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Chuck Ross
As the number of solar power installations continues to grow, spurred on by tax incentives and improved performance, system designers are becoming increasingly concerned regarding the safety of photovoltaic (PV) equipment and, more importantly, the personnel who keep it running. Safety devices for PV equipment, including fuses, need to be tailored to meet their unique design and operating conditions. Fuses for these applications now are covered by the new UL 2579, “Low Voltage Fuses – Fuses for Photovolotaic Systems.”
Environment presents the most obvious stress for PV equipment, with systems subjected to temperatures that can range from extreme heat to extreme cold in a single day. Less obvious, however, is the fact that solar circuits are not subject to the high-magnitude fault circuits electrical professionals are accustomed to seeing in motor circuits and other applications. Instead, fuses need to be designed to protect circuits that can be subject to extended, low-magnitude fault currents.
Fuses may be required at numerous points in a PV system, anywhere from the solar panel, up through the inverter. Larger designs – and they can range up to 1,000 volts dc – also may incorporate combiner boxes, disconnect switches and other connecting points where fuse protection may be required.
“The fuse designs differ, primarily, based on amperage and voltage,” says Mark Hemmann, PE, senior product manager at circuit-protection and power-management equipment maker Cooper Bussmann. “But there is one common UL photovoltaic standard that covers all PV applications and locations.”
Product designs are continuing to evolve, as new approaches and systems come to market. As a result, fuse makers are being challenged to address current situations substantially different from those presented by more traditional electrical equipment.
“This market is different, in that it uses dc voltage, and higher dc voltages,” Hemmann says. “These are making fuse companies take their designs to new voltage and amperage limits.”
Photo courtesy of Cooper Bussmann
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