Page 18 - 2021 High-Reliability, Harsh Environment Connectivity eBook

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4. What can be done to prevent the degradation of the cable? If the selected cable doesn’t perform successfully in field or lab simulations, it doesn’t necessarily mean that the specification process must start anew. It’s possible that changes can be made to the cable composition and/or structure to improve its performance and extend its lifecycle. For example, your cable supplier could reference the test results to:
• Reduce the diameter of the conductors to make the cable more flexible
• Introduce more flexible plastics into the cable composition
• Optimize the cable structure to better protect the wires and prevent performance issues
Cable Considerations for Harsh-Environment Solar Energy Applications
1. What is the electrical rating, rated voltage, and rated current required for the application? Since most of the electronics that comprise solar energy systems are installed outdoors and, as such, exposed to the weather, the connectivity components designed into this equipment must be ruggedized for both high power handling capabilities and harsh outdoor environments.
Outdoor hazards can generally be addressed through materials selections, such as UV-resistant cable jackets, and protective accessories like conduit and heat-shrink boots and tubing.
To address high-power hazards, calculate the technical specifications by confirming the system’s voltage range, identifying string currents at different environments and whether it’s a DC or AC system, and addressing other pertinent operating conditions. Once confirmed, you’ll need to:
• Determine the cable size needed and the appropriate unit of measure (e.g., AWG for the U.S. or square millimeters for Europe), in addition to the number of cable strands needed and suitable dimensions for the outer cable diameter
• Identify the derating factor, which is a standard calculation applied to photovoltaic panel output to account for reduced power levels in real-world operating conditions, such as dirt accumulating on the panels, wiring losses, snow cover, and panel aging
• Calculate the copper resistance and anticipated power loss, if applicable
2. Which safety standards apply? Cable solutions designed into solar energy equipment must meet certain safety standards, which can vary depending on the geographic location of the installation. Three of the most common safety standards solar cabling must comply with are UL4703 for installations in North America; EN50618 and IEC62930 for installations in Europe, Southeast Asia, the Middle East, and China; and S-JET for installations in Japan. It is possible for a single cable to comply with multiple certifications, and it can be wise to specify such solutions when working with global OEMs.
3. Are there any special requirements? Since solar energy equipment is subject to hazards stemming from both high power levels and harsh environments, the cables designed into this equipment often have additional requirements. For instance, many solar cables require specific cable jacket and insulation material, such as halogen-free cross- linked polyolefin (XLPO), which is halogen-free, or cross-linked polyethylene (XLPE), which is ozone-resistant and less susceptible to environmental stress cracking than many other materials. Other special requests can include:
• Tinned copper strands for well contact and assembly • UV and ozone resistance
• Flame retardance
• Halogen-free materials
• RoHS compliance
• Direct burial ratings so that no protective conduit is required • Smoke emission standards compliance
• Acid and alkaline resistance