Method and device for measuring the impedance in an electrical energy supply network

The invention relates to a method and a device for measuring the impedance of a power supply network at its nominal frequency by impressing a test current (3) in the network and measurement (4) of the resulting changes in the grid current and the mains voltage. According to the invention, the mains current and the mains voltage are measured during a first preselected time interval (T1) without and during a second preselected time interval (T2) with impressing of the test current. The test current is formed from at least one periodic signal with at least one deviating from the nominal frequency test frequency (f1, f2). From the measured mains currents and mains voltages, a resulting impedance for the test frequency (f1, f2) is determined by means of a Fourier analysis.