Modified optical fibre sensor for PD detection in high-voltage power equipment

Detection of electrical partial discharges (PDs) inside power transformers is a good indicator of the quality of the insulation system. Ultrasonic pressure waves are produced by partial discharges and can be detected with suitable pressure transducers. The sensitivity of externally mounted sensors is reduced due to signal attenuation and multiple paths. Advances in optical fibre technology enable more accurate measurements even in hostile environments with a high background noise level. An all-optical fibre sensor system is investigated as an alternative which can be safely immersed inside the transformer. The perturbation caused by pressure wave induced stress on the fibre core and affects the light beam traversing the fibre. By using interferometric techniques, the optical phase shift caused by the perturbation can be detected accurately with a phase-modulated type optical sensor.