The aim of this paper is to analyse the spectrum of real transients from a LV network. The spectrum is obtained using the Short-Time Fourier Transform (STFT). The MATLAB function spectrogram is used to obtain the STFT. The STFT is tested with different configurations and applied to several waveforms lengths. Forty transients have been recorded from random devices in an apartment in south Spain. The transients are mostly notches or with minor oscillations. Thirty-three transients with an oscillatory characteristic have been recorded from an induction stove, as well as an oscillatory transient from a PV panel. The spectrum of these transients has been obtained using the STFT and analysed.