As solar energy projects continue to expand in size and complexity, the long-term reliability of PV systems has become a critical concern. While solar modules and inverters often receive the most attention, in practice, it is frequently the cables, connectors, and insulation structures that cause system malfunctions.
This article explores three of the most frequent failure modes—ground faults, short circuits, and insulation degradation—through real-world examples, highlighting root causes and practical measures for prevention.
1. Ground Faults: Hidden Risks That Escalate Over Time
Case Example
At a coastal solar power plant, frequent “DC ground fault” alarms began to occur just two years after commissioning. Upon inspection, engineers discovered cracks on several PV cables. Years of UV radiation and salt mist corrosion had degraded the outer sheath. Rainwater entered the damaged areas, creating leakage paths to ground.
Root Causes
Poor resistance of cable sheath to UV and salt spray.
Sheath abrasion at fastening points, weakening insulation.
Moisture accumulation in humid environments forming conductive paths.
Prevention
Use PV cables tested for UV, ozone, and salt spray resistance.
Improve cable fastening methods to avoid mechanical wear.
Increase inspection frequency for coastal and humid installations.
2. Short Circuits: Fast, Destructive Failures
Case Example
In a large PV project in the Middle East, a severe DC short circuit occurred during peak summer. The failure caused arcing inside a combiner box. Investigators found that installers had bent PV cables too sharply, exceeding the minimum bending radius. Combined with high desert temperatures, the insulation cracked, eventually leading to a direct short.
Root Causes
Excessive pulling or sharp bending during installation.
Insufficient thermal rating of the cable for extreme climates.
Poorly crimped or unsealed connectors allowing water ingress.
Prevention
Follow installation guidelines and maintain recommended bending radius.
Use PV cables rated for -40°C to +90°C with long-term flexibility.
Ensure connectors are IP67-rated or higher and properly crimped.
3. Insulation Degradation: The Silent Efficiency Loss
Case Example
At a high-altitude solar project, operators noticed abnormal power losses after three years of operation. Testing revealed low insulation resistance across several DC strings. Although the cables appeared intact on the outside, dissection showed that the inner insulation had turned brittle and powdered, leading to current leakage.
Root Causes
UV radiation combined with wide daily temperature swings accelerated aging.
Use of low-cost cables with poor cross-linking and unstable materials.
Long-term mechanical stress causing internal micro-cracks.
Prevention
Select PV cables with XLPO insulation for enhanced resistance to aging.
Purchase from manufacturers with TÜV, UL, or EN-certified products.
Perform regular insulation resistance testing to detect early degradation.
Final Thoughts: Prevention is Always Better than Repair
Ground faults, short circuits, and insulation failures rarely happen overnight. Instead, they develop slowly through the combination of UV exposure, thermal stress, poor materials, or improper installation. Left unchecked, minor cracks or abrasions can evolve into major hazards—causing arcing, fires, or costly downtime.
To ensure long-term safety and efficiency, PV system operators should prioritize:
High-quality cable selection with proven UV and weather resistance.
Strict adherence to installation standards to reduce mechanical stress.
Routine inspection and maintenance to identify early signs of degradation.
In the long run, choosing certified, durable PV cables designed for harsh environments is not just a safety precaution—it’s the most cost-effective investment for solar projects.
