Safety Services Company
May 4th 2016
Photovoltaic (PV) energy systems that take advantage of solar energy are still a small, but rapidly growing energy source in this country. And because of its ability to generate electricity right where it will be used, it will continue to be a popular choice for businesses. Yet, this quality of distributed energy creates more challenges and opportunities for hazards. Traditional power plants are kept behind fences, located far away from the public. But this distributed generation of solar power, puts power plants next to residences and businesses.
With 1,000 volt system on the roofs of many homes, personal solar arrays have some potential for fire and electric shock. They need to be correctly installed and maintained so they don’t catch fire. When incorrectly designed or installed by untrained installers they can cause fires and kill.
In 2009 a PV system at a Target in California caught fire because of an expanding and loose conduit connector that had very long runs of about 400 feet and incorrect expansion joints and pinched conductors that led to an undetected ground fault during construction.
Design failures and poor installation similar to this often make the fire difficult to put out. When an electrician was called to the site to open the fuses, there were no DC disconnects to the roof.
Such high profile incidents have caused the National Electric Code (NEC) to address solar arrays.
Before the 2008 NEC, addressing solar PV was unclear and problematic to interconnect such as bus bar ratings. The 2008 NEC release created a good foundation for this technology.
The 2011 NEC addressed: DC safety through the clearance of conductors below the roof, grouping conductors from separate systems (AC, DC), requiring an Arc Fault Circuit Interrupter (AFCI) in the inverter, disconnecting means for replacing fuses, arc-fault detection on rooftops, and 1,000V systems.
Some of the changes in the 2014 NEC include: better ground fault protection, rapid shutdown of the DC system more than 10 feet outside the array, more flexibility of the interconnection point (bus or conductor rating), AFCI everywhere including the AC side, easier implementation of 1,000V systems, greater than 1,000V for non-residential systems, an auxiliary grounding electrode conductor (GEC) for the array, and required grouping of conductors (DC/AC).
This is a constantly evolving technology that will continue to progress and present additional safety hazards and solutions. The next challenge will be storing energy in large batteries so the electricity can better be used when needed.
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