METHOD OF DETECTING PRESENCE OR ABSENCE OF GROUND FAULTS BY UTILIZING IED

摘要

PROBLEM TO BE SOLVED: To provide a method of determining ground faults in a power system with ease by utilizing an IED protection relay.SOLUTION: In a ground fault determination logic shown in Fig. 4, at a step 1, values of a ground fault voltage Vand a ground fault current Ig of a power transmission line are inputted to a calculation part of a ground fault direction protection relay. The value of the ground fault voltage Vis compared with a threshold of 28.5 V, and the value of the ground fault current Ig is compared with a threshold of 200 mA (at a step 2). When those values are equal to or more than the thresholds, vector values of the respective values are calculated (at a step 3). Whether or not the vector value of the ground fault current Ig is more than a phase angle 1 (225 degrees) is determined (at a step 4), and whether or not the vector value is more than a phase angle 2 (45 degrees) is determined (at a step 5). Next, a relay characteristic diagram for a vector diagram of the ground fault voltage Vand the ground fault current Ig is produced, and when Ig is the maximum sensitivity angle of 45 degrees to V, it is determined that there are ground faults (at a step 6 and a step 7).