Analysis of the 220kV line distance protection´s measuring impedance when V/X traction transformer is in short circuit

Both of the traction transformers in the Shanghai-Nanjing intercity railway and Beijing-Shanghai high-speed railway connect two single-phase traction transformers as V/X wiring to form a complete traction transformer. One is operating, and the other one stand-by for it. First, the thesis analyzes the low-voltage side short current of V/V wiring traction transformer, and then calculates the measuring impedance of the interphase and grounding impedance components of 220kV distance protection which is in power supply side substation. Furthermore, it analyzes the measuring impedance of the interphase and grounding impedance components in V/X wiring traction transformer when its low-voltage side is in short circuit. The conclusion has been tested to be correct by simulation experiments. All of the analyses and experiments indicate that 220kV line distance protection´s minimum measuring impedance in power supply side substation is much smaller than the minimum measuring impedance of regular transformer in grid when the short circuit takes place in the low-voltage side of traction transformer. So it should be paid attention to set protection values to avoid setting mistakes. This conclusion is also suitable for the V/X wiring traction transformers which use 110kV and 220kV including the above voltage grade railway power supply network. In conclusion, the thesis puts forward some important opinions which should be paid attention to setting 220kV line distance protection. Type the abstract using Times New Romar font with point size 9. The abstract is an essential part of the paper. Use short, direct, and complete sentences. It should be as brief as possible and concise. It should be complete, self-explanatory, and not require reference to the paper itself. The abstract should be informative giving the scope and emphasize the main conclusions, results, or significance of the work described. Do not use the first person; do not include mathematical expressions; do not refer t- the reference, and try to avoid acronyms.