{"id":4533,"date":"2026-09-16T11:15:26","date_gmt":"2026-09-16T03:15:26","guid":{"rendered":"https:\/\/cnkuangya.com\/?p=4533"},"modified":"2026-09-16T11:15:30","modified_gmt":"2026-09-16T03:15:30","slug":"3-1-vs-4-0-spd","status":"publish","type":"post","link":"https:\/\/cnkuangya.com\/ar\/blog\/3-1-vs-4-0-spd\/","title":{"rendered":"3+1 vs 4+0 SPD: Differences, Wiring & Selection Guide"},"content":{"rendered":"

A 3+1 vs 4+0 SPD comparison often starts with appearance, because both configurations may look almost identical from the outside, especially when they occupy four DIN-rail modules.<\/p>\n\n\n\n

But electrically, they are not the same.<\/p>\n\n\n\n

The main difference is the surge protection path<\/strong>.<\/p>\n\n\n\n

A typical 3+1 surge protective device uses three protection paths from the phase conductors to neutral:<\/p>\n\n\n\n

L1 \u2192 N<\/strong>
L2 \u2192 N<\/strong>
L3 \u2192 N<\/strong><\/p>\n\n\n\n

plus one additional protection path:<\/p>\n\n\n\n

N \u2192 PE<\/strong><\/p>\n\n\n\n

A typical 4+0 configuration instead provides protection paths referenced directly to PE, commonly:<\/p>\n\n\n\n

L1 \u2192 PE<\/strong>
L2 \u2192 PE<\/strong>
L3 \u2192 PE<\/strong>
N \u2192 PE<\/strong><\/p>\n\n\n\n

This difference affects how surge voltage is controlled between line, neutral and protective earth, so 3+1 and 4+0 should not be selected simply by counting modules or poles<\/strong>.<\/p>\n\n\n\n

The correct configuration depends on the earthing system, the protection modes required, the installation point, and the actual internal circuit declared by the SPD manufacturer.<\/p>\n\n\n\n

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\u0625\u062c\u0627\u0628\u0629 \u0633\u0631\u064a\u0639\u0629:<\/strong> 3+1 is commonly used in TT systems and is also available for TN-S systems. 4+0 is commonly used in suitable TN-S applications. Always confirm the wiring diagram and applicable installation requirements instead of assuming that every four-pole SPD is electrically equivalent.<\/p>\n<\/blockquote>\n\n\n\n

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3+1 vs 4+0 SPD at a Glance<\/h2>\n\n\n\n
\u0627\u0644\u0645\u064a\u0632\u0629<\/th>3+1 SPD<\/th>4+0 SPD<\/th><\/tr><\/thead>
Typical phase protection path<\/td>L1-N, L2-N, L3-N<\/td>L1-PE, L2-PE, L3-PE<\/td><\/tr>
Neutral protection<\/td>Separate N-PE path<\/td>N-PE path as part of the 4-path arrangement<\/td><\/tr>
Typical internal design<\/td>MOVs on L-N + switching element\/GDT on N-PE<\/td>Often voltage-limiting elements referenced to PE<\/td><\/tr>
Direct L-N protection<\/td>\u0646\u0639\u0645<\/td>Not necessarily as a dedicated L-N element<\/td><\/tr>
Direct L-PE path<\/td>Through coordinated L-N + N-PE path<\/td>\u0646\u0639\u0645<\/td><\/tr>
Common application<\/td>TT and some TN-S systems<\/td>TN-S systems<\/td><\/tr>
Physical modules<\/td>Often 4<\/td>Often 4<\/td><\/tr>
Same as \u201c4P\u201d?<\/td>\u0644\u064a\u0633 \u062a\u0644\u0642\u0627\u0626\u064a\u0627\u064b<\/td>\u0644\u064a\u0633 \u062a\u0644\u0642\u0627\u0626\u064a\u0627\u064b<\/td><\/tr>
Main selection basis<\/td>Earthing system + wiring diagram + ratings<\/td>Earthing system + wiring diagram + ratings<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

\u0627\u0644\u0646\u0642\u0637\u0629 \u0627\u0644\u0623\u0643\u062b\u0631 \u0623\u0647\u0645\u064a\u0629 \u0647\u064a:<\/p>\n\n\n\n

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Four visible modules do not tell you whether an SPD is 3+1 or 4+0.<\/strong><\/p>\n<\/blockquote>\n\n\n\n

Always check the connection diagram.<\/p>\n\n\n\n

The key to 3+1 vs 4+0 SPD selection is understanding the internal protection paths rather than simply counting the visible modules.<\/p>\n\n\n\n

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What Does 3+1 Mean on an SPD?<\/h1>\n\n\n\n

In a typical three-phase four-wire 3+1 SPD configuration<\/strong>, the three phase conductors are protected relative to neutral.<\/p>\n\n\n\n

The protection paths are:<\/p>\n\n\n\n

Protection element<\/th>Path<\/th><\/tr><\/thead>
Element 1<\/td>L1 \u2192 N<\/td><\/tr>
Element 2<\/td>L2 \u2192 N<\/td><\/tr>
Element 3<\/td>L3 \u2192 N<\/td><\/tr>
Additional element<\/td>N \u2192 PE<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\"3+1
A typical 3+1 SPD uses three phase-to-neutral protection paths plus one N-PE protection path.<\/figcaption><\/figure>\n\n\n\n

The first three protection elements are commonly voltage-limiting devices such as MOVs \u2014 metal oxide varistors<\/strong>.<\/p>\n\n\n\n

The additional N-PE protection element is commonly a spark-gap or gas-discharge-based switching element<\/strong>, depending on the product design.<\/p>\n\n\n\n

For example, KUANGYA’s 3+1 Type 2 AC SPD<\/a> uses three MOV protection paths between L1\/L2\/L3 and N, together with a GDT protection path between N and PE.<\/p>\n\n\n\n

Legrand likewise describes its 3P+N \/ 3+1 configuration as providing L-N and N-PE protection, with the neutral pole protected by an encapsulated spark gap.<\/p>\n\n\n\n

Simplified 3+1 structure<\/h3>\n\n\n\n
L1 \u2500\u2500[MOV]\u2500\u2500\u2510\nL2 \u2500\u2500[MOV]\u2500\u2500\u2524\nL3 \u2500\u2500[MOV]\u2500\u2500\u2524\u2500\u2500 N \u2500\u2500[GDT \/ switching element]\u2500\u2500 PE\n<\/code><\/pre>\n\n\n\n
This is a simplified illustration. The actual internal circuit and protective technology must always be confirmed from the manufacturer’s datasheet.<\/p>\n\n\n\n
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What Does 4+0 Mean on an SPD?<\/h1>\n\n\n\n
\u0646\u0645\u0648\u0630\u062c\u064a 4+0 SPD<\/strong> uses four protection paths referenced to protective earth.<\/p>\n\n\n\n
A common arrangement is:<\/p>\n\n\n\n
L1 \u2500\u2500[SPD]\u2500\u2500 PE\nL2 \u2500\u2500[SPD]\u2500\u2500 PE\nL3 \u2500\u2500[SPD]\u2500\u2500 PE\nN  \u2500\u2500[SPD]\u2500\u2500 PE\n<\/code><\/pre>\n\n\n\n
\"4+0
A typical 4+0 SPD provides separate protection paths referenced toward PE.<\/figcaption><\/figure>\n\n\n\n
In this configuration, the three phases and neutral each have a protection path toward PE.<\/p>\n\n\n\n
For example, KUANGYA’s VSP1S40 4+0 model is intended for TN-S systems and provides L-PE and N-PE protection modes.<\/p>\n\n\n\n
DEHN also identifies its four-path TN-S models as 4+0 configurations<\/strong>, while offering separate 3+1 products for TT and TN-S systems.<\/p>\n\n\n\n
However, this is where buyers need to be careful.<\/p>\n\n\n\n
Different manufacturers may use terms such as:<\/p>\n\n\n\n
4P<\/strong>
3P+N<\/strong>
4+0<\/strong>
3+1<\/strong><\/p>\n\n\n\n
in slightly different ways in catalog titles.<\/p>\n\n\n\n
\u0628\u0646\u0627\u0621\u064b \u0639\u0644\u0649 \u0630\u0644\u0643:<\/p>\n\n\n\n
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Do not identify the internal SPD topology from the product name alone. Check the circuit diagram.<\/strong><\/p>\n<\/blockquote>\n\n\n\n
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3+1 vs 4+0: What Is the Real Difference?<\/h1>\n\n\n\n
The real difference is not the number of modules.<\/p>\n\n\n\n
It is where the surge voltage is controlled and where surge current is diverted<\/strong>.<\/p>\n\n\n\n
\"3+1
The key difference between 3+1 and 4+0 SPD configurations is the internal surge protection path, not the number of visible modules.<\/figcaption><\/figure>\n\n\n\n
3+1 configuration<\/h2>\n\n\n\n
A 3+1 configuration provides direct protection between:<\/p>\n\n\n\n
L1-N<\/strong>
L2-N<\/strong>
L3-N<\/strong><\/p>\n\n\n\n
followed by a separate path between:<\/p>\n\n\n\n
N-PE<\/strong><\/p>\n\n\n\n
This provides direct line-to-neutral protection for loads connected between phase and neutral.<\/p>\n\n\n\n
4+0 configuration<\/h2>\n\n\n\n
A typical 4+0 arrangement provides direct protection between the active conductors and PE:<\/p>\n\n\n\n
L1-PE<\/strong>
L2-PE<\/strong>
L3-PE<\/strong>
N-PE<\/strong><\/p>\n\n\n\n
The line-to-neutral voltage may also be influenced during a surge through the combined operation of protection elements, but this is not the same topology as providing a dedicated L-N protective element.<\/p>\n\n\n\n
This is why two SPDs with:<\/p>\n\n\n\n