A PV 절연 저항 결함 태양광 운영 및 유지보수에서 가장 까다로운 문제 중 하나입니다.

인버터가 아침에 가동을 거부할 수 있습니다. 건조한 상태가 몇 시간 지속되면 경고가 사라졌다가 비가 오면 다시 나타날 수 있습니다. 개방 전압을 측정할 때는 특정 스트링이 정상으로 보일 수 있지만, 전체 PV 어레이는 여전히 낮은 절연 저항 상태를 보고할 수 있습니다.

이러한 결함은 문제가 항상 직접적인 단락(short circuit)으로 나타나지 않기 때문에 진단이 어렵습니다.

태양광 어레이는 정상적인 전압을 계속 생성하는 것처럼 보일 수 있지만, 습기, 손상된 절연체, 오염된 커넥터, 열화된 모듈 부품 또는 결함이 있는 DC 장치로 인해 활성 DC 회로와 접지 사이에 원치 않는 전도성 경로가 형성될 수 있습니다.

그 결과는 다음과 같을 수 있습니다:

• 인버터 절연 알람
• 반복적인 셧다운
• 간헐적인 발전 손실
• 어려운 고장 위치 파악
• 감전 위험 증가
• 점진적인 절연 열화
• 더 심각한 직류(DC) 고장으로 발전 가능성

이 가이드는 태양광(PV) 절연 고장이 발생하는 원인, 간헐적으로 나타나는 이유, 그리고 기술자가 부품을 무작위로 교체하는 대신 체계적인 진단 절차를 활용하는 방법을 설명합니다.

PV 어레이 설계 시 DC 배선, 전기 보호, 접지, 절연 모니터링 및 지락 감지 요구 사항을 고려해야 합니다. 이러한 안전 원칙은 다음 규격에서 다룹니다. 태양광 어레이 설계를 위한 IEC 62548-1. 현재 IEC 62548-1 체계는 PV 어레이 DC 배선, 전기 보호, 스위칭 및 접지 규정을 다루고 있으며, IEC 62446-1은 문서화, 시운전 테스트 및 검사를, IEC 62446-2는 계통 연계형 PV 시스템의 유지보수 및 문제 해결을 다룹니다.

요약: PV 절연 저항 결함의 원인은 무엇인가?

가장 일반적인 원인은 다음과 같습니다:

1. PV 커넥터나 접속함(Junction box) 내부로 물이 유입되는 경우
2. 손상된 직류(DC) 케이블 절연체
3. 모듈 절연체 또는 백시트의 열화
4. 잘못 조립되었거나 호환되지 않는 커넥터 사용
5. 손상되거나 성능이 저하된 DC 서지 보호 장치(SPD)
6. DC 차단기 내부의 오염 또는 내부 손상
7. 케이블의 기계적, 자외선(UV), 동물에 의한 손상 또는 설치 불량
8. 대규모 태양광(PV) 어레이 전반에 걸친 누설 경로 누적

가장 중요한 문제 해결 원칙은 다음과 같습니다:

DC 어레이를 체계적으로 분리하여 테스트하기 전까지는 태양광 절연 결함을 인버터 문제로 간주하지 마십시오.

인버터는 단순히 태양광 필드 상류 어딘가에 위치한 문제를 감지하고 있을 수 있습니다.

1. 태양광(PV) 절연 저항 결함이란 무엇인가?

정상적인 태양광 어레이에서는 양극 및 음극 DC 도체가 시스템 설계에 따라 접근 가능한 도전부 및 접지로부터 적절하게 절연된 상태를 유지해야 합니다.

절연 문제는 통전 중인 DC 회로와 다른 전도성 경로 또는 접지 기준점 사이에 의도치 않은 전도성 경로가 형성될 때 발생합니다.

해당 경로는 다음과 같은 원인으로 생성될 수 있습니다:

• 물
• 먼지 및 오염물
• 손상된 케이블 절연
• 부품 균열
• 탄화된 물질
• 내부 장치 열화
• 모듈 절연체 노후화

결함이 반드시 완전한 금속성 단락으로 시작되는 것은 아닙니다.

비교적 약한 누설 경로로 시작될 수 있습니다.

이것이 PV 시스템이 때때로 다음과 같은 현상을 보이는 이유입니다:

• 건조한 날씨에는 정상적으로 작동함
• 비가 온 후에는 고장이 발생함
• 햇빛이 모듈을 가열한 후에는 복구됨
• 이른 아침 습도가 높을 때만 차단됨
• 문제 해결 과정에서 일관되지 않은 측정값이 나타남

이러한 간헐적인 동작은 절연 결함으로 인해 많은 유지보수 시간이 소요되는 이유 중 하나입니다.

태양광 인버터는 왜 이 문제를 감지합니까?

최신 전력 변환 장비는 작동 전이나 작동 중에 태양광(PV) DC 회로와 접지 사이의 전기적 관계를 모니터링할 수 있습니다.

감지된 절연 상태가 인버터 제조사가 허용하는 범위를 벗어날 경우, 인버터는 다음과 같은 동작을 수행할 수 있습니다:

• 시작 지연
• 절연 결함 표시
• 낮은 절연 저항 보고
• PV 입력 차단
• 전력 변환 중단

정확한 알람 명칭은 제조사마다 다릅니다.

현장에서 흔히 접하는 설명의 예는 다음과 같습니다:

• 절연 결함
• 절연 불량
• 낮은 절연 저항
• PV 절연 낮음
• 접지 절연 결함
• Riso 낮음

중요한 점은 해당 알람이 다음을 식별한다는 것입니다 상태, 반드시 고장 난 부품을 의미하는 것은 아님.

따라서 어레이를 테스트하지 않고 인버터를 교체하는 것은 문제 해결에 실패할 수 있음.

태양광 설치 표준은 어레이 설계, 태양광 장비 설치, 그리고 테스트 및 유지보수 활동을 구분함. 따라서 올바른 진단을 위해서는 전력 변환 장비뿐만 아니라 전체 DC 시스템을 검토해야 함.

그러므로 절연 경보는 인버터만의 개별적인 문제로 취급하기보다 더 넓은 DC 보호 아키텍처의 일부로서 조사되어야 함. 인버터 주변의 서지, 과전류, 아크 결함, 접지 및 절연 위험에 대한 더 광범위한 검토는 당사의 가이드를 참조할 것. 태양광 인버터 보호.

3. 원인 1: PV 커넥터 내부의 물 유입

절연 경보가 날씨와 밀접한 관련이 있을 때 기술자가 가장 먼저 조사해야 할 조건 중 하나가 물 유입임.

커넥터가 기계적으로는 연결된 것처럼 보일 수 있으나, 여전히 전도성 표면에 습기가 유입될 수 있습니다.

가능한 원인은 다음과 같습니다:

• 잘못된 조립
• 손상된 실링 부품
• 부적절한 케이블 준비
• 불완전한 커넥터 체결
• 기계적 스트레스
• 노화
• 균열이 발생한 커넥터 하우징

해당 결함은 재현하기 어려울 수 있습니다.

건조한 날씨에는 누설 경로가 약해져 인버터가 가동될 수 있습니다.

비가 오거나 결로가 발생한 후에는 전도성이 증가하여 알람이 다시 발생합니다.

일반적인 패턴

시스템:

• 며칠 동안 정상적으로 작동함
• 폭우를 겪음
• 다음 날 아침 절연 결함이 보고됨
• 건조한 햇빛이 비친 후 몇 시간 뒤에 복구됨

이 패턴은 습기에 민감한 부품으로 즉시 주의를 돌려야 합니다.

그러나 기술자는 처음 발견한 젖은 커넥터가 유일한 문제라고 단정해서는 안 됩니다.

대규모 어레이에는 여러 개의 열화 지점이 포함되어 있을 수 있습니다.

4. 원인 2: DC 케이블 절연 손상

PV 케이블은 장기간 환경적 및 기계적 스트레스에 노출됩니다.

가능한 손상 메커니즘은 다음과 같습니다:

• 날카로운 금속 모서리
• 부적절한 케이블 지지대
• 압착
• 과도한 굽힘
• Abrasion
• Construction damage
• Cable ties applied too tightly
• Contact with hot surfaces
• Animal damage

A cable does not need to be completely severed to create an insulation problem.

A small damaged area may expose insulation to:

• 수분
• Conductive dust
• Metal mounting structures
• Grounded equipment

The resulting leakage path can be intermittent.

Common Inspection Mistake

Technicians often inspect only visible cable sections.

But cable damage frequently occurs at:

• Module frame edges
• Cable tray entry points
• Conduit transitions
• Roof penetrations
• Clamps
• Areas hidden beneath modules

A good inspection therefore follows the actual cable route rather than only the easy-to-see portions.

5. Cause Three: PV Module Insulation Degradation

Not every insulation fault originates in the field wiring.

The PV module itself can become part of the leakage path.

Potential areas include:

• Junction boxes
• Internal insulation systems
• Backsheets
• Cable exits
• Damaged module edges

Environmental exposure can gradually affect electrical insulation.

The diagnostic challenge is that module output voltage may still appear normal.

A technician may measure acceptable open-circuit voltage and conclude that the module is healthy.

However:

Normal voltage does not prove that insulation to earth is healthy.

These are different electrical conditions.

Module safety requirements are intended to address risks including breakdown of internal or external components that could contribute to electric shock or fire hazards.

6. Cause Four: Incorrect or Poorly Assembled PV Connectors

Connector problems are frequently discussed only as overheating or arc-fault risks.

However, poor connector installation can also contribute to insulation problems.

Possible issues include:

• Incomplete mating
• Incorrect crimping
• Damaged seals
• Poor cable diameter compatibility
• Internal contamination
• Incorrect assembly technique

A connector problem may evolve over time.

The sequence can be:

Mechanical weakness → moisture entry → corrosion or contamination → reduced insulation performance

In another case:

Poor electrical contact → heating → material degradation → carbonized conductive path

This shows why insulation resistance, thermal problems and arc-fault risks should not always be treated as completely separate failure categories.

One defect can develop through several stages.

7. Cause Five: A Degraded DC SPD

A surge protective device is installed to manage transient overvoltage.

However, an SPD is also connected electrically between the protected conductors and the relevant protection path.

After repeated electrical stress or internal deterioration, a damaged device may become part of a leakage problem.

Therefore, when troubleshooting an unexplained insulation fault inside a:

• PV 컴바이너 박스
• DC distribution box
• Inverter input panel

the SPD should be included in the diagnostic process.

Important Warning

Do not simply remove an SPD permanently because the insulation alarm disappears.

That only identifies a possible fault source.

The correct action is to:

1. Confirm the device condition.
2. Check the installation.
3. Verify the correct replacement specification.
4. Restore the required surge protection.

A failed protection device should not be solved by leaving the system unprotected.

IEC 62548-1 includes the design of DC array wiring and electrical protection devices within PV arrays.

8. Cause Six: DC Isolator Contamination or Internal Damage

The DC isolator is another component that should not be ignored.

Inside a DC switching device, insulation performance can be affected by:

• 수분
• 먼지
• Contamination
• Internal tracking
• Heat damage
• Mechanical wear
• Previous arcing

An isolator may still appear to switch mechanically while its internal electrical condition has deteriorated.Moisture ingress, contaminated insulating surfaces, heat damage, and deteriorated internal contacts can also create broader reliability problems. Our detailed guide to DC Isolator Switch Failure explains how these defects develop and how they should be inspected.

Visible warning signs may include:

• 변색
• 화상 자국
• Unusual odor
• 금이 간 하우징
• 부식된 단자
• Signs of moisture

However, not every insulation defect is externally visible.

A systematic diagnostic process may require isolating sections of the circuit to determine whether the fault remains upstream or downstream of a particular device.

9. Cause Seven: Installation and Environmental Damage

Many PV insulation faults are created during installation but appear months or years later.Incorrect cable routing, poor terminal preparation, reversed polarity, unsuitable protection devices, and installation errors can also create hidden DC-side defects. See 10 Common DC Protection Wiring Mistakes for a broader review of installation practices that can reduce long-term system reliability.

Consider a cable that is:

• Slightly crushed beneath a module
• Pulled against a metal edge
• Improperly supported

On the installation day, the insulation may remain intact.

Later, repeated:

• Heating
• Cooling
• Wind movement
• 진동
• 습기 노출

can turn a minor installation defect into an electrical fault.

Environmental Conditions Matter

Projects in different environments may experience different dominant risks.

Desert and Dusty Sites

Possible concerns include:

• 먼지 축적
• 고온
• Abrasion
• Thermal cycling

Coastal Sites

Possible concerns include:

• Salt contamination
• 부식
• 수분

Rooftop Systems

Possible concerns include:

• Cable contact with roofing materials
• Sharp mounting edges
• High surface temperatures
• Difficult inspection access

The same alarm code can therefore have very different physical causes depending on the project environment.

10. Cause Eight: Distributed Leakage Across a Large PV Array

Sometimes technicians search for one dramatically failed component.

But a large array may have no single obvious fault.

Instead, many small leakage paths can combine.

A large installation contains:

• Thousands of modules
• Long DC cable runs
• Many connectors
• Multiple combiner boxes
• Numerous protection devices

Each individual component may contribute only a small leakage path.

Together, however, the total insulation condition seen by the monitoring system can become problematic.

This is especially important when troubleshooting:

• Large commercial arrays
• Utility-scale systems
• Systems with multiple parallel strings

The diagnostic method must therefore be capable of dividing the system into smaller sections.

Without sectional isolation, technicians may spend hours looking for one visibly damaged component that does not exist.

11. Why Insulation Faults Often Appear in the Morning

This is one of the most useful diagnostic clues.

A solar plant may report:

Low insulation resistance at 6:30 a.m.

Then:

Normal operation at 10:00 a.m.

왜 그럴까요?

One possible explanation is environmental moisture.

Overnight:

• Temperature drops
• Humidity rises
• Condensation may form
• Moisture-sensitive leakage paths become more conductive

After sunrise:

• Equipment warms
• Moisture evaporates
• Insulation resistance improves

The system appears to “repair itself.”

It has not.

The underlying defect may still exist.

This is why maintenance teams should record:

• Time of alarm
• Weather
• Rain history
• Humidity conditions
• 온도

Fault timing can provide important information before the first electrical test is performed.

12. PV Insulation Fault vs Ground Fault vs Short Circuit

These terms are often used incorrectly.

Insulation Resistance Fault

An unwanted conductive path reduces the electrical isolation between the live circuit and earth or other conductive parts.

It may be relatively weak or intermittent.

접지 오류

A live conductor develops an unintended connection toward ground or grounded conductive material.

The severity depends on the electrical system and fault path.

단락 회로

A low-impedance connection occurs between points that should remain at different electrical potentials.

This can produce much higher current.

아크 결함

Current crosses an unintended gap through an electrical arc.

An arc fault may be:

• 시리즈
• 병렬

A system can also experience more than one fault mechanism simultaneously.

예를 들어

Damaged insulation → leakage → carbonization → arc formation

Therefore, accurate diagnosis is more useful than simply assigning one general label such as “electrical fault.”

13. A Practical Diagnostic Workflow

Random component replacement is one of the least efficient ways to troubleshoot a large PV system.

A better method is progressive isolation.

Step 1: Record the Fault Conditions

Before resetting the system, record:

• Exact alarm
• Time
• Weather
• Recent maintenance
• Recent storms
• Whether the problem is intermittent

This information may later reveal a pattern.

Step 2: Follow Safe Isolation Procedures

PV arrays can remain energized when exposed to sufficient light.

Technicians should follow the required site procedures, equipment instructions and applicable electrical safety practices before disconnecting, testing or opening equipment.

IEC 62446-1 addresses commissioning tests and inspection, while IEC 62446-2 provides maintenance-related requirements and recommendations for grid-connected PV systems, including corrective maintenance and troubleshooting.

Step 3: Divide the System into Sections

The key question is:

Is the fault in the inverter, main DC circuit, combiner box, string wiring or module section?

Large systems should be progressively divided into smaller electrical sections.

The objective is to determine:

Fault remains → problem is still inside the connected section

또는

Fault disappears → investigate the isolated section

This is more efficient than testing every module immediately.

Step 4: Compare Strings

When multiple strings are available, compare the suspected string with healthy strings.

Useful comparisons may include:

• 전압
• Insulation behavior
• Physical condition
• Weather response
• 커넥터 상태

The objective is to identify the abnormal branch.

Step 5: Inspect High-Risk Locations

Prioritize locations such as:

• 커넥터
• Cable entry points
• 컴바이너 박스
• Module junction boxes
• DC 아이솔레이터(절연기)
• SPD
• Damaged cable routes

Visual inspection should support electrical testing rather than replace it.

Step 6: Narrow the Fault Further

Once a problematic string is identified, divide the string or circuit into smaller sections where the system design and safe procedures allow.

This transforms:

“The entire PV plant has an insulation fault.”

into:

“The problem is located within this specific section.”

That is the central principle of efficient fault localization.

Step 7: Repair the Cause, Not the Alarm

After identifying the fault source:

• Replace damaged components
• Correct cable routing
• Restore sealing
• Replace defective protection devices
• Repair damaged insulation

Then verify that the system has returned to an acceptable condition before normal operation.

14. Why Simply Restarting the Inverter Is Not a Repair

An intermittent fault creates a dangerous temptation.

The technician resets the inverter.

The system starts.

The service ticket is closed.

Then the alarm returns after the next rain.

Restarting may temporarily restore generation, but it does not answer:

• Why did the insulation condition change?
• Which component is deteriorating?
• Will the problem become worse?
• Could the same defect develop into another fault type?

Repeated resets can turn a diagnosable early-stage problem into a more expensive failure.

15. How to Prevent PV Insulation Resistance Problems

Use Correct Cable Routing

Avoid:

• Sharp edges
• Unsupported cable loops
• 압착
• Excessive mechanical stress

Protect Connectors from Mechanical Stress

Connectors should not carry unnecessary cable weight or remain in positions where water and contamination can accumulate.

Control Enclosure Ingress

Combiner boxes and other outdoor enclosures require:

• 올바른 케이블 글랜드
• Proper sealing
• Suitable installation
• Periodic inspection

Inspect After Major Weather Events

Heavy rain and extreme environmental conditions can reveal developing insulation weaknesses.

Include Insulation Testing in Maintenance

Do not wait until an inverter refuses to start.

Periodic inspection and testing can help identify deterioration before it becomes a prolonged production problem.

IEC 62446-2 specifically addresses preventive, corrective and performance-related maintenance of grid-connected PV systems, including maintenance for reliability, safety, fire prevention and troubleshooting.

16. A Better O&M Strategy: Diagnose by Pattern

Experienced troubleshooting teams do not look only at the alarm.

They look at the pattern.

This table is not a substitute for testing.

Its purpose is to help determine where investigation should begin.

17. Frequently Asked Questions

What does low insulation resistance mean in a solar system?

It generally means that the electrical isolation between the live PV DC circuit and earth or other conductive parts is lower than the equipment or system expects.

The cause must be identified through inspection and testing.

Why does my solar inverter show an insulation fault after rain?

Moisture may create or strengthen an unintended leakage path in:

• 커넥터
• Cables
• Junction boxes
• Enclosures
• Damaged components

The fact that the fault disappears after drying does not mean the system is permanently repaired.

Can a PV module cause an insulation resistance fault?

예.

Possible sources can include the module junction box, external leads or deterioration of the module insulation system.

Normal open-circuit voltage alone does not prove healthy insulation.

Can an SPD cause a PV isolation fault?

A damaged or degraded device connected to the DC protection circuit may need to be considered during diagnosis.

The device should be tested or replaced appropriately rather than permanently removed from the protection system.

Can a DC isolator cause low insulation resistance?

Potentially.

Moisture, contamination, heat damage or internal electrical degradation may affect the condition of the device.

Why does the fault disappear during the day?

Temperature and moisture conditions may change.

Morning condensation or humidity can strengthen a leakage path that becomes less conductive as equipment dries and warms.

Should I replace the inverter when it reports an insulation fault?

Not automatically.

The inverter may simply be detecting an upstream PV array problem.

The DC field should be systematically investigated before the inverter is assumed to be defective.

Is an insulation fault the same as an arc fault?

아니요.

They are different electrical fault mechanisms, although deterioration can sometimes allow one fault condition to develop into another.

결론

A PV 절연 저항 결함 should not be treated as a mysterious inverter error.

It is an electrical condition that requires structured fault localization.

가장 일반적인 원인은 다음과 같습니다:

• 물 유입
• Cable insulation damage
• Module deterioration
• Connector problems
• Damaged DC protection devices
• DC isolator defects
• Environmental damage
• Distributed leakage across large arrays

The most effective diagnostic strategy is not random replacement.

It is:

Record → Isolate → Divide → Compare → Inspect → Test → Repair → Verify

This method turns a plant-wide alarm into a manageable electrical problem.

As photovoltaic systems become larger and DC architectures become more complex, insulation integrity remains a fundamental part of safe and reliable PV operation. Current IEC frameworks separately address PV array design, electrical installation, testing, inspection and maintenance, reinforcing the need to treat insulation performance as a system-level engineering issue rather than simply an inverter alarm.