The Application of Bushing Tap Method in the Transformer Winding Deformation Test

Abstract

Electric power industry standard DL/T911-2004 Frequency Response Analysis Method of Power Transformer Winding Deformation, it is definition of winding deformation: Under the action of mechanical force or electric force, the power transformer windings axial or radial size changes, usually it characterized by winding locally twisted, bulgin or shift characteristics. Under short-circuit current shocked or suffered a collision during transport transformer could happen for the winding deformation phenomenon, it will directly affect the safe operation of the transformer. The main cause of transformer winding deformation (1) Short-circuit fault current shock Power transformer in the operation process, will inevitably suffer from all kinds of short-circuit fault current shock, especially the short-circuit fault in the transformer exports or the area near ,the huge short-circuit current shock will make transformer winding be subjected to the huge electric force(it is dozens of times to hundreds of times for the normal operation), and make the winding temperature rapidly. At higher temperatures, the mechanical strength of the wire becomes small,electric power is more easily to make the winding damage or deformation. (2) In the transport, installation or cover lifting by the accidental collision In the process of the transport, installation or cover lifting, power transformer may be subject to collision accident, bumps and vibrations, etc., Lead to the winding deformation. (3) The winding withstand ability of short-circuit is not enough When the winding appears short-circuit, due to it not withstands short-circuit current shock force and it occurs deformation. In recent years, for the country's 110 kV and above power transformer accident statistical analysis shows that because of the winding withstand ability of short-circuit is not enough has become the most important internal reason for the power transformer accident, seriously affect the safe and reliable operation of the power transformer[1-3]. The dangers of winding deformation The winding deformation is a great hidden danger for the safe operation of the power transformer. Many sets of transformer's actual test experience has shown that after winding deformation, the insulation test and the oil test are difficult to find, so the performance is the latent fault. According to the evaluation of the twelfth session of CIGRE committee, many insulation fault of the transformer winding are caused by the initial mechanical damage of insulation. When transformer suffer in the short-circuit fault current shock and the winding product local deformation, even if not immediately damage, may also have left serious hidden danger. The research background of the bushing taps method The research of the bushing tap method and the application project in transformer winding