Studies on structural integrity for separate-cooling/sheet-winding gas-insulated transformer

Research leading to the development of a separate-cooling sheet-winding gas-insulated transformer is described. Basic models and full-scale models were used to conduct tests on the structural strength of the transformer, and the structural integrity of a 300 MVA transformer was investigated. The sheet winding is shown to have excellent characteristics with respect to the electromagnetic forces occurring in it. The thrust force generated in the sheet winding is much lower than in conventional wire winding. The cooling panel is strong enough to withstand the coolant pressure rise under a short-circuit condition. It is also that the actual transformer has no possibility of resonance, because the natural frequency in it is higher than the vibration frequency that occurs in transit or during an earthquake. The structural integrity of the transformer is ensured by the fact that the sheet winding is supported at both its top and its bottom