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- Acoustic emission (5)
- Partial discharge (4)
- Silicone elastomer (4)
- High voltage cable accessories (3)
- Stress cone (3)
- Fibre-optic condition monitoring (2)
- Sensors (2)
- Acoustic sensors (1)
- Acoustic waveguide (1)
- Dielectric ageing (1)
Recent progress in the development of ultrasonic fibre-optic sensors for detecting acoustic emission from partial discharge in elastomeric insulations is presented. These sensors are an important part of a proposed comprehensive scheme for the fibre-optic monitoring of cable accessories. After specifying the underlying design goals the improved fibre-optic sensor design is outlined. It is experimentally shown that it offers about ten-fold improvement over a previously investigated resonant cantilever-type design in terms of detection limit, making it competitive with conventional piezoelectric transducers, however with the added compatibility with strong electrical fields and electromagnetically noisy environments.
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.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Konventionelle elektrische Verfahren zur Erfassung von Teilentladungen (TE) in hochspannungstechnischen Bauteilen und Betriebsmitteln erfordern elektromagnetisch ungestörte Messbedingungen und sind für die Überprüfung von Anla-gen während des laufenden Betriebs nicht unproblematisch. Daher werden für Prüfung und Überwachung im Feld zu-nehmend unkonventionelle elektromagnetische (HF, VHF, UHF) und akustische Detektionsverfahren eingesetzt. Wegen ihrer prinzipiellen Immunität gegen elektromagnetische Störungen sind darüber hinaus faseroptische Verfahren der TE-Detektion in Erprobung. Im vorliegenden Beitrag werden zwei Typen akustisch-faseroptischer Sensoren (a-FOS) vorgestellt und auf ihre Eignung untersucht, Teilentladungen in elastomeren Isolierkörpern, wie etwa Silikon-Feldsteuerelementen von Kabelgarnituren, zu detektieren. Die hier präsentierten Laborergebnisse zeigen, dass die zur Detektion von TE mit kritischer Intensität (z.B. in Kabelgarnituren) notwendige Empfindlichkeit erreicht werden kann. Darauf basierend wird das Potential der faseroptisch-akustischen Detektion von TE in der hochspannungstechnischen Zustandsüberwachung allein und in Kombination mit fasergekoppelten fluoreszenzoptischen Sensoren diskutiert.
Fibre-optic acoustic detection of damage processes in elastomeric insulation under AC and DC stress
(2013)
New sensors for the detection of partial discharges (PDs) in high-voltage (HV) cable accessories are being de-veloped consisting of a fluorescent polymer optical fiber (F-POF) as sensing element. Depending on the fiber material F-POFs can be attached to and even integrated into the translucent silicone rubber insulation of HV cable terminations. As the embedment into the insulation material plays an important role, the sensor should not weaken the dielectric strength of the insulation material and should not be the origin of PD incidents. A sensor consisting of a commercial F-POF has been tested in the high-voltage lab regarding its PD detection ability un-der AC in comparison to a conventional electrical sensor. New silicone rubber F-POF (Si-F-POF) fiber models functionalized with coumarin dyes have been produced. The optical properties of these dye functionalized silox-anes are presented. These potential sensor fibers are highly flexible and might be embeddable at medium to high-voltage level. An additional way to further improve the level of PD light detection is to modify the translucent type of silicone rubber used in HV cable accessories in terms of optical transparency. In this context we present our first results of the optical and mechanical properties of new elastomeric transparent silicone materials specif-ically designed for the application as HV insulation materials in stress cones.
Partial discharge in elastomeric high voltage insulations is a major reason for device failure. The special challenges of the high voltage environment limit the use of conventional acoustic emission sensors. Fibre-optic sensors can cope with these challenges thanks to their optical sensing principle and the use of all-dielectric materials. In this contribution, improvements to a previously introduced design of ultrasonic fibre-optic acoustic partial discharge sensors for elastomeric insulations are presented. The improved performance of fibre-optic acoustic sensors in detecting AC partial discharge is demonstrated. Furthermore, their ability to detect low-level damage processes in elastomeric insulation under DC dielectric stress is shown to outperform the highly sensitive electrical detection method.
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.