A coating was made by electrostatic spraying of epoxy resin / TiO2 particles for the purpose of suppressing audible noise caused by corona discharge on high-voltage transmission lines. Wetting property of the coating was improved by oxygen plasma treatment. It was found that the coating became more wettable as the increase of TiO2 content during electrostatic spraying process. With respect to the coating for suppression of audible noise from transmission lines, the optimal mass ratio of TiO2 particles (diameter:5-10μm ) to epoxy resin was 30%, and the contact angle was 73°on the epoxy / TiO2 coating surface which could be reduced to less than 5°after oxygen plasma treatment for 20s.

UHVDC transmission could deliver high-power electricity over long distances effectively, while the DC stray current led to corrosion of grounding device and the surrounding buried metal during the operation inevitably. This paper reviewed the research progress of HVDC corrosion at home and abroad in recent years. It elaborated corrosion research direction of HVDC system from three aspects, which were pole, grounding grid and the neighboring tower grounding body buried pipeline respectively. Describing the anti-corrosion measures on grounding devices and buried pipeline, and explaining the advantages and defects of various anti-corrosion technology. At last, we proposed that it was necessary to expand the research in UHVDC field, grasp the erosion rule of DC stray current in soil comprehensively to enhance the security of UHVDC transmission system of national grid.

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This paper attempts to develop a variable sampling plan based on the lifetime performance index CL for exponentially distributed products.Practitioners can use the proposed sampling plan to determine the required sample size and the corresponding critical acceptance value,to make reliable decisions in product acceptance.We also tabulate the required sample size and the corresponding critical acceptance value for various producers risk and the consumers risk.

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