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Application: Module-level Disconnect for Safest Solar

AC Loss - Rapid Shutdown Solution

NOTE: Automatic Operation can comply with NEC 2014/2017 690.12 standards. See the link at the bottom of this article for details

In an emergency situation such as a fire, standard procedure for first responders is to disconnect the AC circuit breaker for the building.  This loss of power from the grid causes the inverter and the Cloud Connect (CC) or Cloud Connect Advanced (CCA) to turn off. Whenever the CC (or CCA) and inverter both shut off, the TS4 units capable of safety (TS4-S, TS4-O and TS4-L) automatically enter module level disconnect mode and turn off output voltage and power completely. Thus, even if the emergency personnel do not activate module level disconnect directly, the TS4 units are equipped to detect standard safety protocol and respond to the emergency.

Sample system with Cloud Connects on the same AC service as the inverters

 For the criteria required to meet NEC 2014/2017 690.12 requirements, click here.

Tigo PV-Safe®

The Tigo PV-Safe switch enables the shut down of an array at the module level, which is by far the safest way to deactivate a solar system.   When PV-Safe mode is activated, the TS4 disconnects the PV module from the string, leaving it with zero power and zero voltage output.  When module voltage output is zero, it is safe for emergency personnel and scheduled maintenance workers to navigate a PV system.

 

 

 Real time chart demonstrating PV Safe activation; current per module is shown in green, voltage in grey

 

PV-Safe - Manual Operation

NOTE: Only AC Loss is an NEC 2014/2017 690.12 compliant solution 

For on-site activation, pressing the PV-Safe button on the CC will trigger the unit to send an “off” command to all TS4.  Once deactivated, the TS4 units will not turn on again until they receive an active “on” command from the user via the CC on site. 

Detecting and Communicating Module-Level Hazards

The TS4 is constantly monitoring PV module parameters such as over voltage and over temperature. The unit will enter PV-Safe mode if a safety hazard is detected and report its status to the CC (or CCA). The CC (or CCA) will decide whether there is a local threat that can be avoided by just shutting down the single module, or if there is a potential system safety hazard and PV-Safe mode is needed for the entire system.

If a single module or the entire system is in PV-Safe mode due to such a hazard, it will automatically resume power production once the problem went away.  

Conclusion 

With manual and automatic activation as well as regular module-level monitoring, Tigo's safety function greatly increases piece of mind for a solar system owner. Unlike standard DC switches, it cuts the voltage at the module level, bringing down string voltage to zero in case of emergency.

The Tigo TS4 system was tested to show compliance with NEC 2014 690.12 Rapid Shutdown requirements by Intertek as of October 2014, and by UL January 2017 for NEC 2017 690.12. 

Click here to learn more about compliance with Rapid Shutdown.

Click here to view our rapid shutdown certificates.

To learn more on our PV-Safe technology see the attached whitepaper below.

 

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