A device for an electric system, the device comprising: a plurality of signal inputs (P1, P2, P3, P4), wherein each signal input of the plurality of signal inputs is configured to receive a signal associated with the electric system and indicative of the momentary state of the electric system at a specific time, and a processing unit, wherein the processing unit is configured to perform a determining operation, wherein, in the determining operation, a signal value of the signal received at one of, more of or all of the signal inputs is determined, e.g. measured, the determined signal value being indicative of the momentary state of the electric system at the specific time, wherein the electric system is a multi-phase alternating current system, and wherein the processing unit is configured to perform a simulation operation which uses the signal value determined by the processing unit, the signal value being indicative of the momentary state of one phase of the multi-phase alternating current system at the specific time, and wherein the signal value is used to simulate a signal value indicative of the momentary state of another phase of the multi-phase alternating current system at the specific time, wherein the device comprises an energy harvesting unit which is configured to harvest electrical energy, wherein the device comprises a switching unit, the switching unit being operable to switch transfer of signals received by the device via the plurality of inputs between the processing unit and the energy harvesting unit or a combination of both, wherein the switching unit is configured such that signals received via each input can be switched independently between the processing unit and the energy harvesting unit or a combination of both, and wherein the device has an energy storage unit configured to store harvested energy a plurality of signal inputs (P1, P2, P3, P4), wherein each signal input of the plurality of signal inputs is configured to receive a signal associated with the electric system and indicative of the momentary state of the electric system at a specific time, and a processing unit, wherein the processing unit is configured to perform a determining operation, wherein, in the determining operation, a signal value of the signal received at one of, more of or all of the signal inputs is determined, e.g. measured, the determined signal value being indicative of the momentary state of the electric system at the specific time, wherein the electric system is a multi-phase alternating current system, and wherein the processing unit is configured to perform a simulation operation which uses the signal value determined by the processing unit, the signal value being indicative of the momentary state of one phase of the multi-phase alternating current system at the specific time, and wherein the signal value is used to simulate a signal value indicative of the momentary state of another phase of the multi-phase alternating current system at the specific time, wherein the device comprises an energy harvesting unit which is configured to harvest electrical energy, wherein the device comprises a switching unit, the switching unit being operable to switch transfer of signals received by the device via the plurality of inputs between the processing unit and the energy harvesting unit or a combination of both, wherein the switching unit is configured such that signals received via each input can be switched independently between the processing unit and the energy harvesting unit or a combination of both, and wherein the device has an energy storage unit configured to store harvested energy