| 摘要 |
PROBLEM TO BE SOLVED: To simply detect a ground fault by detecting a current flowing through a grounding wire by a through type current transformer disposed in the grounding wire where a metal shield layer of a secondary power cable of a main transformer of a specified kV distributing transformation equipment is grounded at only one side to determine the occurrence of a ground fault in the secondary power cable. SOLUTION: When a ground fault occurs in a secondary power cable 2 of a main transformer 1 of 6.6 kV distributing transformation equipment, a charging current by ground electrostatic capacity Co of distributing wire 6 flows toward a ground fault point in the cable 2 to return as a current Igco from a metal shield layer 4 of the cable 2 through an earth wire 3 from the ground. Furthermore, it returns as a current Igr limited by a tertiary limit resistor of GPT through a grounding wire of a grounding transformer GPT also to a bus bar part 5. Then, a charging current Ici in the cable 2 returns to the shield layer 4 via the ground fault point. The ground fault current at the ground fault point is expressed by Ig=Igco+Igr+Ici. The current Ici will not flow through the ground fault wire 3 to become a detected failure current Ics=Igco+Igr at a through current type transformer CS.
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