DIRECTIONNAL AND DIFFERENTIAL GROUND FAULT PROTECTIVE RELAY SYSTEM FOR UNGROUNDED DC TRACTION POWER FEED SYSTEM AND GROUND FAULT PROTECTIVE RELAY APPARATUS FOR DETECTING GROUND FAULT CURRENT

摘要

The present invention relates to a ground fault protective relay apparatus for an electric railroad. In the ground fault protective relay apparatus, the negative bus of a rectifier is grounded through a resistor and a current limiting device to detect a ground fault current for operating the ground fault protective relay apparatus in an ungrounded Direct Current (DC) traction power feed system. The current limiting device exhibits a high resistance characteristic during normal operation, thus limiting the leakage current to a reference value or less, whereas the current limiting device exhibits a low resistance characteristic at the time of occurrence of a ground fault, thus allowing a ground fault current, whose amount is sufficient to allow a ground fault to be detected, to flow.