電力機器における絶縁材料技術の横断的評価

Abstract

The prospective impact of this paper lies in its contribution to the development of electrical insulating material technology, based on physical mechanisms that dominate discharge phenomena and electrical insulation performance, and the rationalization of insulation design for power equipment by understanding the current limits of size reduction and increased stress. In addition, technological guidelines on decision-making for life extension and refurbishment of future high-voltage power equipment with various kinds of insulating materials are expected to be developed. Concretely, the following contents are described. Common and divergent points on insulation techniques from material and equipment viewpoints were clarified. Especially, internal stresses of insulating materials for power equipment were compared, where the ratio of ac testing stress to operating stress can be used as an index to show the long-term deterioration or the complexity of insulation structure. The relationship between insulating material and electric charge behavior was investigated and systematically interpreted by introducing a new index. When the charge density was analyzed by the surface resistivity of solid insulators, comparative evaluation of insulation characteristics in different power equipment was possible. The relationship between the deterioration processes of the insulating material and insulation design of power equipment was investigated. Factors and evaluation parameters that will determine the life of equipment were analyzed. Then the differences were attributed to the basic insulation structure. The relationship between harmful partial discharge levels and kind of insulating material was discussed. Cross-equipment comparison was made in terms of preferable sensitivity, present possible sensitivity, decision criteria and the level determined by standard. The concept on insulation design stress for different insulating materials and power equipment was systematically summarized, taking into account various factors that appear explicitly in the procedure of determining the design stress, such as statistical data deviation, long-term deterioration, design margin and so on. And cross-equipment comparison was made from the view point of how severe design to carry out. Then the future prospects of the insulation design were discussed.