Optically based partial discharge continuous monitoring system for HV cable joints

This paper describes the further development of a novel partial discharge continuous monitoring technique. The measurement mechanism applies capacitive coupler measured partial discharge signals across a LiNbO₃ electro-optic modulator to modulate the intensity of the transmitted laser light. Recent research has applied an in-fine fibre polarizer for use with the modulator. A polarization scrambler is placed after the laser source to generate unpolarized light, which is transmitted over long length of standard single mode fibres and fed to the fibre polarizer and the modulator. Both the fibre polarizers and modulators, which are placed near cable joints, are passive without any power requirement.