{"id":1741,"date":"2026-07-21T01:33:45","date_gmt":"2026-07-20T17:33:45","guid":{"rendered":"https:\/\/jutrion.com\/?p=1741"},"modified":"2026-07-21T01:33:47","modified_gmt":"2026-07-20T17:33:47","slug":"%ec%84%9c%ec%a7%80-%eb%b3%b4%ed%98%b8-%ec%9e%a5%ec%b9%98-%ea%b0%80%ec%9d%b4%eb%93%9c","status":"publish","type":"post","link":"https:\/\/jutrion.com\/ko\/surge-protective-device-guide\/","title":{"rendered":"\uc11c\uc9c0 \ubcf4\ud638 \uc7a5\uce58(SPD)\ub780 \ubb34\uc5c7\uc778\uac00? \uc720\ud615, \uc791\ub3d9 \uc6d0\ub9ac \ubc0f \uc120\uc815\uc5d0 \ub300\ud55c \uc644\ubcbd \uac00\uc774\ub4dc"},"content":{"rendered":"<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-1\"><strong><strong>\uc11c\uc9c0 \ubcf4\ud638 \uc7a5\uce58(SPD)\ub780 \ubb34\uc5c7\uc778\uac00?<\/strong><\/strong><\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">\uc11c\uc9c0 \ubcf4\ud638 \uc7a5\uce58(SPD)\ub294 \uc77c\uc2dc\uc801\uc778 \uacfc\uc804\uc555\uc744 \uc81c\ud55c\ud558\uace0 \uc11c\uc9c0 \uc804\ub958\ub97c \ubd84\uc0b0\uc2dc\ud0a4\ub3c4\ub85d \uc124\uacc4\ub41c \uc804\uae30 \ubcf4\ud638 \uc7a5\uce58\uc785\ub2c8\ub2e4. \uc815\uc0c1 \uc791\ub3d9 \uc870\uac74\uc5d0\uc11c SPD\ub294 \ub192\uc740 \uc784\ud53c\ub358\uc2a4 \uc0c1\ud0dc\ub97c \uc720\uc9c0\ud558\uba70 \uc804\uae30 \uc2dc\uc2a4\ud15c\uc5d0 \uac70\uc758 \ub610\ub294 \uc804\ud600 \uc601\ud5a5\uc744 \ubbf8\uce58\uc9c0 \uc54a\uc2b5\ub2c8\ub2e4. \ub099\ub8b0, \uc804\ub825 \uacc4\ud1b5 \uc804\ud658, \ubaa8\ud130 \uae30\ub3d9 \ubc0f \uc815\uc9c0 \ub610\ub294 \uae30\ud0c0 \uc77c\uc2dc\uc801 \ud604\uc0c1\uc73c\ub85c \uc778\ud574 \uc120\ub85c \uc804\uc555\uc774 \uae09\uaca9\ud788 \uc0c1\uc2b9\ud558\uba74 SPD\ub294 \ube60\ub974\uac8c \ub0ae\uc740 \uc784\ud53c\ub358\uc2a4\uc758 \ub3c4\uc804 \uc0c1\ud0dc\ub85c \uc804\ud658\ub429\ub2c8\ub2e4. \uc774\ub294 \uc11c\uc9c0 \uc804\ub958\uc758 \ubc29\uc804 \uacbd\ub85c\ub97c \uc81c\uacf5\ud558\ub294 \ub3d9\uc2dc\uc5d0 \ud558\ub958 \uc7a5\ube44\uc5d0 \ub3c4\ub2ec\ud558\ub294 \uc794\ub958 \uc804\uc555\uc744 \uc81c\ud55c\ud558\uc5ec \uc808\uc5f0 \ud30c\uad34, \uc804\uc790 \ubd80\ud488 \uc190\uc0c1, \uc7a5\ube44 \uace0\uc7a5 \ubc0f \uacc4\ud68d\ub418\uc9c0 \uc54a\uc740 \uac00\ub3d9 \uc911\ub2e8\uc758 \uc704\ud5d8\uc744 \uc904\uc785\ub2c8\ub2e4.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">SPD\uc758 \uc124\uacc4, \uc131\ub2a5 \uc2dc\ud5d8 \ubc0f \uc2e4\uc81c \uc801\uc6a9\uc740 \uad00\ub828 \ud45c\uc900\uc744 \uc900\uc218\ud574\uc57c \ud569\ub2c8\ub2e4. <strong><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314?utm_source.com\" target=\"_blank\" rel=\"noopener\">IEC 61643-11<\/a><\/strong> \uc740 \uc800\uc555 AC \uc804\ub825 \uc2dc\uc2a4\ud15c\uc5d0 \uc5f0\uacb0\ub41c \uc11c\uc9c0 \ubcf4\ud638 \uc7a5\uce58\uc758 \uc131\ub2a5 \uc694\uad6c \uc0ac\ud56d\uacfc \uc2dc\ud5d8 \ubc29\ubc95\uc744 \uaddc\uc815\ud558\uba70, <strong><a href=\"https:\/\/www.nfpa.org\/codes-and-standards\/nfpa-70-standard-development\/70?utm_source.com\" target=\"_blank\" rel=\"noopener\">NFPA 70, \uad6d\uac00\uc804\uae30\uaddc\uc815(NEC) \uc81c242\uc870<\/a>,<\/strong> \ub294 \ubbf8\uad6d \uc804\uae30 \uc124\ube44\uc5d0\uc11c\uc758 \uc11c\uc9c0 \ubcf4\ud638 \uc801\uc6a9\uc744 \ub2e4\ub8f9\ub2c8\ub2e4. \uc774\ub7ec\ud55c \ud45c\uc900\uc740 SPD\uc758 \uc2dc\ud5d8, \uc120\uc815 \ubc0f \uc124\uce58\uc5d0 \uc911\uc694\ud55c \uc9c0\uce68\uc744 \uc81c\uacf5\ud558\uc5ec \ud604\ub300 \uc800\uc555 \ubc30\uc804 \uc2dc\uc2a4\ud15c\uc758 \uc548\uc804\uc131\uacfc \uc2e0\ub8b0\uc131\uc744 \ud5a5\uc0c1\uc2dc\ud0a4\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub429\ub2c8\ub2e4.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-2\"><strong>\uc804\uae30 \uc11c\uc9c0\ub780 \ubb34\uc5c7\uc778\uac00?<\/strong><\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">\uc804\uae30 \uc11c\uc9c0\ub294 \uc804\ub825, \uc81c\uc5b4 \ub610\ub294 \ud1b5\uc2e0 \ud68c\ub85c\ub97c \ud1b5\ud574 \uc804\ub2ec\ub418\ub294 \uc9e7\uc740 \uc9c0\uc18d \uc2dc\uac04\uc758 \uc804\uc555 \ub610\ub294 \uc804\ub958 \uc2a4\ud30c\uc774\ud06c\uc785\ub2c8\ub2e4. \uc77c\ubc18\uc801\uc73c\ub85c \ub9e4\uc6b0 \ube60\ub974\uac8c \uc0c1\uc2b9\ud55c \ud6c4 \ub354 \uae34 \uc2dc\uac04\uc5d0 \uac78\uccd0 \uac10\uc1e0\ud569\ub2c8\ub2e4.<br>\uc774 \ud604\uc0c1\uc740 \ubd88\uacfc \uba87 \ub9c8\uc774\ud06c\ub85c\ucd08 \ub3d9\uc548\ub9cc \uc9c0\uc18d\ub420 \uc218 \uc788\uc9c0\ub9cc, \uadf8 \uacb0\uacfc \ubc1c\uc0dd\ud558\ub294 \uc804\uc555\uc740 \uc808\uc5f0, \uc804\uc790 \ubd80\ud488, \uc81c\uc5b4 \uc7a5\ube44 \ubc0f \uae30\ud0c0 \ubbfc\uac10\ud55c \ubd80\ud558\ub97c \uc190\uc0c1\uc2dc\ud0ac \ub9cc\ud07c \ub192\uc744 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<br><strong>IEC 60050-161<\/strong> \uc740 \uc11c\uc9c0\ub97c \uc120\ub85c \ub610\ub294 \ud68c\ub85c\ub97c \ub530\ub77c \uc804\ud30c\ub418\ub294 \uacfc\ub3c4\ud30c\ub85c \uc815\uc758\ud558\uba70, \ube60\ub978 \uc0c1\uc2b9 \ud6c4 \ub290\ub9b0 \uac10\uc1e0\uac00 \ud2b9\uc9d5\uc785\ub2c8\ub2e4.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>\uc804\uae30 \uc11c\uc9c0\uc758 \uc6d0\uc778\uc740 \ubb34\uc5c7\uc778\uac00?<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">\uc804\uae30 \uc11c\uc9c0\ub294 \uc77c\ubc18\uc801\uc73c\ub85c \ub099\ub8b0 \uad00\ub828 \ud604\uc0c1\uacfc \uc804\ub825 \uc2dc\uc2a4\ud15c \ub0b4\uc758 \uac1c\ud3d0 \uc791\ub3d9\uc774\ub77c\ub294 \ub450 \uac00\uc9c0 \uc8fc\uc694 \uc6d0\uc778\uacfc \uad00\ub828\uc774 \uc788\uc2b5\ub2c8\ub2e4.<br>\ub099\ub8b0\ub294 \uc9c1\uc811 \ub099\ub8b0, \uc778\uadfc \ub099\ub8b0 \ub610\ub294 \uc5f0\uacb0\ub41c \ub3c4\uccb4\uc758 \uc720\ub3c4 \uc804\uc555\uc744 \ud1b5\ud574 \uc77c\uc2dc\uc801\uc778 \uacfc\uc804\uc555\uc744 \uc720\ubc1c\ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uac1c\ud3d0 \uc11c\uc9c0\ub294 \ubaa8\ud130, \ubcc0\uc555\uae30, \ucee4\ud328\uc2dc\ud130 \ubc45\ud06c, \uc811\ucd09\uae30, \uacc4\uc804\uae30 \ub610\ub294 \uae30\ud0c0 \uace0\uc804\ub825 \ubd80\ud558\uac00 \ud22c\uc785\ub418\uac70\ub098 \ucc28\ub2e8\ub420 \ub54c \ubc1c\uc0dd\ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<br><strong><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/4223?utm_source.com\" target=\"_blank\" rel=\"noopener\">IEC 61000-4-5<\/a> <\/strong>\ub294 \ub099\ub8b0 \ud6a8\uacfc\uc640 \uc804\ub825 \uc2dc\uc2a4\ud15c \uac1c\ud3d0 \uacfc\ub3c4\ud604\uc0c1\uc73c\ub85c \uc778\ud55c \ub2e8\ubc29\ud5a5 \uc11c\uc9c0\uc5d0 \ub300\ud55c \uc804\uae30 \ubc0f \uc804\uc790 \uc7a5\ube44\uc758 \ub0b4\uc131 \uc2dc\ud5d8\uc744 \uc704\ud55c \ud45c\uc900\ud654\ub41c \ubc29\ubc95\uc744 \uc81c\uacf5\ud569\ub2c8\ub2e4.<\/p>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color has-medium-font-size wp-elements-3 wp-block-paragraph\"><strong>\ub099\ub8b0 \uc11c\uc9c0\uc640 \uac1c\ud3d0 \uc11c\uc9c0\uc758 \ube44\uad50<\/strong><\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>\ub9e4\uac1c\ubcc0\uc218<\/strong><\/th><th><strong>\ub099\ub8b0 \uc11c\uc9c0<\/strong><\/th><th><strong>\uac1c\ud3d0 \uc11c\uc9c0<\/strong><\/th><\/tr><\/thead><tbody><tr><td><strong>\uc77c\ubc18\uc801\uc778 \ud30c\ud615<\/strong><\/td><td>\uc9c1\uc811 \ub099\ub8b0 \uc804\ub958\uc758 \uacbd\uc6b0 10\/350 \u03bcs, \uc720\ub3c4 \uc11c\uc9c0 \uc804\ub958\uc758 \uacbd\uc6b0 8\/20 \u03bcs, \ud1b5\uc2e0 \uc120\ub85c\uc758 \uacbd\uc6b0 10\/700 \u03bcs<\/td><td>2\/50 \u03bcs \uc804\uc555\ud30c \ubc0f 8\/20 \u03bcs \uc804\ub958\ud30c<\/td><\/tr><tr><td><strong>\ubc1c\uc0dd \ube48\ub3c4<\/strong><\/td><td>\ube44\uad50\uc801 \ub4dc\ubb3c\uba70 \uc8fc\ub85c \ub1cc\uc6b0\uc640 \uad00\ub828\ub428<\/td><td>\ub354 \ube48\ubc88\ud558\uba70 \uc804\uae30 \uc7a5\ube44\uac00 \ucf1c\uc9c0\uac70\ub098 \uaebc\uc9c8 \ub54c\ub9c8\ub2e4 \ubc1c\uc0dd\ud560 \uc218 \uc788\uc74c<\/td><\/tr><tr><td><strong>\uc5d0\ub108\uc9c0 \uc218\uc900<\/strong><\/td><td>\ub9e4\uc6b0 \ub192\uc740 \uc5d0\ub108\uc9c0\ub85c \uc218\ubc31 \ud0ac\ub85c\uc904\uc5d0 \ub3c4\ub2ec\ud560 \uc218 \uc788\uc73c\uba70 \uc989\uac01\uc801\uc778 \uc7a5\ube44 \uc190\uc0c1\uc744 \uc720\ubc1c\ud568<\/td><td>\uc77c\ubc18\uc801\uc73c\ub85c \uc5d0\ub108\uc9c0\uac00 \ub0ae\uc9c0\ub9cc \ubc18\ubcf5\uc801\uc778 \ub178\ucd9c\uc740 \ubd80\ud488\uc744 \uc810\uc9c4\uc801\uc73c\ub85c \uc5f4\ud654\uc2dc\ud0ac \uc218 \uc788\uc74c<\/td><\/tr><tr><td><strong>\uad8c\uc7a5 \ubcf4\ud638 \ubc29\uc2dd<\/strong><\/td><td>\uc8fc \uc778\uc785\uad6c\uc5d0 Type 1 SPD\ub97c \uc124\uce58\ud55c \ud6c4 \ud558\ub958\uc5d0 \uc870\uc815\ub41c \uc11c\uc9c0 \ubcf4\ud638 \uc801\uc6a9<\/td><td>\ubd84\uc804\ubc18 \ub610\ub294 \ubbfc\uac10\ud55c \uc7a5\ube44 \uac00\uae4c\uc774\uc5d0 Type 2 \ub610\ub294 Type 3 SPD \uc124\uce58<\/td><\/tr><tr><td><strong>\uc77c\ubc18\uc801\uc778 \uacfc\uc804\uc555 \ubc94\uc704<\/strong><\/td><td>\uc218 \ud0ac\ub85c\ubcfc\ud2b8\uc5d0\uc11c \uc218\uc2ed \ud0ac\ub85c\ubcfc\ud2b8\uae4c\uc9c0<\/td><td>\uc218\ubc31 \ubcfc\ud2b8\uc5d0\uc11c \uc218 \ud0ac\ub85c\ubcfc\ud2b8\uae4c\uc9c0<\/td><\/tr><tr><td><strong>\uc77c\ubc18\uc801\uc778 \uc6d0\uc778<\/strong><\/td><td>\uc9c1\uc811 \ub099\ub8b0, \uc778\uc811 \ub099\ub8b0, \ub300\uc9c0 \uc804\uc704 \uc0c1\uc2b9 \ubc0f \uc720\ub3c4 \ub099\ub8b0 \ud6a8\uacfc<\/td><td>\ubaa8\ud130, \ubcc0\uc555\uae30, \ucee4\ud328\uc2dc\ud130 \ubc45\ud06c, \uc811\ucd09\uae30, \uacc4\uc804\uae30 \ubc0f \uae30\ud0c0 \uc2a4\uc704\uce6d \uc7a5\uce58<\/td><\/tr><tr><td><strong>\uc77c\ubc18\uc801\uc778 \uc601\ud5a5<\/strong><\/td><td>\uc808\uc5f0 \ud30c\uad34, \uc12c\ub77d, \ucf00\uc774\ube14 \uc190\uc0c1, \ud654\uc7ac \ub610\ub294 \uc989\uac01\uc801\uc778 \uc7a5\ube44 \uace0\uc7a5<\/td><td>\uc804\uc790 \ubd80\ud488 \uc131\ub2a5 \uc800\ud558, \uc81c\uc5b4 \uc2dc\uc2a4\ud15c \uc624\uc791\ub3d9, \ub370\uc774\ud130 \uc624\ub958 \ub610\ub294 \uc7a5\ube44 \uc218\uba85 \ub2e8\ucd95<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-4\">\uc11c\uc9c0 \ubcf4\ud638 \uc7a5\uce58(SPD)\ub294 \uc5b4\ub5bb\uac8c \uc791\ub3d9\ud558\ub098\uc694?<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">\uc11c\uc9c0 \ubcf4\ud638 \uc7a5\uce58(SPD)\ub294 \uc790\ub3d9\ud654\ub41c \ucd08\uace0\uc18d <strong>\uc804\uae30 \uc555\ub825 \ub9b4\ub9ac\ud504 \ubc38\ube0c<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">\ucc98\ub7fc \uc791\ub3d9\ud569\ub2c8\ub2e4. \uc815\uc0c1\uc801\uc778 \uacc4\ud1b5 \uc870\uac74\uc5d0\uc11c SPD\ub294 \ub0b4\ubd80 \uc800\ud56d(\uc784\ud53c\ub358\uc2a4)\uc774 \ub9e4\uc6b0 \ub192\uc740 \uac1c\ubc29 \uc2a4\uc704\uce58 \uc5ed\ud560\uc744 \ud558\uc5ec \uc804\ub958\uac00 \ud750\ub974\uc9c0 \ubabb\ud558\uac8c \ud569\ub2c8\ub2e4. \uadf8\ub7ec\ub098 \ub099\ub8b0\ub098 \uacc4\ud1b5 \uc2a4\uc704\uce6d\uc73c\ub85c \uc778\ud55c \uacfc\uc804\uc555 \uc2a4\ud30c\uc774\ud06c\uac00 \uc2dc\uc2a4\ud15c\uc5d0 \uc720\uc785\ub418\uba74 SPD\ub294 <strong>\ub098\ub178\ucd08<\/strong>, \uc774\ub0b4\uc5d0 \uc989\uc2dc \ubc18\uc751\ud558\uc5ec \uc800\ud56d\uc744 \uac70\uc758 0\uc5d0 \uac00\uae5d\uac8c \ub5a8\uc5b4\ub728\ub9bd\ub2c8\ub2e4. \uc774\ub85c \uc778\ud574 \ub300\uaddc\ubaa8 \uc11c\uc9c0 \uc804\ub958\ub97c \ubbfc\uac10\ud55c \uc7a5\ube44\ub85c\ubd80\ud130 \uc6b0\ud68c\uc2dc\ucf1c \uc811\uc9c0\ub85c \uc9c1\uc811 \ud758\ub824\ubcf4\ub0b4\ub294 \uc548\uc804\ud55c \ubcd1\ub82c \uacbd\ub85c\uac00 \ub9cc\ub4e4\uc5b4\uc9d1\ub2c8\ub2e4.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"905\" height=\"302\" src=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/how-surge-protective-device-works.png\" alt=\"How a surge protective device (SPD) works in three steps.\" class=\"wp-image-1742\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/how-surge-protective-device-works.png 905w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/how-surge-protective-device-works-300x100.png 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/how-surge-protective-device-works-768x256.png 768w\" sizes=\"auto, (max-width: 905px) 100vw, 905px\" \/><figcaption class=\"wp-element-caption\"><em>\uc11c\uc9c0 \ubcf4\ud638 \uc7a5\uce58\uc758 3\ub2e8\uacc4 \uc791\ub3d9 \ubc29\uc2dd\uc744 \ubcf4\uc5ec\uc8fc\ub294 \ub2e4\uc774\uc5b4\uadf8\ub7a8: \uc815\uc0c1 \uace0\uc784\ud53c\ub358\uc2a4 \uc791\ub3d9, \uc11c\uc9c0 \uc751\ub2f5, \uc811\uc9c0\ub85c\uc758 \uc804\ub958 \uc6b0\ud68c \ud6c4 \uc790\ub3d9 \ub9ac\uc14b.<\/em><\/figcaption><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\">3\ub2e8\uacc4 \uc791\ub3d9 \ud504\ub85c\uc138\uc2a4<\/h3>\n\n\n\n<ol start=\"1\" class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Normal State (High Impedance): When line voltage remains within normal operational limits, internal components maintain an impedance of several megohms. The SPD remains &#8220;invisible&#8221; to the circuit and draws virtually no leakage current.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Surge Event (Instantaneous Low Impedance): The moment a transient voltage exceeds the SPD&#8217;s clamping threshold (Uc), the non-linear internal elements switch from high resistance to low resistance in less than 25 nanoseconds.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Current Diversion &amp; Reset (Energy Dissipation): The surge energy is safely channeled through the grounding conductor (PE). Once the transient spike subsides and the line voltage returns to normal, the internal components automatically recover to their high-impedance state, restoring standard circuit operations.<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\">The Core Components Inside: MOV vs. GDT<\/h3>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"739\" height=\"370\" src=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/mov-vs-gdt-surge-protection-components.png\" alt=\"MOV vs. GDT components inside a surge protective device (SPD).\" class=\"wp-image-1743\" style=\"width:750px;height:auto\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/mov-vs-gdt-surge-protection-components.png 739w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/mov-vs-gdt-surge-protection-components-300x150.png 300w\" sizes=\"auto, (max-width: 739px) 100vw, 739px\" \/><figcaption class=\"wp-element-caption\">Comparison of MOV and GDT, the two most common surge protection components used in SPDs.<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The working mechanism relies on high-performance non-linear electrical components built inside the module:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Metal Oxide Varistors (MOV): The most widely used component in Type 2 AC and DC SPDs. MOVs exhibit a sharp drop in electrical resistance as voltage increases, offering exceptional energy absorption capacities and sub-nanosecond response times.<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Gas Discharge Tubes (GDT): Commonly deployed in Type 1 spark-gap architectures or communication line protection. GDTs spark over and ionize gas when triggered, capable of discharging high lightning currents without thermal destruction.<\/li>\n<\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-5\"><strong>What Are the Main Types of Surge Protective Devices?<\/strong><\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">A sudden lightning event or the switching and startup of high-power equipment in an industrial facility can generate a high-magnitude transient overvoltage within a very short period. Such surges may damage expensive controllers, servers, variable frequency drives, and other sensitive electronic equipment. In severe cases, they can even cause an entire production line to shut down. However, not every surge protective device is designed to withstand high-energy lightning currents, and not every type of SPD is suitable for installation at the same point in the electrical distribution system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">A surge protective device can be understood as the electrical system\u2019s \u201cairbag,\u201d but each SPD type has a clearly defined protective role. From the first line of defense at the building\u2019s service entrance, where high-energy surge currents are diverted, to intermediate protection in distribution panels and fine protection near sensitive equipment, <em><strong>Type 1, Type 2, and Type 3 SPDs<\/strong> <\/em>operate at different levels of the protection system. In addition, <strong><em>Type 1+2 combined SPDs<\/em><\/strong> integrate the lightning-current discharge capability of a Type 1 device with the voltage-limiting performance of a Type 2 device in a single unit, making them a practical solution for service entrances and main distribution boards. Effective surge protection depends on selecting and coordinating these devices according to the system risk, installation location, and impulse withstand capability of the protected equipment.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\">Type 1 Surge Protective Device<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Type 1 SPDs are primary surge protection devices installed on the line side of the main service entrance (between the secondary of the utility transformer and the main service disconnect).<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Primary Function: Designed to withstand high-energy transients caused by direct or nearby lightning strikes and utility grid switching before the surge reaches the main distribution panel.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Test Standard &amp; Waveform: Evaluated under IEC 61643 standards using the 10\/350 \u03bcs impulse current waveform (Iimp), which simulates high-peak energy discharges.<\/li>\n<\/ul>\n\n\n\n<div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\">\n<h3 class=\"wp-block-heading has-medium-font-size\">Type 2 Surge Protective Device<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Type 2 SPDs serve as secondary protection and are installed on the load side of the main service disconnect, typically located within sub-distribution boards or branch control panels.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Primary Function: Clamps residual impulse voltages that pass through Type 1 SPDs and mitigates internally generated surges caused by inductive switching loads (e.g., HVAC units, motors, and variable frequency drives).<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Test Standard &amp; Waveform: Tested using the 8\/20 \u03bcs current waveform, characterized by nominal discharge current (In) and maximum discharge current (Imax).<\/li>\n<\/ul>\n<\/div>\n\n\n\n<div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\">\n<h3 class=\"wp-block-heading has-medium-font-size\">Type 3 Surge Protective Device<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Type 3 SPDs provide localized point-of-use protection for highly sensitive terminal equipment.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Primary Function: Filters residual low-level transient overvoltages right at the load terminal to prevent insulation breakdown or data corruption in microelectronics.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Installation Requirement: Must be installed downstream with a minimum conductor distance (typically at least 10 meters \/ 30 feet) from the upstream Type 2 SPD to ensure proper decoupling and energy coordination.<\/li>\n<\/ul>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\">Type 1+2 Surge Protective Device (Combined Type)<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Type 1+2 SPDs (also classified as Class I+II) combine the high-energy impulse discharge capacity of a Type 1 device with the low voltage protection level (Up) of a Type 2 device into a single compact unit.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Primary Function: Directly diverts high-energy direct lightning currents while simultaneously clamping low-level switching transients, providing seamless protection without requiring minimum decoupling distance between separate Type 1 and Type 2 units.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Test Standard &amp; Waveform: Dual-tested under IEC 61643 standards for both 10\/350 \u03bcs impulse currents (Iimp) and 8\/20 \u03bcs nominal\/maximum discharge currents (In \/ Imax).<\/li>\n<\/ul>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-6 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Engineering Note<\/strong>\uff1a<br>Effective surge protection relies on coordinated protection at different levels. Type 1 or Type 1+2 SPDs handle high-energy surges at the system entrance, Type 2 SPDs protect distribution circuits, and Type 3 SPDs provide fine protection for sensitive equipment.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\" style=\"margin-top:var(--wp--preset--spacing--70)\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-7\"><strong><strong>Type 1, Type 2, Type 3, and Type 1+2 SPD: Key Differences<\/strong><\/strong><\/h2>\n<\/blockquote>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Feature<\/strong><\/th><th><strong>Type 1 SPD<\/strong><\/th><th><strong>Type 1+2 SPD<\/strong><\/th><th><strong>Type 2 SPD<\/strong><\/th><th><strong>Type 3 SPD<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Main Function<\/td><td>Diverts direct lightning current<\/td><td>Combines lightning current discharge and surge protection<\/td><td>Protects against induced lightning and switching surges<\/td><td>Final protection for sensitive equipment<\/td><\/tr><tr><td>Installation Location<\/td><td>Service entrance<\/td><td>Service entrance or main distribution board<\/td><td>Main or sub-distribution board<\/td><td>Close to the protected equipment<\/td><\/tr><tr><td>Test Waveform<\/td><td>10\/350 \u03bcs<\/td><td>10\/350 \u03bcs and 8\/20 \u03bcs<\/td><td>8\/20 \u03bcs<\/td><td>Combination wave<\/td><\/tr><tr><td>Main Parameters<\/td><td>Iimp, Up<\/td><td>Iimp, In, Imax, Up<\/td><td>In, Imax, Up<\/td><td>Uoc, Up<\/td><\/tr><tr><td>Protection Stage<\/td><td>Primary protection<\/td><td>Primary and secondary protection<\/td><td>Secondary protection<\/td><td>Final protection<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color has-small-font-size wp-elements-8 wp-block-paragraph\">The table above provides a quick comparison of the four main SPD types. In practice, selecting the right surge protective device depends on the installation location, lightning exposure risk, system configuration, and the required level of protection. In many installations, multiple SPD types are coordinated to achieve effective surge protection throughout the electrical system.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\" style=\"margin-top:var(--wp--preset--spacing--70)\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-9\">How to Select the Right Surge Protective Device (SPD)<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-10 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Choosing the right Surge Protective Device (SPD) involves more than simply selecting the highest discharge current rating. The system voltage, installation location, lightning exposure, grounding arrangement, and coordination between protection stages all play a critical role in determining overall surge protection performance. The following example illustrates why proper SPD selection is essential.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">In late 2023, a severe thunderstorm swept through an industrial manufacturing facility in central Texas. A direct lightning strike struck the utility line less than 200 meters from the facility&#8217;s main power distribution yard. The plant did have a basic surge suppressor installed in the main low-voltage switchboard, leading plant management to believe their operations were fully protected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Within milliseconds, the reality of incomplete surge protection unfolded:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Massive Financial Loss: The initial high-energy impulse overwhelmed the single panel protector, sending a severe voltage transient surging through the internal distribution network.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Catastrophic Equipment Damage: Over 15 variable frequency drives (VFDs), dozens of programmable logic controllers (PLCs), sensitive sensor arrays, and computerized CNC machining centers suffered immediate insulation breakdown and circuit board failure.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Costly Unplanned Downtime: The entire automated production line was knocked offline for 16 days while replacement components were sourced and re-engineered, resulting in over $1.2 million in direct hardware replacement costs and lost operational productivity.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">A forensic engineering analysis conducted after the incident revealed the root cause: a lack of cascaded, multi-stage surge protection. The facility relied on a single protection device at the main entrance, expecting it to absorb high-energy lightning currents while simultaneously clamping low-level voltage spikes for sensitive microelectronics downstream\u2014a task no single device is engineered to accomplish alone.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Transient overvoltages\u2014whether generated externally by direct or indirect lightning strikes, or internally by heavy inductive load switching\u2014follow predictable physical paths. Protecting an industrial, commercial, or residential infrastructure requires a layered, step-down protection architecture defined by recognized international standards such as <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65315?utm_source.com\" target=\"_blank\" rel=\"noopener\">IEC 61643-01<\/a> \uadf8\ub9ac\uace0 <a href=\"https:\/\/www.ul.com\/services\/surge-protection-device-testing-and-certification-services?utm_sourcet.com\" target=\"_blank\" rel=\"noopener\">UL 1449.<\/a><\/p>\n\n\n\n<p class=\"has-palette-color-4-color has-text-color has-link-color wp-elements-11 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong><em>To select the right SPD, several key factors must be considered, including the power system, operating voltage, SPD type, protection level, and installation requirements.<\/em><\/strong><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"has-palette-color-4-color has-text-color has-link-color has-large-font-size wp-elements-12 wp-block-paragraph\"><strong>SPD Selection at a Glance<\/strong><\/p>\n<\/blockquote>\n\n\n\n<ul style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-list has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-13\">\n<li><strong>Step 1: Confirm the Power System and Select Uc<\/strong><\/li>\n\n\n\n<li><strong>Step 2: Select the SPD Type Based on Installation Location and LPZ<\/strong><\/li>\n\n\n\n<li><strong>Step 3: Determine Iimp, In, and Imax<\/strong><\/li>\n\n\n\n<li><strong>Step 4: Check the Voltage Protection Level Up<\/strong><\/li>\n\n\n\n<li><strong>Step 5: Confirm the Number of Poles, Disconnection Device, Remote Signaling, and Backup Protection<\/strong><\/li>\n\n\n\n<li><strong>Step 6: Verify Energy Coordination Between Multiple SPDs<\/strong><\/li>\n<\/ul>\n\n\n\n<p class=\"has-palette-color-4-color has-text-color has-link-color wp-elements-14 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>The following sections explain each step in more detail and show how these factors affect SPD selection.<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Step 1: Confirm the Power System and Select Uc<\/strong><\/h3>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Power System<\/strong><\/th><th><strong>Typical Uc Selection<\/strong><\/th><th><strong>Selection Note<\/strong><\/th><\/tr><\/thead><tbody><tr><td>230\/400 V TN-S, TN-C-S or TT System<\/td><td>275 V AC for L\u2013N protection<\/td><td>Common selection for standard 230 V AC distribution systems<\/td><\/tr><tr><td>400 V IT System<\/td><td>Select according to the highest possible line-to-earth voltage<\/td><td>The voltage to earth may increase during the first insulation fault<\/td><\/tr><tr><td>Solar PV DC System<\/td><td>Ucpv must be higher than the maximum PV array open-circuit voltage<\/td><td>Consider low-temperature Voc rise and system voltage, such as 600 V, 1000 V or 1500 V DC<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Step 2: Select the SPD Type Based on Installation Location and LPZ<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">SPD types should be selected according to the installation location, lightning protection zone, lightning current risk, and the impulse withstand capability of downstream equipment. Common SPD categories for low-voltage systems include Type 1, Type 2, Type 3, and combined Type 1+2 SPDs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Type 1 SPD \u2013 Lightning Current Protection<\/strong><\/p>\n\n\n\n<ul style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-list\">\n<li><strong>Installation Location:<\/strong> Building service entrance, main low-voltage switchboard, and the boundary between LPZ 0 and LPZ 1.<\/li>\n\n\n\n<li><strong>Main Function: <\/strong>Discharges high-energy lightning currents that may enter the electrical installation through the incoming power supply.<\/li>\n\n\n\n<li><strong>Key Parameters: <\/strong>Tested with a 10\/350 \u03bcs waveform. Common Iimp ratings include 12.5 kA, 25 kA, and higher values. The voltage protection level, Up, is commonly around 2.5 kV, depending on the product design.<\/li>\n\n\n\n<li><strong>Typical Applications: <\/strong>Industrial plants, outdoor facilities, large buildings, and installations with external lightning protection systems or a high risk of direct lightning currents.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-palette-color-9-color has-text-color has-link-color wp-elements-15 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong><em>A Type 1 SPD is mainly intended to handle high lightning current energy. Additional downstream Type 2 or Type 3 protection may still be required to reduce the residual voltage reaching sensitive equipment.<\/em><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Type 2 SPD \u2013 Distribution-Level Surge Protection<\/strong><\/p>\n\n\n\n<ul style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-list\">\n<li><strong>Installation Location:<\/strong> Main distribution boards, sub-distribution boards, workshop power panels, and industrial control cabinets.<\/li>\n\n\n\n<li><strong>Main Function:<\/strong> Protects against induced lightning surges, switching transients, and residual surge energy passing through an upstream Type 1 SPD.<\/li>\n\n\n\n<li><strong>Key Parameters:<\/strong> Tested with an 8\/20 \u03bcs waveform. Common ratings include In of 20 kA and Imax of 40\u201380 kA. The voltage protection level, Up, is commonly between 1.5 and 1.8 kV.<\/li>\n\n\n\n<li><strong>Typical Applications:<\/strong> Residential buildings, commercial facilities, and general industrial power distribution systems.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-palette-color-9-color has-text-color has-link-color wp-elements-16 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong><em>Type 2 SPDs protect electrical systems against induced lightning surges, switching transients, and residual surge energy passing through an upstream Type 1 SPD.<\/em><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Type 3 SPD \u2013 Final Protection for Sensitive Equipment<\/strong><\/p>\n\n\n\n<ul style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-list\">\n<li><strong>Installation Location:<\/strong> Close to PLCs, variable frequency drives, servers, instruments, socket outlets, and other sensitive terminal equipment.<\/li>\n\n\n\n<li><strong>Main Function:<\/strong> Further limits residual overvoltage and provides final-stage protection for sensitive electronic equipment.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Key Parameters:<\/strong> Tested with a combination wave. The main parameters are Uoc and Up, although some products may also specify a nominal discharge current.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Typical Applications:<\/strong> Automation systems, communication equipment, servers, measurement instruments, and other sensitive electronic loads.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-palette-color-9-color has-text-color has-link-color wp-elements-17 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong><em>Type 3 SPDs have limited energy-handling capability and should normally be coordinated with an upstream Type 1, Type 2, or Type 1+2 SPD.<\/em><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Type 1+2 Combined SPD \u2013 Lightning Current and Surge Protection<\/strong><\/p>\n\n\n\n<ul style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-list\">\n<li><strong>Installation Location:<\/strong> Building service entrances, main switchboards, solar PV AC distribution panels, compact distribution boards, and retrofit installations.<\/li>\n\n\n\n<li><strong>Main Function:<\/strong> Combines lightning-current discharge capability and surge-voltage limitation in a single device.<\/li>\n\n\n\n<li><strong>Key Parameters:<\/strong> Iimp, In, Imax, and Up should all be considered. Common Iimp ratings include 12.5 kA and 25 kA per pole, while In is commonly 20 kA or higher. Final values should be confirmed according to the product specifications and project requirements.<\/li>\n\n\n\n<li><strong>Typical Applications:<\/strong> Industrial facilities, commercial buildings, solar PV systems, compact switchboards, and projects where installation space is limited.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-palette-color-9-color has-text-color has-link-color wp-elements-18 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><em><strong>A Type 1+2 SPD meets both Type 1 and Type 2 protection requirements in a single device. It combines high-energy lightning-current discharge capability with voltage-limiting protection.<\/strong><\/em><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"has-text-align-center has-palette-color-4-color has-text-color has-link-color has-medium-font-size wp-elements-19 wp-block-paragraph\"><strong>SPD Selection Guide by Application<\/strong><\/p>\n<\/blockquote>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Application Condition<\/strong><\/th><th><strong>Recommended SPD Type<\/strong><\/th><th><strong>Typical Installation Location<\/strong><\/th><th><strong>\uc8fc\uc694 \ub9e4\uac1c\ubcc0\uc218<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Building with an external lightning protection system<\/td><td>Type 1 or Type 1+2<\/td><td>Service entrance or main switchboard<\/td><td>Iimp, Up<\/td><\/tr><tr><td>General residential or commercial distribution system<\/td><td>Type 2<\/td><td>Main or sub-distribution board<\/td><td>In, Imax, Up<\/td><\/tr><tr><td>Sensitive electronic equipment<\/td><td>Type 3<\/td><td>Close to the protected equipment<\/td><td>Uoc, Up<\/td><\/tr><tr><td>Industrial facility with high lightning exposure<\/td><td>Type 1+2 with downstream Type 2 protection<\/td><td>Main switchboard and sub-distribution boards<\/td><td>Iimp, In, Up<\/td><\/tr><tr><td>Solar PV DC system<\/td><td>DC Type 1+2 or DC Type 2<\/td><td>PV combiner box or DC distribution board<\/td><td>Ucpv, Iimp or In, Up<\/td><\/tr><tr><td>Sensitive loads located far from the main distribution board<\/td><td>Additional Type 2 or Type 3<\/td><td>Near the downstream equipment<\/td><td>Up, coordination<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong><strong>Step 3: Determine Iimp, In, and Imax<\/strong><\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The discharge current rating of an SPD should be selected according to the expected surge energy, installation location, lightning exposure, and SPD type. The three main current parameters are Iimp, In, and Imax.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Iimp \u2013 Impulse Discharge Current<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Iimp represents the lightning impulse current that a Type 1 or Type 1+2 SPD can discharge under a 10\/350 \u03bcs waveform.<br>It is mainly used to evaluate the SPD\u2019s ability to withstand high-energy lightning currents at the service entrance or LPZ 0\u2013LPZ 1 boundary.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Common In ratings include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">10 kA for light-duty terminal protection<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">20 kA for general residential and commercial distribution<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">30\u201340 kA or higher for industrial and high-exposure installations<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">For most main and sub-distribution boards, an In rating of 20 kA or higher is commonly selected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Imax \u2013 Maximum Discharge Current<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Imax represents the maximum 8\/20 \u03bcs surge current that an SPD can discharge once or a limited number of times without failing.<br>Imax is normally higher than In, but it should not be used as the only selection criterion because it does not represent the SPD\u2019s repeated operating capability.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Typical Imax ratings include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">20\u201340 kA for general distribution systems<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">40\u201380 kA for industrial installations<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Higher values for severe surge environments<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Practical Selection Guide<\/strong><\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Installation Condition<\/strong><\/th><th><strong>Recommended Parameter Focus<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Building service entrance with lightning protection system<\/td><td>Prioritize Iimp<\/td><\/tr><tr><td>Main or sub-distribution board<\/td><td>Prioritize In and Imax<\/td><\/tr><tr><td>High lightning exposure industrial facility<\/td><td>Higher Iimp and In<\/td><\/tr><tr><td>Sensitive terminal equipment<\/td><td>Lower Up is usually more important than a very high current rating<\/td><\/tr><tr><td>Type 1+2 SPD<\/td><td>Check Iimp, In, Imax, and Up together<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<div class=\"wp-block-group has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-20 is-layout-constrained wp-block-group-is-layout-constrained\">\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Engineering Note<\/strong><br>A higher discharge current rating does not automatically mean better protection. SPD selection should balance discharge capacity, voltage protection level, installation location, backup protection, and energy coordination. An SPD with a very high Imax but an unsuitable Up or Uc may still fail to provide effective protection.<\/p>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Step 4: Check the Voltage Protection Level Up<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The voltage protection level, <strong>Up<\/strong>, indicates the SPD\u2019s ability to limit surge voltage under specified test conditions. It is a declared value provided by the manufacturer and represents the protection level achieved when the SPD discharges the specified impulse current.<br>A lower Up generally means that less surge voltage is allowed to pass toward downstream equipment. However, Up should not be evaluated alone. It must be considered together with the system voltage, maximum continuous operating voltage Uc, discharge-current capacity, temporary overvoltage withstand capability, and the impulse withstand voltage of the protected equipment.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Compare Up with the Equipment Impulse Withstand Voltage<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The selected SPD should limit the surge voltage to a level below the impulse withstand voltage of the downstream equipment.<br>A practical selection principle is:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><em>The effective protection level at the equipment should remain below the equipment\u2019s rated impulse withstand voltage.<\/em><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">A sufficient safety margin should be allowed because the actual voltage reaching the equipment may be higher than the Up value stated in the datasheet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Consider Installation Cable Length<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The Up value is measured at the SPD terminals under specified laboratory conditions. In an actual installation, the inductance of the connecting conductors can add extra voltage during surge discharge.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Therefore:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Keep the connecting conductors as short and direct as possible.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Avoid unnecessary loops and sharp bends.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Position the SPD close to the protected circuit.<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Install additional downstream protection when the protected equipment is far from the main SPD.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Long connecting cables can reduce the effectiveness of even a low-Up SPD. Correct installation is therefore just as important as product selection. Phoenix Contact also notes that excessively long connection conductors can create installation problems and recommends attention to cable length and layout.&nbsp;<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Practical Selection Focus<\/strong><\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Protection Position<\/strong><\/th><th><strong>Main Selection Focus<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Building service entrance<\/td><td>Balance Iimp and Up<\/td><\/tr><tr><td>Main or sub-distribution board<\/td><td>Check In, Imax, and Up<\/td><\/tr><tr><td>Sensitive electronic equipment<\/td><td>Select a sufficiently low Up and install the SPD close to the load<\/td><\/tr><tr><td>Type 1+2 combined SPD<\/td><td>Check Iimp, In, and Up together<\/td><\/tr><tr><td>Long distance between distribution boards<\/td><td>Consider an additional downstream SPD<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-21 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Engineering Note<\/strong>\uff1a<br>Do not select an SPD based only on the lowest Up value. An SPD with a low Up but insufficient discharge capacity may be damaged by the expected surge current. Conversely, an SPD with high discharge capacity but an excessively high Up may not adequately protect sensitive equipment.<br>The final selection should balance:<br><strong>Uc + Up + Iimp\/In\/Imax + equipment withstand voltage + installation distance<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Step 5: Confirm the Number of Poles, Disconnection Device, Remote Signaling, and Backup Protection<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">After selecting the SPD type and electrical ratings, confirm that the device matches the system configuration and installation requirements. The number of poles, internal disconnection function, remote signaling option, and backup protective device all affect the safety and reliability of the installation.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Confirm the Number of Poles<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The SPD pole configuration should match the power system, conductor arrangement, and protection mode.<\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Power System<\/strong><\/th><th><strong>Common SPD Configuration<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Single-phase L\u2013N system<\/td><td>1P+N or 2P<\/td><\/tr><tr><td>Three-phase three-wire system<\/td><td>3P<\/td><\/tr><tr><td>Three-phase four-wire system<\/td><td>3P+N or 4P<\/td><\/tr><tr><td>TN-C system<\/td><td>Protection between phase conductors and PEN<\/td><\/tr><tr><td>TN-S or TN-C-S system<\/td><td>Protection between L\u2013N and N\u2013PE, depending on the selected circuit<\/td><\/tr><tr><td>TT system<\/td><td>Commonly uses a 3+1 or 1+1 circuit<\/td><\/tr><tr><td>DC or PV system<\/td><td>Select the pole configuration according to system voltage, polarity, and grounding arrangement<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The number of poles alone is not enough to determine suitability. The protection circuit must also match the system earthing arrangement and the voltage that may appear between conductors.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Check the Disconnection Device<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Most SPDs include an internal thermal disconnection device that separates the protective component from the power system when it reaches the end of its service life or overheats.<br>The disconnection device helps reduce the risk of:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Thermal runaway<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Overheating<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Short circuit<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Fire caused by a failed MOV or other protective component<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The SPD should also provide a clear status indicator so that maintenance personnel can identify when the protection module needs replacement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Determine Whether Remote Signaling Is Required<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">A remote signaling contact allows the SPD operating status to be monitored from a control panel, alarm system, PLC, or building management system.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Remote signaling is particularly useful in:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Unattended substations<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Industrial production lines<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Data centers<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Telecom facilities<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Solar PV plants<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Critical power systems<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">When remote monitoring is required, check the contact type, terminal arrangement, rated voltage, and rated current of the signaling contact.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Select the Backup Protective Device<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">An SPD may require an upstream fuse or circuit breaker to protect the circuit if the SPD fails or develops an internal short circuit.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The backup protective device should be selected according to:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The manufacturer\u2019s specified maximum backup fuse or circuit breaker<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The available short-circuit current at the installation point<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The SPD\u2019s short-circuit current rating<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The type and cross-sectional area of the connecting conductors<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Coordination with the upstream protective device<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Do not select the backup fuse or circuit breaker only according to the SPD discharge-current rating. Follow the manufacturer\u2019s coordination table and installation instructions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Practical Selection Guide<\/strong><\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Selection Item<\/strong><\/th><th><strong>Main Point to Confirm<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Number of poles<\/td><td>Match the phase conductors, neutral conductor, and earthing system<\/td><\/tr><tr><td>Disconnection device<\/td><td>Confirm internal thermal disconnection and visible status indication<\/td><\/tr><tr><td>Remote signaling<\/td><td>Confirm whether remote alarm or system monitoring is required<\/td><\/tr><tr><td>Backup protection<\/td><td>Follow the manufacturer\u2019s recommended fuse or circuit-breaker rating<\/td><\/tr><tr><td>Replaceable module<\/td><td>Check whether the protection cartridge can be replaced without changing the base<\/td><\/tr><tr><td>Short-circuit rating<\/td><td>Confirm suitability for the prospective short-circuit current<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-22 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Engineering Note<\/strong><br>An SPD with the correct Uc, Up, and discharge-current rating may still be unsuitable if the pole configuration or backup protection is incorrect. Always verify the complete installation arrangement rather than selecting the SPD only from its front-label parameters.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Step 6: Verify Energy Coordination Between Multiple SPDs<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">When several SPDs are installed at different levels of the electrical system, they must operate in a coordinated sequence. The upstream SPD should discharge the highest surge energy, while the downstream SPD further reduces the residual voltage before it reaches sensitive equipment.<br>Proper energy coordination prevents a downstream SPD from being overloaded before the upstream device has diverted the main surge current.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Typical Cascaded Protection Arrangement<\/strong><\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Protection Level<\/strong><\/th><th><strong>Typical SPD Type<\/strong><\/th><th><strong>Typical Installation Location<\/strong><\/th><th><strong>Main Function<\/strong><\/th><\/tr><\/thead><tbody><tr><td>First stage<\/td><td>Type 1 or Type 1+2<\/td><td>Service entrance or main switchboard<\/td><td>Discharge high-energy lightning currents<\/td><\/tr><tr><td>Second stage<\/td><td>Type 2<\/td><td>Sub-distribution board or control cabinet<\/td><td>Limit residual surges and switching overvoltages<\/td><\/tr><tr><td>Final stage<\/td><td>Type 3<\/td><td>Close to sensitive equipment<\/td><td>Further reduce residual voltage<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Check the Distance Between SPDs<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Cable length between two SPDs affects how surge energy is shared. The inductance of the connecting cable can help create the voltage difference required for the upstream and downstream SPDs to operate in the correct sequence.<br>However, there is no single spacing rule that applies to every SPD combination. The required distance depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">SPD technology and internal design<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Upstream and downstream Up values<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Discharge-current ratings<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Cable routing and conductor length<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Manufacturer-tested coordination data<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Some installations use cable length to provide natural decoupling. Where the available distance is insufficient, a coordinated SPD combination or a specified decoupling element may be required.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Use Manufacturer-Verified Combinations<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The safest method is to select upstream and downstream SPDs that have been tested and confirmed as an energy-coordinated combination by the manufacturer.<br>Check the manufacturer\u2019s documentation for:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Permitted upstream and downstream SPD combinations<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Minimum separation distance<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Whether an additional decoupling element is required<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Maximum discharge-current capability<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Backup protective device requirements<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Effective voltage protection level at the load<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Do not assume that two SPDs are coordinated simply because one is Type 1 and the other is Type 2.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Consider the Distance to the Protected Equipment<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">When sensitive equipment is located far from the main SPD, an additional downstream SPD may be necessary. Long cables can pick up new induced surges and can also increase the voltage reaching the equipment.<br>For long distribution circuits, consider installing:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Type 2 protection in downstream distribution boards<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Type 3 protection close to sensitive terminal equipment<\/li>\n\n\n\n<li style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Additional SPDs where required by the project design or manufacturer\u2019s instructions<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Practical Coordination Checklist<\/strong><\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Item to Verify<\/strong><\/th><th><strong>Selection Requirement<\/strong><\/th><\/tr><\/thead><tbody><tr><td>SPD sequence<\/td><td>Type 1 or Type 1+2 upstream, followed by Type 2 and Type 3 where required<\/td><\/tr><tr><td>Energy capacity<\/td><td>Upstream SPD handles the highest surge energy<\/td><\/tr><tr><td>Voltage limitation<\/td><td>Downstream SPD provides a lower effective protection level<\/td><\/tr><tr><td>Separation distance<\/td><td>Follow manufacturer-tested requirements<\/td><\/tr><tr><td>Cable layout<\/td><td>Keep all SPD connections short and direct<\/td><\/tr><tr><td>Product compatibility<\/td><td>Use verified coordinated combinations where possible<\/td><\/tr><tr><td>Protected-equipment distance<\/td><td>Add downstream protection when the load is far from the main SPD<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-23 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Engineering Note<\/strong><br>Energy coordination is not achieved simply by installing several SPDs in series. The devices must share surge energy correctly without overloading the downstream unit.<br>A poorly coordinated system may cause the Type 2 or Type 3 SPD to operate too early and absorb more energy than it can withstand. Final coordination should therefore follow the manufacturer\u2019s tested combination data and installation instructions.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\" style=\"margin-top:var(--wp--preset--spacing--70)\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-24\"><strong>Where Are Surge Protective Devices Commonly Used?<\/strong><\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Surge protective devices are widely used in residential, commercial, industrial, communication, renewable energy, transportation, and outdoor electrical systems. Their main purpose is to protect electrical and electronic equipment from transient overvoltages caused by lightning, switching operations, and power system disturbances.<br>The required SPD type depends on the system voltage, installation location, earthing arrangement, equipment sensitivity, and expected surge exposure.<\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Application<\/strong><\/th><th><strong>Typical Equipment Protected<\/strong><\/th><th><strong>Common Protection Approach<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Residential buildings<\/td><td>Household appliances, computers, security systems, and smart home devices<\/td><td>Type 2 at the main distribution board; Type 1 or Type 1+2 may be required for buildings with external lightning protection<\/td><\/tr><tr><td>Commercial buildings<\/td><td>Elevators, HVAC systems, fire alarms, CCTV, servers, and building management systems<\/td><td>Type 1 or Type 1+2 at the service entrance, followed by Type 2 protection in downstream boards<\/td><\/tr><tr><td>Industrial facilities<\/td><td>PLCs, variable-frequency drives, sensors, automation equipment, and production lines<\/td><td>Coordinated Type 1, Type 2, and Type 3 protection<\/td><\/tr><tr><td>Data centers and communication systems<\/td><td>Servers, UPS systems, network equipment, communication devices, and signal lines<\/td><td>Power-line SPDs combined with dedicated data and signal-line protection<\/td><\/tr><tr><td>\ud0dc\uc591\uad11 PV \uc2dc\uc2a4\ud15c<\/td><td>PV modules, combiner boxes, inverters, and AC\/DC distribution circuits<\/td><td>DC SPDs on the PV side and AC SPDs on the inverter output side<\/td><\/tr><tr><td>EV charging stations<\/td><td>AC chargers, DC fast chargers, controllers, payment modules, and communication equipment<\/td><td>SPD protection at the incoming supply and charging equipment<\/td><\/tr><tr><td>Wind power and energy storage systems<\/td><td>Converters, inverters, battery management systems, control cabinets, and monitoring equipment<\/td><td>AC and DC SPDs selected according to the system architecture<\/td><\/tr><tr><td>Outdoor equipment and LED lighting<\/td><td>Streetlights, traffic systems, cameras, electronic signs, and outdoor control cabinets<\/td><td>Local SPD protection close to exposed outdoor equipment<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"has-palette-color-4-color has-text-color has-link-color wp-elements-25 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>In practice, larger or more complex systems usually require multi-stage surge protection. A high-energy SPD may be installed at the main service entrance, while additional Type 2 or Type 3 SPDs are installed closer to downstream distribution boards and sensitive equipment.<\/strong><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\" style=\"margin-top:var(--wp--preset--spacing--70)\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-26\"><strong>Where Should a Surge Protective Device Be Installed?<\/strong><\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">The effectiveness of a surge protective device depends not only on selecting the correct SPD type, but also on installing it at the appropriate location within the electrical system. Proper installation helps ensure that surge energy is safely diverted to earth before it reaches sensitive electrical or electronic equipment.<br>In most low-voltage installations, SPDs are installed in stages to provide coordinated protection from the service entrance to the final load.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.234), 17px);\"><strong>Typical SPD Installation Locations<\/strong><\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Installation Location<\/strong><\/th><th><strong>Recommended SPD Type<\/strong><\/th><th><strong>Primary Purpose<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Service entrance<\/td><td>Type 1 or Type 1+2<\/td><td>Divert high-energy lightning currents entering the building<\/td><\/tr><tr><td>Main distribution board<\/td><td>Type 2<\/td><td>Protect downstream electrical circuits from switching surges and residual lightning surges<\/td><\/tr><tr><td>Sub-distribution board<\/td><td>Type 2<\/td><td>Provide additional protection for branch circuits<\/td><\/tr><tr><td>Close to sensitive equipment<\/td><td>Type 3<\/td><td>Reduce the remaining surge voltage before it reaches sensitive electronic equipment<\/td><\/tr><tr><td>PV combiner box or DC distribution board<\/td><td>DC Type 1+2 or DC Type 2<\/td><td>Protect photovoltaic DC circuits and inverters<\/td><\/tr><tr><td>Control cabinets and communication systems<\/td><td>Type 2, Type 3, or signal-line SPDs<\/td><td>Protect PLCs, communication equipment, and control electronics<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Installation Recommendations<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">To achieve the best protection performance, SPDs should be installed as close as possible to the equipment or distribution point they protect. The connecting conductors should be short and direct to minimize additional inductive voltage during surge discharge.<br>When the distance between the main SPD and the protected equipment is relatively long, an additional downstream SPD may be required to maintain an effective protection level.<\/p>\n\n\n\n<div class=\"wp-block-group has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-27 is-layout-constrained wp-block-group-is-layout-constrained\">\n<p class=\"wp-block-paragraph\">When planning an SPD installation, the following principles should always be considered:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Install the appropriate SPD type at each protection level.<\/li>\n\n\n\n<li>Keep all connecting conductors as short and straight as possible.<\/li>\n\n\n\n<li>Ensure reliable bonding to the earthing system.<\/li>\n\n\n\n<li>Follow the manufacturer\u2019s recommendations for backup protection and coordination.<\/li>\n\n\n\n<li>Use coordinated multi-stage protection for large or complex electrical installations.<\/li>\n<\/ul>\n<\/div>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\" style=\"margin-top:var(--wp--preset--spacing--70)\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-28\"><strong>Common SPD Installation Mistakes<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"667\" height=\"284\" src=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/common-spd-installation-mistakes.png\" alt=\"Illustration of common surge protective device (SPD) installation mistakes, including incorrect grounding, excessive lead length, poor coordination, and improper installation practices.\" class=\"wp-image-1745\" style=\"aspect-ratio:2.3486835417302023;width:722px;height:auto\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/common-spd-installation-mistakes.png 667w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/common-spd-installation-mistakes-300x128.png 300w\" sizes=\"auto, (max-width: 667px) 100vw, 667px\" \/><\/figure>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">Even a correctly selected surge protective device may fail to provide effective protection if it is installed incorrectly. Common installation mistakes can increase the residual voltage, reduce the SPD\u2019s service life, or prevent the surge current from being safely diverted.The following issues should be checked during installation and commissioning.<\/p>\n\n\n\n<figure style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><strong>Common Mistake<\/strong><\/th><th><strong>Why It Is a Problem<\/strong><\/th><th><strong>Recommended Practice<\/strong><\/th><\/tr><\/thead><tbody><tr><td>Installing the wrong SPD type<\/td><td>A Type 2 or Type 3 SPD may not be able to withstand the surge energy expected at the service entrance<\/td><td>Match the SPD type to the installation location and surge exposure<\/td><\/tr><tr><td>Selecting an incorrect Uc<\/td><td>A Uc value that is too low may cause premature operation or damage; a value that is too high may reduce protection effectiveness<\/td><td>Select Uc according to the system voltage and earthing arrangement<\/td><\/tr><tr><td>Using excessively long connecting conductors<\/td><td>Long conductors add inductive voltage during surge discharge and increase the effective protection level<\/td><td>Keep the connection path short, direct, and free from unnecessary loops<\/td><\/tr><tr><td>Poor earthing or equipotential bonding<\/td><td>A high-impedance earth path can prevent surge current from being discharged effectively<\/td><td>Ensure reliable earthing and equipotential bonding<\/td><\/tr><tr><td>Ignoring backup protection<\/td><td>An internal SPD fault may not be safely disconnected from the power system<\/td><td>Install the fuse or circuit breaker specified by the manufacturer<\/td><\/tr><tr><td>Installing only one SPD in a large system<\/td><td>A single SPD may not provide sufficient protection for distant distribution boards or sensitive loads<\/td><td>Use coordinated multi-stage protection where required<\/td><\/tr><tr><td>Using an incorrect pole or circuit configuration<\/td><td>The SPD may not protect all required conductors or may be unsuitable for the earthing system<\/td><td>Match the SPD circuit to the phase, neutral, polarity, and grounding arrangement<\/td><\/tr><tr><td>Failing to coordinate multiple SPDs<\/td><td>A downstream SPD may absorb more surge energy than it can withstand<\/td><td>Use manufacturer-verified coordinated combinations<\/td><\/tr><tr><td>Installing the SPD too far from the protected equipment<\/td><td>Long downstream cables may allow additional induced surges or increase the voltage reaching the equipment<\/td><td>Add downstream Type 2 or Type 3 protection when necessary<\/td><\/tr><tr><td>Failing to inspect or replace a failed SPD<\/td><td>Once the SPD reaches end of life, the circuit may no longer be protected<\/td><td>Check the status indicator and replace failed modules promptly<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>To avoid these mistakes:<\/strong><\/p>\n\n\n\n<ul style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\" class=\"wp-block-list\">\n<li>Select the SPD according to the system voltage, earthing arrangement, and installation location.<\/li>\n\n\n\n<li>Keep the total connection path as short and direct as practical.<\/li>\n\n\n\n<li>Use the correct backup protective device.<\/li>\n\n\n\n<li>Ensure reliable earthing and equipotential bonding.<\/li>\n\n\n\n<li>Verify coordination between upstream and downstream SPDs.<\/li>\n\n\n\n<li>Inspect the SPD status indicator during routine maintenance.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-29 wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\"><strong>Engineering Note<\/strong><br>The SPD itself is only one part of the surge protection system. Its actual performance also depends on conductor routing, earthing quality, backup protection, installation distance, and coordination with other SPDs.<br>A high-performance SPD can still provide poor protection if the installation layout is incorrect.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\" style=\"margin-top:var(--wp--preset--spacing--70)\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-30\"><strong>Frequently Asked Questions About Surge Protective Devices<\/strong><\/h2>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Can an SPD Be Used Without a Backup Fuse or Circuit Breaker?<\/strong><\/h3>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">It depends on the SPD design and the manufacturer\u2019s installation requirements. Some SPDs require an external backup fuse or circuit breaker, while others may include integrated overcurrent protection.<br>The backup protective device is used to disconnect the SPD safely if it develops an internal short circuit or reaches the end of its service life. Its rating should not be selected only according to the SPD\u2019s discharge-current rating.<br>Always follow the manufacturer\u2019s specified maximum backup fuse or circuit-breaker rating, short-circuit current requirements, and coordination instructions.<\/p>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong><strong>How Should a Surge Protective Device Be Maintained?<\/strong><\/strong><\/h3>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">SPD maintenance mainly involves regular inspection rather than internal repair. During routine electrical maintenance, check the status indicator, remote signaling contact, terminal tightness, signs of overheating, and the condition of the backup protective device.<br>The SPD should also be inspected after severe thunderstorms, lightning events, major power-system faults, or repeated tripping of the upstream protective device.<br>Replace the SPD or plug-in protection module if:<\/p>\n\n\n\n<ul class=\"wp-block-list has-small-font-size\">\n<li>The status indicator shows failure.<\/li>\n\n\n\n<li>A remote alarm is activated.<\/li>\n\n\n\n<li>The enclosure is discolored, cracked, or overheated.<\/li>\n\n\n\n<li>The backup fuse or circuit breaker has operated because of an SPD fault.<\/li>\n\n\n\n<li>The manufacturer\u2019s replacement criteria have been reached.<\/li>\n<\/ul>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong><strong>How Long Does a Surge Protective Device Last?<\/strong><\/strong><\/h3>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">An SPD does not have a fixed service life. Its lifespan depends on the number, magnitude, and duration of the surges it absorbs, as well as system voltage, temporary overvoltages, environmental conditions, and product quality.<br>An SPD may remain operational for many years in a low-surge environment, but a single severe surge can significantly reduce its remaining capacity or cause immediate failure.<br>The status indicator and remote signaling contact should therefore be used to determine whether the SPD is still operational. Replacement should be based on actual condition and manufacturer guidance rather than a fixed number of years alone.<\/p>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong><strong><strong>Do I Need Both AC and DC Surge Protection?<\/strong><\/strong><\/strong><\/h3>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">Both AC and DC surge protection may be required when a system contains separate AC and DC circuits. An AC SPD cannot automatically replace a DC SPD because the two devices are designed for different voltage characteristics, arc-extinguishing requirements, and system configurations.<br>For example, a solar PV system may require:<\/p>\n\n\n\n<ul class=\"wp-block-list has-small-font-size\">\n<li>A DC SPD on the PV array, combiner box, or inverter DC input.<\/li>\n\n\n\n<li>An AC SPD on the inverter output or AC distribution board.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">Energy storage systems, EV charging systems, and industrial DC control circuits may also require separate AC and DC protection.<br>The selected SPD must be rated for the actual system voltage, polarity, grounding arrangement, and maximum continuous operating voltage.<\/p>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong><strong><strong><strong>Can a Damaged SPD Continue Protecting Equipment?<\/strong><\/strong><\/strong><\/strong><\/h3>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">A damaged SPD should not be assumed to provide effective protection. Some SPDs contain an internal disconnection device that isolates the failed protection component while allowing the electrical circuit to remain energized.<br>In this condition, the connected equipment may continue operating, but surge protection may already be partially or completely lost.<br>If the status indicator shows failure or the remote alarm is activated, replace the SPD or protection module as soon as possible. Continuing to operate without replacement may leave downstream equipment unprotected.<\/p>\n<\/blockquote>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong><strong><strong><strong><strong>Are SPDs Required for Solar PV Systems?<\/strong><\/strong><\/strong><\/strong><\/strong><\/h3>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">SPD requirements for solar PV systems depend on the applicable electrical standard, lightning protection design, installation risk, cable routing, and local regulations.<br>PV systems are particularly exposed to induced surges because modules and DC cables are usually installed outdoors and may cover a large area. SPDs are commonly installed on the DC side, AC side, or both.<br>Typical locations include:<\/p>\n\n\n\n<ul class=\"wp-block-list has-small-font-size\">\n<li>PV combiner boxes<\/li>\n\n\n\n<li>Inverter DC inputs<\/li>\n\n\n\n<li>Inverter AC outputs<\/li>\n\n\n\n<li>Main AC distribution boards<\/li>\n<\/ul>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">The required SPD type depends on whether the building has an external lightning protection system, the separation distance, the system voltage, and the lightning exposure level.<br>Therefore, SPDs are not selected simply because the system is photovoltaic. The need, type, and installation position should be determined by the applicable project requirements and risk assessment.<\/p>\n<\/blockquote>\n\n\n\n<div class=\"wp-block-group has-palette-color-6-background-color has-background is-layout-constrained wp-block-group-is-layout-constrained\" style=\"margin-top:var(--wp--preset--spacing--70);margin-bottom:var(--wp--preset--spacing--70)\">\n<p class=\"has-text-align-left has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-31 wp-block-paragraph\"><strong><strong>LOOKING FOR A SUITABLE SPD FOR YOUR PROJECT?<\/strong><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\" style=\"font-size:clamp(14px, 0.875rem + ((1vw - 3.2px) * 0.078), 15px);\">After understanding the different SPD types, selection parameters, installation locations, and coordination requirements, you may also explore our complete range of surge protective devices for AC and DC applications.<br>Visit our <strong><a href=\"https:\/\/jutrion.com\/ko\/spd\/\"><em>Surge Protective Devices (SPD) product<\/em><\/a><\/strong> category to compare available models, voltage ratings, discharge current levels, pole configurations, and application options.<\/p>\n<\/div>\n\n\n\n<div class=\"wp-block-group has-palette-color-8-color has-palette-color-9-background-color has-text-color has-background has-link-color wp-elements-32 is-layout-constrained wp-block-group-is-layout-constrained\">\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>ABOUT THIS GUIDE<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This guide was prepared to help engineers, panel builders, electrical contractors, system integrators, and industrial buyers better understand surge protective devices (SPDs), their operating principles, selection criteria, installation practices, and common applications.<\/p>\n<\/div>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<div class=\"wp-block-group is-layout-constrained wp-block-group-is-layout-constrained\">\n<p class=\"has-palette-color-4-color has-text-color has-link-color has-large-font-size wp-elements-33 wp-block-paragraph\"><strong>REFERENCES AND TECHNICAL SOURCES<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u2060<a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314?utm_source.com\" target=\"_blank\" rel=\"noopener\">IEC 61643-11:2025 \u2013 Low-Voltage Surge Protective Devices \u2013 Requirements and Test Methods<\/a> \u2014 International Electrotechnical Commission.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/32531\" target=\"_blank\" rel=\"noopener\">IEC 61643-12 \u2013 Low-Voltage Surge Protective Devices \u2013 Selection and Application Principles<\/a> \u2014 International Electrotechnical Commission.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.ul.com\/services\/surge-protection-device-testing-and-certification-services?utm_source.com\" target=\"_blank\" rel=\"noopener\">UL 1449 \u2013 Standard for Surge Protective Devices<\/a> \u2014 UL Solutions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.nfpa.org\/codes-and-standards\/nfpa-70-standard-development\/70?utm_source.com\" target=\"_blank\" rel=\"noopener\">NFPA 70 \u2013 National Electrical Code (NEC) <\/a>\u2014 National Fire Protection Association.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/standards.ieee.org\/ieee\/C62.41.2\/2859\/?utm_source.com\" target=\"_blank\" rel=\"noopener\">\u2060IEEE C62.41.2 \u2013 Recommended Practice on Characterization of Surges in Low-Voltage AC Power Circuits<\/a> \u2014 Institute of Electrical and Electronics Engineers.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.nema.org\/membership\/products\/view\/low-voltage-surge-protective-devices?utm_source.com\" target=\"_blank\" rel=\"noopener\">NEMA \u2013 Low Voltage Surge Protective Devices Guidance<\/a>\u2014 National Electrical Manufacturers Association.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/29590\" target=\"_blank\" rel=\"noopener\">\u2060IEC 62305-4 \u2013 Protection Against Lightning \u2013 Electrical and Electronic Systems Within Structures<\/a>\u2014 International Electrotechnical Commission.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/30774\" target=\"_blank\" rel=\"noopener\">IEC 61643-32 \u2013 Surge Protective Devices Connected to the DC Side of Photovoltaic Installations<\/a>\u2014 International Electrotechnical Commission.<\/p>\n<\/div>\n<\/blockquote>","protected":false},"excerpt":{"rendered":"<p>What Is a Surge Protective Device (SPD)? A Surge Protective Device (SPD) is an electrical protection device designed to limit transient overvoltages and divert surge currents. Under normal operating conditions, the SPD remains in a high-impedance state and has little to no effect on the electrical system. When lightning, utility switching, motor starting and stopping, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":1746,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"[]"},"categories":[1],"tags":[],"class_list":["post-1741","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-electrical-guides"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/posts\/1741","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/comments?post=1741"}],"version-history":[{"count":2,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/posts\/1741\/revisions"}],"predecessor-version":[{"id":1747,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/posts\/1741\/revisions\/1747"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/media\/1746"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/media?parent=1741"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/categories?post=1741"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jutrion.com\/ko\/wp-json\/wp\/v2\/tags?post=1741"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}