Measurement arrangement and method for detecting an ac voltage as a rail potential in dc railway systems and use of the measurement arrangement

The invention relates to a measurement arrangement (1, 22) for a rail potential in a DC railway system, wherein rails (10) of the DC railway system are connected to earth (2) by means of at least one switchable semiconductor element (32), wherein the at least one switchable semiconductor element (32) can be switched to be conductive when a threshold value for the rail potential is exceeded, and wherein the measurement arrangement (1, 22) connects rails (10) and earth (2) in a current path running parallel to the at least one switchable semiconductor element and has an evaluation device (31) for detecting DC voltages, characterised in that the measurement arrangement is also designed to detect AC voltages (34) in the rail potential and is equipped with a rectification device (6), which rectifies periodically occurring voltage peaks (35), wherein the periodically occurring voltage peaks (35) can be generated by the at least one switchable semiconductor element (32) when an AC voltage (34) is present in the rail potential, and is equipped with a storage device (33), which stores the rectified voltage peaks (40) and generates a longer-lasting DC voltage (41) of a duration that can be detected by the evaluation device (31) from the rectified voltage peaks (40). The invention further relates to a method and a use of the measurement arrangement.