Abstract: A partial discharge fault in a transformer tank is determined by sensing supersonic vibrations at a multiplicity of points about the tanks and establishing a threshold amplitude and a frequency range for pulse vibrations to be evaluated. The signals from the multiplicity of points are multiplexed, synchronized and localized and then processed in a series of steps. After the existence of triggering pulse vibrations exceeding an established threshold amplitude and within an established frequency and range is initially determined, a wavelet transform is conducted on the multiplexed signals two at a time with one signal being the signal from the first sensor found to provide a signal above the threshold amplitude. The wavelet transform provides both frequency and time domain.