Fronius’s Symo Advanced three-phase string inverter began shipping in January 2019 and has now become the first inverter on the market to receive the official SunSpec Rapid Shutdown certification. The Symo Advanced comes with an integrated Power Line Communication (PLC) transmitter based on the SunSpec Rapid Shutdown communication standard.
The SunSpec Alliance announced seven SunSpec Authorized Test Laboratory (ATL) partners at the beginning of the year to provide SunSpec Certified testing services to a global roster of SunSpec Alliance member companies.
The SunSpec Certified program for Rapid Shutdown (RSD) verifies compliance to the SunSpec Communication Signal for Rapid Shutdown Functional Specification to meet the requirement established by National Electrical Code (NEC) 2017. 29 members of the SunSpec Alliance defined an open industry standard for communication between modules, inverters and string combiners to support module level rapid shutdown requirements. This multi-vendor industry standard went through 34 iterations and was published in September of 2017.
“Adoption of the SunSpec Rapid Shutdown specification is continuing to mature,” said Thomas Tansy, chairman of the SunSpec Alliance. “The foundation was set by a large quorum of solar industry firms dedicating time to the development of a SunSpec open source communications interface to meet NEC 2017 requirements. Firms have moved product into the market with the RSD spec incorporated on a compliant basis. The next maturation phase is now underway with the Fronius product certification. SunSpec Certified Rapid Shutdown is a strong signal to installers, first responders and local authorities that solar power systems with this mark meet NEC 2017 communications requirements.”
“We are excited to offer the first inverter that is officially certified for SunSpec Rapid Shutdown,” said Richard Baldinger, head of marketing at Fronius. “We believe in driving industry standards and supporting industry innovation to drive down cost and allow customer choice.”
Module-level rapid shutdown is made possible by pairing the Symo Advanced with SunSpec-based components such as the Tigo TS4-F module-level electronics. The inverter comes in ten models ranging from 10 kW to 24 kW for commercial applications.
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While protecting utility linemen and first responders with rapid shutdown has been the goal all along. The new “system” topology may well be smart grid enabled and therefore would have their own automatic transfer switch and be able to switch to emergency backup power if the local grid shuts down. This will allow the home or business owner some power to what could be a dedicated Circuit Breaker split. On utility power or grid tied operation, the secondary C.B. panel would run on solar PV inverted power with utility if more power than the system is required. If the grid fails, the Automatic Transfer Switch can run some house circuits off of the inverter while the grid is down.
I believe the code required quick disconnect knife switches mounted externally and clearly marked will still be a part of the system for first responder safety. These systems are still complex and more expensive than the early and simple series/parallel solar PV panel wiring connected to a home inverter that detects grid fails and shuts down. Now storing energy, being able to switch power to ‘some’ of the home or being able to run the inverter as a grid tied or off grid with the change of a transfer switch is possible.