2026 Common DC SPD Failure Causes in PV Systems & How to Avoid Them (with KUANGYA Protection Tips)

The global photovoltaic (PV) industry is booming, with installed capacity growing at a double-digit rate year over year. As PV systems become more widespread—from residential rooftops to utility-scale solar farms—ensuring the safety and reliability of every component is critical.

Among these components, the DC Surge Protection Device (DC SPD) plays an irreplaceable role. It diverts transient overvoltages caused by lightning, grid switching, or inductive loads, protecting sensitive PV equipment such as inverters, combiner boxes, and solar panels from irreversible damage.

However, DC SPD failure is a common issue that plagues many PV projects. It leads to equipment burnout, system downtime, reduced power generation, and even fire hazards.

In fact, industry statistics show that DC SPD failures account for nearly 30% of all PV system electrical faults, resulting in millions of dollars in losses annually. This blog will systematically analyze the most common causes of DC SPD failure in PV systems, provide practical solutions to avoid these pitfalls, and introduce KUANGYA’s high-reliability DC SPD solutions—engineered specifically to address the unique challenges of PV environments and minimize failure risks.

1. Understanding DC SPD: Its Role in PV System Safety

Before diving into failure causes, it’s essential to clarify the core function of DC SPD in PV systems. Unlike AC SPDs, which are designed for alternating current circuits, DC SPDs are tailored to the high-voltage, low-frequency characteristics of PV DC-side circuits.

Solar panels generate continuous direct current, and long cable runs increase the risk of surge-induced damage. A high-quality DC SPD acts as a “safety valve”: when a transient overvoltage (such as a lightning strike or grid switching surge) occurs, it quickly conducts the excess current to the ground.

This limits the voltage across PV equipment to a safe level. Without a reliable DC SPD, even a small surge can destroy expensive inverters, damage PV modules, or trigger electrical fires.

Notably, DC SPDs in PV systems must comply with strict international standards to ensure effectiveness. The latest IEC 61643-41:2025 standard is specifically developed for DC low-voltage power system surge protection.

It sets rigorous requirements for DC SPD performance, including surge current handling, voltage protection level, and thermal stability—critical factors that directly impact failure rates.

KUANGYA’s DC SPD series fully complies with IEC 61643-41:2025 and IEC 61643-31 (the dedicated standard for PV system SPDs), ensuring compatibility and reliability in all PV scenarios.

Offical Standard Link: IEC 61643-41:2025 Official Standard

2. Common DC SPD Failure Causes in PV Systems (With Real-World Examples)

DC SPD failure in PV systems is rarely random; it is almost always caused by a combination of improper selection, installation, maintenance, or environmental factors. Below are the 6 most common causes, supported by real-world project cases and technical analysis.

2.1 Incorrect SPD Type and Parameter Selection (The main Cause)

The most frequent and costly mistake in PV projects is using the wrong type of SPD or selecting one with mismatched parameters. Many installers mistakenly use AC SPDs in DC circuits, or choose DC SPDs with voltage ratings, surge current capacity, or protection levels that do not match the PV system’s requirements.

AC SPDs are designed to handle alternating current, which has natural zero-crossing points that help extinguish arcs—something DC circuits lack. Using an AC SPD in a PV DC circuit will cause it to fail rapidly.

It cannot handle the continuous DC voltage or the arc generated by surge currents.

Another common parameter mismatch is the maximum continuous operating voltage (Uₙ) of the DC SPD. PV systems operate at high open-circuit voltages (Voc), which can reach 1500V DC for utility-scale projects.

If the DC SPD’s Uₙ is lower than the system’s maximum Voc, it will experience continuous overvoltage stress. This leads to premature aging of internal components (such as metal oxide varistors, MOVs) and eventual failure.

Similarly, if the SPD’s surge current capacity (Iₙ) is insufficient to handle the expected surge energy (e.g., from lightning strikes in high-risk areas), it will be destroyed during a surge event.

Real-World Example: A 10MW utility-scale PV project in Southeast Asia installed AC SPDs on the DC side of combiner boxes to cut costs. Within 3 months, 12 out of 50 combiner boxes experienced SPD failures, leading to inverter damage and 2 weeks of system downtime. The root cause was the use of AC SPDs, which could not handle the 1500V DC voltage and failed to extinguish arcs during minor surges.

2.2 Poor Installation and Wiring Errors

Even the highest-quality DC SPD will fail if installed incorrectly. Common installation mistakes include improper wiring, poor grounding, and incorrect placement.

All of these undermine the SPD’s ability to divert surge currents effectively.

First, wiring errors: DC SPDs require correct polarity (positive and negative connections) to function properly. Reversing the polarity will cause the SPD to malfunction.

It may either fail to trigger during a surge or conduct continuously, leading to overheating and burnout. Additionally, using undersized or low-quality cables for SPD wiring increases resistance.

This limits the surge current diversion and causes the SPD to overheat.

Second, poor grounding: DC SPDs rely on a low-impedance ground connection to divert surge currents to the earth. If the ground resistance is too high (exceeding 4Ω, as recommended by IEC standards), surge energy cannot be dissipated quickly.

This leads to voltage buildup and SPD failure. In many PV projects, installers cut corners by using inadequate grounding conductors or failing to connect the SPD to the system’s main ground network.

Third, incorrect placement: DC SPDs should be installed as close as possible to the equipment they protect (e.g., within 1 meter of combiner boxes or inverter DC inputs). Long cable runs between the SPD and protected equipment increase inductive voltage.

This allows surge energy to bypass the SPD and damage the equipment—rendering the SPD useless. A cascaded installation (Type 1 + Type 2 SPDs) is often required for large PV systems.

But many projects skip this step, leaving critical equipment unprotected.

Authority Link: GRL: Why PV Systems Fail With SPDs Installed

2.3 Environmental Factors: Harsh Conditions Degrade SPD Performance

PV systems are typically installed outdoors, exposing DC SPDs to extreme temperatures, humidity, UV radiation, dust, and corrosion. All of these factors accelerate component aging and failure.

Most low-quality DC SPDs are not designed to withstand these harsh conditions, leading to premature failure.

Extreme temperatures are a major culprit: high temperatures (above 60°C) reduce the lifespan of MOVs, the core component of DC SPDs. Low temperatures (below -25°C) increase the SPD’s response time, making it unable to trigger quickly during a surge.

Humidity and moisture can seep into the SPD’s housing, causing internal short circuits and corrosion of metal components. UV radiation degrades the SPD’s plastic housing, leading to cracks and water ingress.

In coastal areas, salt spray corrosion further damages the SPD’s terminals and internal circuits.

Real-World Example: A residential PV project in a coastal region used unprotected DC SPDs without corrosion-resistant housing. After 1 year of exposure to salt spray, 80% of the SPDs failed due to terminal corrosion, leading to intermittent system shutdowns and reduced power generation.

2.4 Lack of Regular Maintenance and Inspection

DC SPDs are not “set-it-and-forget-it” components. Over time, their internal components (MOVs, gas discharge tubes) degrade due to repeated surge events and environmental stress.

Without regular maintenance and inspection, degraded SPDs will fail to provide protection when needed most. However, many PV project owners and operators overlook this critical step, leading to unexpected failures.

Common maintenance oversights include: failing to check the SPD’s status indicator (green = normal, red = failed), not testing the SPD’s leakage current and voltage protection level, and ignoring signs of physical damage (e.g., bulging, scorching, or cracks).

Additionally, dust and debris buildup on the SPD’s terminals can cause poor contact and overheating, further accelerating failure.

2.5 Incompatibility with Other PV Components

DC SPDs must work in harmony with other PV components, such as fuses, circuit breakers, and inverters. Incompatibility between these components can lead to SPD failure or ineffective protection.

For example, if the DC SPD is not coordinated with the system’s fuses, the fuse may blow before the SPD can divert the surge current—leaving the equipment unprotected.

Alternatively, if the SPD’s response time is slower than the inverter’s surge tolerance, the inverter may be damaged before the SPD triggers.

2.6 Low-Quality SPDs: Cutting Costs Leads to Higher Risks

To reduce project costs, some installers choose low-quality, uncertified DC SPDs. These SPDs use inferior components (e.g., low-grade MOVs, thin copper conductors) and do not undergo rigorous testing to meet international standards.

As a result, they have shorter lifespans, higher failure rates, and cannot provide reliable protection during surge events. In the long run, the cost of replacing failed SPDs, repairing damaged equipment, and lost power generation far exceeds the initial savings from using low-quality products.

3. Key Comparison: DC SPD Failure Risks vs. Prevention Measures

The following table summarizes the common DC SPD failure causes, their risks, and practical prevention measures—including tips for selecting and using KUANGYA DC SPDs to minimize failure.

4. KUANGYA DC SPD: Designed for Reliability in PV Systems

As a leading manufacturer of electrical protection solutions for renewable energy, KUANGYA has engineered a dedicated series of DC SPDs. These SPDs are designed to address the unique challenges of PV systems—minimizing failure risks and ensuring long-term reliability.

Our DC SPDs are built based on years of industry experience, strict compliance with international standards, and a deep understanding of PV system requirements.

4.1 Core Features of KUANGYA DC SPD (Reducing Failure Risks)

KUANGYA DC SPDs are built to avoid the common failure causes outlined above, with the following key features:

1. Full Compliance with International Standards: Fully compliant with IEC 61643-41:2025 and IEC 61643-31, ensuring compatibility with global PV grid codes. Each unit undergoes rigorous testing for surge current handling, voltage protection, and thermal stability—guaranteeing reliable performance.
2. Optimized Parameter Matching: Available in Uₙ ratings from 600V DC to 1500V DC, Iₙ from 10kA to 40kA, and voltage protection levels (Uₚ) as low as 5.2kV. This allows precise matching to any PV system size, from residential (1000V DC) to utility-scale (1500V DC).
3. Harsh Environment Resistance: Designed to operate in extreme temperatures (-25°C to +70°C), with IP20 ingress protection, UV-resistant plastic housing, and corrosion-resistant copper terminals. This ensures durability in outdoor, coastal, and desert PV environments.
4. Fast Response and Arc Extinction: Equipped with advanced MOV technology and gas discharge tubes (GDTs) for ultra-fast response times (≤25ns), ensuring surge currents are diverted before they damage PV equipment. The DC-specific arc extinction design solves the problem of arc persistence in DC circuits, preventing SPD burnout.
5. Easy Installation and Maintenance: Standard DIN-rail mounting, clear polarity labels, and visible status indicators (green = normal, red = failed) simplify installation and maintenance. The compact design fits easily into combiner boxes and inverter enclosures, reducing installation time and labor costs.
6. Smart Monitoring Compatibility: Optional remote alarm contacts allow integration with PV system monitoring platforms, enabling real-time status updates and fault alerts. This allows operators to proactively replace degraded SPDs before they fail.

4.2 KUANGYA DC SPD Application Scenarios in PV Systems

KUANGYA DC SPDs are suitable for all PV system DC-side applications, including:

• PV string DC input protection (combiner boxes)
• Inverter DC input protection
• Battery energy storage (ESS) DC circuit protection (for PV+storage systems)
• Utility-scale PV farm DC distribution protection
• Residential and commercial rooftop PV system protection

(Product Image Placeholder: High-resolution image of KUANGYA DC SPD, showcasing its compact design, status indicators, terminal connections, and certification logos (IEC, CE, TÜV). Include a close-up of the polarity labels and DIN-rail mounting design.)

4.3 Real-World Success: KUANGYA DC SPD in PV Projects

A 50MW utility-scale PV project in Northern China faced frequent DC SPD failures. The issues stemmed from harsh winter temperatures (-30°C) and summer heat (+60°C).

After replacing low-quality SPDs with KUANGYA DC SPDs (1500V DC, 40kA Iₙ), the failure rate dropped from 28% to less than 2% over 2 years.

The project also reported a 15% reduction in maintenance costs and no equipment damage from surge events—proving the reliability of KUANGYA’s solution.

5. FAQ: Common Questions About DC SPD Failure in PV Systems

Below are the most frequently asked questions about DC SPD failure. They include practical answers and KUANGYA-specific tips to help PV project owners and operators avoid pitfalls.

Q1: How can I quickly identify a failed DC SPD in my PV system?

A1: The easiest way is to check the SPD’s status indicator: green means the SPD is working normally, while red indicates failure. For more precise verification, use a multimeter or SPD tester to measure leakage current and voltage protection level.

Normal leakage current for DC SPDs should be ≤1mA. If the leakage current exceeds 5mA or the voltage protection level deviates from the nominal value by ±10%, the SPD is degraded and should be replaced.

KUANGYA DC SPDs feature clear, easy-to-see status indicators and are compatible with smart testers for quick diagnosis.

Q2: Can I use an AC SPD instead of a DC SPD to save costs?

A2: No. AC SPDs are not designed for DC circuits and will fail quickly. DC circuits lack the zero-crossing points that AC SPDs rely on to extinguish arcs.

This leads to continuous conduction, overheating, and burnout. Using an AC SPD in a PV DC circuit also violates IEC standards and may void equipment warranties.

KUANGYA DC SPDs are competitively priced and offer long-term cost savings by reducing failure and maintenance costs.

Q3: What is the recommended maintenance schedule for DC SPDs in PV systems?

A3: We recommend the following maintenance schedule:

– Monthly: Check the status indicator and ensure terminals are tight and free of dust/corrosion.

– Quarterly: Test leakage current and voltage protection level using a dedicated SPD tester.

– Annually: Inspect the SPD’s housing for cracks, water ingress, or physical damage; check grounding continuity and resistance (should be ≤4Ω).

– Before thunderstorm season: Conduct a full inspection and replace any degraded SPDs. KUANGYA provides maintenance guides and technical support to help operators implement this schedule efficiently.

Q4: How do I choose the right KUANGYA DC SPD for my PV system?

A4: Follow these steps:

1. Determine your PV system’s maximum open-circuit voltage (Voc) and select a DC SPD with Uₙ ≥ 1.1 × Voc (e.g., 1500V DC system → Uₙ = 1650V DC).

2. Assess the surge risk (e.g., high thunderstorm areas need Iₙ ≥ 40kA; low-risk areas can use Iₙ = 10-20kA).

3. Match the SPD’s pole configuration (2P/4P) to your system’s DC circuit (2P for single-string, 4P for three-phase DC).

4. Choose optional features (e.g., remote alarm) based on your monitoring needs. KUANGYA’s technical team can provide personalized selection recommendations based on your project details.

Q5: Can KUANGYA DC SPDs be retrofitted into existing PV systems?

A5: Yes. KUANGYA DC SPDs feature standard DIN-rail mounting and compact design, making them easy to retrofit into existing combiner boxes and inverter enclosures.

Retrofitting with KUANGYA DC SPDs improves system safety, ensures compliance with IEC standards, and reduces failure risks.

We provide retrofitting guidance and technical support to minimize downtime during installation.

6. Conclusion: Avoid DC SPD Failure, Protect Your PV Investment

DC SPD failure is a preventable issue that costs PV project owners millions of dollars annually. The losses come from equipment damage, downtime, and lost power generation.

The key to avoiding these failures lies in three core steps: selecting the right DC SPD (DC-specific, parameter-matched, certified), installing it correctly (proper wiring, grounding, placement), and implementing regular maintenance.

By avoiding the common pitfalls outlined in this blog, you can ensure your PV system’s DC SPDs provide reliable protection for years to come.

KUANGYA’s DC SPD series is engineered to address the unique challenges of PV systems. It features strict compliance to international standards, harsh environment resistance, and optimized performance.

Our products are designed to minimize failure risks, reduce maintenance costs, and protect your PV investment.

Whether you’re building a new PV project or retrofitting an existing one, KUANGYA DC SPDs are the reliable choice for safe, efficient, and long-lasting surge protection.

Don’t let DC SPD failure derail your PV project. Choose KUANGYA—your trusted partner for PV electrical protection.

If you want to know more product information, please click the link below：

• https://cnkuangya.com/
• https://cnkuangya.com/dc-spd/