CONCLUSION

In order to solve the problem of false operation of 64D protection device after a ground fault occurs in the power supply track of low and medium speed magnetic levitation, this paper proposes a protection method for the traction power supply system of low and medium speed magnetic levitation transportation based on the fault traveling wave characteristics. The difference between the positive and negative currents of the double-ended stations is used to determine the fault zone and constitute a protection action with the supply station. And on this basis, the double-ended station fault voltage travelling wave frequency distribution is analysed and the fault distance is calculated. The following conclusions can be drawn from theoretical analysis and simulation verification:
The use of the station’s positive and negative current difference to locate the fault zone allows the fault point to be accurately located, avoiding the problem of large area outages caused by protection malfunctions.
The frequency of the travelling wave of a fault at a double-ended station is not affected by the impedance within the station, but is only related to the location of the fault point and the time of arrival of the travelling wave at both ends of the line.
The double-ended frequency difference ratio is used to calculate the fault distance, independent of the fault point location, transition resistance and noise interference, and the distance measurement error is always kept within a controllable range of 20m, with strong robustness.
The method proposed in this paper is not only applicable to low and medium speed magnetic levitation traffic power supply rail grounding faults, but also to short circuit faults caused by lightning surge voltage penetrating the air gap of the power supply rail. It is also of reference significance for fault location in urban rail transport such as high-speed magnetic levitation, metro and light rail.

Acknowledgments

Financial support from the Beijing Natural Science Foundation (L201018) are here acknowledged.

References