What is a photovoltaic rapid shut-off？

The photovoltaic rapid shutdown device is a safety device used in photovoltaic systems, designed to achieve quick shutdown of the system. It is typically installed between the photovoltaic modules and the inverter. Its main function is to quickly disconnect the power from the photovoltaic modules or the entire system in emergency situations, thereby eliminating DC high voltage, reducing the risk of electric shock, and facilitating rescue and maintenance work.

Module-level rapid shutdown devices allow for independent control of each photovoltaic module, enabling rapid disconnection of the connections between modules during emergencies. String-level rapid shutdown devices are responsible for cutting off the DC voltage between the entire array of panels and the inverter. Compared to module-level rapid shutdown devices, string-level devices offer more obvious cost advantages for the entire photovoltaic system.

Passive mode: When the grid experiences a power failure and islanding protection is triggered, the power supply box shuts down, and the relay in the shutdown box stops working, thereby disconnecting the power. Each photovoltaic string is also disconnected from the inverter equipment, preventing the system from remaining energized.

Active mode: In the event of an urgent grid fault or when someone experiences an electric shock, the emergency control switch on the power supply box can be manually pressed to cut off the power to the shutdown box, isolating the electrical connection of the system. This helps prevent the fault from further escalating, and the status information of the rapid shutdown box is uploaded to the inverter equipment.

Standards and Specifications for Photovoltaic Rapid Shutdown Devices
The standard specifications for photovoltaic rapid shutdown devices mainly include specific requirements for DC series arc protection, voltage limitation, and rapid shutdown functionality.

1. DC Series Arc Protection:
   For systems with a maximum DC system voltage greater than or equal to 120V, the system should have DC series arc protection. This measure aims to reduce the use of DC wiring in photovoltaic systems, thereby lowering the risk of fire.

2. Voltage Limitation:
   During construction, maintenance, and repair activities, the voltage of the DC portion that could be accessed by personnel should be kept within a safe limit of 120V. This regulation ensures the safety of workers and prevents electrical shock accidents due to excessive voltage.

3. Rapid Shutdown Function:
   Within 30 seconds of activating the rapid shutdown device, the voltage within a 305mm boundary beyond the outer edge of the photovoltaic array should drop to below 120V. This functionality is crucial in emergency situations, as it can rapidly reduce the voltage to ensure the safety of personnel and equipment.

These standards ensure that photovoltaic systems can operate safely, reducing risks associated with high voltage and fire hazards, especially during maintenance and emergency scenarios.

Features and Advantages

1. Improved Safety: Photovoltaic systems generate high DC voltage during normal operation. Improper handling or accidents could lead to electric shock. A photovoltaic rapid shutdown device can quickly cut off the power in an emergency, eliminating high DC voltage and significantly reducing the risk of electric shock.

2. Flexible Installation: The device can be selected and installed according to the specific needs of the photovoltaic system, meeting the requirements of different scenarios.

3. Compliance with Regulations: Many countries and regions have strict safety requirements for photovoltaic systems. As an important safety component, the rapid shutdown device helps ensure that the photovoltaic system meets these safety standards.

4. Enhanced System Reliability: In the event of a grid failure or an internal issue within the photovoltaic system, the rapid shutdown device can quickly cut off the power to prevent the fault from spreading and escalating, protecting other parts of the system from damage.