Partial discharge (PD) is a critical phenomenon that often occurs in medium and high voltage electrical equipment due to insulation faults and generates various types of acoustic emissions. The characteristics of the PD signal depend on the type of equipment, physical condition, operating voltage, and insulating substances used (e.g., gases, oils, nonmetallic solids). Corona, arcing, and surface discharges are the most common PD faults. Usually, these faults are quantified by electrical and acoustic detection methods. Acoustic methods gained popularity over electrical methods due to their insensitivity to electrical noise and localization capabilities. PD signals have different levels of acoustic emission, represented by various time-frequency characteristics. Currently, the analysis of PD data, detection and classification of faults is done manually or semi-automatically by experts.