower, cabinet, AC SPD, DC SPD, data SPD, antenna feeder, screens\r\n                  and common earth bar.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Project Situation\">\r\n                  <strong>Critical facility<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Ohm Value\">\r\n                  Treat the value as a complete system-design requirement, not a\r\n                  universal SPD product parameter.\r\n                <\/td>\r\n\r\n                <td data-label=\"Also Verify\">\r\n                  Earth-grid geometry, touch and step voltage, fault current and\r\n                  protection coordination.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Project Situation\">\r\n                  <strong>OEM distribution board<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Ohm Value\">\r\n                  The panel builder cannot determine final site earth resistance from\r\n                  the SPD model or panel drawing alone.\r\n                <\/td>\r\n\r\n                <td data-label=\"Also Verify\">\r\n                  Correct PE terminals, conductor requirements, installation diagram\r\n                  and site commissioning instructions.\r\n                <\/td>\r\n              <\/tr>\r\n            <\/tbody>\r\n          <\/table>\r\n        <\/div>\r\n\r\n        <div class=\"gr-note\">\r\n          <span class=\"gr-note-title\">A low reading is not a complete acceptance test<\/span>\r\n\r\n          <p>\r\n            A site may show a satisfactory electrode result while the SPD is connected\r\n            through a long conductor, corroded joint or separate reference from the\r\n            protected equipment. The complete path must be inspected.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"how-to-measure-spd-grounding-resistance\">\r\n        <h2><span class=\"ez-toc-section\" id=\"how-should-spd-grounding-resistance-be-measured\"><\/span>How Should SPD Grounding Resistance Be Measured?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          There is no special instrument that measures a universal \u201cSPD grounding\r\n          resistance.\u201d The test method depends on whether the engineer needs to assess\r\n          an earth electrode, one branch of a parallel grounding network, a complete\r\n          ground loop or only the continuity of the local PE conductor.\r\n        <\/p>\r\n\r\n        <div class=\"gr-table-wrap\">\r\n          <table>\r\n            <thead>\r\n              <tr>\r\n                <th style=\"width:22%;\">Test Method<\/th>\r\n                <th style=\"width:27%;\">Typical Use<\/th>\r\n                <th style=\"width:26%;\">Main Limitation<\/th>\r\n                <th style=\"width:25%;\">What the Buyer Should Request<\/th>\r\n              <\/tr>\r\n            <\/thead>\r\n\r\n            <tbody>\r\n              <tr>\r\n                <td data-label=\"Test Method\">\r\n                  <strong>3-point fall-of-potential<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Typical Use\">\r\n                  Testing an earth electrode or electrode system using separate\r\n                  current and potential test stakes.\r\n                <\/td>\r\n\r\n                <td data-label=\"Main Limitation\">\r\n                  Requires sufficient test distance and suitable soil access.\r\n                  Parallel paths may need to be considered or isolated.\r\n                <\/td>\r\n\r\n                <td data-label=\"Buyer Request\">\r\n                  Electrode tested, probe positions, test curve or validation points,\r\n                  measured result and site conditions.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Test Method\">\r\n                  <strong>Selective earth test<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Typical Use\">\r\n                  Measuring one section of a parallel grounding system using test\r\n                  stakes plus a current clamp.\r\n                <\/td>\r\n\r\n                <td data-label=\"Main Limitation\">\r\n                  The tester must understand the parallel network and place the clamp\r\n                  on the correct conductor.\r\n                <\/td>\r\n\r\n                <td data-label=\"Buyer Request\">\r\n                  Branch measured, network diagram, clamp position, test-stake layout\r\n                  and result.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Test Method\">\r\n                  <strong>Clamp-on or stakeless test<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Typical Use\">\r\n                  Quick testing where multiple grounding paths create a complete\r\n                  conductive loop.\r\n                <\/td>\r\n\r\n                <td data-label=\"Main Limitation\">\r\n                  It is not suitable for every isolated single electrode because a\r\n                  valid return loop is required.\r\n                <\/td>\r\n\r\n                <td data-label=\"Buyer Request\">\r\n                  Confirmation that a closed parallel loop exists and an explanation\r\n                  of what resistance the instrument measured.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Test Method\">\r\n                  <strong>PE continuity test<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Typical Use\">\r\n                  Checking whether the SPD earth terminal is continuously connected\r\n                  to the PE bar or main bonding point.\r\n                <\/td>\r\n\r\n                <td data-label=\"Main Limitation\">\r\n                  Does not measure earth-electrode resistance or prove low\r\n                  high-frequency impedance.\r\n                <\/td>\r\n\r\n                <td data-label=\"Buyer Request\">\r\n                  Test points, conductor identification, measured continuity and\r\n                  inspection of terminals and joints.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Test Method\">\r\n                  <strong>Visual and torque inspection<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Typical Use\">\r\n                  Detecting loose terminals, corrosion, broken conductors, sharp loops\r\n                  and incorrect reference connections.\r\n                <\/td>\r\n\r\n                <td data-label=\"Main Limitation\">\r\n                  Cannot replace an electrical measurement.\r\n                <\/td>\r\n\r\n                <td data-label=\"Buyer Request\">\r\n                  Photographs, conductor size, route, terminal condition and\r\n                  commissioning record.\r\n                <\/td>\r\n              <\/tr>\r\n            <\/tbody>\r\n          <\/table>\r\n        <\/div>\r\n\r\n        <h3>Minimum Measurement Record for an EPC or Maintenance Team<\/h3>\r\n\r\n        <ul class=\"gr-checklist\">\r\n          <li>Exact electrode, grid or conductor tested<\/li>\r\n          <li>Instrument model and calibration status<\/li>\r\n          <li>Test method used<\/li>\r\n          <li>Probe or clamp positions<\/li>\r\n          <li>Measured value and unit<\/li>\r\n          <li>Whether parallel paths were connected<\/li>\r\n          <li>Soil and weather condition<\/li>\r\n          <li>Test date and seasonal condition<\/li>\r\n          <li>Applicable acceptance limit<\/li>\r\n          <li>Name or role of the qualified tester<\/li>\r\n          <li>Photographs of the connection points<\/li>\r\n          <li>Corrective action and retest result<\/li>\r\n        <\/ul>\r\n\r\n        <div class=\"gr-danger\">\r\n          <span class=\"gr-danger-title\">\r\n            Do not use a multimeter reading as proof of earth-electrode performance\r\n          <\/span>\r\n\r\n          <p>\r\n            A multimeter can help identify an open or obviously poor connection, but\r\n            it cannot replace an appropriate earth tester or demonstrate the complete\r\n            transient impedance of the SPD current path.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"what-to-do-if-grounding-resistance-is-high\">\r\n        <h2><span class=\"ez-toc-section\" id=\"what-should-be-done-if-grounding-resistance-is-too-high\"><\/span>What Should Be Done If Grounding Resistance Is Too High?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          Corrective action should address the cause of the result and the complete\r\n          protection system. Replacing the SPD with a higher-kA model does not repair\r\n          a poor earth or bonding network.\r\n        <\/p>\r\n\r\n        <ol class=\"gr-action-list\">\r\n          <li data-number=\"1\">\r\n            <strong>Verify the measurement<\/strong>\r\n            Confirm that the method is suitable for the electrode configuration and\r\n            that parallel paths, probe spacing and seasonal conditions were considered.\r\n          <\/li>\r\n\r\n          <li data-number=\"2\">\r\n            <strong>Inspect accessible connections<\/strong>\r\n            Check clamps, lugs, bars, buried joint access points and conductors for\r\n            looseness, corrosion, breakage, moisture or mechanical damage.\r\n          <\/li>\r\n\r\n          <li data-number=\"3\">\r\n            <strong>Repair defective joints<\/strong>\r\n            Restore the designed conductive path using suitable materials, connection\r\n            methods and corrosion protection.\r\n          <\/li>\r\n\r\n          <li data-number=\"4\">\r\n            <strong>Review the electrode design<\/strong>\r\n            A qualified engineer may need to modify electrode depth, spacing,\r\n            quantity, ring conductors or the site earth-grid design.\r\n          <\/li>\r\n\r\n          <li data-number=\"5\">\r\n            <strong>Interconnect systems where required<\/strong>\r\n            Avoid adding an unbonded SPD-only earth rod. Separate structures and\r\n            services must be coordinated according to the project design.\r\n          <\/li>\r\n\r\n          <li data-number=\"6\">\r\n            <strong>Improve local SPD connections<\/strong>\r\n            Keep connections to live conductors and the PE or bonding bar short,\r\n            direct and free from unnecessary loops.\r\n          <\/li>\r\n\r\n          <li data-number=\"7\">\r\n            <strong>Coordinate power and signal protection<\/strong>\r\n            Check AC, DC, RS485, Ethernet, coaxial, shields and metal services so that\r\n            one unprotected path does not bridge two transient potentials.\r\n          <\/li>\r\n\r\n          <li data-number=\"8\">\r\n            <strong>Retest and document<\/strong>\r\n            Record the corrective action, repeat the appropriate test and update the\r\n            as-built drawing and maintenance file.\r\n          <\/li>\r\n        <\/ol>\r\n\r\n        <div class=\"gr-warning\">\r\n          <span class=\"gr-warning-title\">\r\n            Do not add a separate earth rod only for the SPD without engineering review\r\n          <\/span>\r\n\r\n          <p>\r\n            An uncoordinated isolated electrode can create a dangerous transient\r\n            voltage difference between the SPD, the equipment PE and communication\r\n            systems. A low value at one isolated rod does not guarantee safe\r\n            equipotential protection.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"earthing-system-assessment\">\r\n        <h2><span class=\"ez-toc-section\" id=\"how-earthing-system-type-changes-the-spd-assessment\"><\/span>How Earthing-System Type Changes the SPD Assessment<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <div class=\"gr-table-wrap\">\r\n          <table>\r\n            <thead>\r\n              <tr>\r\n                <th style=\"width:17%;\">System<\/th>\r\n                <th style=\"width:29%;\">Relevant SPD Path<\/th>\r\n                <th style=\"width:54%;\">Grounding and Bonding Check<\/th>\r\n              <\/tr>\r\n            <\/thead>\r\n\r\n            <tbody>\r\n              <tr>\r\n                <td data-label=\"System\"><strong>TN-S<\/strong><\/td>\r\n\r\n                <td data-label=\"Relevant SPD Path\">\r\n                  L\u2013PE, N\u2013PE or L\u2013N paths depending on the SPD topology.\r\n                <\/td>\r\n\r\n                <td data-label=\"Grounding Check\">\r\n                  Confirm that the SPD connects to the panel PE bar and common\r\n                  metallic PE network through a short and direct path. The local\r\n                  electrode result alone may not describe this path.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"System\"><strong>TT<\/strong><\/td>\r\n\r\n                <td data-label=\"Relevant SPD Path\">\r\n                  Commonly L\u2013N protection plus a coordinated N\u2013PE path in a 1+1\r\n                  or 3+1 arrangement.\r\n                <\/td>\r\n\r\n                <td data-label=\"Grounding Check\">\r\n                  Confirm the installation earth electrode, RCD arrangement,\r\n                  N\u2013PE protection mode and local requirements. Do not create an\r\n                  unauthorised downstream N\u2013PE bond.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"System\"><strong>TN-C-S<\/strong><\/td>\r\n\r\n                <td data-label=\"Relevant SPD Path\">\r\n                  Depends on whether the SPD is positioned before or after PEN\r\n                  separation.\r\n                <\/td>\r\n\r\n                <td data-label=\"Grounding Check\">\r\n                  Identify the PEN split point. Downstream N and PE must be treated\r\n                  according to the installation design and local rules.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"System\"><strong>TN-C<\/strong><\/td>\r\n\r\n                <td data-label=\"Relevant SPD Path\">\r\n                  Phase conductors may be protected to PEN at the applicable point.\r\n                <\/td>\r\n\r\n                <td data-label=\"Grounding Check\">\r\n                  Confirm the permitted installation position and conductor\r\n                  arrangement. Do not assume that separate N and PE exist at that point.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"System\"><strong>IT<\/strong><\/td>\r\n\r\n                <td data-label=\"Relevant SPD Path\">\r\n                  Project-specific phase-to-earth or pole-to-earth arrangement.\r\n                <\/td>\r\n\r\n                <td data-label=\"Grounding Check\">\r\n                  Confirm system voltage to earth, first-fault behaviour, insulation\r\n                  monitoring, equipment requirements and suitable SPD Uc.\r\n                <\/td>\r\n              <\/tr>\r\n            <\/tbody>\r\n          <\/table>\r\n        <\/div>\r\n\r\n        <p>\r\n          For additional topology guidance, review the\r\n          <a\r\n            href=\"https:\/\/www.cnspd.com\/three-phase-spd-wiring-diagram\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n          >\r\n            Three-Phase SPD Wiring Diagram Guide\r\n          <\/a>\r\n          and the\r\n          <a\r\n            href=\"https:\/\/www.cnspd.com\/3pn-spd-vs-4p-spd\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n          >\r\n            3P+N SPD vs 4P SPD Guide\r\n          <\/a>.\r\n        <\/p>\r\n      <\/section>\r\n\r\n      <section id=\"project-applications\">\r\n        <h2><span class=\"ez-toc-section\" id=\"grounding-checks-for-solar-telecom-and-industrial-projects\"><\/span>Grounding Checks for Solar, Telecom and Industrial Projects<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <div class=\"gr-grid gr-grid-3\">\r\n          <div class=\"gr-card\">\r\n            <span class=\"gr-card-number\">1<\/span>\r\n            <h3>Solar PV Systems<\/h3>\r\n\r\n            <ul>\r\n              <li>Confirm whether an external lightning-protection system exists.<\/li>\r\n              <li>Check module-frame and mounting-rail bonding.<\/li>\r\n              <li>Identify array, inverter and building earth networks.<\/li>\r\n              <li>Review DC, AC and communication cable entry points.<\/li>\r\n              <li>Check corrosion and seasonal soil variation.<\/li>\r\n              <li>Confirm whether separate structures are correctly interconnected.<\/li>\r\n            <\/ul>\r\n          <\/div>\r\n\r\n          <div class=\"gr-card\">\r\n            <span class=\"gr-card-number\">2<\/span>\r\n            <h3>Telecom and Base Stations<\/h3>\r\n\r\n            <ul>\r\n              <li>Coordinate AC, \u221248V DC, data and antenna-line protection.<\/li>\r\n              <li>Inspect tower, cabinet and feeder-screen bonding.<\/li>\r\n              <li>Connect power and signal SPDs to the intended reference.<\/li>\r\n              <li>Check external joints for corrosion and water ingress.<\/li>\r\n              <li>Review separate indoor and outdoor bonding levels.<\/li>\r\n              <li>Follow the telecom operator\u2019s earthing specification.<\/li>\r\n            <\/ul>\r\n          <\/div>\r\n\r\n          <div class=\"gr-card\">\r\n            <span class=\"gr-card-number\">3<\/span>\r\n            <h3>Industrial and Outdoor Cabinets<\/h3>\r\n\r\n            <ul>\r\n              <li>Check incoming power and field-signal cable routes.<\/li>\r\n              <li>Bond enclosures, doors and gland plates where required.<\/li>\r\n              <li>Separate protected and unprotected conductors.<\/li>\r\n              <li>Review PLC, VFD, RS485 and Ethernet interfaces.<\/li>\r\n              <li>Inspect terminal torque, lugs and conductor routing.<\/li>\r\n              <li>Identify nearby structures using another earth reference.<\/li>\r\n            <\/ul>\r\n          <\/div>\r\n        <\/div>\r\n\r\n        <div class=\"gr-note\">\r\n          <span class=\"gr-note-title\">Remote-site risk<\/span>\r\n\r\n          <p>\r\n            When two buildings, PV arrays, cabinets or field instruments are connected\r\n            by copper cables but use separated earth networks, lightning can create a\r\n            large potential difference between them. Power and signal protection must\r\n            be coordinated at the relevant zone boundaries.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"site-information-before-ordering\">\r\n        <h2><span class=\"ez-toc-section\" id=\"information-buyers-should-provide-before-ordering-an-spd\"><\/span>Information Buyers Should Provide Before Ordering an SPD<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          An SPD supplier cannot determine the complete grounding design from system\r\n          voltage and kA rating alone. EPCs, panel builders and project buyers should\r\n          provide the site information below before final product confirmation.\r\n        <\/p>\r\n\r\n        <figure class=\"gr-figure\">\r\n          <img loading=\"lazy\"\r\n            class=\"gr-figure-image\"\r\n            src=\"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/spd-grounding-site-oem-selection-checklist.webp\"\r\n            alt=\"SPD grounding site information and OEM ordering checklist for engineering projects\"\r\n            width=\"1600\"\r\n            height=\"1000\"\r\n            loading=\"lazy\"\r\n            decoding=\"async\"\r\n          >\r\n\r\n          <div class=\"gr-figure-content\">\r\n            <span class=\"gr-figure-title\">\r\n              SPD grounding and site-information checklist for project confirmation\r\n            <\/span>\r\n\r\n            <figcaption>\r\n              Confirm the earthing system, measurement record, SPD position, bonding\r\n              path, incoming conductive services and required product parameters before\r\n              the supplier finalises the configuration.\r\n            <\/figcaption>\r\n          <\/div>\r\n        <\/figure>\r\n\r\n        <ul class=\"gr-checklist\">\r\n          <li>Country and applicable project standard<\/li>\r\n          <li>System voltage and frequency<\/li>\r\n          <li>AC, DC, signal or combined protection requirement<\/li>\r\n          <li>TN-S, TT, TN-C-S, TN-C or IT system<\/li>\r\n          <li>Single-line diagram showing N, PE and PEN<\/li>\r\n          <li>SPD installation position<\/li>\r\n          <li>Main board, sub-board, combiner box or control cabinet<\/li>\r\n          <li>External lightning-protection system: yes or no<\/li>\r\n          <li>Overhead or underground incoming supply<\/li>\r\n          <li>Measured earth resistance and test method<\/li>\r\n          <li>Measurement date and seasonal condition<\/li>\r\n          <li>Number and location of electrodes or grids<\/li>\r\n          <li>Whether structures use separate earth networks<\/li>\r\n          <li>Distance between SPD and protected equipment<\/li>\r\n          <li>Distance from SPD to PE or bonding bar<\/li>\r\n          <li>Required Type 1, Type 1+2 or Type 2<\/li>\r\n          <li>Required Uc, Ucpv, Up, In, Imax and Iimp<\/li>\r\n          <li>RCD and backup-protection arrangement<\/li>\r\n          <li>Power and communication cable entry points<\/li>\r\n          <li>Remote signal-contact requirement<\/li>\r\n          <li>Required certificates and documentation<\/li>\r\n          <li>OEM label, colour and packaging requirement<\/li>\r\n        <\/ul>\r\n\r\n        <div class=\"gr-success\">\r\n          <span class=\"gr-success-title\">Recommended B2B inquiry format<\/span>\r\n\r\n          <p>\r\n            \u201cWe need an SPD for a 400V three-phase outdoor distribution cabinet.\r\n            Earthing system: TT. The measured earth resistance is 12\u03a9 using the\r\n            fall-of-potential method. The site has an external LPS and an RCD.\r\n            The SPD-to-PE-bar connection is approximately 300mm. Please confirm\r\n            the suitable Type 1+2 configuration, N\u2013PE protection mode, Uc, Iimp,\r\n            backup protection and wiring diagram.\u201d\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"common-grounding-mistakes\">\r\n        <h2><span class=\"ez-toc-section\" id=\"common-spd-grounding-mistakes\"><\/span>Common SPD Grounding Mistakes<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <div class=\"gr-table-wrap\">\r\n          <table>\r\n            <thead>\r\n              <tr>\r\n                <th style=\"width:30%;\">Mistake<\/th>\r\n                <th style=\"width:34%;\">Why It Is Risky<\/th>\r\n                <th style=\"width:36%;\">Better Approach<\/th>\r\n              <\/tr>\r\n            <\/thead>\r\n\r\n            <tbody>\r\n              <tr>\r\n                <td data-label=\"Mistake\">\r\n                  <strong>Using an isolated earth rod only for the SPD<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Why It Is Risky\">\r\n                  It can create a large voltage difference between the SPD,\r\n                  equipment PE and other conductive services.\r\n                <\/td>\r\n\r\n                <td data-label=\"Better Approach\">\r\n                  Use the project\u2019s coordinated earthing and bonding design unless\r\n                  a qualified design explicitly requires another arrangement.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Mistake\">\r\n                  <strong>Accepting the site from one ohm reading<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Why It Is Risky\">\r\n                  The reading does not reveal long conductors, poor geometry,\r\n                  reference separation or unprotected services.\r\n                <\/td>\r\n\r\n                <td data-label=\"Better Approach\">\r\n                  Combine measurement, drawing review, visual inspection and\r\n                  current-path verification.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Mistake\">\r\n                  <strong>Increasing the SPD kA rating to compensate<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Why It Is Risky\">\r\n                  Higher Imax or Iimp does not remove voltage developed along a poor\r\n                  connection or isolated bonding network.\r\n                <\/td>\r\n\r\n                <td data-label=\"Better Approach\">\r\n                  Correct the grounding and bonding system, then select the SPD for\r\n                  the actual exposure and installation point.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Mistake\">\r\n                  <strong>Daisy-chaining multiple SPD earth connections<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Why It Is Risky\">\r\n                  Shared connection length can add impedance and allow one SPD current\r\n                  to affect another circuit.\r\n                <\/td>\r\n\r\n                <td data-label=\"Better Approach\">\r\n                  Connect each SPD to the intended common bonding point using the\r\n                  project-approved arrangement.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Mistake\">\r\n                  <strong>Ignoring communication lines<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Why It Is Risky\">\r\n                  Data cables can become the current path between equipment at\r\n                  different transient potentials.\r\n                <\/td>\r\n\r\n                <td data-label=\"Better Approach\">\r\n                  Coordinate power and signal SPDs at the same protection-zone\r\n                  boundary and bonding reference.\r\n                <\/td>\r\n              <\/tr>\r\n\r\n              <tr>\r\n                <td data-label=\"Mistake\">\r\n                  <strong>Calling every value above 10\u03a9 an SPD failure<\/strong>\r\n                <\/td>\r\n\r\n                <td data-label=\"Why It Is Risky\">\r\n                  It applies a generic number without considering the governing\r\n                  standard, earthing system or complete current path.\r\n                <\/td>\r\n\r\n                <td data-label=\"Better Approach\">\r\n                  Compare the result with the project requirement and inspect the\r\n                  full transient-protection system.\r\n                <\/td>\r\n              <\/tr>\r\n            <\/tbody>\r\n          <\/table>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"grounding-resistance-vs-05m-rule\">\r\n        <h2><span class=\"ez-toc-section\" id=\"how-is-this-different-from-the-spd-05m-connection-length-rule\"><\/span>How Is This Different from the SPD 0.5m Connection-Length Rule?<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <div class=\"gr-grid gr-grid-2\">\r\n          <div class=\"gr-card\">\r\n            <h3>0.5m Connection-Length Topic<\/h3>\r\n\r\n            <p>\r\n              Focuses on the local conductors between the supply, SPD and PE or\r\n              bonding point inside the distribution board.\r\n            <\/p>\r\n\r\n            <p>\r\n              Its main concern is the additional inductive voltage caused by\r\n              unnecessarily long SPD connection leads.\r\n            <\/p>\r\n          <\/div>\r\n\r\n          <div class=\"gr-card\">\r\n            <h3>Grounding-Resistance Topic<\/h3>\r\n\r\n            <p>\r\n              Focuses on the wider PE, bonding, earth-electrode and site grounding\r\n              network beyond the SPD terminals.\r\n            <\/p>\r\n\r\n            <p>\r\n              Its main concern is whether the SPD and protected equipment share a\r\n              coordinated reference and complete surge-current path.\r\n            <\/p>\r\n          <\/div>\r\n        <\/div>\r\n\r\n        <div class=\"gr-note\">\r\n          <span class=\"gr-note-title\">Both conditions must be checked<\/span>\r\n\r\n          <p>\r\n            A short SPD lead cannot repair a badly separated grounding network.\r\n            A low electrode-resistance reading cannot cancel voltage added by an\r\n            unnecessarily long SPD connection.\r\n          <\/p>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section id=\"spd-grounding-faq\">\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=\"gr-faq\">\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Does an SPD work if the grounding resistance is high?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  The SPD may still conduct, but the installation may not achieve the\r\n                  expected protection level. Resistance and transient impedance can\r\n                  create additional voltage outside the SPD.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Can an SPD work without a ground connection?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  Some line-to-neutral protection modes may limit differential voltage,\r\n                  but protection modes using PE or earth will not have the required\r\n                  path. An installation without the required PE connection should not\r\n                  be considered fully or safely protected.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Is 10\u03a9 mandatory for every SPD installation?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  No. A 10\u03a9 value may appear in a particular project or grounding\r\n                  specification, but it is not a universal SPD-only requirement for\r\n                  every country and installation.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Is lower grounding resistance always better?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  A lower electrode resistance is generally beneficial, but it does\r\n                  not replace correct bonding, short conductors, suitable geometry\r\n                  and coordinated SPD placement.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>What is the best method for measuring earth resistance?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  There is no single best method for every site. The fall-of-potential\r\n                  method is widely used for electrode testing, while selective and\r\n                  clamp-on methods can be useful where parallel paths exist. The\r\n                  tester must choose a method suitable for the actual grounding network.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Can a clamp meter test an isolated earth rod?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  A clamp-on earth tester normally requires a complete conductive\r\n                  return loop. It may not provide a valid result for a single isolated\r\n                  electrode without another parallel grounding path.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Can an SPD use a separate dedicated earth rod?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  A separate unbonded earth rod can create dangerous potential\r\n                  differences. The SPD should normally be integrated into the\r\n                  coordinated earthing and equipotential-bonding design.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Does a higher-kA SPD solve poor grounding?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  No. A higher discharge-current rating does not remove voltage created\r\n                  by poor conductor routing, corroded joints, separated references or\r\n                  an inadequate earth network.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>Why can equipment fail while the SPD indicator is green?<\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  A green indicator normally shows that the SPD module has not reached\r\n                  its internal end-of-life condition. It does not confirm correct\r\n                  grounding, conductor length, bonding or protection coordination.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n\r\n          <div class=\"gr-faq-item\">\r\n            <details>\r\n              <summary>\r\n                What grounding information should an EPC send to the SPD supplier?\r\n              <\/summary>\r\n\r\n              <div class=\"gr-faq-answer\">\r\n                <p>\r\n                  Send the earthing-system type, single-line diagram, measured\r\n                  resistance, test method, external LPS information, SPD position,\r\n                  distances to the PE bar and equipment, incoming cable routes and\r\n                  applicable project specification.\r\n                <\/p>\r\n              <\/div>\r\n            <\/details>\r\n          <\/div>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section class=\"gr-cta\" aria-label=\"SPD project consultation\">\r\n        <h2><span class=\"ez-toc-section\" id=\"confirm-the-spd-and-grounding-path-before-bulk-ordering\"><\/span>Confirm the SPD and Grounding Path Before Bulk Ordering<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <p>\r\n          Send LEEYEE your single-line diagram, earthing-system type, site test\r\n          record, SPD installation position and project requirements. We will help\r\n          confirm the appropriate AC, DC or signal SPD configuration for your panel,\r\n          solar, telecom or industrial project.\r\n        <\/p>\r\n\r\n        <div class=\"gr-btn-row\">\r\n          <a\r\n            href=\"javascript:void(0);\"\r\n            class=\"gr-btn leeyee-site-popup-btn\"\r\n            aria-label=\"Request an SPD project review\"\r\n          >\r\n            <span>Request Project Review<\/span>\r\n          <\/a>\r\n\r\n          <a\r\n            href=\"https:\/\/www.cnspd.com\/contact\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n            class=\"gr-btn gr-btn-secondary\"\r\n          >\r\n            <span>Send Project Details<\/span>\r\n          <\/a>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section class=\"gr-related\">\r\n        <h2><span class=\"ez-toc-section\" id=\"related-technical-guides\"><\/span>Related Technical Guides<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <div class=\"gr-related-grid\">\r\n          <a\r\n            class=\"gr-related-link\"\r\n            href=\"https:\/\/www.cnspd.com\/three-phase-spd-wiring-diagram\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n          >\r\n            Three-Phase SPD Wiring Diagram Guide\r\n          <\/a>\r\n\r\n          <a\r\n            class=\"gr-related-link\"\r\n            href=\"https:\/\/www.cnspd.com\/3pn-spd-vs-4p-spd\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n          >\r\n            3P+N SPD vs 4P SPD Selection Guide\r\n          <\/a>\r\n\r\n          <a\r\n            class=\"gr-related-link\"\r\n            href=\"https:\/\/www.cnspd.com\/type-2-spd\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n          >\r\n            Type 2 SPD Selection Guide\r\n          <\/a>\r\n\r\n          <a\r\n            class=\"gr-related-link\"\r\n            href=\"https:\/\/www.cnspd.com\/solar-pv-surge-protection\/\"\r\n            target=\"_blank\"\r\n            rel=\"noopener\"\r\n          >\r\n            Solar PV Surge Protection\r\n          <\/a>\r\n        <\/div>\r\n      <\/section>\r\n\r\n      <section class=\"gr-references\">\r\n        <h2><span class=\"ez-toc-section\" id=\"authoritative-references\"><\/span>Authoritative References<span class=\"ez-toc-section-end\"><\/span><\/h2>\r\n\r\n        <ol>\r\n          <li>\r\n            DEHN,\r\n            <a\r\n              href=\"https:\/\/www.dehn-international.com\/en\/faq-power-supply-systems-redliner\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              FAQ Power Supply Systems\r\n            <\/a>.\r\n            Explains that no single earth-resistance value is required specifically\r\n            for every SPD installation and highlights equipotential bonding.\r\n          <\/li>\r\n\r\n          <li>\r\n            NEMA Surge Protection Institute,\r\n            <a\r\n              href=\"https:\/\/www.nemasurge.org\/grounding\/\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              Grounding and Bonding\r\n            <\/a>.\r\n            Discusses low-resistance and low-impedance paths, short direct SPD\r\n            grounding leads and conductor self-inductance.\r\n          <\/li>\r\n\r\n          <li>\r\n            DEHN,\r\n            <a\r\n              href=\"https:\/\/www.dehn-international.com\/en\/knowledge\/basic-knowledge\/lightning-protection-system\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              Lightning Protection Systems and Equipotential Bonding\r\n            <\/a>.\r\n            Explains the use of lightning equipotential bonding to reduce potential\r\n            differences caused by lightning current.\r\n          <\/li>\r\n\r\n          <li>\r\n            Fluke,\r\n            <a\r\n              href=\"https:\/\/www.fluke.com\/en-us\/learn\/blog\/electrical\/dont-forget-the-grounding-system\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              Four Methods to Conduct Earth Ground Testing\r\n            <\/a>.\r\n            Introduces fall-of-potential, selective, stakeless and related earth-test\r\n            methods.\r\n          <\/li>\r\n\r\n          <li>\r\n            Fluke,\r\n            <a\r\n              href=\"https:\/\/www.fluke.com\/en-us\/learn\/blog\/grounding\/earth-ground-fall-potential\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              Fall-of-Potential Measurement\r\n            <\/a>.\r\n            Describes probe positioning and validation considerations for\r\n            fall-of-potential testing.\r\n          <\/li>\r\n\r\n          <li>\r\n            Megger,\r\n            <a\r\n              href=\"https:\/\/www.megger.com\/en-gb\/blog\/march-2020-%281%29\/clamp-confidently\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              Clamp-On Earth Testing\r\n            <\/a>.\r\n            Explains that clamp-on testing requires a complete conductive loop.\r\n          <\/li>\r\n\r\n          <li>\r\n            Megger,\r\n            <a\r\n              href=\"https:\/\/www.megger.com\/en-gb\/et-online\/november-2007\/a-guide-to-earth-testing\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              A Guide to Earth Testing\r\n            <\/a>.\r\n            Covers fall-of-potential electrode testing and periodic earth-system checks.\r\n          <\/li>\r\n\r\n          <li>\r\n            DEHN,\r\n            <a\r\n              href=\"https:\/\/www.dehn-international.com\/en\/master-lightning-and-surge-protection-free-field-systems-and-solar-parks\"\r\n              target=\"_blank\"\r\n              rel=\"noopener\"\r\n            >\r\n              Lightning and Surge Protection for Solar Parks\r\n            <\/a>.\r\n            Discusses local and remote equipotential surfaces in free-field PV systems.\r\n          <\/li>\r\n        <\/ol>\r\n      <\/section>\r\n\r\n      <div class=\"gr-disclaimer\">\r\n        This guide supports project communication, SPD selection and engineering\r\n        review. Final earthing, lightning-protection and electrical installation work\r\n        must comply with applicable national codes, project specifications,\r\n        manufacturer instructions and qualified engineering design. Measurements and\r\n        electrical work must be performed by authorised personnel using suitable\r\n        instruments and procedures.\r\n      <\/div>\r\n\r\n    <\/div>\r\n  <\/div>\r\n<\/article>\r\n\r\n<script>\r\ndocument.addEventListener('DOMContentLoaded', function () {\r\n  var popupButtons = document.querySelectorAll('.leeyee-site-popup-btn');\r\n\r\n  popupButtons.forEach(function (button) {\r\n    button.addEventListener('click', function (event) {\r\n      event.preventDefault();\r\n\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\": \"Article\",\r\n  \"headline\": \"SPD Grounding Resistance: Does High Earth Resistance Reduce Protection?\",\r\n  \"description\": \"Learn how grounding resistance, surge-path impedance and equipotential bonding affect SPD protection, how earth resistance is measured and what project buyers should confirm.\",\r\n  \"image\": [\r\n    \"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/spd-grounding-resistance-effective-protection-voltage.webp\",\r\n    \"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/spd-equipotential-bonding-vs-isolated-earth-rod.webp\",\r\n    \"https:\/\/www.cnspd.com\/wp-content\/uploads\/2026\/07\/spd-grounding-site-oem-selection-checklist.webp\"\r\n  ],\r\n  \"inLanguage\": \"en\",\r\n  \"author\": {\r\n    \"@type\": \"Organization\",\r\n    \"name\": \"LEEYEE\"\r\n  },\r\n  \"publisher\": {\r\n    \"@type\": \"Organization\",\r\n    \"name\": \"LEEYEE\",\r\n    \"url\": \"https:\/\/www.cnspd.com\/\"\r\n  },\r\n  \"mainEntityOfPage\": {\r\n    \"@type\": \"WebPage\",\r\n    \"@id\": \"https:\/\/www.cnspd.com\/spd-grounding-resistance\/\"\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\": \"Does an SPD work if the grounding resistance is high?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"The SPD may still conduct, but resistance and transient impedance can create additional voltage outside the SPD and reduce the installed equipment-protection result.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Can an SPD work without a ground connection?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"Some line-to-neutral protection modes may limit differential voltage, but protection modes that use PE or earth require the correct connection. An installation without the required PE path should not be considered fully protected.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Is 10 ohms mandatory for every SPD installation?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"No. A 10-ohm value may apply to a particular project or grounding specification, but there is no universal SPD-only resistance limit for every country and installation.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"What is the best method for measuring earth resistance?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"The suitable method depends on the grounding network. Fall-of-potential testing is widely used for electrodes, while selective or clamp-on testing may be used where valid parallel paths exist.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Can a clamp meter test an isolated earth rod?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"A clamp-on earth tester normally requires a complete conductive return loop, so it may not provide a valid measurement for a single isolated electrode without another parallel grounding path.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Can an SPD use a separate dedicated earth rod?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"A separate unbonded earth rod can create dangerous transient potential differences. The SPD should normally be integrated into the coordinated earthing and equipotential-bonding design.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Does a higher-kA SPD solve poor grounding?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"No. A higher discharge-current rating does not remove voltage caused by poor conductor routing, corroded joints, separated grounding references or an inadequate earth network.\"\r\n      }\r\n    },\r\n    {\r\n      \"@type\": \"Question\",\r\n      \"name\": \"Why can equipment fail while the SPD indicator is green?\",\r\n      \"acceptedAnswer\": {\r\n        \"@type\": \"Answer\",\r\n        \"text\": \"A green indicator normally shows that the SPD module has not reached its internal end-of-life condition. It does not confirm correct grounding, bonding, connection length or protection coordination.\"\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>SPD Engineering, Site Inspection and OEM Selection Guide A low earth-resistance reading is helpful, but it does not by itself prove that an SPD has an effective surge-current path. Engineers must also check PE continuity, transient impedance, equipotential bonding, earthing-system type and the relationship between the SPD and the protected equipment. Solar PV Telecom Sites&#8230;<\/p>","protected":false},"author":18,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,488,422],"tags":[],"class_list":["post-30077","post","type-post","status-publish","format-standard","hentry","category-news","category-surge-protection","category-industry-news"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>SPD Grounding Resistance: Limits, Testing &amp; Site Checks<\/title>\n<meta name=\"description\" content=\"Learn how grounding resistance, surge-path impedance and equipotential bonding affect SPD protection, how earth resistance is tested and what buyers must confirm.\" \/>\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\/it\/spd-grounding-resistance\/\" \/>\n<meta property=\"og:locale\" content=\"it_IT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"SPD Grounding Resistance: Limits, Testing &amp; Site Checks\" \/>\n<meta property=\"og:description\" content=\"Learn how grounding resistance, surge-path impedance and equipotential bonding affect SPD protection, how earth resistance is tested and what buyers must confirm.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.cnspd.com\/it\/spd-grounding-resistance\/\" \/>\n<meta property=\"og:site_name\" content=\"Surge Protector, Surge Arrestor, Isolating Switch - 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