The National Electric Code (NEC) section 690.110.12 for the mechanical execution of work states, “Electrical equipment shall be installed in a neat and workmanlike manner.” Believe it or not, this is the only current cable management standard for the solar industry in 2019. This is a very subjective definition that is open to liberal interpretation from job to job.True, a lot about cable management on any scale is grounded in common sense. Installers must ensure cables are properly secured to avoid damage to the insulating jacket and inner conductor wires. In small scale installations this can usually be managed with a few guide rails, clips and zip ties to protect cables from being exposed to weather and sunlight, from rubbing against rough surfaces and sharp edges, and out of the way of rodents that like to chew on them. While this guidance may be sufficient for the installation of residential rooftop solar systems with just a few cables (pictured), NEC 690.110.12 is woefully inadequate when installing utility-class photovoltaic solar arrays.
When it comes to building large scale solar plants, cable management is often one of the last considerations. Engineers are usually first focused on solar array design and panel positioning to maximize energy production, and address cabling as a secondary issue. That’s a mistake, as the lack of standards can lead to problems and inefficiencies when engineers are forced create cable pathways to work around the unique design elements of the solar array. That makes it hard to control costs, as cabling is not repeatable from project to project, and may require expensive, time consuming field fabrication.
Further, utility-scale solar plants have more panels and cabling than residential systems – a lot more – bringing temperature swings, structure movement and safety issues into the mix. In some parts of the country temperatures can fluctuate 50° to 60° over the course of a day. That causes the panel structure to move, which can result in broken cables from overtightening, stress at connection points, or if the proper bend radius is not maintained to allow for flexibility in the array.
More panels and cables also mean more electricity production. Today’s solar arrays are operating at voltages in excess of 1,500 V and amperages greater than 500 A. Therefore, an individual who is walking around on wet grass in a field of thousands of panels can be at great risk if an exposed cable fails. For this reason, trenching remains a popular and effective method for safely laying cables at solar plants; the ground creates a physical barrier between electrical charges and installers/maintenance personnel. But burying cable is a very labor intensive and expensive process. There is the possibility of delays caused by weather, mud, rocks and other unforeseen terrain issues. Visibility to an exact failure point is impossible and requires more digging. And then there is the issue of derate, factors that can reduce cable wattage capacity by up to 50% when running multiple buried cables in parallel due to heat generation. To compensate, utilities will often use larger, thicker cables to offset heat buildup and safely carry the necessary current, but this only inflates costs without increasing load capacities. [Want to learn more about derate? Click here to read the article, How to Effectively Manage Solar Panel Cables.]
All these issues to contend with, yet your NEC guidance is limited to “Electrical equipment shall be installed in a neat and workmanlike manner.” Fortunately there is another answer and a partner you can turn to for additional direction when designing your next utility-scale solar plant.
Snake Tray’s Solar Snake Max is an above ground (aka “Free Air”) cable containment system that allows for code-compliant cable separation without trenching. Instead, pre-fabricated trays mount to vertical pilings or poles. Free Air installation eliminates derate while holding cables safely in place with the proper amount of support and elasticity to account for panel structure movement caused by thermocycling. The cables are laid faster while requiring less field fabrication, which reduces installation costs. And the cables themselves can be of a smaller diameter – and therefore cheaper – as they can be used to their maximum capacity without suffering derate. This is where the rubber meets the road; when engineers realize they can rapidly cable utility-scale solar plants while saving up to 50% on the cost of conductors! Finally, Free Air installation allows for failure points to be easily pinpointed for better serviceability and fast repair in the event of a broken cable. Learn more about Solar Name Max.
Snake Tray solutions for solar cable management not only exceed NEC 690.110.12, they’ll improve your ROI. Let us help you design your next utility-scale solar plant cabling project for maximum performance, safety and profitability.