Solar/Photovoltaic DC Systems: Basics and Safety

Solar photovoltaic (PV) systems are common and growing, with 42.4 GW of installed capacity currently in the United States and nearly 15 GW added in 2016. This paper will help electrical workers and firefighters understand some basic operating principles and hazards of PV DC arrays. We briefly discuss the effects of solar radiation and temperature on power output; PV module testing standards; methods for calculating the number of modules in a PV string; some National Electrical Code guidelines that are aimed toward improving array safety; DC array commissioning, periodic maintenance, and testing; arc flash hazard potential; ways firefighters can and do work safely around PV arrays; potential risk posed by moonlight and other light sources; and some unique DC-system hazards. We also present some statistics on PV DC array electrical incidents and injuries.