A photovoltaic rapid shutdown device is a safety mechanism used in PV systems to enable rapid deactivation. It is typically installed between PV modules or inverters. Its primary function is to quickly cut off power from PV modules or the entire PV system in emergencies, thereby eliminating high DC voltage, reducing the risk of electric shock, and facilitating rescue and maintenance operations.

• Module-level rapid shutdown devices allow independent control of each PV module, enabling rapid disconnection of individual modules during emergencies.

• String-level rapid shutdown devices are responsible for cutting off DC voltage between the entire PV array and the inverter. Compared to module-level devices, they offer more significant cost advantages for the entire PV system.

Working Principle

1. Passive Mode:

   • When grid power is lost (islanding protection triggered), the power supply box shuts down, the relay in the shutdown box deactivates, and each PV string disconnects from the inverter to prevent continued energization.

2. Active Mode:

   • In case of grid failure or electric shock risk, the emergency control switch on the power supply box can be manually pressed to cut off power to the shutdown box, isolating the system’s electrical connections to prevent further escalation of faults. The shutdown box also transmits status information to the inverter.

Standards & Regulations

PV rapid shutdown devices must comply with standards related to DC series arc protection, voltage limitation, and rapid shutdown functionality:

1. DC Series Arc Protection:

   • Systems with a maximum DC voltage ≥120V must have DC series arc protection to minimize fire risks associated with DC wiring.

2. Voltage Limitation:

   • During installation, maintenance, or inspection, DC voltage exposure must be limited to a safe threshold of 120V to prevent electric shock hazards.

3. Rapid Shutdown Functionality:

   • Within 30 seconds of activation, voltage within a 305mm boundary from the PV array must drop below 120V (or 80V under NEC 2017/2020).

Key Certifications & Standards

• SunSpec Certification: Defines PLC-based communication protocols for PV module-level rapid shutdown.

• NEC Standards (U.S. National Electrical Code):

  • NEC 2014 (690.12): Introduced requirements for rapid shutdown.

  • NEC 2017/2020: Mandates module-level shutdown, requiring voltage to drop below 80V within 30 seconds after activation. The 2020 version introduces "PV Hazard Control Systems" for enhanced safety.

Features & Advantages

1. Enhanced Safety:

   • Mitigates high DC voltage risks during emergencies, significantly reducing electric shock hazards.

2. Flexible Installation:

   • Adaptable to various PV system configurations and requirements.

3. Regulatory Compliance:

   • Helps PV systems meet stringent regional safety regulations.

4. Improved System Reliability:

   • Prevents fault escalation during grid failures or internal issues, protecting system integrity.

Future Trends

With global consensus on achieving "carbon neutrality," the PV industry is rapidly expanding, making system safety a critical focus. PV rapid shutdown devices are evolving toward:

• Higher safety & efficiency

• Greater intelligence & automation

• Innovative R&D to meet international safety standards

This technology ensures safer, more reliable PV systems in alignment with global energy transition goals.