Contribution of inrush current to mechanical failure of power transformers windings

Abstract

This work presents a study regarding the contribution of inrush current to the occurrence of mechanical fatigue in windings of a power transformer and, consequently, the impact of that phenomenon on the equipment's lifetime. In order to perform the study, electromagnetic transient simulations were used to determine the inrush current in a three-phase transformer model. Then, three-dimensional simulations, based on the finite element method, were performed to determine the electromechanical stresses in the equipment windings, under the effect of the inrush current. Next, the methods of critical plans and Palmgren-Miner were applied to perform the fatigue study. From the results, the impact of inrush current on the integrity of the transformer's windings was determined, as well as, to estimate the reduction of lifespan of the equipment due to inrush occurrence. The number of inrushes needed for the total reduction of lifespan of the equipment due to mechanical fatigue was also determined. The results can be used in the transformers design stage, with the purpose of assisting the evaluation of mechanical withstand of equipment, which can minimise the possibility of failure and increase its lifespan.

Power frequency magnetic field interference suppression method for online frequency response analysis of power transformers

“…When the transformer is subjected to a short-circuit current, its windings may be deformed because they cannot withstand the resulting electromagnetic force. A minor winding deformation can gradually develop into a large deformation after experiencing multiple instances of large currents [3], and deformed windings are significantly mechanically weaker than normal windings. Trans-Yangchun Cheng and Xiangdong Liu contributed equally to this work.…”

Inrush Current Reduction Strategy for a Three-Phase Dy Transformer Based on Pre-Magnetization of the Columns and Controlled Switching

“…The transformer inrush transient is not only dangerous because of its large current amplitude but also due to its rapid rise rate [2,3]. When a transformer is frequently exposed to transients, it will deteriorate due to severe mechanical and thermal stresses and may eventually fail [4][5][6]. The high inrush current may disturb or damage the operation of adjacent equipment in the circuit resulting in, e.g., the maloperations of power electronic converters [7,8] and protection relays [9].…”

Novel power distribution short‐circuit testing technique based on supercapacitor and modular multi‐ports AC/DC conversion

“…When the transformer suffers from a short-circuit fault, a strong short-circuit electromagnetic force is produced due to the mutual effect of huge short-circuit current and the leakage magnetic field. This can lead to defects such as displacements, shift of laminations, or deformation of windings, connections or supporting structures, which seriously affects the safe and stable operation of the power system [5][6][7]. In 2010, EDF conducted short-circuit tests on eight amorphous alloy distribution transformers with capacities of 250, 400, and 630 kVA.…”