Micro-analysis of water-tree in XLPE by synchrotron radiation

X-ray micro-analysis of insulating material for XLPE cable was investigated to elucidate the influence of ion to water-tree extension. We analyzed the water-trees by applying a fluorescence scanning x-ray microscope at the beam-line BL16XU in SPring-8. Focused x-ray beam sizes at sample position are about 1μm at 9∼10keV. Then we confirmed the diffusion of the ion in water-tree. The ion diffused toward the electric field. Then the situation of the diffusion of the ion from metal particle was different entirely from the case of electrolyte. And X-ray diffraction was measured by adjusting the beam size to 100×100μm. The diffraction peak of the water-tree region was broadcloth in comparison with a normal region. It was confirmed that the crystal is disordered and that the degree of crystallinity of the BTT region is decreased. It was guessed that the ionized materials in under water were diffused widely by electrophoresis and that the diffusion of the ions promotes the growth of the water-tree.