Abstract: One example discloses a system for determining a power phase and/or a phase rotation in a three-phase power system. The system can comprise at least three different computer nodes that communicate over a network, wherein each of the at least three different computer nodes receives a power signal comprising (i) one of three separate single phase power signals of a three-phase power signal or (ii) a three-phase power signal. The at least three different computer nodes can comprise a master computer node to determine (i) the phase of the power signal provided to each of the at least three computer nodes and/or (ii) a phase rotation of the power signal provided to each of the at least three computer nodes. The determination can be based on power data that characterizes waveform properties of the power signal provided to each of the at least three computer nodes.