{"id":854,"date":"2023-12-18T15:22:31","date_gmt":"2023-12-18T07:22:31","guid":{"rendered":"https:\/\/www.britecelectric.com\/?post_type=blog&#038;p=854"},"modified":"2024-09-05T16:40:16","modified_gmt":"2024-09-05T08:40:16","slug":"understanding-surge-protection-devices-spds","status":"publish","type":"blog","link":"https:\/\/www.britecelectric.com\/da\/blog\/understanding-surge-protection-devices-spds\/","title":{"rendered":"Forst\u00e5else af oversp\u00e6ndingsbeskyttelsesenheder (SPD'er)"},"content":{"rendered":"<strong>Behovet for oversp\u00e6ndingsbeskyttelse<\/strong>\r\n\r\nToday\u2019s world is full of electronic products and electrical devices that are susceptible to damage from overvoltage surges\r\n\r\nSurges caused by static discharge, capacitive and inductive loads or lightning can quickly destroy sophisticated electronic equipment and components used in industrial and commercial applications. These surges cripple operations \u2013 particularly the data and communication systems that virtually every enterprise relies upon today,\r\n\r\n<strong>18. udgave Krav til oversp\u00e6ndingsbeskyttelse<\/strong>\r\n\r\nMens den 17. udgave arbejdede p\u00e5 grundlag af sandsynligheden for et lynnedslag \u2013 den prim\u00e6re \u00e5rsag til elektricitetsstigninger \u2013 efter AQ-kriterierne, overvejer BS7671:2018 i stedet konsekvenserne af et nedslag og tilh\u00f8rende stigning. Forskrift 443.4 siger nemlig, at en SPD skal installeres, hvor konsekvenser for\u00e5rsaget af oversp\u00e6nding omfatter:\r\n<ul>\r\n \t<li>\u2018Alvorlig skade p\u00e5 eller tab af menneskeliv\u2019<\/li>\r\n \t<li>\u2018Afbrydelse af offentlige tjenester og\/eller skade p\u00e5 kulturarv\u2019<\/li>\r\n \t<li>\u2018Afbrydelse af kommerciel eller industriel aktivitet\u2019<\/li>\r\n \t<li>\u2018P\u00e5virker et stort antal samlokaliserede individer\u2019<\/li>\r\n<\/ul>\r\nDet betyder reelt, at alt undtagen sm\u00e5 boliger nu skal have tilstr\u00e6kkelig oversp\u00e6ndingssikring.\r\n\r\n<strong>\u00c5rsager og konsekvenser af elektriske oversp\u00e6ndinger<\/strong>\r\n\r\nDe fleste str\u00f8mst\u00f8d skyldes enten lynnedslag eller str\u00f8mskifte. Et lyn kan b\u00e6re en str\u00f8m p\u00e5 200.000A og er s\u00e6rligt farligt, da overslaget kan for\u00e5rsage brand eller elektrisk st\u00f8d. Skiftst\u00f8d for\u00e5rsaget af nedlukning af store induktive belastninger har tendens til at v\u00e6re mindre ekstreme, men mere gentagne, hvilket potentielt begr\u00e6nser levetiden for systemkomponenter.\r\n<ul>\r\n \t<li>Lynnedslag \u2014 Storskalap\u00e5virkning, h\u00f8j str\u00f8m og sp\u00e6nding, men mindst almindelig forekomst.<\/li>\r\n \t<li>Power switching \u2014 Stigende forekomster:<\/li>\r\n<\/ul>\r\n<ol>\r\n \t<li>Forbrugs- og kundebelastningsskift \u2013 Motorer, store belastninger, fejl, kondensatorbanker, sikring og afbryderdrift mv.<\/li>\r\n \t<li>Kildeskift \u2014 smart grid, generators\u00e6t, solcelleanl\u00e6g og vindkraftproduktion osv.<\/li>\r\n<\/ol>\r\nMed hensyn til SPD'er tjener de til at forhindre skader p\u00e5 alle dele af en elektrisk installation og tilsluttede apparater. Dette er for\u00e5rsaget af forbig\u00e5ende oversp\u00e6nding, der overstiger den nominelle modstandsgr\u00e6nse for elektrisk udstyr, hvilket for\u00e5rsager skader s\u00e5som br\u00e6ndte komponenter, forringet isolering og endda smeltede ledninger.\r\n\r\n<strong>Typer af oversp\u00e6ndingsbeskyttelsesanordninger<\/strong>\r\n\r\nThere are three principal types of surge protection device in common use, depending on where they are installed within an installation.\r\n\r\nFirstly, Type 1 SPDs are capable of discharging partial lightning current with a waveform of 10\/350\u00b5s. This makes them suitable for installation on the supply side of the main service entrance, protecting the whole installation including the service panel from overvoltage. Typically, they use a spark gap to direct the surge to earth and prevent it reaching the building.\r\n\r\nSecondly, Type 2 SPDs are intended to protect equipment attached to an installation. They are positioned on the load side of the main service entrance across phase-neutral or phase-phase and prevent the spread of overvoltage through a metal oxide varistor (MOV) with an 8\/20\u00b5s current wave. MOVs maintain very high resistance until surge voltage is encountered, at which point resistance drops dramatically and excess current can be channeled to earth.\r\n\r\nFinally, Type 3 SPDs are much smaller scale and should only be used in conjunction with a Type 2 device. They are specifically designed for protecting sensitive equipment such as televisions and computers from overvoltage. Their voltage waves tend to be around 1.5\/50\u00b5s and current waves tend to be around 8\/20\u00b5s.\r\n\r\n<strong>Valg og anvendelse af AC Power System SPD<\/strong>\r\n\r\nHaving determined the Class of SPD required, the correct voltage and configuration needs to be determined.\r\n\r\nTN-C System\r\n\r\nIn this system, the neutral and protective earth conductor is combined in a single conductor throughout the system. This conductor is referred to as a PEN, a \u201cProtective Earth &amp; Neutral\u201d. All exposed conductive equipment parts are connected to the PEN.\r\n\r\nTN-S System\r\n\r\nIn this system, a separate neutral and protective earth conductor is run throughout. The Protective Earth (PE) conductor is normally a separate conductor, but can also be the metallic sheath of the power cable. All exposed conductive equipment parts are connected to the PE conductor.\r\n\r\nTN-C-S System\r\n\r\nIn this system, the supply is configured as per TN-C, while the downstream installation is configured as per TN-S. The combined PEN conductor typically occurs between the substation and the entry point into the building, and earth and neutral are separated in the Main Distribution Board. This system is also known as Protective Multiple Earthing (PME) or Multiple Earthed Neutral (MEN). The supply PEN conductor is earthed at a number of points throughout the network and generally as close to the consumer\u2019s point- of-entry as possible.\r\n\r\nTT SYSTEM\r\n\r\nA system having one point of the source of energy earthed and the exposed conductive parts of the installation connected to independent earthed electrodes. The incoming supply neutral is not earthed at the main distribution board.\r\n\r\nIn the TT system, in order for overcurrent protective devices (fuses and circuit breakers) to operate in the intended manner, it is important that SPDs must not connect directly from phase to protective ground, but from phase to neutral and neutral to ground. Therefore, the Neutral-to-PE SPD carries both the PE to neutral impulse current and the PE to phase impulse currents. This SPD is recommended to be a GDT (Gas Discharge Tube) due to their generally superior energy handling characteristics.\r\n\r\nIT SYSTEM\r\n\r\nA system have no direct connection between live parts and earth, but all exposed conductive parts of the installation being connected to independent earthed electrodes. The source is either floating or earthed through a high impedance (to limit fault currents). This means that during a Phase to Earth fault, the systems continues to operate. This is detected, and maintenance efforts commenced to rectify the fault. However, during this time, the Phase to Earth voltage rises to the usual Line to Line voltage, and installed SPDs must withstand this during this time. Most installed IT systems do not utilize a neutral conductor \u2013 equipment is powered from line to line. The IT system is typically used in older installations in countries such as Norway and France. It is also used in special applications, such as intensive care wards of hospitals and special industrial applications.\r\n\r\n<strong>Koordinering af oversp\u00e6ndingsbeskyttelse<\/strong>\r\n\r\nSPDs should have a protection level significantly lower than the rated impulse withstand voltage. SPDs should also always be from the same manufacturer.\r\n\r\nAn important factor to consider when installing surge protection is the total length of the leads connecting the SPD to the installation. They should be as short as possible, preferably totaling less than 0.5m and in no case totaling more than 1m. SPDs should always be installed according to the manufacturer\u2019s instructions and preferably on the supply side of RCDs.","protected":false},"featured_media":855,"parent":0,"menu_order":150,"template":"","meta":{"_acf_changed":false},"blog_category":[8],"class_list":["post-854","blog","type-blog","status-publish","has-post-thumbnail","hentry","blog_category-company-news"],"acf":{"des":"Today\u2019s world is full of electronic products and electrical devices that are susceptible to damage from overvoltage surges","txt":"<strong>The need for surge protection<\/strong>\r\n\r\nToday\u2019s world is full of electronic products and electrical devices that are susceptible to damage from overvoltage surges\r\n\r\nSurges caused by static discharge, capacitive and inductive loads or lightning can quickly destroy sophisticated electronic equipment and components used in industrial and commercial applications. These surges cripple operations \u2013 particularly the data and communication systems that virtually every enterprise relies upon today,\r\n\r\n<strong>18th Edition Surge Protection Requirements<\/strong>\r\n\r\nWhereas the 17th Edition worked on the basis of the likelihood of a lightning strike \u2013 the principal cause of electricity surges \u2013 following the AQ criteria, BS7671:2018 instead considers the consequences of a strike and associated surge. Namely, regulation 443.4 states that an SPD must be installed where consequences caused by overvoltage include:\r\n<ul>\r\n \t<li>\u2018Serious injury to, or loss of, human life\u2019<\/li>\r\n \t<li>\u2018Interruption of public services and\/or damage to cultural heritage\u2019<\/li>\r\n \t<li>\u2018Interruption of commercial or industrial activity\u2019<\/li>\r\n \t<li>\u2018Affecting a large number of collocated individuals\u2019<\/li>\r\n<\/ul>\r\nThis effectively means that everything but small domestic dwellings must now have adequate surge protection.\r\n\r\n<strong>Causes and Consequences of Electrical Surges<\/strong>\r\n\r\nMost electricity surges are caused either by lightning strikes or electricity switching. A bolt of lightning can carry a current of 200,000A and is particularly dangerous as the flashover can cause fire or electric shock. Switching surges caused by shutting down large inductive loads tend to be less extreme but more repetitive, potentially limiting the operating life of system components.\r\n<ul>\r\n \t<li>Lightning strikes \u2014 Large scale impact, high current and voltage, but least common occurrence.<\/li>\r\n \t<li>Power switching \u2014 Increasing occurrences:<\/li>\r\n<\/ul>\r\n<ol>\r\n \t<li>Utility and customer load switching \u2013 Motors, large loads, faults, capacitor banks, fuse and circuit breaker operation, etc.<\/li>\r\n \t<li>Source switching \u2014 smart grid, gensets, photovoltaic power systems and wind power generation, etc.<\/li>\r\n<\/ol>\r\nIn terms of SPDs, they serve to prevent damage to all parts of an electrical installation and attached appliances. This is caused by transient overvoltage exceeding the rated withstand limit of electrical equipment, thus causing damage such as burned components, degraded insulation and even melted wires.\r\n\r\n<strong>Types of Surge Protection Device<\/strong>\r\n\r\nThere are three principal types of surge protection device in common use, depending on where they are installed within an installation.\r\n\r\nFirstly, Type 1 SPDs are capable of discharging partial lightning current with a waveform of 10\/350\u00b5s. This makes them suitable for installation on the supply side of the main service entrance, protecting the whole installation including the service panel from overvoltage. Typically, they use a spark gap to direct the surge to earth and prevent it reaching the building.\r\n\r\nSecondly, Type 2 SPDs are intended to protect equipment attached to an installation. They are positioned on the load side of the main service entrance across phase-neutral or phase-phase and prevent the spread of overvoltage through a metal oxide varistor (MOV) with an 8\/20\u00b5s current wave. MOVs maintain very high resistance until surge voltage is encountered, at which point resistance drops dramatically and excess current can be channeled to earth.\r\n\r\nFinally, Type 3 SPDs are much smaller scale and should only be used in conjunction with a Type 2 device. They are specifically designed for protecting sensitive equipment such as televisions and computers from overvoltage. Their voltage waves tend to be around 1.5\/50\u00b5s and current waves tend to be around 8\/20\u00b5s.\r\n\r\n<strong>Selection and Application of AC Power System SPD<\/strong>\r\n\r\nHaving determined the Class of SPD required, the correct voltage and configuration needs to be determined.\r\n\r\nTN-C System\r\n\r\nIn this system, the neutral and protective earth conductor is combined in a single conductor throughout the system. This conductor is referred to as a PEN, a \u201cProtective Earth &amp; Neutral\u201d. All exposed conductive equipment parts are connected to the PEN.\r\n\r\nTN-S System\r\n\r\nIn this system, a separate neutral and protective earth conductor is run throughout. The Protective Earth (PE) conductor is normally a separate conductor, but can also be the metallic sheath of the power cable. All exposed conductive equipment parts are connected to the PE conductor.\r\n\r\nTN-C-S System\r\n\r\nIn this system, the supply is configured as per TN-C, while the downstream installation is configured as per TN-S. The combined PEN conductor typically occurs between the substation and the entry point into the building, and earth and neutral are separated in the Main Distribution Board. This system is also known as Protective Multiple Earthing (PME) or Multiple Earthed Neutral (MEN). The supply PEN conductor is earthed at a number of points throughout the network and generally as close to the consumer\u2019s point- of-entry as possible.\r\n\r\nTT SYSTEM\r\n\r\nA system having one point of the source of energy earthed and the exposed conductive parts of the installation connected to independent earthed electrodes. The incoming supply neutral is not earthed at the main distribution board.\r\n\r\nIn the TT system, in order for overcurrent protective devices (fuses and circuit breakers) to operate in the intended manner, it is important that SPDs must not connect directly from phase to protective ground, but from phase to neutral and neutral to ground. Therefore, the Neutral-to-PE SPD carries both the PE to neutral impulse current and the PE to phase impulse currents. This SPD is recommended to be a GDT (Gas Discharge Tube) due to their generally superior energy handling characteristics.\r\n\r\nIT SYSTEM\r\n\r\nA system have no direct connection between live parts and earth, but all exposed conductive parts of the installation being connected to independent earthed electrodes. The source is either floating or earthed through a high impedance (to limit fault currents). This means that during a Phase to Earth fault, the systems continues to operate. This is detected, and maintenance efforts commenced to rectify the fault. However, during this time, the Phase to Earth voltage rises to the usual Line to Line voltage, and installed SPDs must withstand this during this time. Most installed IT systems do not utilize a neutral conductor \u2013 equipment is powered from line to line. The IT system is typically used in older installations in countries such as Norway and France. It is also used in special applications, such as intensive care wards of hospitals and special industrial applications.\r\n\r\n<strong>Coordination of Surge Protection<\/strong>\r\n\r\nSPDs should have a protection level significantly lower than the rated impulse withstand voltage. SPDs should also always be from the same manufacturer.\r\n\r\nAn important factor to consider when installing surge protection is the total length of the leads connecting the SPD to the installation. They should be as short as possible, preferably totaling less than 0.5m and in no case totaling more than 1m. SPDs should always be installed according to the manufacturer\u2019s instructions and preferably on the supply side of RCDs."},"_links":{"self":[{"href":"https:\/\/www.britecelectric.com\/da\/wp-json\/wp\/v2\/blog\/854","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.britecelectric.com\/da\/wp-json\/wp\/v2\/blog"}],"about":[{"href":"https:\/\/www.britecelectric.com\/da\/wp-json\/wp\/v2\/types\/blog"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.britecelectric.com\/da\/wp-json\/wp\/v2\/media\/855"}],"wp:attachment":[{"href":"https:\/\/www.britecelectric.com\/da\/wp-json\/wp\/v2\/media?parent=854"}],"wp:term":[{"taxonomy":"blog_category","embeddable":true,"href":"https:\/\/www.britecelectric.com\/da\/wp-json\/wp\/v2\/blog_category?post=854"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}