Safe DC option with SolarEdge power optimizers

Safe DC option is an integrated feature in SolarEdge power optimizers and inverters. Safety of installers, maintenance personnel and firefighters is ensured with this option. This option shuts down DC current and voltage in strings when inverter is off or disconnected or in safety mode.

High string voltages are de-energized automatically to 1 Vdc per Power Optimizer and max. 50 Vdc per string in any of the above cases. Electrocution and unsafe high voltage risks are eliminated with this Trade Mark option.

Safe DC option can be triggered from SolarEdge fire fighter gateway aswell, providing centralised safety management.

The SolarEdge Solution consists of a Inverter which communicates to Power Optimizers over Power line communication (PLC).
Safe DC is a mechanism which is build into the software of the Inverter and the Power Optimizer.

The Power Optimizers only harvest full power from the panels if the PLC signal is constantly renewed. If it fails the Power Optimizers initiates the Safe DC mechanism, which lowers the DC voltage to 1 Vdc per Optimizer. This feature works even when more than one panel is connected to it.

The 1 Vdc is necessary during installation and maintenance stage to check the proper working of the Power Optimizers.

During installation, panels are connected with Power Optimizers in strings. Safe DC is activated by default, lowering the operational voltage of the Power Optimizer to safe 1 Vdc, if the sun shines.

The maximum number of Power Optimizers in one String of panels is 50, therefore max. string voltage is 50 Vdc if all Power Optimizers are working properly.

Full power harvest can be safely activated when the Power Optimizers are connected and communicate with an SolarEdge inverter.

In case of a fire firefighters, mostly the AC wires of the house were cut to terminate the grid connection. Safe DC is automatically activated by the inverter if the grid connection is lost. This reduces the per power optimizers voltage to 1 Vdc. Eventually, max. 50 Vdc per String, lowering the risk for firefighters tremendously.

If properly educated, firefighters can also manually activate Safe DC by switching off the Inverter, the AC breaker or the AC/DC safety switch.

The Power Optimizers will also activate Safe DC by themselves if their thermal sensor senses a temperature above 85 °C, because such high temperatures typically indicate a fire near the PV System.

To activate Safe DC manually, inverter should be turned off so that it stops sending PLC signals to the Power Optimizers. Safe DC can also be activated if the connection to the AC side is interrupted by switching off the main AC breaker or AC/DC safety switch.

Maintaining PV system should be done regularly. Safe DC should be activated in order to reduce the high DC string voltages to a safe level. Maintenance like cleaning the panels, checking for defects, replacing panels or power optimizers should be considered only after activating the Safe DC mechanism.