| Cable joint is the weak link of the power cable,and the insulation fault on it can easily cause the breakdown,burnout or even explosion.The detection of partial discharge can effectively detect the latent failure of the cable joint insulation.Extrinsic fiber Fabry-Perot interferometry(EFPI)has been used to detect the acoustic signal of liquid insulation,but its acoustic coupling efficiency and response sensitivity are still unclear.In order to analyze the distribution characteristics of local sound field in the cable intermediate joint,a liquid medium was added to the conductor core of the model and the outer shield of the cable intermediate joint,and the distribution law of local acoustic field on the solid surface of the joint was calculated.The arrangement method of EFPI sensor on the joint was proposed,and the response sensitivity of different frequencies and ambient temperature sensors at different local-discharge locations was simulated and analyzed,and the scheme of EFPI sensor effectively coupling acoustic signals in the solid structure of the joint to improve the detection sensitivity was obtained.Based on the acoustic impedance matching method of material to reduce the attenuation of low noise propagation,a solid acoustic detection structure with high modulus medium coupled with acoustic waves entering the oil cavity of EFPI sensor is designed.Solid discharge acoustic insulation testing experiment platform has been built,using EFPI sensor and sensor of piezoelectric ceramic(PZT)sensor at the same time within the crosslinking polyethylene insulation on partial discharge acoustic testing,analysis of EFPI respectively by copper medium and the detection sensitivity of crosslinked polyethylene medium,test results show that high modulus of metal is more advantageous to joint sound waves is put inside bureau,EFPI sensor can be used to effectively detect the local sound signal in the cable joint XLPE,and the sensitivity of EFPI sensor is obviously higher than that of PZT sensor. |
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