Solis Seminar 【Episode 69】: Detecting and Preventing DC Insulation Short Circuits in PV Systems

Download

As the adoption of solar power continues to grow worldwide, ensuring the safety and reliability of PV systems is more crucial than ever. One of the most common, yet overlooked, threats to PV performance is DC insulation short circuits. These faults can lead to power generation losses, expensive repairs, and even fire hazards. In this article, we’ll dive into the causes, risks, and solutions available to combat this issue. 

Understanding the Root Cause

1. Poor Construction Practices: Damaged cables from rough handling, improper junction box installation, or sharp debris in cable trenches can compromise insulation.  

2. Environmental Factors: Rain, humidity, and dust accumulation accelerate insulation degradation, particularly in regions with harsh weather conditions.

3. Aging and Wear: Long-term exposure to harsh conditions causes cable degradation, loose connectors, or internal cell soldering failures.  

4. Animal Interference: Rodents gnawing cables or birds nesting near equipment may directly trigger short circuits.  

The Risks: Why These Faults Matter

1. System Downtime: Short circuits activate inverter protection mechanisms, forcing shutdowns or derating, directly impacting energy production and revenue.  

2. Fire Hazards: Percistent arcing at fault points generates extreme heat, potentially leading to fires.  

3. Equipment Damage: Over-currents may destroy inverters, combiner boxes, and other critical components, raising repair costs or replacements 

4. Safety Threats: Excessive leakage currents pose electrocution risks to maintenance personnel.  

Detection and Diagnosis  

 1. Manual Inspection:  

A) Sectional Testing: Isolate PV strings and measure insulation resistance segment-by-segment to locate faults.  

B) Thermal Imaging: Identify hotspots caused by short circuits using infrared cameras.  

Disadvantages:

● Requires system shutdown, leading to power loss

● Time-consuming and labour-intensive

● Requires specialized personnel and equipment

2. Specialized Tools: 

Deploy DC insulation monitors for real-time system insulation status tracking and fault alerts.  

Disadvantages:

● Requires specialized equipment at additional cost

● May involve additional installation and wiring modifications

● Large equipment clusters to maintain

3. Inverter Insulation Monitoring: 

Many modern inverters feature built-in DC insulation resistance detection. However, traditional systems can only conduct automatic detection before the inverter starts up. Solis, on the other hand, introduces online PV insulation detection, a revolutionary approach that continuously monitors PV-to-ground impedance in real time, ensuring high accuracy and reliability.

üNo Additional Cost: Uses existing inverter capabilities without requiring extra hardware.

üNo Wiring Modifications: Simplifies installation and reduces setup complexity.

üReal-Time, Continuous Monitoring: Ensures immediate detection and prevention of faults.

üPreemptive Protection: Disconnects faults before they escalate into major system failures.

Enhanced System Longevity: Increases lifecycle stability by over 20%.

Enhanced System Longevity: NOTE: At present, only S6-GC3P(150-200)K07-ND and S6-GU350K-EHV have online PV insulation detection function, other models will be added later.

Best Practices for Installation and Ongoing Maintenance

Regular Cleaning & Inspection: Ensure panels and cable joints are clean and free from moisture or debris.

Grounding Verification: Check that all system components, including inverters, PV panels, and distribution boxes, are properly grounded.

Seasonal Insulation Testing: Conduct insulation tests before rainy seasons to mitigate the risk of moisture-induced faults.

Cable Protection: Use conduits and high-quality waterproof connectors to safeguard against mechanical and environmental damage.

Strict Quality Control: Select high-grade components to minimize the risk of insulation failure over time.

Conclusion 

DC insulation short circuits remain a significant challenge for PV system operators, but innovative solutions like Solis’ online PV insulation detection are transforming how the industry manages and mitigates these risks. By adopting real-time monitoring and proactive maintenance strategies, solar power plant owners can enhance safety, minimize downtime, and maximize return on investment.

As the PV industry continues to evolve, staying ahead of potential failures with cutting-edge technology will be key to ensuring long-term sustainability and efficiency.