The Development Of A Line-to-Ground Fault Detection System For A DC Feeding System On A Support Pole
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This paper presents the overview of a Line-to-Ground Fault Detection System of a DC feeding system on a support pole and some test results of the detection function. Sometimes, the voltage of lightning strikes can create closed circuits around insulators, and a DC feeding system is grounded if the supports of the overhead lines are made of steel. Existing protection systems on substations cannot detect the accident because they cannot distinguish between the current of train loads and the current of ground faults. Therefore the current of the ground fault makes an arc around the insulators of the overhead lines. The arc heats the overhead lines and they may be broken by tension. The breakage may occur within 3.1 seconds and there is no conclusive method to prevent the accident. Therefore, we developed a new system to prevent this kind of accident. A detection device having a wireless communication device for transmitting detected information is installed in each support pole. When the detection device senses the ground fault, the information is transmitted by multihop communication through some devices on support poles, and devices on substation open circuit breakers to terminate the ground fault. To detect the ground faults, Giant Magnetoresistance (GMR) sensors were selected. The test results confirmed that the sensors had enough performance against strong magnetic fields produced by the impulse current of lightning strikes. And the test results also confirmed that the sensors could detect 300A of the line-to-ground fault current on the support pole. Keywords: line-to-ground fault, DC feeding system, magnetic field sensors, GMR.
line-to-ground fault, DC feeding system, magnetic field sensors,GMR.