Rail-mounted device, automation system and method for process automation

A head station for an automation system, the head station comprising:

• an electronic control unit that is designed to carry out control tasks of the automation system;
• at least one local bus interface to connect the head station to a local bus of an automation system;
• and
• a power supply unit that has at least one input to connect the head station to a voltage source,
• wherein the head station has a signal input through which a detected voltage drop or voltage loss of the supply voltage is indicated to the head station, and
• wherein the electronic control unit of the head station executes an emergency program in order to transfer the head station into a safe state in an event of a voltage drop or voltage loss indicated through the signal input.

A method for process automation via an automation system, wherein the automation system comprises a head station, a voltage-buffered rail-mounted device, and one or more additional rail-mounted devices, which are connected to one another via a common local bus, the method comprising:

• detecting a voltage drop or voltage loss at an input of a power supply unit of the voltage-buffered rail-mounted device with which the rail-mounted device is connected to a voltage source;
• providing an electrical supply voltage at an output of the power supply unit of the voltage-buffered rail-mounted device from an electrical energy storage device, the output of the power supply unit of the voltage-buffered rail-mounted device being connected to an input of a power supply unit of the head station;
• indicating the detected voltage drop or voltage loss at a minimum of one signal output of the voltage-buffered rail-mounted device, the signal output of the voltage-buffered rail-mounted device being connected to a signal input of the head station;
• and
• executing an emergency program by an electronic control unit of the head station when a detected voltage drop or voltage loss at the signal input of the head station has been indicated by the voltage-buffered rail-mounted device, while the head station is powered with the provided electrical supply voltage through the input of the power supply unit of the head station.