A real-time method for time–frequency detection of transient disturbances in voltage supply systems

•Detection transient disturbances in time–frequency domain.•Capture of a transient in the time domain, detection in the frequency domain.•Detection in real-time of impulsive, oscillatory, transient harmonics, short duration rms variations.•The method is insensitive to harmonic distortion.•The method is low sensitivity to noise.•The method allows the reconstruction of the transient signal in the time domain.

This paper presents a new method for real-time detection, extraction and analysis of transient disturbances in low-voltage supply systems. The algorithm developed is based on the sliding window method and applies the discrete wavelet transform to a difference signal computed in the time domain, comparing each voltage sample with its corresponding sample in the previous period. In the case that the difference signal surpasses a defined threshold, the algorithm proposed computes the energy of the different frequency bands of the difference signal corresponding to one fundamental period, detecting a transient disturbance in the frequency domain within the next period of the input signal when a specific threshold is exceeded. Other voltage events, such as short duration root-mean-square variations can also be detected using the method proposed. The results obtained demonstrate the good performance of the method.