Category: C&I Generation
The growth of solar string inverters is driving increased demand for AC collection systems on both C&I and utility scale solar pv systems. Solar applications present unusual service conditions that go well beyond those seen in normal commercial equipment that is designed per the applicable industry standards. These unusual service conditions must be considered for proper selection and sizing of molded case circuit breakers, their enclosures, and the connected cable systems. Lessons learned from field experience confirm that failure to consider solar factors in system design commonly leads to under-sizing of circuit breakers (or switches and fuses), and cables for these applications. Proper selection is critically important to reduce the potential for “nuisance tripping” by components, and to avoid equipment failures due to heat rise in the enclosure and connected circuit that exceeds industry design standards. It is also important to avoid equipment compliance issues with the Authority Having Jurisdiction (AHJ) during the inspection phase. The ultimate goal is to properly select and specify solar AC collection system equipment that provides cost-effective reliable performance over its operational life.
The speaker review why solar applications present unusual service conditions for installed equipment and the “red flags” that should be considered, including equipment location (ground or rooftop, desert, mountain, etc.), ambient temperature extremes (below -10C and above 40C), direct or reflected solar radiance, and altitude (above 3300 feet). Session attendees will learn how the circuit breakers, enclosure, and the connected cables are a system, each dependent on the other for effective thermal management. Further, the audience will discover how to address the solar “red flags” and apply de-rating factors to the system current and voltage ratings. We will discuss why some additional thermal margin in the system design is a good idea to address other intangibles, like circuit heating due to inverter harmonics. Finally, we will review some simple, but cost effective common sense suggestions on panel design that could be specified to improve enclosure reliability.
Benefiting from this sessions will be system designers, integrators, developers, installing contractors, service engineers, operators, and owners of both C&I and utility scale solar projects.
Lawrence Connor– Senior Application Specialist, Eaton