{"id":858,"date":"2023-12-17T15:26:05","date_gmt":"2023-12-17T07:26:05","guid":{"rendered":"https:\/\/www.britecelectric.com\/?post_type=blog&p=858"},"modified":"2024-09-05T16:40:33","modified_gmt":"2024-09-05T08:40:33","slug":"surge-protective-devices-spd","status":"publish","type":"blog","link":"https:\/\/www.britecelectric.com\/it\/blog\/surge-protective-devices-spd\/","title":{"rendered":"Dispositivi di protezione contro le sovratensioni (SPD)"},"content":{"rendered":"Surge Protective Devices (SPD) are used to protect the electrical installation, which consists of the consumer unit, wiring and accessories, from electrical power surges known as transient overvoltage.\r\n\r\nEvery piece of electronic equipment found in an industrial environment is subjected to power surges generated on the utility grid are transmitted to the equipment via incoming power lines. Users are installing surge protection devices to protect their equipment from surges.\r\n\r\nThere are three different types of Surge Protective Devices:\r\n
    \r\n \t
  1. SPD di tipo 1 installato all'origine, ad es. quadro di distribuzione principale.<\/li>\r\n \t
  2. SPD di Tipo 2 installato su quadri di distribuzione secondaria (sono disponibili SPD di Tipo 1 e 2 combinati e solitamente sono installati nelle unit\u00e0 di consumo).<\/li>\r\n \t
  3. SPD di tipo 3 installato vicino al carico protetto. Devono essere installati solo come integrazione all'SPD di Tipo 2.<\/li>\r\n<\/ol>\r\nLaddove siano necessari pi\u00f9 dispositivi per proteggere l'installazione, questi devono essere coordinati per garantire il corretto funzionamento. \u00c8 necessario verificare la compatibilit\u00e0 degli articoli forniti da diversi produttori; l'installatore e i produttori dei dispositivi sono nella posizione migliore per fornire indicazioni in merito.\r\n\r\nSPD di tipo 1<\/strong>\r\n\r\nSPD Type 1 must be connected upstream of the system, at the point of delivery of power energy. SPD protects buildings and people from the risk of direct lightning (fire and death) and is characterized by:\r\n\r\nIimp 10\/350 Impulse current: Iimp corresponds to the peak value of a 10\/350 \u03bcs current impulse waveform.\r\n\r\nSPD di tipo 2<\/strong>\r\n\r\nSPD Type 2 devices are designed to remove all the overvoltage from supply circuits that are not likely to be directly hit by lightning. SPD Type 2 is connected downstream SPD Type 1 or SPD Type 1+2, (minimum distance 1 m) and they protect machines and tools connected to the ground and reduce the risk of economic loss.\r\n\r\nSPD Type 2 is characterized by:\r\n\r\nIn 8\/20 Nominal discharge current: The peak current (and waveform shape) through the SPD under conditions prescribed by EN 62305 to represent the surge current as a consequence of a lightning strike to the electric supply line.\r\n\r\nImax 8\/20 Maximum discharge current: Peak value of the highest current of an 8\/20 \u03bcs waveform that an SPD can discharge at least once without breaking.\r\n\r\nSPD di tipo 3<\/strong>\r\n\r\nSPD type 3 devices are used to protect the end user from overvoltage. They may be installed in supply networks where SDP types 1 and\/or 2 already exist. They can be installed in fixed or mobile sockets and have the following characteristic parameters:\r\n\r\nUoc: test voltage. This is the peak value of the no-load voltage of the combined test-generator; this has a waveform of 1.2\/50 \u03bcs and can supply at the same time current with waveform 8\/20 \u03bcs\r\n\r\nCos'\u00e8 la sovratensione transitoria?<\/strong>\r\n\r\nLe sovratensioni transitorie sono definite come picchi di energia elettrica di breve durata che si verificano a causa del rilascio improvviso di energia precedentemente immagazzinata o indotta con altri mezzi. La sovratensione transitoria pu\u00f2 essere naturale o provocata dall'uomo.\r\n\r\nLe fonti di sovratensione possono essere esterne o interne.<\/strong>\r\n\r\nExternal transient overvoltage is:\r\n\r\nLightning (most damaging)\r\n\r\nSwitching of capacitor banks\r\n\r\nSwitching of large electrical loads\r\n\r\nPower line disconnection and reconnection\r\n\r\nTransformer switching\r\n\r\nElectrostatic discharges\r\n\r\nPoor power transmission and distribution grid quality\r\n\r\nInternal transient overvoltage is:\r\n\r\nFuse and circuit breaker (MCCB, ACB, etc.)\r\n\r\nElectrical motors and motor starters\r\n\r\nHVAC devices\r\n\r\nVariable frequency drives\r\n\r\nHousehold devices such as microwave oven, computer, refrigerator\r\n\r\nElectronic ballasts\r\n\r\nTecnologie dei dispositivi di protezione dalle sovratensioni<\/strong>\r\n\r\nVaristor:\r\n\r\nThis can be considered as a variable resistance that at nominal voltage has a very high ohmic value. But the resistance rapidly falls to near zero as the voltage surges. In this way, the varistor applies a near short circuit that clamps the surge voltage. The varistor is however subject to progressive degradation due to the small leakage current that occurs at the nominal voltage, and with the number of interventions. With every overvoltage that occurs the leakage current rises and accelerates the end of life for the device \u2013 which is ultimately indicated by the change from green to red in the signal window.\r\n\r\nSpark gap:\r\n\r\nThis comprises two electrodes separated by air or gas. When a surge voltage occurs electrical arc bridges the gap and a surge current flow to limit the surge voltage to a low and constant level. The arc extinguishes only when the surge current falls below about 10 amperes. The gas guarantees a constant level of breakdown voltage since the arc is struck in a protected environment; not exposed to pressure or humidity variations or impurities as would happen if it had occurred in the air. There is, however, a delay before the device arcs and the surge current is diverted, and this is dependent on the magnitude of the original voltage surge and its rate of rising. Therefore, the voltage protection level can vary, although it is guaranteed to be less than up.\r\n\r\nDevo avere gli SPD installati?<\/strong>\r\n\r\nL'attuale edizione dei regolamenti sul cablaggio IET, BS 7671:2018, afferma che, a meno che non venga effettuata una valutazione del rischio, la protezione contro la sovratensione transitoria deve essere fornita laddove la conseguenza causata dalla sovratensione potrebbe:\r\n
      \r\n \t
    • Risultare in gravi lesioni o perdita di vite umane;<\/li>\r\n \t
    • Conseguente interruzione dei servizi pubblici e\/o danneggiamento del patrimonio culturale;<\/li>\r\n \t
    • Comportare l'interruzione dell'attivit\u00e0 commerciale o industriale;<\/li>\r\n \t
    • Colpisce un gran numero di individui co-localizzati.<\/li>\r\n<\/ul>\r\nThis regulation applies to all types of premises which include domestic, commercial and industrial.\r\n\r\nThe decision on whether to purchase SPDs is in the hands of the customer, but they should be provided with enough information to make an informed decision on whether they wish to omit SPDs.\r\n\r\nSurge protection could be installed in an existing consumer unit if appropriate physical space was available or, if enough space was not available, it could be installed in an external enclosure adjacent to the existing consumer unit.","protected":false},"featured_media":859,"parent":0,"menu_order":148,"template":"","meta":{"_acf_changed":false},"blog_category":[8],"class_list":["post-858","blog","type-blog","status-publish","has-post-thumbnail","hentry","blog_category-company-news"],"acf":{"des":"Surge Protective Devices (SPD) are used to protect the electrical installation, which consists of the consumer unit, wiring and accessories, from electrical power surges known as transient overvoltage.","txt":"Surge Protective Devices (SPD) are used to protect the electrical installation, which consists of the consumer unit, wiring and accessories, from electrical power surges known as transient overvoltage.\r\n\r\nEvery piece of electronic equipment found in an industrial environment is subjected to power surges generated on the utility grid are transmitted to the equipment via incoming power lines. Users are installing surge protection devices to protect their equipment from surges.\r\n\r\nThere are three different types of Surge Protective Devices:\r\n
        \r\n \t
      1. Type 1 SPD installed at the origin, e.g. main distribution board.<\/li>\r\n \t
      2. Type 2 SPD installed at sub-distribution boards (Combined Type 1 & 2 SPDs are available and are usually installed in consumer units).<\/li>\r\n \t
      3. Type 3 SPD installed close to the protected load. They must only be installed as a supplement to Type 2 SPD.<\/li>\r\n<\/ol>\r\nWhere multiple devices are required to protect the installation, they must be coordinated to ensure correct operation. Items supplied by different manufacturers should be confirmed for compatibility, the installer and manufacturers of the devices are best placed to provide guidance on this.\r\n\r\nType 1 SPD<\/strong>\r\n\r\nSPD Type 1 must be connected upstream of the system, at the point of delivery of power energy. SPD protects buildings and people from the risk of direct lightning (fire and death) and is characterized by:\r\n\r\nIimp 10\/350 Impulse current: Iimp corresponds to the peak value of a 10\/350 \u03bcs current impulse waveform.\r\n\r\nType 2 SPD<\/strong>\r\n\r\nSPD Type 2 devices are designed to remove all the overvoltage from supply circuits that are not likely to be directly hit by lightning. SPD Type 2 is connected downstream SPD Type 1 or SPD Type 1+2, (minimum distance 1 m) and they protect machines and tools connected to the ground and reduce the risk of economic loss.\r\n\r\nSPD Type 2 is characterized by:\r\n\r\nIn 8\/20 Nominal discharge current: The peak current (and waveform shape) through the SPD under conditions prescribed by EN 62305 to represent the surge current as a consequence of a lightning strike to the electric supply line.\r\n\r\nImax 8\/20 Maximum discharge current: Peak value of the highest current of an 8\/20 \u03bcs waveform that an SPD can discharge at least once without breaking.\r\n\r\nType 3 SPD<\/strong>\r\n\r\nSPD type 3 devices are used to protect the end user from overvoltage. They may be installed in supply networks where SDP types 1 and\/or 2 already exist. They can be installed in fixed or mobile sockets and have the following characteristic parameters:\r\n\r\nUoc: test voltage. This is the peak value of the no-load voltage of the combined test-generator; this has a waveform of 1.2\/50 \u03bcs and can supply at the same time current with waveform 8\/20 \u03bcs\r\n\r\nWhat is transient overvoltage?<\/strong>\r\n\r\nTransient overvoltage is defined as short duration surges of electricity which occur due to the sudden release of energy previously-stored or induced by other means. Transient overvoltage can be either naturally occurring or man-made.\r\n\r\nSources of power surges can be external or internal.<\/strong>\r\n\r\nExternal transient overvoltage is:\r\n\r\nLightning (most damaging)\r\n\r\nSwitching of capacitor banks\r\n\r\nSwitching of large electrical loads\r\n\r\nPower line disconnection and reconnection\r\n\r\nTransformer switching\r\n\r\nElectrostatic discharges\r\n\r\nPoor power transmission and distribution grid quality\r\n\r\nInternal transient overvoltage is:\r\n\r\nFuse and circuit breaker (MCCB, ACB, etc.)\r\n\r\nElectrical motors and motor starters\r\n\r\nHVAC devices\r\n\r\nVariable frequency drives\r\n\r\nHousehold devices such as microwave oven, computer, refrigerator\r\n\r\nElectronic ballasts\r\n\r\nSurge protection device technologies<\/strong>\r\n\r\nVaristor:\r\n\r\nThis can be considered as a variable resistance that at nominal voltage has a very high ohmic value. But the resistance rapidly falls to near zero as the voltage surges. In this way, the varistor applies a near short circuit that clamps the surge voltage. The varistor is however subject to progressive degradation due to the small leakage current that occurs at the nominal voltage, and with the number of interventions. With every overvoltage that occurs the leakage current rises and accelerates the end of life for the device \u2013 which is ultimately indicated by the change from green to red in the signal window.\r\n\r\nSpark gap:\r\n\r\nThis comprises two electrodes separated by air or gas. When a surge voltage occurs electrical arc bridges the gap and a surge current flow to limit the surge voltage to a low and constant level. The arc extinguishes only when the surge current falls below about 10 amperes. The gas guarantees a constant level of breakdown voltage since the arc is struck in a protected environment; not exposed to pressure or humidity variations or impurities as would happen if it had occurred in the air. There is, however, a delay before the device arcs and the surge current is diverted, and this is dependent on the magnitude of the original voltage surge and its rate of rising. Therefore, the voltage protection level can vary, although it is guaranteed to be less than up.\r\n\r\nDo I have to have SPDs installed?<\/strong>\r\n\r\nThe current edition of the IET Wiring Regulations, BS 7671:2018, states that unless a risk assessment is carried out, protection against transient overvoltage shall be provided where the consequence caused by overvoltage could:\r\n
          \r\n \t
        • Result in serious injury to, or loss of, human life;<\/li>\r\n \t
        • Result in interruption of public services and\/or damage to cultural heritage;<\/li>\r\n \t
        • Result in interruption of commercial or industrial activity;<\/li>\r\n \t
        • Affect a large number of co-located individuals.<\/li>\r\n<\/ul>\r\nThis regulation applies to all types of premises which include domestic, commercial and industrial.\r\n\r\nThe decision on whether to purchase SPDs is in the hands of the customer, but they should be provided with enough information to make an informed decision on whether they wish to omit SPDs.\r\n\r\nSurge protection could be installed in an existing consumer unit if appropriate physical space was available or, if enough space was not available, it could be installed in an external enclosure adjacent to the existing consumer unit."},"_links":{"self":[{"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/blog\/858","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/blog"}],"about":[{"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/types\/blog"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/media\/859"}],"wp:attachment":[{"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/media?parent=858"}],"wp:term":[{"taxonomy":"blog_category","embeddable":true,"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/blog_category?post=858"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}