National Semiconductor Corp. has launched the SolarMagic arc detection reference design, consisting of analogue front end ICs and multi-band dynamic filtering (MBDF) firmware, which the company claims is the first commercially available solution for detecting arcs in solar power systems.
Intermittent connections or insulation faults in solar power systems can cause arcing in high-power DC circuits. With temperatures of 3,000 °C or more, these arcs pose safety risks to surrounding infrastructure and personnel. The U.S. National Electrical Code (NEC) 690.11 requires all new solar power installations to include an arc-fault detection and protection system. National Semiconductor’s new SolarMagic arc detection reference design detects arc fault conditions and provides an alert to allow the system to be shut down in order to quench the arc.
According to National Semiconductor , arcing events in solar power arrays are difficult to detect. They do not generate a uniquely identifiable electronic signature, and the power lines of a solar power array act as very effective antennas for a wide range of electromagnetic interference in the vicinity of the array. In addition, inverters generate noise that is coupled into the power lines. Sophisticated signal processing is required to reliably detect the full range of dangerous arcing events without generating false alarms when the solar power array is operating safely. To meet this challenge, National Semiconductor developed patent-pending MBDF signal processing firmware, which uses state-of-the-art abstract pattern recognition that does not require arc signatures to match rigid, predefined profiles.
The SolarMagic chipset forms an analogue front end (AFE) built around three highly integrated ICs. The SM73307MM dual precision 17-MHz low noise CMOS input amplifier provides gain and filtering for the arc signature signal; the SM73308MG low offset, low noise RRO operational amplifier provides the Vref mid-point for the arc-detection AFE; and the SM73201MM 16-bit, 50 to 250 kSPS differential input micropower ADC digitises the signal from the gain and filtering stage and sends the digital samples to a microcontroller. Additional power management ICs provide various support functions.
The SolarMagic arc detection chipset is available in a variety of industry-standard device packages. The chipset comes with a licence for the MBDF firmware.
Image: National Semiconductor