PURPOSE: To reduce a case of necessity of a loop point changeover switch by previously calculating a loop cross current flowing when a loop is closed at a plurality of loop points before a loop service is started at each normally open point zone switch installing point, and selectively closing the loop point in which the loop current may be minimum.
CONSTITUTION: Cross detection sensors LIS1, LIS2 capable of calculating a cross current value at the time of loop service from a voltage difference of a power distribution system before a loop service is started at a power distribution line and a current value flowing when a cross current calculating impedance is connected to a loop point are installed in parallel at each normally open point zone switches LS1, LS2, calculated results of the respective points are transmitted to a service branch, the point in which the loop cross current becomes minimum is selected at the branch, and a closure command is applied to the switches LS1, LS2 at the branch. Thus, since the loop service can be started with the minimum cross current point, an opportunity of requiring the loop changeover switch can be reduced.
ISAHAYA KEIJI
MAEDA KOJI
TSUKAMOTO JUNICHIRO
KANEDA AKIRA
