New method of observation and diagnosis of three-phase systems is developed and tested. Unsymmetrical conditions concerning the machine impedance or valves operation are reflected in the spectrum of the current space-phasor. Spectrum of the space-phasor with the help of the Wigner-Ville Distribution (WVD) was estimated and its time-frequency representation with excellent time and frequency resolution has been obtained. The proposed method was tested with non-stationary multiple-component signals occurring during the fault operation of inverter-fed drives and transmission lines.