Uma pergunta comum após uma tempestade com raios, evento de comutação ou surto de tensão inesperado é: um DPS precisa ser substituído após um surto?

A resposta curta é não — não automaticamente.

Um dispositivo de proteção contra surtos (DPS) foi projetado para limitar sobretensões transitórias e desviar a corrente de surto. Se o surto estiver dentro da capacidade do DPS e o dispositivo não tiver atingido o fim da sua vida útil, ele poderá continuar protegendo o sistema após o evento.

No entanto, um surto severo, estresse elétrico repetido, sobretensão temporária, superaquecimento ou degradação a longo prazo podem danificar os componentes de proteção dentro de um DPS. Nesses casos, o módulo de proteção pode desconectar-se internamente e o DPS pode precisar ser substituído.

Portanto, a pergunta correta não é simplesmente:

“O DPS sofreu um surto?”

É:

“Qual é a condição do DPS após o surto?”

Este guia explica o que acontece com um DPS durante um surto, como reconhecer sinais de danos, o que um indicador de status verde ou vermelho realmente significa e quando você deve substituir o módulo de proteção ou o DPS completo.

Principais conclusões

• Um DPS faz não necessitam automaticamente de substituição após cada surto.
• Um surto severo pode levar um DPS ao fim da sua vida útil, enquanto eventos menores podem não causar o mesmo efeito.
• O estresse elétrico e térmico repetido pode alterar gradualmente as características dos DPS baseados em MOV.
• Uma indicação vermelha ou de falha normalmente requer atenção de acordo com as instruções do fabricante.
• Um indicador de status normal ou verde não informa a capacidade exata de surto restante do DPS.
• Sinais visíveis de sobreaquecimento, fissuras, derretimento ou outros danos físicos são motivos fortes para retirar o DPS de serviço e investigar.
• Um multímetro básico não consegue verificar totalmente se um DPS ainda atende ao seu desempenho original de proteção contra surtos.

Um DPS precisa ser substituído após um surto?

Se um DPS deve ser substituído depende da sua condição após o evento.

O ponto importante é que um evento de surto por si só não é uma indicação de fim de vida útil.

A condição real do DPS e as instruções de manutenção do fabricante devem determinar o próximo passo.

Assista a esta breve explicação antes de decidir se deve substituir um DPS após um surto.

O que acontece com um DPS durante um surto?

Para entender por que um DPS não precisa necessariamente ser substituído após cada surto, é útil compreender o que o dispositivo realmente faz.

Durante a operação normal

Muitos DPS de potência são conectados em paralelo com o circuito que protegem.

Durante a tensão de operação normal, os componentes limitadores de tensão dentro do DPS permanecem em um estado de alta impedância. Portanto, a corrente de carga normal não precisa fluir através do elemento de proteção do DPS.

É também por isso que os DPS são normalmente instalados em paralelo em vez de serem simplesmente colocados em série com a carga.

Quando ocorre um surto

Quando uma sobretensão transitória atinge o DPS, seus componentes de proteção reagem.

Em um DPS baseado em MOV, o varistor de óxido metálico muda de um estado de alta impedância para um estado condutivo à medida que a tensão sobe acima de sua região de operação.

O DPS então ajuda a:

limitar a tensão transitória

e

desviar a corrente de surto para longe de equipamentos sensíveis.

Quando o evento transitório termina, o elemento de proteção normalmente retorna ao seu estado de alta impedância.

Este princípio de operação é fundamental para dispositivos de proteção contra surtos: eles contêm componentes não lineares projetados para limitar a tensão de surto e desviar a corrente de surto. Os requisitos atuais da IEC utilizam a mesma definição básica.

Portanto, o fato de um DPS ter operado durante um surto não significa, por si só, que ele falhou.

Um único surto danifica um DPS?

Não necessariamente.

O resultado depende de fatores como:

• magnitude do surto
• forma de onda do surto
• duração
• número de eventos de surto
• projeto do DPS
• capacidade de corrente de descarga
• tensão do sistema
• condições de sobretensão temporária
• temperatura
• esforço elétrico prévio

Um surto que permaneça dentro da capacidade do DPS pode ser suportado sem causar o fim da vida útil do dispositivo.

Um evento muito mais severo pode causar danos significativos em uma única ocorrência.

Eventos de surto pequenos ou moderados

Um DPS é projetado para responder a sobretensões transitórias.

Se um evento permanecer dentro da capacidade operacional e de manuseio de surtos pretendida para o produto, o DPS poderá continuar funcionando posteriormente.

É por isso que seria incorreto aplicar uma regra como:

“Um surto = uma substituição.”

O dispositivo deve ser avaliado de acordo com a sua condição real.

Eventos de surto severos

Um evento suficientemente severo pode fazer com que o elemento de proteção atinja o seu fim de vida útil em uma única ocorrência.

Dependendo do projeto do DPS, isso pode resultar em:

• ativação de um desconectador térmico interno
• uma indicação de status vermelho ou de falha
• operação de um contato de sinalização remota
• danos visíveis por calor
• desconexão do módulo de proteção
• operação de um dispositivo de proteção de retaguarda externo

O comportamento exato da falha varia de acordo com o design do produto.

Eventos de surto repetidos

A degradação do DPS também não se limita a um único evento de raio dramático.

Tensões elétricas repetidas podem afetar gradualmente as características elétricas de um MOV.

No entanto, isto não deve ser descrito como uma contagem decrescente de energia fixa simples, onde cada surto remove uma quantidade idêntica de vida útil restante.

A degradação do MOV depende da magnitude, duração, repetição, tensão de operação, temperatura e outros esforços aplicados ao componente. A norma IEC TR 61643-333:2026 aborda especificamente as equações características e a avaliação da vida útil para MOVs de óxido de zinco, ilustrando que a vida útil do MOV é mais complexa do que um simples “balanço de joules” fixo.”

Why Can an SPD Wear Out Over Time?

Many Type 2 SPDs use metal oxide varistors as their primary voltage-limiting elements.

Under normal voltage, an MOV has high resistance.

When the applied voltage rises sharply during a transient event, the MOV becomes conductive and helps limit the voltage.

Over time, electrical and thermal stress can change the MOV’s characteristics.

A simplified aging path may look like this:

Repeated electrical stress

↓

Change in MOV characteristics

↓

Possible increase in leakage current

↓

Additional heating

↓

Thermal protection operates if necessary

↓

Protection element disconnects

↓

SPD indicates an end-of-life or fault condition

The precise sequence depends on the SPD design.

Modern MOV-based SPDs commonly include thermal protection because an MOV that becomes unstable or overheated must be safely disconnected from the power system.

For example, Schneider Electric describes some of its SPDs as using thermally protected MOVs and instructs replacement of the module when the corresponding indication shows loss of protection.

This internal disconnection is one reason a failed SPD can sometimes leave the protected equipment powered while surge protection for that mode is no longer available.

7 Signs Your SPD Should Be Replaced

There is no single inspection method that applies identically to every SPD.

If you are not sure whether an SPD has failed, see our guide on como saber se um DPS está avariado.

However, the following signs usually justify replacement or further investigation.

1. The Status Indicator Shows Red or Fault

For many pluggable DIN-rail SPDs, the front status window provides the fastest visual indication of the protection module’s condition.

Um arranjo comum é:

Normal indication → protection element has not reported end of life

Red/fault indication → affected module requires replacement

Por exemplo, ABB describes mechanical SPD indicators that change from green to red at end of life and states that once this occurs, the SPD should be changed because protection is no longer guaranteed.

However, indicator colors and meanings are product-specific.

Always check the markings, datasheet, or instructions for the exact SPD you are inspecting.

Do not assume that every SPD from every manufacturer uses the same color logic.

2. The Remote Signaling Contact Reports a Fault

Some SPDs include remote signaling terminals, often using a changeover dry contact with terminals such as:

COM

NÃO

NC

These contacts allow the SPD’s status to be reported remotely to equipment such as:

• Sistemas PLC
• alarms
• building-management systems
• monitoring systems
• Sistemas SCADA

When the monitored SPD reaches the state defined by the manufacturer, the remote contact changes state.

But a remote alarm should still be verified.

Check:

1. the local SPD indicator
2. the manufacturer’s contact diagram
3. COM/NO/NC wiring
4. the monitoring circuit

The remote contact tells you about the monitored SPD state. It does not directly measure the SPD’s actual surge-clamping performance.

3. You See Burn Marks, Melting, or Serious Discoloration

Visible heat damage is not a normal service condition.

Warning signs include:

• blackened areas
• melted plastic
• severe discoloration
• damaged terminals
• signs of arcing
• heat-damaged conductors

If these conditions are present, the SPD should not simply be returned to service because its indicator still appears normal.

The circuit should be made safe according to the applicable electrical procedure, and both the SPD and surrounding installation should be inspected.

The cause also matters.

Replacing the SPD without identifying a wiring problem, abnormal system voltage, short-circuit condition, or other fault can result in another failure.

4. The SPD Housing Is Cracked or Deformed

A cracked housing may result from:

• mechanical damage
• excessive heat
• a severe electrical event
• environmental deterioration
• improper installation

Even if the internal condition cannot be seen, physical enclosure damage is a reason to treat the SPD as suspect.

An electrical protection device depends not only on its MOV or other internal component but also on proper insulation, spacing, mechanical connections, and safe containment.

If these have been compromised, replacement is normally the safer maintenance decision.

5. There Is a Burning Smell or Evidence of Overheating

Not every internal problem immediately produces an obvious red indicator.

If you notice:

• a burning smell
• abnormal heat
• softened plastic
• terminal overheating
• heat damage around the DIN rail or conductors

disconnect and investigate the equipment using the required safe electrical procedure.

Do not continue using an SPD simply because power is still reaching the protected equipment.

A parallel-connected SPD can lose its protective function while the main circuit continues supplying the load.

6. A Replaceable Protection Module Has Disconnected

Many modular SPDs use plug-in cartridges.

If an internal disconnector has operated and the cartridge indicates end of life, the affected cartridge normally needs replacement.

That does not necessarily mean the complete SPD base must always be replaced.

If:

• the base is undamaged
• the contacts are in good condition
• there are no signs of overheating
• the correct compatible replacement module is available

the manufacturer may allow replacement of the cartridge only.

Schneider Electric, for example, provides model-specific replacement modules for certain modular SPD families rather than requiring replacement of every part of the assembly.

But never assume that a pluggable SPD cartridge is automatically safe to remove while energized.

Pluggable does not mean hot-swappable.

Follow the manufacturer’s instructions and the required electrical isolation procedure before servicing the SPD.

7. The New SPD Keeps Failing Again

One of the most important warning signs is not the first failure.

É repeated early failure after replacement.

If a newly installed SPD quickly reaches its fault or end-of-life condition again, simply installing another identical device may not solve the problem.

Investigate possible causes such as:

• incorrect Uc or MCOV selection
• system voltage higher than expected
• temporary overvoltage
• neutral or earthing-system problems
• wrong SPD configuration for the electrical system
• incorrect AC/DC application
• inadequate coordination
• installation errors
• severe or unusually frequent surge exposure
• unsuitable backup protection

For PV applications, correct voltage selection is especially important. See how to select the correct DC SPD voltage rating for a solar PV system.

Current IEC SPD requirements specifically consider system and fault conditions such as expected short-circuit current and temporary-overvoltage stresses when evaluating SPD applications.

Repeated failure should therefore be treated as a system-level troubleshooting problem, not merely a replacement problem.

Can an SPD Still Be Good If the Indicator Is Green?

Usually, a manufacturer-defined normal indication means the SPD has not reported its end-of-life condition through that indicator mechanism.

For a deeper explanation, see what an SPD green indicator can and cannot tell you about the protection condition.

But there is an important distinction:

Normal indicator ≠ exact measurement of remaining SPD life.

A basic mechanical indicator normally does not tell you:

• remaining surge-current capacity
• percentage of MOV life remaining
• exact degradation level
• future number of surges the SPD can withstand
• whether the original voltage-protection level has been independently verified

So avoid statements such as:

“Green means the SPD is 100% healthy.”

ou

“Green means the SPD has full surge capacity remaining.”

A more technically accurate interpretation is:

The SPD’s normal status indication shows that its internal monitoring or disconnection mechanism has not indicated end of life according to the product design.

That is useful information—but it is not the same as a complete electrical performance test.

ABB’s guidance illustrates this distinction well: the mechanical indicator is specifically an end-of-life indicator, changing state when the device reaches the defined replacement condition.

Should You Replace an SPD After a Major Lightning Event?

Not automatically—but the inspection should be more thorough.

The words “lightning event” can describe very different electrical stresses.

A distant lightning event that induces a relatively small transient is not the same as a severe nearby or direct lightning-current event.

The correct SPD type and coordinated protection system also matter.

For example, a Type 2 SPD is primarily tested for surge-current conditions different from those associated with the lightning-current testing of a Type 1 SPD.

So after a known major event, check more than just the color window.

Inspect:

• the SPD status indicator
• remote signaling status
• plug-in modules
• SPD base
• terminals
• conductors
• backup fuse or circuit breaker
• upstream and downstream protective devices
• evidence of damage elsewhere in the system

If nearby electrical equipment has also been damaged, or the lightning event was unusually severe, a more detailed electrical inspection is justified even when the status window has not changed.

For critical installations, follow the site’s maintenance plan, lightning-protection procedure, and manufacturer-specific recommendations.

Replace the SPD Cartridge or the Whole SPD?

For modular SPDs, a failed cartridge does not always require replacing the complete assembly.

Use the physical condition of the base and the manufacturer’s instructions to make the decision.

A regra mais importante é:

Replace only what the manufacturer allows you to replace.

A cartridge from a different series may physically look similar while having a different Uc, discharge rating, protection level, internal circuit, or coding system.

Always use the specified replacement module.

How to Check an SPD After a Surge

A practical post-surge inspection can follow seven basic steps.

Step 1: Check the Status Indicator

Start with the front status window.

Look for the manufacturer-defined normal, fault, or end-of-life condition.

Step 2: Check Remote Signaling

If the SPD includes remote contacts, verify whether the monitoring system has received a fault signal.

Compare the result with the manufacturer’s COM/NO/NC diagram.

Step 3: Look for Physical Damage

Verifique se há:

• burns
• cracking
• melting
• discoloration
• loose parts
• abnormal smell

Step 4: Inspect the Module and Base

For a modular SPD, inspect both the plug-in cartridge and the base.

A new cartridge should not be installed into a heat-damaged or mechanically damaged base.

Step 5: Inspect Connections

Loose or heat-damaged conductors can affect both safety and surge protection.

Also check the SPD connection conductors and protective-earth connection according to the installation instructions.

In solar PV systems, the distance between the SPD and inverter and the connection lead length can also affect practical surge protection performance.

Step 6: Understand the Event

Ask what happened before the SPD changed state.

Was there:

• a thunderstorm?
• a known lightning event?
• a supply fault?
• an abnormal system voltage?
• equipment switching?
• a neutral problem?
• repeated SPD failure?

This information can help distinguish normal end-of-life behavior from a broader installation problem.

Step 7: Replace or Test as Required

If the SPD has reached its defined end-of-life state or shows physical damage, replace the affected component according to the manufacturer’s instructions.

If the condition is uncertain and the application justifies deeper verification, use the appropriate professional SPD testing method or manufacturer-approved test equipment.

Can You Test an SPD After a Surge With a Multimeter?

A multimeter can be useful around an SPD, but it cannot fully prove that the SPD still has its original surge-protection performance.

For example, a multimeter may help with:

• checking a remote signaling contact
• confirming whether a dry contact is open or closed
• limited resistance or continuity checks where permitted
• troubleshooting associated wiring

But an ordinary multimeter does not reproduce the electrical conditions used to determine major SPD parameters such as:

• voltage protection level, Up
• nominal discharge current, In
• maximum discharge current, Imax
• impulse current, Iimp

If these ratings are unfamiliar, our Guia de especificações de DPS CC explains Ucpv, In, Imax, Up and other common SPD markings in more detail.

Portanto:

A successful multimeter continuity or resistance check is not proof that the SPD still meets its original surge-protection specification.

Professional SPD verification may require dedicated equipment capable of testing the relevant electrical characteristics.

Phoenix Contact, for example, provides dedicated CHECKMASTER equipment for electrical testing of compatible pluggable SPDs and notes that visual inspection alone may not reliably determine an SPD’s functional capability.

Also remember that some electrical tests performed elsewhere in an installation can interact with an SPD.

ABB installation guidance, for example, specifies that the SPD should be disconnected before certain insulation testing because the SPD can respond to the test voltage as though it were an overvoltage.

Always follow the SPD and test-equipment manufacturer’s instructions.

For a more complete inspection procedure, see our guide on como testar um DPS.

How Long Does an SPD Last?

There is no universal fixed service life that applies to every SPD.

It would therefore be misleading to say:

“Every SPD must be replaced after three years.”

ou:

“An SPD always lasts ten years.”

Actual service life depends on many variables, including:

• electrical stress history
• surge magnitude and repetition
• tensão do sistema
• Uc or MCOV selection
• condições de sobretensão temporária
• SPD technology
• temperatura ambiente
• installation quality
• coordination with other SPDs
• lightning exposure
• manufacturer design

A severe event may cause end of life much earlier than expected.

Another SPD in a relatively quiet installation may remain serviceable for many years.

For that reason, condition-based inspection and manufacturer-defined status indications are generally more useful than assigning one universal expiration date.

SPD Replacement Decision Checklist

Use this quick decision guide after a surge event.

Perguntas frequentes

Does an SPD need to be replaced after every surge?

Não.

SPDs are designed to respond to transient overvoltages. Experiencing a surge does not automatically mean the SPD has reached end of life.

Replace or service it when the manufacturer’s status indication, inspection results, electrical testing, or physical condition shows that it is no longer serviceable.

Can an SPD work more than once?

Sim.

Many SPDs are designed to withstand multiple surge events within their specified capability.

However, the number and severity of events an SPD can withstand cannot be reduced to one universal number because different surge stresses and product designs produce different effects.

Can one lightning strike destroy an SPD?

Sim.

A sufficiently severe lightning-related event can cause an SPD to reach end of life in one occurrence.

Whether this happens depends on the actual current and voltage stress reaching the SPD, the SPD type and ratings, installation, and the overall lightning and surge protection system.

Does a green SPD indicator mean the SPD is still good?

It normally means the SPD has not indicated its manufacturer-defined end-of-life state through that indicator.

It should not normally be interpreted as an exact measurement of remaining surge capacity.

Always check the product instructions for the specific meaning of its status window.

Should a red SPD be replaced?

For SPDs where red is defined as the end-of-life or replacement indication, yes—the affected module or device should be serviced or replaced according to the manufacturer’s instructions.

ABB, for example, states that when its standard SPD indicator changes from green to red at end of life, the SPD must be changed because protection is no longer guaranteed.

Can I replace only the SPD cartridge?

If the SPD uses manufacturer-approved replaceable modules and the base remains undamaged, replacing only the affected cartridge may be permitted.

Check that the replacement module has the correct model, voltage rating, and compatibility.

If the base, terminals, housing, or contacts have been damaged, replace the complete affected assembly as required.

Can I replace a pluggable SPD module while the circuit is energized?

Do not assume that you can.

A pluggable design makes maintenance easier, but it does not automatically mean the module is approved for energized replacement.

Follow the manufacturer’s instructions and the required electrical isolation and safety procedure before removing or installing an SPD module.

Can a multimeter tell if an SPD is still good?

Not completely.

A multimeter may help test remote contacts or perform limited circuit checks, but it cannot reproduce the surge test conditions needed to verify the SPD’s full protection performance.

Dedicated test equipment or manufacturer-defined electrical testing may be required for more detailed verification.

Final Decision: When Should You Replace an SPD?

Do not replace an SPD simply because a surge occurred.

An SPD is specifically designed to respond to transient overvoltage events, and one surge does not automatically mean the device has reached end of life.

Instead, base the decision on the actual condition of the SPD.

Replacement is normally justified when:

• the manufacturer-defined end-of-life indicator has operated
• the remote monitoring system reports a confirmed SPD fault
• an internal protection module has disconnected
• the housing or base is physically damaged
• there is evidence of overheating, burning, or melting
• manufacturer-approved testing shows the SPD is no longer serviceable

A normal status indication and the absence of physical damage generally mean there is no obvious end-of-life indication, but they do not provide an exact measurement of remaining surge capacity.

And if an SPD repeatedly fails shortly after replacement, do not simply install another one.

Investigate the system voltage, Uc or MCOV selection, temporary overvoltage conditions, electrical configuration, wiring, backup protection, and the severity of the surge environment.

The best replacement decision is therefore based not on:

“Did a surge happen?”

but on:

“What does the SPD condition tell us after the surge?”

About KUANGYA Surge Protective Devices

KUANGYA provides AC and DC surge protective devices for electrical distribution and solar PV applications, including modular designs with visual status indication and optional remote signaling functions for easier inspection and maintenance.

For photovoltaic DC applications, SPD selection should consider factors such as maximum PV system voltage, Ucpv, SPD type, discharge-current ratings, voltage protection level, system configuration, and installation position.

PV-side SPDs are specifically addressed by IEC 61643-31 for photovoltaic installations up to 1500 V DC.

If you need help selecting a replacement SPD, send us your:

AC or DC application + system voltage + required SPD type + quantity

and KUANGYA can help you check a suitable model.