Study On Harmonics And Negative Sequence Caused By Electric Railway And The Corresponding Effects On Differential Transformer Protection

With the rapid development of electrified railways, the adverse effects on the public power grid brought by traction power-supply system have been increasingly taken into account by railway and utility company. The inrush characteristics of the electrified railways as well the corresponding harmonic and negative current will cause many adverse effects on transformer differential protection device. Detail researches are taken for this device and the main works of the paper are as follows:In order to analyze the influence of harmonics and negative sequence to protection device, a model based on Tianjin regional grid parameters have been established in PSCAD/EMTDC, which contains electric locomotive, typical electrified railways traction system and transformer differential protection device.The sympathetic inrush occurring in the system transformer with no-load electric locomotive startup or no-load closing of traction transformer is studied. The different sympathetic inrush situations with electric locomotive startup in different switching angle are analyzed, and the potentially influence to properties of transformer differential protection are studied.The RTDS experiments for the transformer differential protection based on second-order harmonics restrained principle are carried out to analyze the influence on transformer differential protection device by electric locomotive harmonics and negative sequence. Some useful conclusions are obtained with the experiments.