Very fast transient overvoltage (VFTO) is generated by the operation of isolation switches and circuit breakers in substations, which can affect the safe and reliable operation of power secondary equipment based on cable transmission and spatial radiation. VFTO is a type of transient interference pulse which contains multiple frequency band interference components. The frequency of VFTO is up to 100MHz. The electromagnetic interference models and experimental standards are difficult to describe the time-frequency characteristics of VFTO interference waveforms. Firstly, the generation mechanism and transmission path of VFTO in substations are analyzed. The measurement method for VFTO in substations is proposed. The macro and micro pulses of VFTO are measured on the secondary side of voltage transformers during isolation switch operation. Secondly, the time-frequency characteristic analysis method of VFTO is proposed based on synchronous compressed wavelet transform, which can obtain the time-frequency characteristics of VFTO and improve the time-domain and frequency-domain resolution. Finally, the VFTO interference model for substation is established based on attenuated damping oscillation waves. The model parameters extraction method is proposed for VFTO models based on difference evolutionary algorithm. The experimental results show that the model results are basically consistent with the measured results and the coefficient R 2 is 0.85 between the above results. It can describe the time-frequency characteristics of VFTO interference waveform, which can provide a basis for the formulation of VFTO immunity standards and the operation and maintenance of power equipment.