Influences of blocking hollow strands and cooling structure change on insulating property for water cooled turbo-generators

The local high temperature of the strand insulation caused by the blocking failure in water cooled turbo-generator will cause the inter-turn short circuit, which will increase the severity of the faults. In this paper, the conjugate heat transfer model of 1000 MW supercritical turbo-generator was established. The heat transfer coefficient of the stator core surface cooling by hydrogen was obtained using finite volume method. The temperature change laws of the strand insulation with blocking hollow strands was investigated. The relationship of strand insulation temperature and blocking strand numbers and locations was studied. The study finds that the strand insulation temperature is effect observably by the distance of blocking strand when two strands were blocked simultaneously. The influences of a new stator cooling structure on the strand insulation temperature were studied. Adapting the new structure, the highest temperature of the strand insulation can be reduce 44.3°C when the hollow strands were blocked. The research for the influence of the blocking degree on strands insulation performance provide theory basis, which is helpful for preventing strand insulation short caused by high temperature in strand insulation.