UHF Spiral antenna is a partial discharge sensor designed to receive electromagnetic (EM) emissions from a PD occurring in the monitored asset. It is a broadband antenna with a flat response which makes Spiral antenna suitable in a number of different applications. It has been optimized to operate in a frequency range typical for PD activity and it was designed to provide maximum sensitivity and high gain. It can be virtually applied in any electrical equipment provided that it has apertures or EM transparent surfaces.