The Study On The On-line Diagnosis Of Transformer Winding Status With The Method Of Mechanical Vibration

Transformers are the most important equipments in the electrical system. Its operational stability has enormous effect on the electrical system security. With the increase of the electrical network capacity, short-circuit capacity increases gradually. Electromagnetic force, which is generated by impulse current caused by outlet short-circuit of transformers, poses a threat to mechanical strength and dynamic stability of transformer windings. This may lead to the deformation and loosening of transformer windings, which are accidents potential of electrical network's operation.At present, the major monitoring methods of windings status include frequency response method and short-circuit impedance method. Both methods use electric measuring method. The basic principle is that electrical parameters vary with deformation of transformer windings. These methods suits for the obviously deformed transformer windings. However, they fail under the condition that the electrical parameters have no obvious change, especially when the decrease of axial pressing force leads to the loosening of windings. This can be shown from the following test results. The method of mechanical vibration tells whether the transformer winding runs well or not by analyzing the vibration signals which are collected with accelerometers adsorbing on the body of the transformer. The paper uses the method of mechanical vibration for the online monitoring of transformer windings. The method can diagnose the winding loosening and deformation by monitoring its vibration character under the shock of short-circuit.The online test is made at the quality supervision test center in Hushitai, Shenyang. The paper analyzes the test data with the method of mechanical vibration. These conclusions are compared with the results of inspecting the tested transformer by lifting the core. Compared to the electrical test method, the mechanical vibration method has greater measurement sensitivity, which can show the status change of transformer windings well.