The analysis of electromagnetic compatibility of electric transport systems as well as the solution of numerous problems in the electric power industry are unreliable without a spectral analysis of their traction voltages and currents, which are stochastic processes. However, the existing concepts and methods of analysis do not allow performing the evaluation of spectra of voltage and current dependencies in real time to the full extent and for all modes. In particular, they do not take into account that the traction-regenerative current is a pulse random sequence and that the voltage and current have a finite duration; therefore it is not correct to perform their integration in the range from negative to positive infinity in the Khinchin’s form for the spectral density. To determine the spectra of stochastic voltages and currents, new definitions were introduced in the paper – actual and instantaneous spectra. The spectral functions of these spectra, as functions of frequency and time, allow conducting the spectroscopic analysis of fronts and decays as well as short intervals of the voltages and currents records in transient modes. With this purpose, the analytical expressions of the amplitudes and initial phases of the k-th harmonics are obtained using the discrete Fourier Transform method. Numerical calculations of the spectral composition of random processes of voltages across current collectors and traction-regenerative currents are performed for the VL8 and DE1 electric locomotives as well as the trams with rheostatic control. Registration of necessary time dependencies of voltages and currents was carried out under the real operating conditions on the sections of Prydniprovsk railway and on the tram routes in Dnipro. For the comparative analysis, the actual and instantaneous spectra were determined as well as the spectra of total realizations and “tails” of the correlation functions of the voltages and currents.

railway transport, random process, correlation function, spectrum.