Study On Numerical Simulation Analysis Method Of Turn To Turn Insulation Fault In Power Transformer

Transformer is one of the principal equipment of power system, while the incidence of inter-turn insulation failure of transformer is relatively high which is able to damage the power system severely. If the types of faults and positions of the spoiled points can be judged accurately before the transformer’s overhaul, it will reduce the workload of maintenance personnel and the waste of manpower and material resources. Transformer is a highly nonlinear model combining the primary and secondary coil by the magnetic field. As the mechanism of the turn-to-turn insulation fault is complex, incomplete and inaccurate understanding of transformer’s internal fault has restricted the development of diagnosis of transformer’s fault. Based on the complexity of the interior of transformer, this paper studies the numerical simulations of the inter-turn insulation failure in the transformer, and particularly analyses the faulty transformer’s internal magnetic field and electrical quantity of ending winding, in order to provide theoretical proof for diagnosing and locating faults of transformer’s windings.A finite element model in the normal and faulted condition of the transformer is established by ANSYS, in order to calculate and analyze internal magnetic field of the faulty transformer. This paper put forward a method to calculate transformer internal magnetic field based on the finite element model, and it calculate the distribution of magnetic field of transformer while the different degrees of inter-turn insulation failure occurring in different windings positions. The author analyzes the relationship among transformer faulty types, degrees, positions and transformer internal magnetic flux leakages based on the simulation results of the magnetic field. The results demonstrate that the more short-circuit turns, the more the magnetic flux leakages are, the closer points of failure to the winding middle, and the more obvious changes of the magnetic field distribution is. These results provide a reference to diagnose and locate insulation faults of transformer’s windings.In order to further study the inter-turn insulation failure characteristics of the transformer and explore the electrical feature parameters that representing the degree of fault, this paper establishes inter-turn short circuit fault simulation model based on the feature parameters of transformer. Finally the electrical feature parameters are obtained by the analysis the change rule of the electric parameters before and after fault. The author establishes model of faulty transformer by Simulink of MATLAB, research the electric parameters of windings when short-circuit turns and locations changed, and analyses the harmonic of faulty voltage and current at the transformer winding end. The simulation results show that the voltage amplitude will have significantly lower and greatly increase the total harmonic distortion when the failure occurring, which provide theoretical basis for the on-line diagnosis of the turn-to-turn short circuit of transformer.