应用激光扫描法测置XLPE电缆绝缘中杂质颗粒的研究

Sizing and Counting of Contaminant Particles in HV XLPE Cable Using Laser Scanning

本文作者们研制了一激光扫描测量系统,可对较大体积XLPE 电缆绝缘中杂质颗粒进行非切片的快速测量。由实验获得等效杂质颗粒直径与信号脉冲的关系;电子线路采用独特的量化方法;为区分黑色颗粒和半透明颗粒,应用了光学空间频率滤波技术。对比实验表明,新方法与传统方法测得的结果吻合较好,测量结果有较好的重复性。

Inspection of contaminant particles in high voltage crosslinkedpolyethylene(HV XLPE)cable insulation with a large sampling volume cangain a good statistical reliability of the inspection.This paper describes thedevelopment of an automatic laser scanner for this purpose.A large volume sample of XLPE cable insulation which have been paticula-rly treated was immersed in silicon oil in a transparent glass cell and heateduntil it became transparent.A thin laser beam passed through the sample wi-th high speed scanning.When laser beam impinges on a particle,there willbe a negative inpulse in the signal.Quantizing the impulse sequence,thechecked particles are divided into three size level to be counted and recorded.Sizing of the particles is based on light obscuration principle and the rela-tion between the signal and the particle size was obtained experimentally.Anunique quantizer was developed to quantize high speed impulse train.The pa-per also disscused the method for the distinguish of the black paticles andsemi-transparent one(amber).The method is based on the Fourier Optics.After analyzing the light amplitute distribution on the second focal plane ofreceiving lens,a spatial frequency filter was used on this plane.The ambercaused a positive impulse instead of negative one in the signal this time.An experiment was carried out on a 33.6cm^3 sample cut from 66kV XLPEcable made by sheng yang cable works.Geometry of the sample was detailedin the paper.silicon oil also acted as index-matching oil.After the test wi-th new device,the sample was cut into many thin slices and inspected withmicroscope.The experiment indicated that the results of two method inspec-tion agreed well with good reproducibility.