태양광 인버터 내장형 SPD는 중요한 서지 보호 기능을 제공할 수 있지만, 데이터시트에 “DC Type II SPD”가 명시되어 있다고 해서 전체 PV 시스템이 보호된다는 의미는 아닙니다.

때로는 사양에 다음과 같이 기재되어 있기도 합니다:

내장형 Type II DC 및 AC SPD

처음에는 결론이 명확해 보입니다:

“인버터에 이미 서지 보호 장치가 있는데, 왜 또 다른 SPD를 설치해야 하지?”

그러고 나서 PV 결합함(Combiner box)을 살펴보면 내부에 또 다른 DC SPD가 있는 것을 발견하게 됩니다.

또는 설치 기사가 PV 어레이 근처에 추가적인 SPD를 설치해야 한다고 말할 수도 있습니다.

이제 질문이 혼란스러워집니다.

두 개의 SPD가 동일한 역할을 수행합니까?

외부 SPD가 불필요한 것입니까?

아니면 인버터 내부의 SPD가 PV 시스템의 일부만 보호하는 것입니까?

빠른 답변

내장형 DC SPD가 있다고 해서 외부 SPD가 필요 없다는 것을 의미하지는 않습니다.

실제 정답은 다음 사항에 따라 달라집니다:

• 인버터에 실제로 어떤 유형의 SPD가 내장되어 있는지;
• DC 측, AC 측 또는 양쪽 모두에 설치되어 있는지 여부;
• PV 어레이와 인버터 사이의 거리;
• PV 결합함(combiner box) 사용 여부;
• 건물에 외부 피뢰 시스템이 설치되어 있는지 여부;
• 필요한 이격 거리를 유지할 수 있는지 여부;
• 인버터 제조사 및 해당 프로젝트 요구사항에서 명시하는 내용.

따라서 핵심 질문은 다음이 아닙니다.

“내 인버터에 SPD가 있는가?”

더 나은 질문은 다음과 같습니다.

“SPD는 어디에 위치하며, 시스템의 어느 부분을 보호하고, 서지가 그 지점에 도달하기 전에는 어떤 일이 발생하는가?”

이러한 사고방식의 변화는 이 주제를 훨씬 더 이해하기 쉽게 만들어 줍니다.

내장형 SPD: 무엇을 알려주고 무엇을 알려주지 않는가

인버터 데이터시트를 읽을 때, “내장형 SPD”라는 문구는” 유용한 정보를 제공하지만, 알아야 할 모든 것을 알려주지는 않습니다.

이것이 첫 번째 실무 교훈임:

인버터 데이터시트에서 “SPD”를 확인하는 것은 첫 단계일 뿐임. SPD 유형, DC 측 또는 AC 측 설치 여부, 그리고 실제 기술 사양을 확인해야 함.

30초 SPD 라벨 검토

내장형 인버터 SPD에 대해 논의하기 전에, 실제 DC SPD 라벨을 간단히 검토해 보겠습니다.

이 정품 KUANGYA 1000V Type 2 DC SPD의 주요 사양 값을 식별할 수 있습니까?

1. 이 DC SPD의 최대 연속 동작 전압을 나타내는 값은 무엇입니까?

Up: 3.5kV Uc: 1000Vdc Imax: 40kA In: 20kA

정답: Uc: 1000Vdc

Uc는 이 SPD가 견딜 수 있도록 설계된 최대 연속 동작 전압을 나타냅니다.

2. 이 Type 2 SPD의 최대 방전 전류를 나타내는 값은 무엇입니까?

Uc: 1000Vdc Up: 3.5kV Imax: 40kA EN/IEC 61643-11

정답: Imax: 40kA

Imax는 Type 2 SPD가 지정된 시험 조건 하에서 견딜 수 있는 최대 방전 전류입니다.

전압 보호 레벨을 나타내는 값은 무엇입니까?

In: 20kA Up: 3.5kV Uc: 1000Vdc KYPV/1000

정답: Up: 3.5kV

Up은 전압 보호 레벨입니다. 이는 SPD가 서지를 제한하는 동안 SPD 단자에 남아 있을 수 있는 전압 레벨을 나타냅니다.

이 표시들에 대해 확실하지 않으신가요?

이전 가이드에서 Uc, In, Imax, Up 및 기타 DC SPD 라벨 값에 대해 더 자세히 설명하고 있습니다.

DC SPD 라벨 읽는 법: Class II, Ucpv, In, Imax, Up 및 Iscpv 설명 →

다시 시도

태양광 인버터 내장형 SPD는 실제로 무엇을 보호하는가?

내장형 DC SPD는 일반적으로 인버터의 DC 입력 측에 서지 보호 기능이 통합되어 있음을 의미합니다.

그러나 인버터 설계는 모두 동일하지 않습니다.

일부 제조업체는 Type 2 보호 기능을 표준으로 설치합니다.

일부 제품은 DC 측과 AC 측 모두에 보호 기능이 있습니다.

일부 상업용 모델은 DC 측에 Type 1+2 보호 기능을 사용합니다.

일부 인버터 플랫폼은 SPD를 사전 설치된 상태로 주문하거나 나중에 개조할 수 있도록 지원합니다.

이는 항상 다음 사항을 확인해야 함을 의미합니다. 정확한 인버터 모델, 특정 제조사의 모든 인버터가 동일한 보호 방식을 사용한다고 가정해서는 안 됩니다.

유용한 인버터 매뉴얼이나 데이터시트는 다음 몇 가지 사항을 식별하는 데 도움이 됩니다.

SPD가 DC 측에 있습니까, 아니면 AC 측에 있습니까?

이는 매우 기본적인 사항입니다.

PV 어레이는 DC 측을 통해 인버터에 전력을 공급합니다.

인버터는 AC 측을 통해 배전 시스템에 연결됩니다.

AC SPD가 동일한 인버터 인클로저 내부에 설치되었다고 해서 단순히 DC 측 보호 장치가 되는 것은 아닙니다.

어떤 유형의 SPD가 설치되어 있습니까?

확인 사항:

• 유형 1
• 유형 2
• 유형 1+2

이러한 유형 간의 차이점을 잘 모르시겠습니까? 다음을 참조하십시오. Type 1 대 Type 2 대 Type 1+2 DC SPD 비교.

이 질문을 다음 내용으로 대체하지 마십시오:

“어떤 제품의 kA 수치가 가장 큽니까?”

SPD 유형은 방전 전류 정격과는 다른 정보를 제공합니다.

SPD는 교체가 가능합니까?

이는 유지보수 측면에서 특히 중요합니다.

일부 통합형 SPD는 교체 가능한 모듈이나 카트리지를 사용합니다. 다른 제품들은 특정 서비스 절차를 요구합니다.

예를 들어, Fronius는 Verto 문서에서 SPD가 작동하면 기계식 표시기가 녹색에서 빨간색으로 바뀌며, 완전한 보호 기능을 유지하기 위해 작동된 SPD를 교체해야 한다고 명시하고 있습니다.

따라서 “내장형”이 “영구적인 무보수”를 의미하는 것은 아닙니다.”

실제 인버터 사례를 통해 “내장형 SPD'가 단일 표준 구성이 아님을 확인

가상의 인버터 사양을 설정하는 대신, 여러 실제 제품과 공식적으로 게시된 문서를 살펴보겠습니다.

Real-World Inverter Examples

These examples are useful because they show something that a generic statement like “modern inverters have SPD” cannot explain.

Different real inverters use different protection concepts.

For example, Sungrow’s current SG3.0RS-L product information specifies built-in Type II DC & AC SPD.

But Sungrow’s SG30CX-P2 and SG50CX-P2 datasheet lists DC Type I+II / AC Type II.

The conclusion is simple:

“My inverter has an SPD” is only the beginning of the conversation.

Check three things next:

What type is it?
DC side or AC side?
Where is it installed?

Why SPD Location Can Matter More Than SPD Quantity

A common way to think about surge protection is:

One SPD = protected
Two SPDs = more protected

That is not a good design principle.

Two SPDs installed at the wrong places do not automatically create better protection than one correctly positioned and coordinated system.

The better question is:

Where is the surge protective device in relation to the equipment and cable route that need protection?

Consider these two simplified systems.

System A

PV array → 4 m DC cable → inverter with built-in Type 2 SPD

System B

PV array → 35 m DC cable → building entry → inverter with built-in Type 2 SPD

The inverter may be exactly the same.

The built-in SPD may also be exactly the same.

But the installation is not the same.

In System B, a much longer outdoor DC cable exists between the PV array and the inverter.

That changes the surge-protection problem.

Why Does Cable Distance Matter?

PV systems often contain long conductors exposed across rooftops, facades, open ground or industrial buildings.

During nearby lightning activity, electromagnetic effects can induce transient overvoltages into those conductors.

A surge does not have to arrive only from the utility grid.

This means that long PV cable routes must be considered as part of the protection concept.

If the only SPD is located inside the inverter, that protective point is located at one end of the cable.

It does not physically move closer to the PV modules because the inverter manufacturer integrated it into the enclosure.

This is why published PV surge-protection guidance considers not only what SPD is used, but also where it is installed.

Phoenix Contact’s current PV guidance identifies the DC side of the inverter as an additional protection location when the cable length to the PV panels is 10 m or more, and also identifies another protection position near the PV panels or building entrance.

Its technical guidance also states that if the cable length between PV panels and inverter exceeds 10 m, an additional protection device should be installed at the other end of the cable near the PV panels.

DEHN publishes similar rooftop PV guidance, stating that if more than 10 m of cable exists between the PV system and inverter, a further arrester is required in the roof area for the arrangement it describes.

Does That Mean 10.1 m Always Requires Two SPDs Everywhere?

아니요.

This is where technical articles often become misleading.

다음을 수행해야 합니다. not take “10 m” and turn it into a universal sentence such as:

“Every PV system longer than 10 meters must always have exactly two Type 2 SPDs.”

The actual design still depends on:

• applicable standards;
• local electrical requirements;
• external lightning protection;
• separation distance;
• system architecture;
• manufacturer instructions;
• and project specifications.

The useful lesson is simpler:

Around this distance, cable length stops being something you should ignore and becomes an important design consideration.

A Practical Distance Table

The important point is that distance affects location decisions, not merely product quantity.

What About a PV Combiner Box?

A 컴바이너 박스 is another reason why you should inspect the whole PV system before ordering another SPD.

Imagine a project where the inverter datasheet says:

Built-in DC Type 2 SPD

A buyer may then request another external Type 2 SPD because they assume the array side has no protection.

But the project’s combiner box may already include:

• string fuses;
• DC isolator;
• DC SPD;
• monitoring;
• and other protective components.

In that situation, surge protection may already exist at more than one point.

So before buying another SPD, ask:

“Is there already an SPD inside the combiner box?”

This sounds obvious, but in real purchasing work, different components are often quoted by different suppliers.

The inverter may come from one manufacturer.

The combiner box comes from another.

The electrical protection devices come from a third.

A buyer looking only at individual product datasheets can easily lose sight of the complete single-line diagram.

External Lightning Protection Changes the Answer

Now consider a building with an external lightning protection system.

This can include:

• air terminals;
• lightning conductors;
• down conductors;
• bonding;
• and an earthing system designed as part of a lightning protection concept.

At this point, the question:

“Do I need one more Type 2 SPD?”

may be too simple.

One critical factor is whether the required separation distance between the PV installation and the external lightning protection system can be maintained.

Phoenix Contact’s current PV guidance distinguishes between systems:

1. without external lightning protection;
2. with external lightning protection where separation distance is maintained;
3. and with external lightning protection where separation distance is not maintained.

For the DC side, its published selection table shows Type 2 protection where separation distance is maintained, while Type 1 protection is specified for the relevant protection positions when separation distance is not maintained.

So if your building has external lightning protection, do not simply ask:

“Should I add another SPD?”

물어보세요:

“What lightning protection concept applies to this building, and can the required separation distance be maintained?”

That question is much more useful.

Built-In SPD vs External SPD

It is easy to assume that one must be better than the other.

That is not really the point.

Built-In SPD

Advantages can include:

• protection very close to inverter electronics;
• compact integration;
• shorter internal connections;
• easier equipment packaging;
• and, depending on the inverter design, monitoring or replaceable modules.

Its main limitation is obvious:

its location is fixed inside or directly at the inverter.

External SPD

An external SPD can be installed where the system design requires another protection point.

Typical locations include:

• PV combiner box;
• near the PV array;
• building entrance;
• external DC protection box;
• near the inverter;
• AC distribution board.

So instead of asking:

“Is an external SPD better than the inverter’s built-in SPD?”

ask:

“Which protection locations does this installation require, and which of those locations are already covered?”

That is the more professional question.

A Real Manufacturer Example: Why the SPD Is Part of a Larger Protection Concept

Fronius describes the SPD in its Verto documentation as contributing to the protection of PV system components as part of an overall lightning protection concept. It also specifies maintenance behavior: when the SPD has operated, the mechanical status indication changes from green to red and the device should be replaced to maintain protection.

This is an important practical idea.

The inverter’s SPD is not a magical shield around the entire PV installation.

It is one protective component inside a larger electrical protection concept.

That concept includes:

• surge protection;
• earthing;
• equipotential bonding;
• conductor routing;
• lightning protection where applicable;
• overcurrent protection;
• correct installation;
• and maintenance.

This is why the answer cannot come from one specification line alone.

Three Installation Scenarios

The following are illustrative installation scenarios, not claimed customer projects. They are designed to show how the same inverter specification can lead to different questions.

Scenario A: Small Residential Rooftop

System:

• residential rooftop PV;
• string inverter;
• built-in DC Type 2 SPD;
• PV array approximately 5 m from inverter;
• no external lightning protection system;
• no remote combiner box.

In this situation, it would be wrong to automatically say:

“You definitely need another external Type 2 SPD.”

Instead, check:

• the inverter manual;
• the built-in SPD specification;
• local requirements;
• earthing;
• actual cable routing;
• and whether another SPD is already present elsewhere.

A short and simple installation is very different from a large commercial rooftop.

Scenario B: Commercial Rooftop with a 35 m DC Cable Route

System:

• large PV array;
• remote combiner box;
• inverter room inside the building;
• approximately 35 m DC cable route;
• inverter includes DC Type 2 protection.

Now the situation is different.

The built-in SPD provides protection at the inverter end.

But there is a long DC route between the array and inverter.

This is precisely the type of installation where published manufacturer guidance about additional protection locations on long cable runs becomes relevant.

The correct question becomes:

“Is coordinated surge protection also required near the array or combiner box?”

Not:

“Does the inverter have an SPD?”

Scenario C: Rooftop PV with External Lightning Protection

System:

• commercial building;
• external lightning protection system;
• rooftop PV;
• inverter includes DC Type 2 protection.

Before deciding whether to add another Type 2 SPD, you need another piece of information:

Can the required separation distance be maintained?

If it cannot, the required protection concept may involve Type 1 protection at relevant locations rather than simply duplicating Type 2 devices. Phoenix Contact’s published PV guidance explicitly distinguishes these conditions.

The presence of a built-in Type 2 SPD therefore does not answer the whole lightning-protection question.

Does AC Type 2 SPD Protect the PV DC Side?

아니요.

This is one of the easiest misunderstandings to avoid.

A modern inverter may have:

DC SPD: Type II

및

AC SPD: Type II

because the DC and AC sides are separate electrical paths.

The PV array reaches the inverter through DC conductors.

The grid or AC distribution system connects through the inverter AC side.

Surges can reach equipment through different paths.

Real inverter datasheets demonstrate this separation clearly.

For example, Sungrow’s SG30CX-P2 / SG50CX-P2 specification lists the DC and AC surge protection separately: DC Type I+II / AC Type II.

That would make little sense if one SPD automatically protected both sides.

There Is Another Path People Forget: Communication Lines

Power cables are not the only conductors connected to modern PV systems.

An inverter may also use:

• RS-485;
• Ethernet;
• weather station connections;
• digital inputs;
• monitoring cables;
• control signals;
• power-management communication.

Phoenix Contact specifically points out that overvoltages can also enter inverter electronics through network or control interfaces and recommends considering surge protection for communication interfaces such as Ethernet, RS-485 and weather-station connections.

This is a useful reminder:

“My DC and AC sides both have SPDs” still does not necessarily mean every electrical path entering sensitive equipment has been considered.

Common Misunderstandings

Can I Simply Add More SPDs to Be Safe?

꼭 그렇지는 않습니다.

Surge protection should be coordinated, not accumulated randomly.

Installing another SPD without considering:

• SPD type;
• voltage;
• installation point;
• conductor routing;
• earthing;
• protection level;
• distance;
• upstream and downstream devices;
• and manufacturer instructions

does not automatically improve the installation.

Imagine putting two Type 2 SPDs next to each other inside the same cabinet when the actual problem is a 40 m cable route from a remote PV array.

You have increased the number of SPDs.

But you may not have solved the real problem.

This is why good design starts with the system layout.

Do Not Forget SPD Wiring

Even a correctly selected SPD can lose effectiveness if its installation is poor.

During a surge event, connection conductors are not electrically “invisible.”

Long or unnecessarily looped conductors add inductive voltage.

This means two systems can use exactly the same SPD but achieve different real protection performance.

Installation A

SPD located close to the protected equipment with short, direct conductors.

Installation B

Same SPD, but connected through long looping conductors inside the cabinet.

The product label is identical.

The installation is not.

This is why selecting a device only by looking at:

1000 V

20 kA

40 kA

is incomplete.

The SPD and its installation must work together.

Before Buying Another SPD: Check These 7 Things

This is the checklist worth saving.

If you can provide these seven pieces of information, an installer or SPD supplier can give you a much more useful answer.

A Simple Decision Flow

Step 1 — Does the inverter have a clearly specified DC SPD?

아니요

Evaluate DC-side surge protection for the PV installation.

예

Continue to Step 2.

Step 2 — What type is it?

Check:

유형 1

유형 2

또는

유형 1+2

Do not guess from the size of the inverter.

Use the actual datasheet.

Step 3 — Where is it installed?

If it is built into the inverter, you have a protection point at the inverter.

Now look at the rest of the DC cable route.

Step 4 — How far is the PV array from the inverter?

If the cable route is short, check the inverter instructions and applicable installation requirements before adding another device.

If the cable route is long, evaluate whether another coordinated protection point is required closer to the PV array or combiner box.

Published PV guidance from Phoenix Contact and DEHN specifically treats longer cable distances as a reason to consider protection at additional locations.

Step 5 — Is external lightning protection installed?

아니요

Continue with the applicable surge-protection design for the PV installation.

예

Check whether the required separation distance can be maintained.

If it cannot, Type 1 protection may become relevant at the applicable installation points.

Step 6 — Is another SPD already installed?

Check:

• PV combiner box;
• array-side protection enclosure;
• inverter DC protection box;
• main distribution;
• AC distribution;
• building entry point.

Do not add products based on assumptions.

Check the actual system.

Real Example: Same Manufacturer, Different Answer

This is perhaps the easiest way to understand why checking the exact model matters.

Consider two real Sungrow inverter families.

Sungrow SG3.0RS-L

The current official product page states:

Built-in Type II DC & AC SPD.

Now consider:

Sungrow SG30CX-P2 / SG50CX-P2

The official datasheet specifies:

DC Type I+II / AC Type II.

Both products are Sungrow inverters.

Both include surge protection.

But the published DC SPD configuration is not the same.

That alone shows why questions such as:

“Does a Sungrow inverter already have an SPD?”

are too broad.

The correct question is:

“Which Sungrow model, and what does its datasheet specify?”

The same principle applies to other manufacturers.

What Information Should You Send an SPD Supplier?

If you are a purchaser, distributor or project buyer, you do not need to design the complete lightning protection system yourself.

But sending the correct information can dramatically improve the quality of the recommendation you receive.

Instead of sending:

“Need 1000V 40kA SPD. Please quote.”

send:

PV system information

• 최대 태양광 시스템 전압
• Maximum string Voc if available
• Inverter brand and model
• Built-in SPD specification
• Approximate PV-to-inverter cable distance
• Combiner box information
• External lightning protection: yes/no
• Required SPD installation position
• 수량
• Applicable standard or project requirement

Why is this better?

Because:

1000V + 40kA

does not tell the supplier whether the SPD is intended:

• near the inverter;
• in a combiner box;
• near the array;
• in a system with external lightning protection;
• or as part of a Type 1+2 protection concept.

A specification is useful only when it is connected to an application.

자주 묻는 질문

1. My inverter already has a DC Type 2 SPD. Do I always need another external SPD?

아니요.

The correct decision depends on the complete installation.

Cable distance, SPD location, combiner-box configuration, external lightning protection, separation distance and manufacturer requirements should all be considered.

Do not automatically add another SPD, but do not automatically remove external protection simply because the inverter includes one.

2. If the inverter and PV array are more than 10 m apart, do I always need exactly two SPDs?

Do not treat the number as an isolated universal rule.

However, 10 m is an important design threshold in published PV surge-protection guidance.

Phoenix Contact identifies additional DC-side protection locations where the distance between the inverter and PV panels is 10 m or more, while DEHN likewise identifies additional protection on longer cable routes in its rooftop PV guidance.

Use the distance as a reason to evaluate the system—not as a substitute for engineering judgment or applicable requirements.

3. Does an AC Type 2 SPD inside the inverter protect the DC side?

아니요.

AC and PV DC are separate electrical paths.

Check the datasheet specifically for DC SPD, PV SPD, or the manufacturer’s equivalent terminology.

4. Is Type 1+2 always better than Type 2?

Not simply because it sounds like a higher number.

Type 1+2 and Type 2 are intended for different surge and lightning-protection conditions.

For example, Phoenix Contact’s PV guidance differentiates SPD type according to whether external lightning protection is present and whether separation distance is maintained.

Select the appropriate type for the installation rather than choosing by label alone.

5. If my combiner box already has an SPD, do I still need the inverter’s built-in SPD?

Possibly.

The two devices may be protecting different points along a longer cable route.

This is exactly why you should evaluate the distance and location relationship rather than asking which one of the two devices is unnecessary.

6. Can a built-in inverter SPD fail?

예.

SPDs are protective components and can reach end of life after electrical stress.

Fronius, for example, documents a mechanical status indication that changes from green to red when its SPD is triggered and states that the SPD should then be replaced to maintain protection.

Always follow the inverter manufacturer’s inspection and replacement instructions.

7. What if the inverter datasheet only says “surge protection”?

Look deeper into the technical documentation.

Try to confirm:

• DC or AC side;
• SPD type;
• relevant voltage rating;
• discharge characteristics;
• replaceability;
• and whether the function is standard or optional.

Do not assume that every use of the phrase “surge protection” describes the same device.

The Most Important Lesson: Stop Looking Only at the Inverter

It is natural to focus on the inverter.

It is one of the most valuable and technically complex components in a PV system.

But a solar installation is larger than the inverter.

Think about the complete path:

태양광 모듈

↓

DC string cables

↓

combiner or protection equipment

↓

long DC cable route

↓

inverter DC input

↓

inverter

↓

AC output

↓

distribution system

and possibly:

Ethernet / RS-485 / monitoring / control lines

A solar inverter built-in SPD sits at one protection point within this larger system. It should therefore be evaluated together with the PV cables, combiner equipment, AC side and other relevant protection locations.

That is why the best question is not:

“How many SPDs do I have?”

올바른 질문은 다음과 같습니다.

“Where can transient overvoltage enter this system, and where should it be limited before it reaches sensitive equipment?”

Once you start thinking this way, the confusing question of “internal SPD versus external SPD” becomes much easier.

They are not necessarily competitors.

They may be parts of the same coordinated protection concept.

Final Takeaway

Seeing:

“DC SPD Type II Built-In”

on an inverter datasheet is useful information.

But it is not the end of your surge-protection assessment.

Before deciding whether an external SPD is necessary, check four things first:

1. What SPD is actually built into the inverter?

DC, AC, Type 1, Type 2 or Type 1+2?

2. Where is it?

A built-in SPD provides a protection point at the inverter. Consider what exists between that point and the PV array.

3. How long is the cable route?

Cable distance can change whether another protection location needs to be evaluated.

4. Is external lightning protection involved?

If yes, the lightning protection concept and separation distance become important.

If you can answer these four questions, you are already making a much better decision than someone who simply reads:

“Built-in SPD”

and stops there.

And if terms such as Ucpv, In, Imax, Up and Iscpv still look confusing, learn how to read the SPD label before comparing different devices.

Related Guide: How to Read a DC SPD Label: Class II, Ucpv, In, Imax, Up & Iscpv Explained

Need Help Checking a PV SPD Application?

KUANGYA manufactures surge protective devices for photovoltaic DC applications.

If you are unsure which SPD configuration fits your project, you can provide:

• PV system voltage;
• inverter brand and model;
• existing built-in SPD information;
• cable distance;
• intended installation position;
• required SPD type, if specified;
• and project quantity.

This allows the application to be checked before selecting a specification based only on voltage and kA values.