Protection device for objects included in electrical power supply networks

Protection device for elements of electrical networks, comprising for each object at least one directional wave detector means, means connecting each of said directional wave detector means to the network, filter means (11) in said connecting means for filtering out the components of the input signals which have the same frequency as the network, each wave detector means comprising at least one wave detector unit per phase for sensing current and voltage transients occurring in the object in case of faults in the network, each wave detector unit (WD) including directional detector means and having at least one output for tripping signals and at least one output for blocking signals connected to said directional detector means included in the wave detector, a plurality of level detectors, said signal outputs each being connected to one of said level detectors, a logic system for the protection of the object, in which one directional wave detector (WD) is arranged for each connection to the object which is to be protected and connected through the level detectors to the logic system, said logic system including means to compare the output signals from the directional wave detectors for the object and to disconnect the object in response to a tripping signal from any of said directional wave detectors only when none of the wave detectors has emitted a blocking signal.