The utility-scale solar industry is booming, but with its rapid growth come challenges that can significantly impact the success and longevity of solar projects. According to the recently released SolarGrade PV Health Report, wiring and connectors remain the leading causes of solar project failures, with 72% of inspections identifying safety and reliability issues requiring urgent remediation. Understanding and addressing these issues is crucial for ensuring the efficiency and durability of solar installations. Here’s a guide on the common pitfalls related to wiring and connectors and how to avoid them.
1. String Wires: Compatibility and Sizing Challenges
One of the most common issues with utility-scale solar installations involves the compatibility of MC4 connectors, which are the industry-standard connectors used to interconnect PV modules. However, despite being labeled as "MC4," not all connectors are created equal. Different vendors produce MC4 connectors that may not be fully compatible with each other, leading to potential issues in the system.
Solution: Whenever possible, source all MC4 connectors from the same vendor to ensure compatibility. If this isn't feasible, carefully verify compatibility before installation. Additionally, consider the sizing of string wires. In the global PV industry, the standard conductor size is 6 square millimeters double jacketed, but in North America, the closest equivalent is 10 AWG (approximately 5.26 square millimeters) and it has a single insulation layer. This discrepancy can lead to compatibility issues with connectors and insulation thickness. Opting for European industry-standard double-jacketed PV wires in the U.S. can mitigate these risks, although it may be a bit more expensive.
2. Proper Termination of DC String Wires
Another significant issue often arises with the termination of DC string wires inside the DC combiner. Industry practices often involve using fine-stranded PV string wire, which requires the use of a bootlace ferrule—a small cylindrical sleeve that helps achieve a secure connection within the terminal. However, many contractors skip this step to save time and labor costs, leading to improper contact and potential hotspots.
Solution:Always use bootlace ferrules when terminating fine-stranded PV string wires in DC combiner terminals. While it might add a small amount of time to each connection, the improved reliability and safety are well worth the effort. This practice is mandatory in Europe and should be adopted in North America to prevent future issues.
3. Cable Lugs Crimping: Ensuring Proper Connections
Cable lug crimping is another area where poor workmanship can lead to failures. Inadequate crimping often results from using low-quality tools that don't apply sufficient pressure, leading to loose connections that can cause overheating and hotspots.
Solution:Invest in high-quality crimping tools from trusted vendors and ensure that they are used correctly. Additionally, after commissioning a project, conduct infrared testing to identify any hotspots caused by improper crimping. This proactive step can catch issues before they lead to larger failures. Be vigilant when sourcing materials, as some vendors might provide slightly undersized conductors (e.g., 480 kcmil instead of 500 kcmil), which can cause improper crimping and loose connections.
4. Transformer Bushing Compatibility: Avoiding Mismatches
Transformer bushings, the medium-voltage terminals inside transformers, are another critical component that can lead to failures if not properly managed. Transformers ordered from overseas may be equipped with IEC global standard bushings, which differ slightly from the IEEE standard used in North America. Although the differences might seem minor, they can result in overheating and failures if not correctly addressed.
Solution:To avoid compatibility issues, order domestically produced transformers with IEEE standard bushings whenever possible. If using IEC-standard equipment, ensure that all components, including elbow connectors, are compatible with the IEC standard. This can prevent mismatches that could lead to project failures. Hiring a procurement manager with the appropriate technical expertise can help ensure that all components are compatible and that costly mistakes are avoided.
Solar projects require meticulous attention to details, especially when it comes to wiring and connectors, which are among the most common causes of failure. By adhering to best practices—such as ensuring compatibility of MC4 connectors, properly terminating DC string wires, using high-quality crimping tools, and verifying transformer bushing compatibility—you can significantly reduce the risk of project failures. Get in touch with a technical expert at Castillo Engineering for support with your utility-scale solar projects.