VERIFICATION OF DC GROUND FAULT DETECTOR FOR THE SIGNAL EQUIPMENT ROOM

The feeder circuit protection system of the DC substation is protected by the DC overcurrent device, DC fault selective relay and ground fault overvoltage relay. The DC overcurrent device detects an accident when a current exceeds the set value, and the feeder fault selective relay detects a sudden change in the current during the fluctuation time. In addition, the ground fault overvoltage relay detects an accident when the potential between the rail and the ground of the substation mesh earth exceeds the set value and continues for a certain period of time. However, high-resistance ground faults flow only several hundred amperes. Therefore, the high-resistance ground faults cannot be detected by the DC overcurrent device and feeder fault selection relay installed in the substation. In addition, the rail potential is too small to be detected by ground fault overvoltage relay. If the high resistance ground fault continues, the signal equipment will burn out and transport disorder will occur. There was no way to protect the signal equipment room from high-resistance ground faults. Therefore, we have developed a DC ground fault detector with the aim of protecting the signal equipment room from high-resistance ground faults and preventing defect in transport. This time, a field test was conducted to determine the protection set value of the DC ground fault detector and evaluate the weather resistance. In conclusion, it was confirmed that the developed DC ground fault detector for the signal equipment room was no malfunction. Also, considering that the operating voltage of the signal protector operates at 470V DC ± 20%, the major fault setting value was set to 350V DC so that the ground fault current can be cut off due to a serious fault before the protector operates.