| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem in a multiple direct earth system, where sometimes ground fault protection can not be surely practiced and a ground overcurrent relay 30N has to be artificially locked. SOLUTION: There are provided CTs 101 attached to respective phases on a transmission end of a high voltage distribution line, overcurrent relays 30 connected to the CTs, distribution transformers 50 attached to respective phases of the respective sections of the high voltage distribution line, CTs 51 connected respectively to the secondary sides of the distribution transformers 50, current converters 52 connected to the respective CTs 51, and a current comparator 90 which receives the respective phase currents of the transmission end of the high voltage distribution line, makes the vector sum of the respective phase currents to generate a zero-phase current S, receives the respective phase currents of the load end of the high voltage distribution line, makes the vector sum of the respective phase currents to generate a zero-phase current R, compares the levels of the zero-phase currents S and R with each other, and, if the level of the zero-phase current S is larger, makes a ground protective relay operate. With such a constitution, it can be decided whether a zero-phase current applied to a neutral line is caused by the unbalance of a load or not. COPYRIGHT: (C)2003,JPO
|
