Analysis on harmonic current and its impact on track circuit in high speed railway

The Traction current harmonics caused by rolling stock or EMU are main interference source on signaling system, especially on track circuits in high speed railway. Obviously, it is essential to estimate the potential value of each harmonic current within the signal frequency band for the reliable operation of track circuit. In Europe, EN 50238 and CLC/TC 50238, using FFT to calculate harmonic components, were established to control the harmonics from rolling stock. At first, considering that traditional FFT is applicable for steady current due to result accuracy of the frequency and amplitude, the transient interference processing method is discussed based on principle of Wavelet transform modulus maximum for the singularity detection. Then, since the measured current data in the field are usually not the maximal value, based on the least square fitting method, the regularity of harmonic proportion is studied and evaluated after interpolating windowed FFT in harmonic frequency analysis. Finally, adopting the test data of Chinese CRH-X type EMU in operation, the transient current and the steady current data are analyzed to get harmonic components. It is proved that the compatibility between the rolling stock and the track circuits can be achieved under present condition.