In 95 % of all PV systems, panels are serially connected in strings. This can cause life-threatening DC voltages up to 1,000 V. Safety regulations apply for protection against electrical shock when working with electrical equipment with a voltage higher than 120 V DC. Thus, the systems are to be disconnected from the power supply prior the start of work.
This is a difficult matter in string systems: The disconnection at the inverter or via additional DC switches does interrupt the flow of power, but not the voltage. Occupational safety can only be guaranteed when each panel is disconnected automatically. Solarcheck RSD is a self-controlling system which automatically disconnects each PV module in case of error or when service is required.