An apparatus (10) for detecting the occurrence of partial discharge in
electrical equipment, such as high voltage transformers. The apparatus
comprises a detecting means including an ultrasonic transducer (11)
mounted at one end of an electrically insulating elongate rod (13). The
ultrasonic transducer (11) is adapted to detect ultrasonic pulses or
waves generated by the occurrence of a partial discharge in the
electrical equipment. A radio frequency (RF) transducer (17) is also
utilized to detect radio frequency (RF) pulses or waves also generated by
the partial discharge. The rod (13) can be mounted in the wall of the
electrical equipment and so provide a mechanism for adjusting the
position of the detecting means within the electrical equipment. The
apparatus is also removable from the electrical equipment and
re-locatable to other equipment.