Calculation Method for Harmonic Impedance of Traction Substation Grounding Grid

Due to the high harmonic content in the traction return current, it is inappropriate to calculate the rail potential and other parameters by grounding impendence of traction substation under power frequency, and it is necessary to take harmonic grounding impendence into consideration. The effect of the harmonic grounding return current on the grounding grid is studied, and a calculation method for the harmonic impedance of the traction substation grounding grid is proposed based on the combination of field measurement and simulation. In the method, an equivalent model of grounding grid is established by software SIMULINK and the model parameters are calculated on the basis of the power frequency grounding impendence. It is found that harmonic current not only affects grounding impedance, but also leads to the increase of the surface potential, and the potential distribution is not uniform. The proposed method is verified by the comparison with software CDEGS.