Research And Engineering Application Of Traction Transformer Differential Protection Algorithm Based On Time Domain Signal Characteristics

Traction transformer is one of the important electrical equipment in the traction power supply system,and its running state plays a very important role in the safe and stable operation of the entire traction power supply system.As the main protection of the traction transformer,the differential protection has many problems in identifying the inrush current.Therefore,it is very important to propose a new algorithm for the differential protection of the traction transformer.First of all,this thesis expounds the structural characteristics and working principles of traction transformers with different wiring forms,and introduces the existing differential protection of traction transformers.At the same time,the generation mechanism of the magnetizing inrush current of the traction transformer and the existing identification methods of the magnetizing inrush current are explained.Secondly,aiming at the limitation of the existing second harmonic blocking principle,this thesis proposes a traction transformer differential protection algorithm based on fractal correlation dimension.The algorithm identifies the inrush current and the short-circuit fault current through the difference in the eigenvalues of the correlation dimension in different operating conditions of the transformer.According to the equivalent circuit and electrical parameters of the traction transformer and line,the simulation parameters of each power element are calculated and configured into the simulation model of each functional module;the V/X-type traction transformer and the simulation model based on the fractal protection algorithm are built.After uploading it to the real-time digital simulation platform RT-plus,the system model is compiled,and simulation experiments under different working conditions are carried out to verify the correctness of the algorithm.Finally,the transformer differential protection based on fractal algorithm is applied to the KF6536 protection device,RT-plus is connected to the protection device through the power amplifier to form a closed-loop system,and a large number of closed-loop experiments are carried out.The experimental results show that the transformer differential protection scheme based on fractal algorithm is The fault current and inrush current that cannot be distinguished by the second harmonic principle can be identified,the sensitivity and accuracy of the differential protection are improved,and the effectiveness of the protection algorithm is further verified.