Una pregunta común después de una tormenta eléctrica, un evento de conmutación o una sobretensión inesperada es: ¿es necesario reemplazar un SPD después de una sobretensión?

La respuesta corta es no, no automáticamente.

Un dispositivo de protección contra sobretensiones (SPD) está diseñado para limitar las sobretensiones transitorias y desviar la corriente de sobretensión. Si la sobretensión está dentro de la capacidad del SPD y el dispositivo no ha llegado al final de su vida útil, puede seguir protegiendo el sistema después del evento.

Sin embargo, una sobretensión severa, el estrés eléctrico repetido, una sobretensión temporal, el sobrecalentamiento o la degradación a largo plazo pueden dañar los componentes de protección dentro de un SPD. En estos casos, el módulo de protección puede desconectarse internamente y es posible que el SPD deba ser reemplazado.

Por lo tanto, la pregunta correcta no es simplemente:

“¿Ha experimentado el SPD una sobretensión?”

Es:

“¿En qué estado se encuentra el SPD después de la sobretensión?”

Esta guía explica qué le sucede a un SPD durante una sobretensión, cómo reconocer los signos de daño, qué significa realmente un indicador de estado verde o rojo, y cuándo debe reemplazar el módulo de protección o el SPD completo.

Principales conclusiones

• Un SPD hace no necesitan reemplazo automático después de cada sobretensión.
• Una sobretensión severa puede hacer que un SPD llegue al final de su vida útil, mientras que eventos menores pueden no hacerlo.
• El estrés eléctrico y térmico repetido puede cambiar gradualmente las características de los SPD basados en MOV.
• Una indicación roja o de fallo normalmente requiere atención de acuerdo con las instrucciones del fabricante.
• Un indicador de estado normal o verde no le indica la capacidad de sobretensión restante exacta del SPD.
• El sobrecalentamiento visible, las grietas, la fusión u otros daños físicos son motivos suficientes para retirar el SPD de servicio e investigar.
• Un multímetro básico no puede verificar completamente si un SPD aún cumple con su rendimiento original de protección contra sobretensiones.

¿Es necesario reemplazar un SPD después de una sobretensión?

Si un SPD debe ser reemplazado depende de su estado después del evento.

El punto importante es que un evento de sobretensión por sí solo no es una indicación de fin de vida útil.

El estado real del SPD y las instrucciones de mantenimiento del fabricante deben determinar el siguiente paso.

Vea esta breve explicación antes de decidir si reemplazar un SPD después de una sobretensión.

¿Qué sucede con un SPD durante una sobretensión?

Para entender por qué un SPD no necesita ser reemplazado necesariamente después de cada sobretensión, es útil comprender qué hace realmente el dispositivo.

Durante el funcionamiento normal

Muchos SPD de potencia se conectan en paralelo con el circuito que protegen.

Durante la tensión de funcionamiento normal, los componentes limitadores de tensión dentro del SPD permanecen en un estado de alta impedancia. Por lo tanto, la corriente de carga normal no necesita fluir a través del elemento de protección del SPD.

Esta es también la razón por la cual los SPD se instalan normalmente en paralelo en lugar de simplemente colocarse en serie con la carga.

Cuando ocurre una sobretensión

Cuando una sobretensión transitoria llega al SPD, sus componentes de protección responden.

En un SPD basado en MOV, el varistor de óxido metálico cambia de un estado de alta impedancia a un estado conductor a medida que el voltaje supera su región de operación.

El SPD entonces ayuda a:

limitar el voltaje transitorio

y

desviar la corriente de sobretensión lejos de los equipos sensibles.

Cuando el evento transitorio termina, el elemento de protección normalmente regresa a su estado de alta impedancia.

Este principio de funcionamiento es fundamental para los dispositivos de protección contra sobretensiones: contienen componentes no lineales diseñados para limitar el voltaje de sobretensión y desviar la corriente de sobretensión. Los requisitos actuales de la IEC utilizan la misma definición básica.

Por lo tanto, el hecho de que un SPD haya operado durante una sobretensión no significa por sí mismo que haya fallado.

¿Un solo sobrevoltaje daña un SPD?

No necesariamente.

El resultado depende de factores tales como:

• magnitud del sobrevoltaje
• forma de onda del sobrevoltaje
• duración
• número de eventos de sobrevoltaje
• diseño del SPD
• capacidad de corriente de descarga
• tensión del sistema
• condiciones de sobretensión temporal
• temperatura
• estrés eléctrico previo

Una sobretensión que se mantiene dentro de la capacidad del SPD puede ser gestionada sin causar que el dispositivo llegue al final de su vida útil.

Un evento mucho más severo puede causar daños significativos en una sola ocurrencia.

Eventos de sobretensión pequeños o moderados

Un SPD está diseñado para responder a sobretensiones transitorias.

Si un evento se mantiene dentro de la capacidad operativa y de manejo de sobretensiones prevista para el producto, el SPD puede seguir funcionando después.

Por esta razón, sería incorrecto aplicar una regla como:

“Una sobretensión = un reemplazo”.”

El dispositivo debe evaluarse de acuerdo con su condición real.

Eventos de sobretensión severos

Un evento lo suficientemente severo puede hacer que el elemento de protección alcance su fin de vida útil en un solo suceso.

Dependiendo del diseño del SPD, esto puede resultar en:

• la activación de un desconectador térmico interno
• una indicación de estado rojo o de fallo
• funcionamiento de un contacto de señalización remota
• daños visibles por calor
• desconexión del módulo de protección
• funcionamiento de un dispositivo de protección de respaldo externo

El comportamiento exacto ante fallos varía según el diseño del producto.

Eventos de sobretensión repetidos

La degradación del SPD tampoco se limita a un único evento de rayo importante.

Las tensiones eléctricas repetidas pueden afectar gradualmente las características eléctricas de un MOV.

Sin embargo, esto no debe describirse como una simple cuenta regresiva de energía fija donde cada sobretensión elimina una cantidad idéntica de vida útil restante.

La degradación de los MOV depende de la magnitud, duración, repetición, tensión de funcionamiento, temperatura y otros esfuerzos aplicados al componente. La norma IEC TR 61643-333:2026 aborda específicamente las ecuaciones características y la evaluación de la vida útil de los MOV de óxido de zinc, ilustrando que la vida útil de un MOV es más compleja que un simple “balance de julios” fijo.”

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 cómo saber si un SPD está defectuoso.

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.

Una disposición común es:

Normal indication → protection element has not reported end of life

Red/fault indication → affected module requires replacement

Por ejemplo, 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

NO

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.

Es 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.”

o

“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.

La regla más importante es:

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

Compruébalo:

• 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 Guía de especificaciones de SPD de CC explains Ucpv, In, Imax, Up and other common SPD markings in more detail.

Por lo tanto:

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 cómo probar un SPD.

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.”

o:

“An SPD always lasts ten years.”

Actual service life depends on many variables, including:

• electrical stress history
• surge magnitude and repetition
• tensión del sistema
• Uc or MCOV selection
• condiciones de sobretensión temporal
• 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.

Preguntas frecuentes

Does an SPD need to be replaced after every surge?

No.

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?

Sí.

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?

Sí.

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.