Temporal Fluctuated Features of Metro Traction Load Current in DC Railway

24-hour traction current based on Wuhan Metro Line 6 are reported. The fluctuation features, which corresponding to the interval of vehicle operation, indicate that there are four types of inrush current periodically appearing throughout the all-day waveforms. The first type consists of two positive sharp waves. The second type is saddle shaped, and consists of two positive peaks and an anti-peak. The third type consists of two double peaks followed by a sharp peak about 1 minute later. The fourth type consists of two hump shaped waveforms. The whole operation time can be divided into the peak and off-peak hours according to these repetitive segments. The interval of any two adjacent vehicles is 9 minutes and 11 minutes, respectively, in peak and off-peak hours. The distribution and the positive average value of feeder current per hour from 6:00-24:00 are counted and analyzed. Results show that the current distribution in off-peak hours is more concentrated in a narrower range than that in peak hours. The differences in averages between various 15-minute periods in an hour can be as high as tens of amperes, due to the occurrence time of repetitive segments. The rail potential has relatively consistent variation with feeder currents, but it matched best with the sum of up-line and down-line in a same section instead of one of the two lines.