A rapid shutdown device (RSD) is an electrical safety mechanism designed to quickly shut down a solar power system in the event of an emergency. It is a requirement of the National Electrical Code (NEC) in the United States, which mandates that all solar power systems must have a means to rapidly de-energize the system in case of a fire or other emergency situation.
The purpose of an RSD is to minimize the risk of electrocution for firefighters and other emergency responders who may need to work on or near the solar power system during an emergency. By quickly shutting down the system, the RSD helps to prevent the flow of electrical current, reducing the risk of electrical shock.
There are several types of RSDs available, including module-level RSDs and string-level RSDs. Module-level RSDs are installed at the individual solar panel level, while string-level RSDs are installed at the string or circuit level. Both types of RSDs can quickly and safely shut down a solar power system in the event of an emergency, and can be configured to meet the specific needs of the system and its environment.