The directional and differential ground fault protective relaying scheme in ungrounded DC traction power supply system and the current limiting device for the ground fault current detection

摘要

The present invention relates to a ground fault protection relays for electric railways, especially in the DC power supply system of the non-grounded approach for the ground current is detected for the operation of the ground fault protection relay grounded to the negative bus of the rectifier through a resistor and a current limiting means. The characteristics of the current limiting means for normal operation and limit the leakage current exhibits a high resistance characteristic to a reference value or less is necessary to flow a ground current of sufficient size to detect the ground fault resistance characteristic exhibits a very small accident. ; In the present invention determines the presence or absence of the ground fault current is performed the values detected by the substation as compared with the reference current value, the judgment of the ground segment of the left and right direction relative to the substation comparing the sum of the currents flowing through the power supply line and return line to each other and to provide a ground fault sensing direction differential ground fault protection is performed by the ground fault detection signal whether or not relay system and method that are transmitted from the neighboring substations.