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