In this paper, the features of a compact spherical antenna, already efficiently used for ultra wide band applications, are investigated by exploiting the possibility of detecting electromagnetic transients with frequency content up to the very high frequency range. Transient phenomena with the above mentioned frequency content are those encountered, for example, in partial discharge detection. The behaviour of the adopted compact spherical antenna enables to successfully detect the waveform of typical partial discharge transient radiated electromagnetic field, so preserving the information necessary for the subsequent pattern analysis, typically carried out by using classical conducted measures results. The compact antenna is firstly modelled by using two different moments method approaches in frequency domain: surface and thin-wire models are adopted in order to investigate different case studies so obtaining useful information about the behaviour of the antenna both in frequency and in time domain. Some comparisons with measured transient electromagnetic field data obtained with a real spherical antenna probe enable to successfully validate the use of the compact spherical antenna in detecting electromagnetic transients with frequency content up to the very high frequency range. A recent patent has been obtained also by one of the author by using this type of sensor.