DC excitation of transformers due to geomagnetically induced currents was studied by model experiments. First, differences in the DC excitation phenomenon due to the iron core structure were studied ...using three typical small-scale models. The results verified that single-phase three-legged cores were most susceptible and three-phase three-legged cores least susceptible to such excitation effects. Secondly, the local heating due to DC excitation was quantitatively assessed using large-scale core form and shell form models with the most susceptible single-phase three-legged cores. The results demonstrated that the maximum temperature rise was approximately 110/spl deg/C due to the GIC (200 A/3 phases).< >
Properties of aged oil impregnated paper power capacitor Oshi, T.; Tsukao, S.; Ishii, T. ...
Proceedings of the 7th International Conference on Properties and Applications of Dielectric Materials (Cat. No.03CH37417),
2003, Letnik:
1
Conference Proceeding
The oil impregnated paper capacitor had been produced until 1982, and most capacitors are operated still. Because the operated years pass 20 years or more, and the troubles occurred in some operated ...capacitors, the research of the deterioration mechanism and development of diagnosing method for the operated capacitor have been continued. In this paper, the chemical composition of the insulating oil and its chemical deterioration under the high electrical field are investigated, and the accelerated life test is carried out by using the miniature capacitor in order to verify the deterioration mechanism. As the result, it is verified that the wax (deterioration product) is generated from the insulating oil by the high electrical field at the edge of electrodes, and the electrical properties of the capacitor are deteriorated by the wax. In addition the breakdown occurred in the damaged part at the insulating paper. These results lead to construct the flow diagram of the deterioration and breakdown process of the oil impregnated paper capacitor.
The authors report on an optical current transformer (CT) based on the principle of the Faraday effect. The information measured by the optical CT is transmitted to the ground side through optical ...fibers contained in an insulator. An application of the optical CT, a new fault location system, is described.< >
In 1989, a 154 kV, 200 MVA gas-insulated power transformer was commissioned and has been operated with a satisfactory operating record. Utilizing this development experience and introducing new ...technology, a 275 kV, 300 MVA gas-insulated power transformer has been developed. The compact design of the main-gap insulation is important, and its reliability has been verified. The turn-to-turn insulation, which is made of PET film insulation has also been verified under severely stressed test conditions. The design of the 300 MVA gas-insulated transformer is described.< >
Analysis of gases dissolved in insulating oil offers the most important and efficient diagnostic method to detect the faults in oil-filled transformers. We carried out a survey of decomposed products ...from various kind of solid-materials through simplified model tests and current using model tests. The gas chromatography-mass spectrometer and the purge/trap gas extraction equipment are employed to condense and analyze very small decomposed products. As a result, we found out effective decomposed products for diagnosis. This paper describes the new technique for diagnosis based on the decomposed products utilizing the condensing analysis with a view to early detection and location of abnormal part in oil-filled transformers.
Shed materials for hollow composite insulator (silicone rubbers, EVA and EPDM) were examined by accelerated weathering tests and their weathering resistances were evaluated from changes of surface ...and bulk properties. For silicone rubber, changes in the content of low molecular weight silicone (silicone oil) related to the maintenance of water repellency were investigated. The results showed that silicone rubbers had excellent weathering resistance and keep high water repellency during long term weathering tests. (4 pages)
To meet the demands of increasing electrical power supply, substations must be constructed underground in urban areas. For underground substation equipment, oilless equipment is preferable and ...therefore a gas-insulated power transformer was developed. The separate-cooling/sheet-winding design concept is employed. In 1989, a 154 kV-200 MVA gas-insulated power transformer was commissioned and has been operated with satisfactory operating records. Utilizing this development experience and introducing new technology, a 275 kV-300 MVA gas-insulated power transformer has been developed. The compact design of the main-gap insulation is very important and its reliability has been verified. The turn-to-turn insulation, which is made of PET film insulation, has also been verified under severely-stressed test conditions. The design of the 300 MVA gas-insulated transformer is described.< >
