雷雨、開閉サージ、または予期せぬ電圧サージが発生した後に頻繁に寄せられる質問は以下の通りです。 サージ発生後にSPDを交換する必要がありますか？

結論から言うと いいえ、自動的に交換する必要はありません。.

サージ防護デバイス（SPD）は、過渡過電圧を制限し、サージ電流を逃がすように設計されています。サージがSPDの許容範囲内であり、デバイスが寿命に達していない場合は、イベント後もシステムを保護し続けることができます。.

しかし、激しいサージ、繰り返される電気的ストレス、一時的な過電圧、過熱、または長期的な劣化は、SPD内部の保護素子を損傷させる可能性があります。このような場合、保護モジュールが内部的に切り離され、SPDの交換が必要になることがあります。.

したがって、正しい問いは単に次のようなものではありません。

“SPDはサージを経験しましたか？”

正しくは次の通りです。

“サージ後のSPDの状態はどうなっていますか？”

本ガイドでは、サージ発生時にSPD内部で何が起こるのか、損傷の兆候をどのように見分けるか、緑色または赤色のステータス表示が何を意味するのか、そして保護モジュールまたはSPD全体をいつ交換すべきかについて説明します。.

要点

• SPDは ない すべてのサージ発生後に自動的に交換が必要になるわけではありません。.
• 1回の強力なサージでSPDが寿命に達することもあれば、小さなサージではそうならないこともあります。.
• 繰り返し受ける電気的および熱的ストレスにより、MOVベースのSPDの特性は徐々に変化する可能性があります。.
• 赤色または故障の表示が出た場合は、通常、メーカーの指示に従って対応する必要があります。.
• 正常または緑色のステータス表示は、SPDの正確な残存サージ耐量を示すものではありません。.
• 過熱、ひび割れ、溶融、またはその他の物理的な損傷が目視で確認できる場合は、SPDを運用から外し、調査を行うべき強力な理由となります。.
• 一般的なマルチメーターでは、SPDが当初のサージ保護性能を維持しているかどうかを完全に検証することはできません。.

サージ発生後にSPDを交換する必要はありますか？

SPDを交換すべきかどうかは、サージ発生後の状態に依存します。.

重要な点は サージイベントの発生のみが寿命の指標ではないということです.

SPDの実際の状態とメーカーの保守指示に基づいて、次のステップを決定すべきです.

サージ発生後にSPDを交換するかどうかを判断する前に、この簡単な解説動画をご覧ください.

サージ発生時、SPD内部では何が起こるのか？

サージが発生するたびにSPDを交換する必要がない理由を理解するには、そのデバイスが実際にどのような動作をしているのかを知ることが重要です。.

通常運転時

多くの電源用SPDは、保護対象の回路に対して並列に接続されます。.

通常の動作電圧下では、SPD内部の電圧制限素子は高インピーダンス状態を維持します。そのため、通常の負荷電流がSPDの保護素子を流れる必要はありません。.

これが、 SPDが通常並列に設置される理由であり、 負荷に対して単に直列に配置されるわけではない理由です。.

サージ発生時

過渡過電圧がSPDに到達すると、その保護素子が応答します。.

MOVベースのSPDでは、電圧が動作領域を超えて上昇すると、酸化亜鉛バリスタは高インピーダンス状態から導通状態へと変化します。.

その後、SPDは以下の役割を果たします。

過渡電圧を制限する。

そして

サージ電流を敏感な機器から逸らして逃がす。.

過渡現象が終了すると、保護素子は通常、高インピーダンス状態に戻ります。.

この動作原理はサージ防護デバイスの基本であり、サージ電圧を制限しサージ電流を逸らすように設計された非線形コンポーネントが含まれています。現在のIEC規格でも、この基本的な定義が採用されています。.

したがって、サージ発生時にSPDが動作したという事実だけでは、SPDが故障したことを意味するわけではありません。.

1回のサージでSPDは損傷しますか？

必ずしもそうではない。.

結果は以下の要因に依存します：

• サージの大きさ
• サージ波形
• 持続時間
• サージの発生回数
• SPDの設計
• 放電耐量
• システム電圧
• 一時的な過電圧状態
• 温度
• 以前の電気的ストレス

SPDの許容範囲内のサージであれば、デバイスの寿命を縮めることなく処理できる場合がある。.

はるかに深刻な事象が発生した場合、一度の発生で重大な損傷を引き起こす可能性がある。.

小規模または中規模のサージ事象

SPDは過渡過電圧に応答するように設計されている。.

事象が製品の意図された動作およびサージ処理能力の範囲内であれば、SPDはその後も動作を継続できる可能性がある。.

このため、以下のようなルールを適用することは不適切です。

“「サージ1回につき交換1回」”

デバイスは、その実際の状態に基づいて評価されなければなりません。.

重大なサージイベント

十分に重大なイベントが発生した場合、1回の発生で保護素子が寿命に達することがあります。.

SPDの設計によっては、以下の結果を招く可能性があります。

• 内部熱断路器の作動
• 赤色または故障状態の表示
• 遠隔信号接点の動作
• 目視可能な熱損傷
• 保護モジュールの切り離し
• 外部バックアップ保護装置の動作

正確な故障挙動は製品設計によって異なります。.

繰り返されるサージ事象

SPDの劣化は、一度の激しい落雷事象に限定されるものではありません。.

繰り返される電気的ストレスは、MOVの電気的特性に徐々に影響を与える可能性があります。.

しかし、これはすべてのサージが同量の残存寿命を奪うような、単純な固定エネルギーのカウントダウンとして説明されるべきではありません。.

MOVの劣化は、コンポーネントに印加される大きさ、持続時間、繰り返し回数、動作電圧、温度、およびその他のストレスに依存します。IEC TR 61643-333:2026は、酸化亜鉛MOVの特性方程式と寿命評価について具体的に言及しており、MOVの寿命が単純な固定の「ジュールバランス」よりも複雑であることを示しています。“

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 SPDの故障を見分ける方法.

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.

一般的な構成は以下の通りです：

Normal indication → protection element has not reported end of life

Red/fault indication → affected module requires replacement

例えば、, 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

ノー

NC

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

• PLCシステム
• alarms
• building-management systems
• monitoring systems
• SCADAシステム

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.

それは 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.”

または

“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.

最も重要なルールは以下の通りです：

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

をチェックする：

• 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 DC SPD仕様ガイドをご参照ください explains Ucpv, In, Imax, Up and other common SPD markings in more detail.

したがって：

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 how to test an 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.”

または：

“An SPD always lasts ten years.”

Actual service life depends on many variables, including:

• electrical stress history
• surge magnitude and repetition
• システム電圧
• Uc or MCOV selection
• 一時的な過電圧状態
• SPD technology
• 周囲温度
• 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.

よくある質問

Does an SPD need to be replaced after every surge?

そうだ。.

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?

そうだ。.

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?

そうだ。.

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.