NOVELTY - The device has upper and lower electrical measuring conduits (7, 8) defining a surface, which lies between a surface side (4) of a housing (1) and a primary or secondary coil (2). An outer contour of the surface surrounds an outer contour of the coil during projection on the surface side. The conduits are connected with an electrical impedance measuring device, which detects a measuring value based on an impedance between the conduits. The measuring device is connected with an evaluation device, which derives a signal from the detected value, where the signal displays a state of the side.    USE - Device for state monitoring of a housing of a primary or secondary coil i.e. planar winding, of an inductive power transmission device for inductive transmission of electrical power from a stationary unit i.e. charging station, to an electric vehicle i.e. lorry, to charge a rechargeable battery of the electric vehicle.    ADVANTAGE - The electrical impedance measuring device detects the measuring value based on the impedance between the conduits, and the evaluation device derives the signal from the detected measuring value, thus early and reliably detecting the unallowed state of the housing, and avoiding endangering of persons, and occurrence of large damages of the charging station and the vehicle and mechanical damage of the housing during startup of inductive transmission, hence improving operational safety of the device. The device is simple and inexpensive, and avoids interfering of measurement by a magnetic field of the primary coil.    DETAILED DESCRIPTION - The measuring conduits are formed by a conducting path with a carrier i.e. plastic film.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic longitudinal sectional view of a primary or secondary coil with simple and safety-relevant damage of a housing.    Housing (1)    Primary or secondary coil (2)    Surface side (4)    Upper electrical measuring conduit (7)    Lower electrical measuring conduit (8)