Research On The Calibration Of The Anti-short Circuit Ability In Power Transformers

The power transformer is the important device to ensure the safe and reliable operationof the power grid. In recent years, the weakness of the anti-short circuit ability has becomethe leading cause of the transformer accident. To reduce the damage of the power systemcaused by the transformer short-circuit accident, transformer accident must be preventedand reduced. So it is imperative to check and improve the transformers’ anti-short circuitability.Considering the influence of system impedance, this paper used the impedancenetwork to calculate the short-circuit current when the three-phase symmetric and singlephase short-circuit faults happen. Based on Matlab simulation software, the simulationmodel of short-circuit current calculation is built to get the three-phase and single phaseshort-circuit current waveforms.Besides, based on the Ansys simulation software, two dimension axisymmetric modeland three dimension model of the transformer were built to calculate the leakage magneticfield inside the transformer. Besides the two dimension axisymmetric models includedsimple winding model, the line disc model and the actual ampere-turn partition model. Inthe simulation, the saturation effect of the transformer iron coin steel sheet was considered.Compared the simulation results of different models, it turned out that the two dimensionaxisymmetric simulation model based on the ampere-turn partition of every transformerwinding was relatively simple and relatively effective model to simulate the transformers’leakage magnetic field.At the end, according to the calculation of the leakage magnetic field result, calculatedthe axial and radial short-circuit forces on each line disc of both the double windingtransformer and three phase three column transformer with three windings, and calculatedthe stress of conductor. Also the transformers’ dynamic stability critical strength werecalculated. Also the transformers’ themal ability to withstand short-circuit was considered.Made comprehensive judgments for the anti-short circuit ability of the transformers fromtwo aspects which were the dynamic stability and the thermal stability. At the end, according to the calibration process, some relevant measures were put forward to enhancethe anti-short circuit ability of the transformers.