When buyers compare surge protective devices, the Up value is often misunderstood. A lower Up usually means better voltage limitation, but it does not automatically mean the SPD is the right choice for every panel, system, or protected device.
Up, or voltage protection level, is the maximum residual voltage measured at SPD terminals during a specified surge test. A lower Up usually means better voltage limitation, but buyers must compare it under the same SPD Type, standard, voltage rating, discharge current condition, protection mode, and installation condition.
This guide explains what SPD Up voltage protection level means, how it relates to residual voltage and equipment impulse withstand voltage, and what buyers should check before confirming a model for distribution boards, OEM panels, industrial cabinets, and sensitive equipment.
Table des matières
Quick Answer: What Should Buyers Know About SPD Up?
Up is the voltage protection level of an SPD. It is also commonly understood as residual voltage or let-through voltage during a surge test.
Usually yes for voltage limitation. But Up must be checked together with Uc, In, Imax, Iimp, SPD Type, and installation cable length.
The voltage reaching downstream equipment should stay below the equipment impulse withstand level, with a reasonable safety margin.
The datasheet Up is measured at the SPD terminals. Long connection leads and backup protection may increase the actual voltage seen by protected equipment.
Need help checking whether the Up value is suitable?
Send us your system voltage, grounding type, SPD Type, protected equipment, and cabinet layout. LEEYEE can help recommend a suitable SPD model for distribution boards, OEM panels, and project supply.
What Does Up Mean on an SPD Datasheet?
Haut de la page means voltage protection level. In practical purchasing language, it tells you the residual voltage level that may remain when the SPD conducts surge current under specified test conditions.
An SPD does not make the surge voltage disappear. It diverts surge current and limits the voltage to a lower level. That limited voltage is what buyers use Up to understand.
This is why Up is very important for sensitive equipment. If the residual voltage is still higher than what the equipment can withstand, the downstream device may still be damaged even though an SPD is installed.
Up Is Not the Same as Uc
Buyers often compare Uc and Up together because both appear as voltage values on SPD datasheets. But they answer different questions.
| Paramètres | Nom complet | What It Tells You | Signification pour l'Acheteur |
|---|---|---|---|
| Uc | Tension de fonctionnement maximale continue | The highest voltage the SPD can withstand continuously without abnormal operation. | Use it to check whether the SPD can safely work on the actual system voltage. |
| Haut de la page | Niveau de protection de la tension | The residual voltage level at the SPD terminals during a specified surge test. | Use it to check whether downstream equipment can be protected from excessive surge voltage. |
In simple terms: Uc tells you whether the SPD can live on the system. Up tells you how much voltage may still reach the equipment during a surge.
If you are still confirming Uc for AC systems, read our Guide de sélection SPD Uc before comparing Up values.
Up vs Residual Voltage vs Clamping Voltage vs MOV Voltage
Buyers may see different words in datasheets, supplier emails, or general surge protection articles. These terms are related, but they should not always be treated as the same thing.
| Terme | Practical Meaning | Utilisation par l'acheteur | Common Risk |
|---|---|---|---|
| Haut de la page | Declared SPD voltage protection level under specified test conditions. | Use it for SPD protection coordination and equipment protection assessment. | Comparing Up without checking SPD Type, test condition, or protection mode. |
| Residual voltage | The voltage remaining while the SPD is conducting surge current. | A practical way to understand what Up means during surge limitation. | Assuming residual voltage at the SPD terminals is always the same as voltage at the equipment. |
| Tension de serrage | A common general term for voltage limitation behavior. | Can help explain the concept, but buyers must confirm whether the supplier means SPD Up or component data. | Mixing marketing language with standard datasheet parameters. |
| MOV voltage | A component-level parameter of the metal oxide varistor inside many SPDs. | Useful for component engineering, but not enough for selecting a finished SPD product. | Using MOV component data instead of the finished SPD datasheet value. |
Up and Equipment Impulse Withstand Voltage
The real purpose of checking Up is not to choose the most attractive number on a label. The real purpose is to coordinate the SPD with the protected equipment.
The voltage reaching the downstream equipment should be lower than the equipment’s impulse withstand voltage. For sensitive equipment, designers may need a lower effective protection level or additional coordinated SPD stages.
Protection coordination logic
Installed protection level is clearly below the equipment withstand level.
Installed protection level is close to or above the equipment withstand level.
| Protected Equipment | Buyer Concern | How to Read Up |
|---|---|---|
| Tableau de distribution principal | Protection for switchgear and downstream circuits | Check Up together with SPD Type, Iimp / In, installation position, and equipment impulse withstand rating. |
| Tableau de sous-distribution | Protection closer to loads | Type 2 SPD Up becomes more important because the SPD is closer to downstream equipment. |
| PLC or control cabinet | Sensitive electronics and control modules | A lower effective protection level may be required, often with coordinated upstream and downstream protection. |
| Panneau électrique OEM | Repeatable model selection for batch orders | Up should match the panel application, target market, system voltage, and required certification. |
| Solar inverter AC side | Protection for inverter input and control electronics | Check Up together with Uc, Type 2 or Type 1+2 requirement, earthing system, and cable length. |
Effective Protection Level Is Higher Than Datasheet Up
The Up value printed on the SPD datasheet is measured at the SPD terminals. In a real cabinet, the protected equipment may see a higher voltage because the installation adds extra voltage.
This does not mean the datasheet Up is useless. It means buyers should use Up as the starting point, then check how the SPD will be installed in the actual panel.
| Facteur | How It Can Increase Actual Protection Level | Buyer / Panel Builder Action |
|---|---|---|
| Connection lead length | Long conductors add extra voltage during surge current flow. | Keep L/N/PE conductors short, direct, and without unnecessary loops. |
| PE path | A long or indirect PE path can reduce the real protection effect. | Use a short and direct PE connection to the grounding bar. |
| Protection de secours | Fuses or breakers used for SPD backup protection may add voltage during surge conditions. | Follow the SPD manufacturer’s recommended backup protection and installation method. |
| Distance to equipment | If protected equipment is far from the SPD, the equipment may still see a higher surge voltage. | Consider coordinated downstream Type 2 or Type 3 protection for sensitive loads. |
Do not judge protection only by the label
A good SPD installed badly may give poor real protection. For OEM panels and distribution boards, Up should be checked together with wiring layout, cable length, backup protection, and the location of the protected equipment.
Is a Lower Up Value Always Better?
A lower Up value usually means the SPD limits surge voltage to a lower residual level. This is good for protecting downstream equipment.
But buyers should not select an SPD by Up alone. A very low Up value is not useful if the SPD does not match the system voltage, discharge current requirement, installation position, or SPD Type.
Important buyer warning
Do not ask only, “Which SPD has the lowest Up?” A better question is: “Which SPD gives a suitable protection level for my equipment, while also matching Uc, In, Imax, Iimp, system voltage, grounding type, protection mode, and installation layout?”
| Selection Mistake | Why It Is Risky | Better Buyer Action |
|---|---|---|
| Choosing the lowest Up without checking Uc | The SPD may not be suitable for the real continuous operating voltage. | Confirm system voltage, voltage fluctuation, grounding system, and Uc first. |
| Comparing Type 1, Type 2, and Type 3 only by Up | Different SPD Types have different roles and test duties. | Compare Up within the correct SPD Type and installation position. |
| Comparing Up under different protection modes | L-PE, L-N, N-PE, and L-L values may not be directly interchangeable. | Check the same protection mode when comparing supplier datasheets. |
| Ignoring In, Imax, or Iimp | The SPD may have a good Up but insufficient discharge capacity for the risk level. | Check discharge current ratings together with Up. |
| Ignoring connection lead length | The actual protection level at the equipment may be higher than the datasheet Up. | Keep SPD connection conductors short and direct. |
| Using Type 3 SPD as main protection | Type 3 SPDs are normally for fine protection close to terminal equipment, not main incoming surge current duty. | Use coordinated Type 1 / Type 2 / Type 3 protection where required. |
How Different SPD Types Affect Up Selection
Up must be understood together with SPD Type. A Type 1 SPD, Type 2 SPD, Type 1+2 SPD, and Type 3 SPD do not serve the same role in the protection system.
| Type de DOCUP | Typical Installation Position | Main Selection Focus | How to Understand Up |
|---|---|---|---|
| DOCUP de type 1 | Main incoming panel, lightning protection zone entry | Iimp, follow current behavior, system earthing, main protection coordination | Up matters, but Type 1 is mainly selected for lightning current discharge capability. |
| Type 1+2 SPD | Main distribution board where combined protection is required | Balance between lightning current capability and voltage limitation | Often used to reduce protection stages when the product is properly coordinated. |
| DOCUP de type 2 | Distribution board, sub-distribution board, OEM panel | Uc, In, Imax, Up, pole configuration, certification | Up is very important because Type 2 SPD is commonly used to protect downstream electrical equipment. |
| DOCUP de type 3 | Proche de l'équipement terminal | Fine protection and coordination with upstream Type 1 / Type 2 SPD | Up is usually lower, but Type 3 should not be treated as a replacement for upstream surge protection. |
For general SPD model selection beyond Up, you can also read our Guide de sélection SPD.
Why Installation Cable Length Changes the Real Protection Level
The Up value on the datasheet is measured at the SPD terminals. In a real distribution board, the protected equipment may see a higher voltage because the SPD connection leads add extra voltage during surge current flow.
This is why installation is not just a wiring detail. It directly affects the actual protection result.
What buyers should ask installers or panel builders to confirm
- Where will the SPD be installed inside the cabinet?
- How long are the conductors from busbar or terminal to the SPD?
- How long is the PE connection path?
- Is the PE path direct, or does it loop around other components?
- Is the protected equipment far from the SPD?
- Does the system need additional downstream Type 2 or Type 3 protection?
Up Must Be Checked Together With Uc, In, Imax, and Iimp
Up is a protection performance value. But it does not tell the full story of SPD selection.
| Paramètres | Ce que cela signifie | Why It Matters When Checking Up |
|---|---|---|
| Uc | Tension de fonctionnement maximale continue | If Uc is not suitable, the SPD may age early or fail under real grid conditions. |
| Haut de la page | Voltage protection level / residual voltage | Shows how much voltage may remain during a surge test. |
| En | Courant de décharge nominal | Shows routine surge discharge capability and durability under repeated surge stress. |
| Imax | Maximum discharge current for Type 2 SPD | Shows severe surge tolerance under the Type 2 test waveform. |
| Iimp | Courant d'impulsion pour ESD de Type 1 | Shows lightning current discharge capability for Type 1 applications. |
Related guides: SPD In Rating Selection, SPD Imax Selectionet IEC 61643-11 vs IEC 61643-31.
Common Up Ranges Buyers May See on Datasheets
Different SPD Types and product designs may show different Up values. Do not compare the number without checking the application.
| Example Up Level | How Buyers May See It | Important Reminder |
|---|---|---|
| ≤ 1.0 kV or lower | Often associated with fine protection, lower-voltage applications, or protection close to terminal equipment. | Check SPD Type, discharge current rating, system voltage, and whether it is suitable as main protection. |
| ≤ 1.2 kV / ≤ 1.5 kV | Commonly seen in many low-voltage DIN rail SPD datasheets. | Often attractive for distribution boards, but still check Uc, In, Imax, protection mode, and wiring length. |
| ≤ 2.0 kV / ≤ 2.5 kV | May appear on higher-energy or upstream protection devices. | Not automatically bad. It may be part of a coordinated upstream protection design. |
| Higher Up values | May appear depending on SPD Type, test condition, voltage rating, or protection mode. | Check whether additional downstream SPD is needed for sensitive equipment. |
These are not universal recommendations. Actual Up values depend on SPD Type, system voltage, protection mode, test waveform, discharge current condition, and the manufacturer’s datasheet. Always confirm the exact value from the product datasheet and required standard.
How to Compare Up Between Suppliers
When comparing quotations from different SPD suppliers, do not compare only one number. Ask for the complete parameter context.
Before comparing Up values, confirm:
- SPD Type: Type 1, Type 1+2, Type 2, or Type 3
- System voltage and required Uc
- Protection mode: L-PE, L-N, N-PE, L-L
- Courant de décharge nominal In
- Courant de décharge maximal Imax
- Impulse current Iimp for Type 1 SPD
- Test waveform and standard
- Number of poles and wiring system
- Certification: CE, TUV, CB, or project-specific requirement
- Installation position and expected cable length
For OEM and distributor orders, Up should be part of a full parameter confirmation process. It should not be treated as a standalone “best number”.
Buyer Examples: How to Read Up in Real Projects
| Project Situation | What the Buyer May Ask | Better Technical Response |
|---|---|---|
| 230/400V distribution board | Can I choose the SPD with the lowest Up? | First confirm Uc, Type 2 requirement, In/Imax, grounding system, protection mode, and installation lead length. Then compare Up. |
| Main incoming panel with external lightning protection | Is a low-Up Type 2 SPD enough? | Check whether Type 1 or Type 1+2 protection is required. Iimp may be more important at the incoming side. |
| PLC cabinet or sensitive control panel | Why do I still need downstream protection? | If the equipment is sensitive or far from the upstream SPD, coordinated Type 2 or Type 3 protection may be needed. |
| OEM panel for export | Which Up value should we put into the model requirement? | Define target market, system voltage, SPD Type, certification, protected equipment withstand level, and cabinet layout before finalizing the model. |
Send Your Panel Requirement Before Choosing by Up
For batch orders, OEM panels, and distribution board projects, LEEYEE can help check Up together with Uc, In, Imax, Iimp, grounding system, protection mode, backup protection, and cabinet installation layout.
Before Ordering: Information to Send the Supplier
If you want a supplier to recommend the correct SPD instead of only sending a price list, provide the following information.
- Tension nominale du système
- Maximum voltage fluctuation, if known
- Grounding system: TN-S, TN-C-S, TT, or IT
- SPD Type required: Type 1, Type 1+2, Type 2, or Type 3
- Installation position: main panel, sub-panel, cabinet, or terminal equipment
- Protected equipment type
- Equipment impulse withstand voltage, if available
- Required Uc
- Required In / Imax / Iimp
- Required Up or maximum acceptable protection level
- Protection mode: L-PE, L-N, N-PE, or L-L
- Backup protection requirement
- Cabinet wiring layout or photo
- Certification or standard requirement
- OEM label, packaging, or private label requirement
FAQ About SPD Up Voltage Protection Level
What does Up mean on an SPD?
Up means voltage protection level. It describes the residual voltage that may appear at the SPD terminals when the SPD is discharging surge current under specified test conditions.
Is Up the same as residual voltage?
In buyer language, Up is often understood as the declared voltage protection level related to residual or let-through voltage. It helps buyers understand how much voltage may still reach downstream equipment during a surge event.
Is SPD Up the same as clamping voltage?
Not always. Clamping voltage is often used as a general term for voltage limitation, but finished SPD selection should use the declared Up value from the SPD datasheet. Buyers should not confuse SPD Up with MOV component voltage.
Is a lower Up SPD always better?
Lower Up is usually better for voltage limitation, but it is not the only selection factor. Buyers must also check Uc, In, Imax, Iimp, SPD Type, protection mode, grounding system, and installation cable length.
Can I choose SPD only by Up?
No. Up tells you the protection level, but it does not tell whether the SPD can safely operate on your system voltage or discharge the required surge current. It must be checked as part of a full SPD selection.
Why is the actual protection level higher than the datasheet Up?
Datasheet Up is measured at the SPD terminals. In a real cabinet, connection leads, PE path, backup protection devices, and installation layout can add extra voltage, so the equipment may see a higher effective protection level.
Why does cable length affect SPD protection?
During surge current flow, long or looped conductors add extra voltage. This can make the actual voltage at the protected equipment higher than the Up value shown on the SPD datasheet.
What Up value is suitable for a distribution board?
It depends on the system voltage, SPD Type, protected equipment, equipment impulse withstand level, protection mode, and installation layout. For standard distribution boards, Type 2 SPD Up is commonly checked together with Uc, In, and Imax.
Does Type 3 SPD have lower Up than Type 2 SPD?
Type 3 SPD is normally used close to terminal equipment and may have a lower protection level. But it should be coordinated with upstream Type 1 or Type 2 SPD and should not be used as the only main protection where high surge current discharge is required.
What should OEM buyers confirm before ordering SPD by Up value?
OEM buyers should confirm system voltage, Uc, SPD Type, pole configuration, In, Imax or Iimp, protection mode, required standard, protected equipment, installation position, backup protection, and label or packaging requirements.
