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Modern optical partial discharge (PD) detection system based on fiber-optic sensors for PD on-line health monitoring in high-voltage (HV) cable terminations necessarily requires optically transparent or translucent insulation materials. The optically compatible silicone rubbers are the key to facilitate such innovative technology. In this work, AC 50 Hz dielectric strength Eb and mechanical properties of three types of commercially available silicone rubbers have been investigated.The investigations revealed that the translucent silicone rubber has a good mechanical performance but its Eb value is considered too low. However it is sufficiently good for use as base material for rubber stress cones. Unfortunately, its optical transmittance is poor compared to optically clear transparent silicones. On the other hand, the mechanical properties of transparent silicone rubbers do not comply with those demanded from push-on stress cones. In particular, their elongation at break is considered too low for that application.However they provide the Eb values of about 28 kV/mm to 29 kV/mm at 0.5 mm thickness, which are higher than those of the translucent type. Moreover, it was found that the post-curing process does not provide a positive impact on the ultimate elongation of silicone rubbers.

In high-voltage facilities of power stations and transmission networks, discharge activities leading to catastrophic failure can occur. Early detection of partial discharges (PD) in polymeric insulations of HV cable terminations and joints is therefore increasingly important. This paper describes a monitoring methodology to detect PD activity in silicone elastomer by two independent fibre-optic sensor types. Fluorescent fibre-based sensors are sensitive to plasma optical emission already at the onset of PD while an acoustic fibre-optic sensor responds to acoustic emission from the PD during its progression. The sensitivities of both sensor types are compared, and it is demonstrated that they provide complementary information for fibre-optic sensor-based monitoring of high-voltage cable accessories.

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