PURPOSE: To detect faulty section in short time by measuring the impedance of a plurality of slave stations connected in parallel with an aerial wire.

CONSTITUTION: Upon occurrence of fault on a distribution line 3, impedance in the fault detection/transmission circuit of slave stations 6-1-6-n is connected in parallel with coupling transformers 15-1-15-n, and faulty section can be detected by measuring the impedance to be connected upon occurrence of fault through a faulty section detector. A faulty section detector 14 provides a predetermined signal between an aerial wire 9 and the ground through a signal generator 14-1 and a resistor 14-2, then the voltage and current of the signal are measured through a voltmeter 14-3 and an ammeter 14-4 and employed for calculation of impedance connected in parallel. By such arrangement, the number of slave stations 6-1-6-n where the fault occurring point exists at the source side or the load side is calculated and employed for detection of fault occurring section.