{"id":758,"date":"2023-12-19T20:49:46","date_gmt":"2023-12-19T12:49:46","guid":{"rendered":"https:\/\/www.britecelectric.com\/?post_type=blog&p=758"},"modified":"2024-09-05T16:35:18","modified_gmt":"2024-09-05T08:35:18","slug":"low-voltage-power-supply-systems","status":"publish","type":"blog","link":"https:\/\/www.britecelectric.com\/it\/blog\/low-voltage-power-supply-systems\/","title":{"rendered":"Sistemi di alimentazione a bassa tensione"},"content":{"rendered":"Terminologia CEI<\/strong>\r\n\r\nInternational standard IEC 60364 distinguishes three families of earthing arrangements, using the two-letter codes TN, TT, and IT.\r\n\r\nThe first letter indicates the connection between earth and the power-supply equipment (generator or transformer):\r\n\r\n\u201cT\u201d \u2014 Direct connection of a point with earth\r\n\r\n\u201cI\u201d \u2014 No point is connected with earth, except perhaps via high impedance.\r\n\r\nThe second letter indicates the connection between earth or network and the electrical device being supplied:\r\n\r\n\u201cT\u201d \u2014 Earth connection is by a local direct connection to earth, usually via a ground rod.\r\n\r\n\u201cN\u201d \u2014 the earth connection is supplied by the electricity supply network, either separately to the neutral conductor (TN-S), combined with the neutral conductor (TN-C), or both (TN-C-S). These are discussed below.\r\n\r\nTipi di reti TN<\/strong>\r\n\r\nIn a TN earthing system, one of the points in the generator or transformer is connected with earth, usually the star point in a three-phase system. The body of the electrical device is connected with earth via this earth connection at the transformer. This arrangement is a current standard for residential and industrial electric systems particularly in Europe.\r\n\r\nThe conductor that connects the exposed metallic parts of the consumer\u2019s electrical installation is called protective earth (PE; see also: Ground). The conductor that connects to the star point in a three-phase system, or that carries the return current in a single-phase system, is called neutral (N). Three variants of TN systems are distinguished:\r\n\r\nTN\u2212S<\/strong>\r\n\r\nPE e N sono conduttori separati collegati insieme solo vicino alla fonte di alimentazione.\r\n\r\n\"\"\r\n\r\nTN\u2212C<\/strong>\r\n\r\nUn conduttore PEN combinato svolge le funzioni sia di un conduttore PE che di un conduttore N. (Su impianti a 230\/400 V normalmente utilizzati solo per reti di distribuzione)\r\n\r\n\"\"\r\n\r\nTN\u2212C\u2212S<\/strong>\r\n\r\nParte del sistema utilizza un conduttore PEN combinato, che a un certo punto viene suddiviso in linee PE e N separate. Il conduttore PEN combinato si trova generalmente tra la sottostazione e il punto di ingresso nell'edificio, mentre la terra e il neutro sono separati nella testata di distribuzione. Nel Regno Unito, questo sistema \u00e8 noto anche come messa a terra multipla di protezione (PME), a causa della pratica di collegare il conduttore combinato neutro-terra tramite il percorso pi\u00f9 breve praticabile ai dispersori locali alla fonte.e ad intervalli lungo le reti di distribuzione in ogni sede, per fornire sia la messa a terra del sistema che quella delle apparecchiature in ciascuno di questi luoghi. Sistemi simili in Australia e Nuova Zelanda sono designati come neutro con messa a terra multipla (MEN) e, in Nord America, come neutro con messa a terra multipla (MGN).\r\n\r\n\"\"\r\n\r\nRete TT<\/strong>\r\n\r\nIn un sistema di messa a terra TT, il collegamento a terra protettivo per l'utente \u00e8 fornito da un dispersore locale, mentre sul generatore ne \u00e8 installato un altro indipendentemente. Non c\u2019\u00e8 alcun \u2018filo di terra\u2019 tra i due. L'impedenza del circuito di guasto \u00e8 pi\u00f9 elevata e, a meno che l'impedenza dell'elettrodo non sia davvero molto bassa, un'installazione TT dovrebbe sempre avere un RCD (GFCI) come primo isolatore.\r\n\r\n\"\"\r\n\r\nRete informatica<\/strong>\r\n\r\nIn una rete IT, il sistema di distribuzione elettrica non ha alcun collegamento a terra oppure ha solo un collegamento ad alta impedenza.\r\n\r\n\"\"","protected":false},"featured_media":780,"parent":0,"menu_order":183,"template":"","meta":{"_acf_changed":false},"blog_category":[8],"class_list":["post-758","blog","type-blog","status-publish","has-post-thumbnail","hentry","blog_category-company-news"],"acf":{"des":"International standard IEC 60364 distinguishes three families of earthing arrangements, using the two-letter codes TN, TT, and IT.","txt":"IEC terminology<\/strong>\r\n\r\nInternational standard IEC 60364 distinguishes three families of earthing arrangements, using the two-letter codes TN, TT, and IT.\r\n\r\nThe first letter indicates the connection between earth and the power-supply equipment (generator or transformer):\r\n\r\n\u201cT\u201d \u2014 Direct connection of a point with earth\r\n\r\n\u201cI\u201d \u2014 No point is connected with earth, except perhaps via high impedance.\r\n\r\nThe second letter indicates the connection between earth or network and the electrical device being supplied:\r\n\r\n\u201cT\u201d \u2014 Earth connection is by a local direct connection to earth, usually via a ground rod.\r\n\r\n\u201cN\u201d \u2014 the earth connection is supplied by the electricity supply network, either separately to the neutral conductor (TN-S), combined with the neutral conductor (TN-C), or both (TN-C-S). These are discussed below.\r\n\r\nTypes of TN networks<\/strong>\r\n\r\nIn a TN earthing system, one of the points in the generator or transformer is connected with earth, usually the star point in a three-phase system. The body of the electrical device is connected with earth via this earth connection at the transformer. This arrangement is a current standard for residential and industrial electric systems particularly in Europe.\r\n\r\nThe conductor that connects the exposed metallic parts of the consumer\u2019s electrical installation is called protective earth (PE; see also: Ground). The conductor that connects to the star point in a three-phase system, or that carries the return current in a single-phase system, is called neutral (N). Three variants of TN systems are distinguished:\r\n\r\nTN\u2212S<\/strong>\r\n\r\nPE and N are separate conductors that are connected together only near the power source.\r\n\r\n\"\"\r\n\r\nTN\u2212C<\/strong>\r\n\r\nA combined PEN conductor fulfills the functions of both a PE and an N conductor. (On 230\/400 V systems normally only used for distribution networks)\r\n\r\n\"\"\r\n\r\nTN\u2212C\u2212S<\/strong>\r\n\r\nPart of the system uses a combined PEN conductor, which is at some point split up into separate PE and N lines. The combined PEN conductor typically occurs between the substation and the entry point into the building, and earth and neutral are separated in the service head. In the UK, this system is also known as protective multiple earthing (PME), because of the practice of connecting the combined neutral-and-earth conductor via the shortest practicable route to local earth rods at the source and at intervals along the distribution networks to each premises, to provide both system earthing and equipment earthing at each of these locations. Similar systems in Australia and New Zealand are designated as multiple earthed neutral (MEN) and, in North America, as multi-grounded neutral (MGN).\r\n\r\n\"\"\r\n\r\nTT network<\/strong>\r\n\r\nIn a TT earthing system, the protective earth connection for the consumer is provided by a local earth electrode, and there is another independently installed at the generator. There is no \u2018earth wire\u2019 between the two. The fault loop impedance is higher, and unless the electrode impedance is very low indeed, a TT installation should always have an RCD (GFCI) as its first isolator.\r\n\r\n\"\"\r\n\r\nIT network<\/strong>\r\n\r\nIn an IT network, the electrical distribution system has no connection to earth at all, or it has only a high-impedance connection.\r\n\r\n\"\""},"_links":{"self":[{"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/blog\/758","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\/780"}],"wp:attachment":[{"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/media?parent=758"}],"wp:term":[{"taxonomy":"blog_category","embeddable":true,"href":"https:\/\/www.britecelectric.com\/it\/wp-json\/wp\/v2\/blog_category?post=758"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}