{"id":72453,"date":"2026-09-02T11:19:23","date_gmt":"2026-09-02T14:19:23","guid":{"rendered":"https:\/\/a3aengenharia.com\/?post_type=articles&#038;p=72453"},"modified":"2026-09-14T19:41:13","modified_gmt":"2026-09-14T22:41:13","slug":"175v-275v-spd-uc-network-voltage-how-to-choose","status":"publish","type":"articles","link":"https:\/\/a3aengenharia.com\/en-us\/content\/technical-articles\/175v-275v-spd-uc-network-voltage-how-to-choose\/","title":{"rendered":"175 V or 275 V SPD: Difference, Uc, Network Voltage and How to Choose"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">The choice between a 175 V and 275 V SPD should not be made only by looking at the nominal voltage printed on a panel or repeating a rule of thumb. These values are mainly associated with <code>Uc<\/code>, the maximum RMS continuous operating voltage that may remain applied to the SPD protection mode without causing unintended operation or degradation incompatible with its function.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><code>Uc<\/code> must be compatible with the voltage that actually appears between the terminals to which the SPD is connected. This depends on network voltage, earthing arrangement, mode of protection and device position \u2014 phase-neutral, phase-PE, neutral-PE or phase-phase. The same system can therefore require different values for different modes of protection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">There is also a trade-off. Excessively low <code>Uc<\/code> may make the SPD more susceptible to temporary overvoltages, or TOV. Very high <code>Uc<\/code> can increase continuous-operation margin, but does not guarantee better voltage limitation and may move the selection away from the protected equipment&#8217;s actual need.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The correct technical question is not \u201c175 V or 275 V, which is better?\u201d but rather: <strong>which <code>Uc<\/code> is compatible with the continuous voltage and TOV of the protection mode while maintaining <code>Up<\/code> and <code>Up\/f<\/code> suitable for the equipment&#8217;s <code>Uw<\/code> withstand?<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">What is Uc in an SPD?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ABNT NBR IEC 61643-11 defines <code>Uc<\/code> as the <strong>maximum RMS voltage that can be continuously applied to the SPD mode of protection<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This definition contains two important points:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1. <code>Uc<\/code> is a continuous operating voltage, not the voltage level that the SPD limits during a surge; 2. the value applies to a <strong>specific mode of protection<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An SPD may have modes between:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>phase and neutral;<\/li><li>phase and PE;<\/li><li>neutral and PE;<\/li><li>phase and phase.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The voltage present in each pair can be different, and the manufacturer must declare <code>Uc<\/code> for the intended modes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For an overview of the other parameters, see <a href=\"https:\/\/a3aengenharia.com.br\/solucoes\/engenharia-eletrica\/dispositivos-de-protecao-contra-surtos\/\">Surge Protective Devices (SPDs)<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Uc is not Up<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>Uc<\/code> and <code>Up<\/code> answer different questions.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>Parameter<\/td><td>Question it answers<\/td><\/tr><tr><td><code>Uc<\/code><\/td><td>what RMS voltage may remain continuously applied to the SPD?<\/td><\/tr><tr><td><code>Up<\/code><\/td><td>what protection voltage level is declared during the surge test?<\/td><\/tr><tr><td><code>Up\/f<\/code><\/td><td>what is the effective level in the installation, including connection voltage drops?<\/td><\/tr><tr><td><code>Uw<\/code><\/td><td>what impulse voltage can the protected equipment withstand?<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A 275 V SPD may have lower or higher <code>Up<\/code> than a 175 V SPD depending on the product design. There is no universal equivalence such as \u201clower Uc = lower Up.\u201d<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Why do 175 V and 275 V SPDs exist?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">These values are used because different networks and connection modes require different maximum continuous operating voltages.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In practical terms:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>networks with phase-neutral voltage around 127 V may allow SPDs with lower <code>Uc<\/code> in certain modes;<\/li><li>networks with phase-neutral voltage around 220 V normally require higher <code>Uc<\/code>;<\/li><li>phase-phase connections may require still higher values;<\/li><li>phase-PE or neutral-PE connections depend on the earthing arrangement and possible overvoltages.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Selection must nevertheless be based on the voltage <strong>between the terminals of the mode of protection<\/strong>, not merely on the overall network label.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">What NBR 5410 establishes for Uc<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">ABNT NBR 5410:2004, corrected version 2008, establishes minimum <code>Uc<\/code> values as a function of the earthing arrangement and the points between which the SPD is connected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The logic uses:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><code>Uo<\/code>: phase-neutral voltage;<\/li><li><code>U<\/code>: phase-phase voltage.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">According to connection mode, the standard requires minimum <code>Uc<\/code> related to <code>1.1 Uo<\/code>, <code>\u221a3 Uo<\/code>, <code>Uo<\/code> or <code>U<\/code>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This shows why there is no single universal value for every network.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Example using Uo<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">If phase-neutral voltage is 127 V, <code>1.1 Uo<\/code> is approximately 140 V. An SPD with <code>Uc = 175 V<\/code> can, in certain modes and arrangements, provide sufficient margin above this minimum.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If phase-neutral voltage is 220 V, <code>1.1 Uo<\/code> is approximately 242 V. In this case, <code>Uc = 175 V<\/code> would be below the continuous voltage required for a typical phase-neutral mode, while 275 V may be compatible.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This does not mean that \u201c127 V = 175 V\u201d and \u201c220 V = 275 V\u201d is a complete rule. Arrangement, mode and TOV must be considered.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">175 V SPD on a 127 V network<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">On a network with 127 V phase-neutral voltage, an SPD with <code>Uc = 175 V<\/code> is frequently found in compatible phase-neutral or phase-PE applications.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The potential advantage is operation with <code>Uc<\/code> closer to nominal voltage, which in some technologies and product families may allow a lower limiting level.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">But selection must check:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>actual network tolerance;<\/li><li>permanent voltage rises;<\/li><li>neutral loss;<\/li><li>TOV due to faults;<\/li><li>TN, TT or IT arrangement;<\/li><li>connection mode;<\/li><li><code>Up<\/code>;<\/li><li>backup protection.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A 175 V SPD should not be placed on every \u201c127 V\u201d circuit without analyzing these conditions.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">275 V SPD on a 127 V network: can it be used?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A technically acceptable application may exist, but that does not mean it is always the best choice.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Higher <code>Uc<\/code> increases margin against continuous voltage and certain TOV, but may come with a different <code>Up<\/code>. The designer must compare the final protection offered to the equipment.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If a 275 V SPD has sufficiently low <code>Up<\/code> and meets the other requirements, it can be used. But choosing 275 V only \u201cso the SPD will not burn out\u201d may unnecessarily sacrifice performance.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">175 V SPD on a 220 V network: why it is normally problematic<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">If the SPD is connected between phase and neutral on a network whose continuous voltage is approximately 220 V, a <code>Uc<\/code> of 175 V is below the normal voltage of the mode itself.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This can cause:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>unintended conduction;<\/li><li>heating;<\/li><li>accelerated degradation;<\/li><li>disconnector operation;<\/li><li>device failure.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Selection must always keep <code>Uc<\/code> above the permissible continuous voltage expected for the mode of protection.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">275 V SPD on a 220 V network<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">On networks with approximately 220 V phase-neutral, <code>Uc = 275 V<\/code> is common because it provides margin above continuous voltage and can meet minimum values derived from <code>1.1 Uo<\/code> in certain configurations.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Even so, it is necessary to verify:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>utility voltage variation;<\/li><li>TOV;<\/li><li>earthing arrangement;<\/li><li><code>Up<\/code>;<\/li><li>class;<\/li><li>surge current;<\/li><li><code>ISCCR<\/code>;<\/li><li>manufacturer instructions.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u201c275 V\u201d is not a complete specification.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">SPD on a 220\/380 V network<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">On a 220\/380 V network:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>phase-neutral: approximately 220 V;<\/li><li>phase-phase: approximately 380 V.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">An SPD installed phase-neutral sees a different voltage from one installed phase-phase.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A 275 V device may therefore be suitable for phase-neutral mode, but not necessarily for phase-phase mode.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The architecture must define modes of protection according to the earthing arrangement.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">SPD on a 127\/220 V network<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">On a 127\/220 V network:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>phase-neutral: approximately 127 V;<\/li><li>phase-phase: approximately 220 V.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This explains why different <code>Uc<\/code> values may exist within the same installation depending on how the SPDs are connected.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The solution should not be selected only from the statement \u201cthe network is 220 V,\u201d because this may mean 220 V phase-phase with 127 V phase-neutral or 220 V phase-neutral in another system.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The importance of the earthing arrangement<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">NBR 5410 distinguishes connections in:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>TN-S;<\/li><li>TN-C;<\/li><li>TN-C-S;<\/li><li>TT;<\/li><li>IT with neutral;<\/li><li>IT without neutral.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The arrangement changes:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>which modes of protection are used;<\/li><li>which voltages appear between terminals;<\/li><li>fault behavior;<\/li><li>TOV;<\/li><li>relative position to RCDs.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The correct <code>Uc<\/code> therefore also depends on the grounding architecture.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">SPD between phase and neutral<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In a phase-neutral connection, the SPD is continuously subjected to phase-neutral voltage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Selection must consider:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><code>Uo<\/code>;<\/li><li>tolerance;<\/li><li>harmonics and network conditions;<\/li><li>neutral voltage rise;<\/li><li>neutral loss;<\/li><li>TOV.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">In many systems, this is where the 175 V versus 275 V comparison originates.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">SPD between phase and PE<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Phase-PE voltage depends on the system and on neutral\/earth conditions.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In TN-S, for example, phase-PE tends to follow phase-neutral under normal operation. In TT and IT systems, fault and temporary-overvoltage conditions may differ.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Selection must consider the continuous voltage and TOV expected for this mode.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">SPD between neutral and PE<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The neutral-PE mode has particular behavior.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In normal operation, N-PE voltage may be small, but faults and system events can increase this potential difference.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The N-PE SPD should therefore not be selected only from normal voltage. TOV and conduction capability are also decisive.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In specific NBR 5410 connection arrangements, the N-PE device may receive the sum of currents coming from multiple phase conductors during a surge, requiring its own current assessment.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">SPD between phases<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In a phase-phase connection, <code>Uc<\/code> must be compatible with phase-phase voltage <code>U<\/code>, not with <code>Uo<\/code>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This makes a 275 V SPD unsuitable in many phase-phase circuits at 380 V or 440 V.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In such cases, products with higher <code>Uc<\/code> are required.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">What is TOV?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">TOV means <strong>Temporary Overvoltage<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Unlike a microsecond surge, a TOV remains for much longer. It can result from:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>neutral loss;<\/li><li>earth faults;<\/li><li>medium-voltage network faults;<\/li><li>neutral-point displacement;<\/li><li>abnormal operating conditions.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">An SPD must withstand specified TOV or fail safely according to the applicable tests.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Why Uc and TOV are linked<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">If <code>Uc<\/code> is very close to continuous voltage, a temporary rise may cause the SPD to conduct for too long.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A varistor, for example, can heat progressively under TOV and enter thermal degradation.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">On the other hand, selecting excessively high <code>Uc<\/code> only to withstand TOV may increase the limiting level in some product families.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The design must balance:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>continuous operation;<\/li><li>TOV;<\/li><li>surge protection.<\/li><\/ul>\n\n\n\n<div class=\"wp-block-a3a-destaque\">\n<p class=\"wp-block-paragraph\"><strong>Are there recurring SPD failures, neutral loss or abnormal network behavior?<\/strong><\/p>\n\n\n<p class=\"wp-block-paragraph\">In this scenario, changing 175 V to 275 V \u2014 or the reverse \u2014 without diagnosis may only mask the cause. <a href=\"https:\/\/a3aengenharia.com.br\/servicos\/levantamento-e-diagnostico\/inspecao-diagnostico-adequacao-dps-mps\/\">SPD and SPM Inspection, Diagnosis and Upgrade<\/a> checks actual voltage, TOV, connections, grounding, device condition and compatibility with the installation.<\/p>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Neutral loss and SPDs<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Neutral loss is a critical condition in three-phase systems with unbalanced loads.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Phase-neutral voltages can shift significantly. An SPD with <code>Uc<\/code> selected too close to nominal voltage can be subjected to severe temporary overvoltage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The solution must verify the TOV behavior declared by the manufacturer, not only <code>Uc<\/code>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Does higher Uc always increase safety?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Not in every sense.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Higher <code>Uc<\/code> may reduce the probability of operation during temporary rises, but surge protection must not be assessed independently of residual voltage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In some technologies, increasing <code>Uc<\/code> may result in higher <code>Up<\/code>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The correct question is whether the <code>Uc + TOV + Up + Up\/f<\/code> combination meets system requirements.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">What is Up and why does it matter when choosing 175 or 275 V?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>Up<\/code> is the declared voltage protection level.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Two SPDs with similar currents and different <code>Uc<\/code> may have different <code>Up<\/code>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">To protect a load, <code>Up<\/code> must be compatible with <code>Uw<\/code> and with the physical installation.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">NBR 5419-4:2026 establishes the concept of <code>Up\/f<\/code>, the effective level including voltage drops in the branch.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Up\/f: actual voltage can be higher than the catalog value<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">For voltage-limiting SPDs:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><code>Up\/f = Up + \u0394U<\/code><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u0394U<\/code> includes voltage drop in conductors, connections and associated branch elements.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">NBR 5419-4 presents as a reference that 1 m of connection carrying 10 kA can add approximately 1 kV.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Thus, discussing 175 V versus 275 V without controlling connection length can mean optimizing one parameter while losing protection in another.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Uw: load withstand<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>Uw<\/code> represents equipment impulse withstand voltage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">SPD selection must ensure that effective voltage remains within load capability, considering distance and criticality.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For sections no longer than 10 m, NBR 5419-4 uses margins such as <code>Up\/f \u2264 0.8 Uw<\/code>, reaching <code>0.5 Uw<\/code> in critical systems.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If distance exceeds 10 m, additional measures may be necessary.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">How to select Uc: an eight-step method<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. Identify actual system voltage<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Do not use only \u201c127,\u201d \u201c220\u201d or \u201c380\u201d without knowing whether the value is phase-neutral or phase-phase.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Record:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><code>Uo<\/code>;<\/li><li><code>U<\/code>;<\/li><li>operating tolerance;<\/li><li>alternative sources.<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2. Identify the earthing arrangement<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Define TN-S, TN-C, TN-C-S, TT or IT.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3. Define the modes of protection<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Specify phase-neutral, phase-PE, N-PE and\/or phase-phase.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">4. Determine continuous voltage in each mode<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Use the actual topology, not a generic table.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">5. Check the minimum normative Uc<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Compare with NBR 5410 criteria for the corresponding arrangement and mode.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">6. Evaluate TOV<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Consider neutral loss, faults and manufacturer data.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">7. Compare Up and Up\/f with Uw<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Do not select <code>Uc<\/code> in isolation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">8. Document the decision<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Record the value and rationale for each mode of protection.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Example: 127\/220 V TN-S network<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a network with:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>127 V phase-neutral;<\/li><li>220 V phase-phase;<\/li><li>TN-S.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For a phase-neutral SPD, the reference calculation based on <code>1.1 Uo<\/code> gives a minimum near 140 V. <code>Uc = 175 V<\/code> may be technically compatible provided TOV, <code>Up<\/code> and manufacturer data are suitable.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a phase-phase mode, voltage is 220 V. A 175 V device would not be compatible with the mode&#8217;s continuous voltage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The example shows why one \u201c175 V SPD for a 127\/220 V network\u201d does not describe every mode.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Example: 220\/380 V TN-S network<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Here:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><code>Uo = 220 V<\/code>;<\/li><li><code>U = 380 V<\/code>.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">For phase-neutral, <code>1.1 Uo<\/code> is approximately 242 V. <code>Uc = 275 V<\/code> can meet the minimum requirement in many applications.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For phase-phase, 275 V is below the continuous 380 V and is not suitable for that mode.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Example: TT system<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In TT, the relationship between neutral, PE and local earth requires special attention.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">SPD position relative to the RCD and TOV resulting from faults must be analyzed.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">NBR 5410 provides specific conditions for SPDs upstream of the RCD in TT and for the N-PE mode.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The simple 175\/275 V choice does not resolve the architecture.<\/p>\n\n\n\n<div class=\"wp-block-a3a-destaque\">\n<p class=\"wp-block-paragraph\"><strong>Does the installation operate in TT, IT or have complex interfaces between neutral, PE and RCDs?<\/strong><\/p>\n\n\n<p class=\"wp-block-paragraph\">Defining <code>Uc<\/code> must consider the protection mode and temporary overvoltages possible in each arrangement. In complex installations, the <a href=\"https:\/\/a3aengenharia.com.br\/servicos\/planejamento\/projeto-eletrico-baixa-tensao\/\">Low-Voltage Electrical Design<\/a> should coordinate SPDs, RCDs, grounding, panels and operating conditions.<\/p>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Example: IT system<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In IT, phase-earth voltage can change significantly during the first fault.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">NBR 5410 therefore establishes different <code>Uc<\/code> requirements for certain modes in IT with or without neutral.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is one of the scenarios in which applying a residential rule based only on 127 or 220 V is particularly unsuitable.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">440 V and 460 V SPDs<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In installations with higher voltages, such as 380\/440 V phase-phase or 440 V in certain modes, SPDs with <code>Uc<\/code> of 440 V, 460 V or other values are available.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The same methodology remains valid:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>identify voltage between terminals;<\/li><li>verify TOV;<\/li><li>compare <code>Up<\/code>;<\/li><li>verify class and current;<\/li><li>confirm the connection arrangement.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The principle does not change merely because the number is higher.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Uc and SPD class are independent<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">You can find:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Class I 275 V;<\/li><li>Class II 275 V;<\/li><li>Class II 175 V;<\/li><li>combined T1+T2 devices with different <code>Uc<\/code>.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Class describes the energy\/test regime. <code>Uc<\/code> describes continuous voltage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Mixing the concepts leads to errors such as \u201cClass I must be 275 V.\u201d<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For more detail on classification, see <a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/artigos-tecnicos\/dps-classe-1-classe-2-classe-3\/\">Class 1, Class 2 and Class 3 SPDs<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Uc and discharge current are also independent<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A 175 V SPD can exist with 20 kA, 40 kA or other capacities. The same applies to 275 V.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Surge current relates to energy stress. <code>Uc<\/code> relates to continuous operation.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The current comparison is detailed in <a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/artigos-tecnicos\/dps-20ka-40ka-45ka-60ka-como-escolher\/\">20 kA, 40 kA, 45 kA or 60 kA SPD<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Uc does not define ISCCR<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>ISCCR<\/code> represents the rated short-circuit current associated with the SPD and specified disconnectors.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A 275 V 40 kA SPD may have <code>ISCCR<\/code> unsuitable for a main LV switchboard with high short-circuit current.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Voltage and surge current therefore do not replace short-circuit verification.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The interface with circuit breakers and fuses is covered in <a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/artigos-tecnicos\/dps-disjuntor-protecao-retaguarda-dimensionamento\/\">SPD and Circuit Breaker<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Uc and coordination between SPDs<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In a cascade, devices may have different <code>Uc<\/code> and <code>Up<\/code>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Coordination must ensure:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>stability of each stage at continuous voltage;<\/li><li>compatible energy capability;<\/li><li>progressive protection levels;<\/li><li>absence of unintended operation;<\/li><li>final load protection.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Not every SPD in an installation needs exactly the same <code>Uc<\/code>, provided each mode and point is correctly specified.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Common mistakes when choosing 175 V versus 275 V<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Selecting from phase-phase voltage without identifying Uo<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A \u201c220 V\u201d network may be 127\/220 V or may have 220 V phase-neutral in another configuration.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Using 175 V in a mode permanently near 220 V<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">This can cause conduction and degradation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Always using 275 V \u201cfor safety\u201d<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">This can increase TOV margin, but must be checked against <code>Up<\/code> and required protection.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ignoring neutral loss<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Severe TOV can destroy an SPD correctly sized only for normal operation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ignoring TN, TT and IT<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The earthing arrangement changes voltages and modes.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Confusing Uc with Up<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">They are different quantities.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Confusing Uc with class<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Class I, II or III does not determine maximum continuous voltage.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Not checking the datasheet by mode<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Multipole SPDs may behave differently between L-N, L-PE and N-PE.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">How to specify Uc in a design memorandum<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A technical memorandum should record at least:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>network nominal voltage;<\/li><li><code>Uo<\/code> and <code>U<\/code>;<\/li><li>earthing arrangement;<\/li><li>mode of protection;<\/li><li>minimum calculated or required <code>Uc<\/code>;<\/li><li>selected <code>Uc<\/code>;<\/li><li>TOV considered;<\/li><li><code>Up<\/code>;<\/li><li>estimated <code>Up\/f<\/code>;<\/li><li>load <code>Uw<\/code> or applicable category;<\/li><li>class;<\/li><li><code>In<\/code>\/<code>Iimp<\/code>;<\/li><li><code>ISCCR<\/code>;<\/li><li>backup protection;<\/li><li>reference model.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This turns \u201c275 V SPD\u201d from a purchase line into a verifiable specification.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">How to audit an installed 175\/275 V SPD<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In existing installations, check:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1. actual panel voltage; 2. connection mode; 3. earthing arrangement; 4. model <code>Uc<\/code>; 5. <code>Up<\/code>; 6. indicator condition; 7. backup protection; 8. available short-circuit current; 9. connection length; 10. history of TOV or neutral loss; 11. network modifications; 12. coordination with other SPDs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An SPD that has operated for years is not automatically correctly specified. It may simply not yet have been subjected to the critical event or may be operating with inadequate margin.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a field assessment, see <a href=\"https:\/\/a3aengenharia.com.br\/servicos\/levantamento-e-diagnostico\/inspecao-diagnostico-adequacao-dps-mps\/\">SPD and SPM Inspection, Diagnosis and Upgrade<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">When Uc selection requires SPM design<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The analysis should be treated as a design when there are:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>LPS;<\/li><li>multiple panels;<\/li><li>complex TN\/TT\/IT networks;<\/li><li>critical equipment;<\/li><li>multiple power sources;<\/li><li>generators;<\/li><li>UPS systems;<\/li><li>photovoltaic systems;<\/li><li>signal lines;<\/li><li>history of failures;<\/li><li>long distances;<\/li><li>interconnected structures.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The <a href=\"https:\/\/a3aengenharia.com.br\/servicos\/planejamento\/projeto-medidas-protecao-contra-surtos-mps\/\">Surge Protection Measures Design<\/a> consolidates <code>Uc<\/code>, TOV, <code>Up<\/code>, <code>Up\/f<\/code>, classes, currents, LPZ, coordination, grounding and documentation.<\/p>\n\n\n\n<div class=\"wp-block-a3a-destaque\">\n<p class=\"wp-block-paragraph\"><strong>Do you need to specify SPDs in a critical or multi-panel installation?<\/strong><\/p>\n\n\n<p class=\"wp-block-paragraph\">When the decision involves more than choosing \u201c175 V or 275 V,\u201d specification should move from component level to system engineering. See the <a href=\"https:\/\/a3aengenharia.com.br\/servicos\/planejamento\/projeto-medidas-protecao-contra-surtos-mps\/\">Surge Protection Measures (SPM) Design<\/a>.<\/p>\n<\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Summary: 175 V or 275 V SPD?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The decision should follow this sequence:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1. identify <code>Uo<\/code> and <code>U<\/code>; 2. identify the earthing arrangement; 3. define the mode of protection; 4. calculate\/check the applicable minimum <code>Uc<\/code>; 5. consider TOV; 6. compare <code>Up<\/code>; 7. verify <code>Up\/f<\/code> against <code>Uw<\/code>; 8. verify class, current and <code>ISCCR<\/code>; 9. coordinate with other SPDs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">On many networks with 127 V phase-neutral, 175 V may be appropriate for certain modes. On many networks with 220 V phase-neutral, 275 V may be the coherent choice. But these associations are valid only when the mode, arrangement, TOV and other parameters confirm the application.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Correct selection is not \u201c175 V for 127 V and 275 V for 220 V.\u201d Correct selection is <strong>Uc compatible with continuous voltage and TOV while preserving the protection level required by the equipment<\/strong>.<\/p>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Technical references<\/summary>\n<p class=\"wp-block-paragraph\">[1] ASSOCIA\u00c7\u00c3O BRASILEIRA DE NORMAS T\u00c9CNICAS. <strong>ABNT NBR IEC 61643-11:2021, corrected version 2022<\/strong> \u2014 Dispositivos de prote\u00e7\u00e3o contra surtos de baixa tens\u00e3o \u2014 Parte 11. Available at: <a href=\"https:\/\/www.abntcatalogo.com.br\/\" target=\"_blank\" rel=\"noopener noreferrer\">ABNT Catalog<\/a>.<\/p>\n\n\n<p class=\"wp-block-paragraph\">[2] ASSOCIA\u00c7\u00c3O BRASILEIRA DE NORMAS T\u00c9CNICAS. <strong>ABNT NBR 5410:2004, corrected version 2008<\/strong> \u2014 Instala\u00e7\u00f5es el\u00e9tricas de baixa tens\u00e3o. Available at: <a href=\"https:\/\/www.abntcatalogo.com.br\/\" target=\"_blank\" rel=\"noopener noreferrer\">ABNT Catalog<\/a>.<\/p>\n\n\n<p class=\"wp-block-paragraph\">[3] ASSOCIA\u00c7\u00c3O BRASILEIRA DE NORMAS T\u00c9CNICAS. <strong>ABNT NBR 5419-4:2026<\/strong> \u2014 Prote\u00e7\u00e3o contra descargas atmosf\u00e9ricas \u2014 Parte 4. Available at: <a href=\"https:\/\/www.abntcatalogo.com.br\/\" target=\"_blank\" rel=\"noopener noreferrer\">ABNT Catalog<\/a>.<\/p>\n\n\n<p class=\"wp-block-paragraph\">[4] INTERNATIONAL ELECTROTECHNICAL COMMISSION. <strong>IEC 61643-11:2011<\/strong> \u2014 Low-voltage surge protective devices \u2014 Part 11. Available at: <a href=\"https:\/\/webstore.iec.ch\/en\/publication\/5682\" target=\"_blank\" rel=\"noopener noreferrer\">IEC Webstore<\/a>.<\/p>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Frequently asked questions<\/summary>\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-qual-a-diferen-a-entre-dps-175-v-e-275-v-e64f2ec1\"><strong class=\"schema-faq-question\">What is the difference between a 175 V and 275 V SPD?<\/strong> <p class=\"schema-faq-answer\">The main difference is maximum continuous operating voltage Uc. The value must be compatible with the voltage between the terminals of the protection mode and with temporary overvoltages on the network.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-dps-175-v-serve-para-rede-127-v-afde91b9\"><strong class=\"schema-faq-question\">Is a 175 V SPD suitable for a 127 V network?<\/strong> <p class=\"schema-faq-answer\">It can often be appropriate in certain modes of protection on 127 V phase-neutral networks, but selection depends on earthing arrangement, TOV, Up and connection mode.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-dps-275-v-serve-para-rede-220-v-5913a734\"><strong class=\"schema-faq-question\">Is a 275 V SPD suitable for a 220 V network?<\/strong> <p class=\"schema-faq-answer\">On many 220 V phase-neutral networks, Uc of 275 V is compatible with the continuous-voltage requirement, but the design must also verify TOV, Up, class and other parameters.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-posso-usar-dps-275-v-em-rede-127-v-a39d9012\"><strong class=\"schema-faq-question\">Can I use a 275 V SPD on a 127 V network?<\/strong> <p class=\"schema-faq-answer\">It may be technically possible, but it is not automatically the best choice. Check whether Up and final performance remain appropriate for the load.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-posso-usar-dps-175-v-em-rede-220-v-fd5fb13f\"><strong class=\"schema-faq-question\">Can I use a 175 V SPD on a 220 V network?<\/strong> <p class=\"schema-faq-answer\">In phase-neutral mode with approximately 220 V continuously present, Uc of 175 V is normally below operating voltage and tends to be unsuitable.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-o-que-uc-no-dps-2e46ec6d\"><strong class=\"schema-faq-question\">What is Uc in an SPD?<\/strong> <p class=\"schema-faq-answer\">Uc is the maximum RMS voltage that may be continuously applied to an SPD mode of protection.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-uc-a-mesma-coisa-que-up-4a007a5c\"><strong class=\"schema-faq-question\">Is Uc the same as Up?<\/strong> <p class=\"schema-faq-answer\">No. Uc concerns permissible continuous voltage; Up is the protection voltage level during a surge.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-o-que-tov-ac1fabd8\"><strong class=\"schema-faq-question\">What is TOV?<\/strong> <p class=\"schema-faq-answer\">TOV is a temporary overvoltage lasting much longer than a transient surge and may occur, for example, because of neutral loss or system faults.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-perda-de-neutro-pode-queimar-dps-fdcd5828\"><strong class=\"schema-faq-question\">Can neutral loss damage an SPD?<\/strong> <p class=\"schema-faq-answer\">It can subject the SPD to high TOV. Suitability depends on Uc, the product&#8217;s TOV behavior and network architecture.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-dps-275-v-pode-ser-usado-entre-fases-de-380-v-0a407f93\"><strong class=\"schema-faq-question\">Can a 275 V SPD be used phase-to-phase at 380 V?<\/strong> <p class=\"schema-faq-answer\">Not if continuous voltage between its terminals is 380 V, because Uc of 275 V would be below the normal voltage of that mode.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-tn-tt-e-it-mudam-a-escolha-da-uc-8142e0c2\"><strong class=\"schema-faq-question\">Do TN, TT and IT change Uc selection?<\/strong> <p class=\"schema-faq-answer\">Yes. The earthing arrangement changes connection modes, terminal voltages and behavior under faults and TOV.<\/p><\/div><div class=\"schema-faq-section\" id=\"faq-question-como-escolher-entre-175-v-e-275-v-ffd756ba\"><strong class=\"schema-faq-question\">How do I choose between 175 V and 275 V?<\/strong> <p class=\"schema-faq-answer\">Identify Uo, U, earthing arrangement and mode of protection; verify the applicable minimum Uc, TOV, Up, Up\/f, class, current and ISCCR.<\/p><\/div><\/div>\n<\/details>\n\n\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary>Supplementary technical materials<\/summary>\n<h3 class=\"wp-block-heading\">Related solutions<\/h3>\n<ul class=\"wp-block-list\"><li><a href=\"https:\/\/a3aengenharia.com.br\/solucoes\/engenharia-eletrica\/dispositivos-de-protecao-contra-surtos\/\">Surge Protective Devices (SPDs)<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/solucoes\/engenharia-eletrica\/medidas-de-protecao-contra-surtos\/\">Surge Protection Measures (SPM)<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/solucoes\/engenharia-eletrica\/aterramento-eletrico\/\">Grounding and Equipotential Bonding<\/a><\/li><\/ul>\n<h3 class=\"wp-block-heading\">Related engineering services<\/h3>\n<ul class=\"wp-block-list\"><li><a href=\"https:\/\/a3aengenharia.com.br\/servicos\/planejamento\/projeto-medidas-protecao-contra-surtos-mps\/\">Surge Protection Measures (SPM) Design<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/servicos\/levantamento-e-diagnostico\/inspecao-diagnostico-adequacao-dps-mps\/\">SPD and SPM Inspection, Diagnosis and Upgrade<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/servicos\/planejamento\/projeto-eletrico-baixa-tensao\/\">Low-Voltage Electrical Design<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/servicos\/planejamento\/projeto-de-aterramento\/\">Grounding Design<\/a><\/li><\/ul>\n<h3 class=\"wp-block-heading\">Related technical content<\/h3>\n<ul class=\"wp-block-list\"><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/artigos-tecnicos\/dps-o-que-e-e-como-instalar\/\">SPD: what it is, purpose, classes, sizing and installation<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/artigos-tecnicos\/coordenacao-selecao-dps-instalacoes-eletricas-2\/\">SPD Coordination<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/artigos-tecnicos\/nbr-5410\/\">NBR 5410: LV electrical installations, grounding, SPDs and compliance<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/artigos-tecnicos\/dps-disjuntor-protecao-retaguarda-dimensionamento\/\">SPD and Circuit Breaker<\/a><\/li><\/ul>\n<h3 class=\"wp-block-heading\">Guides and references<\/h3>\n<ul class=\"wp-block-list\"><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/guias-tecnicos\/guia-completo-sobre-instalacoes-eletricas-de-baixa-tensao\/\">Complete Guide to Low-Voltage Electrical Installations<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/guias-tecnicos\/guia-completo-sobre-spda-e-mps\/\">Complete Guide to LPS and SPM<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/whitepapers\/whitepaper-metodo-projeto-dimensionamento-instalacoes-eletricas-baixa-tensao\/\">Low-Voltage Electrical Installation Design and Sizing Method<\/a><\/li><li><a href=\"https:\/\/a3aengenharia.com.br\/conteudo\/ebooks\/aterramento-eletrico\/\">Electrical Grounding: Fundamentals, Design and Standards<\/a><\/li><\/ul>\n<\/details>\n","protected":false},"excerpt":{"rendered":"<p>Understand the difference between 175 V and 275 V SPDs, what Uc means, its relationship with 127\/220 V systems, L-N\/L-PE modes, TN\/TT\/IT, TOV, Up and selection criteria.<\/p>\n","protected":false},"author":1,"featured_media":78279,"parent":0,"template":"","meta":{"_a3a_global_related_solutions":[],"_a3a_global_related_services":[],"_a3a_global_related_materials":[],"_a3a_post_lang":"en-us","_a3a_translation_group_id":"ad330b58-fa28-496c-8502-76e741c3fd91","_a3a_i18n_canonical_slug":"175v-275v-spd-uc-network-voltage-how-to-choose","_a3a_prod_post_id":"","_a3a_lang_url_en-us":"","_a3a_lang_url_es-es":""},"categories":[],"segments":[],"mercados":[],"etapas":[],"class_list":["post-72453","articles","type-articles","status-publish","has-post-thumbnail","hentry"],"_links":{"self":[{"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/articles\/72453","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/articles"}],"about":[{"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/types\/articles"}],"author":[{"embeddable":true,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":1,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/articles\/72453\/revisions"}],"predecessor-version":[{"id":74062,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/articles\/72453\/revisions\/74062"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/media\/78279"}],"wp:attachment":[{"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/media?parent=72453"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/categories?post=72453"},{"taxonomy":"segments","embeddable":true,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/segments?post=72453"},{"taxonomy":"mercados","embeddable":true,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/mercados?post=72453"},{"taxonomy":"etapas","embeddable":true,"href":"https:\/\/a3aengenharia.com\/en-us\/wp-json\/wp\/v2\/etapas?post=72453"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}