Submarine equipment and fault locating method for a submarine communication system

Submarine equipment for a submarine cable communication system, which is inserted in a submarine cable connecting a plurality of cable landing stations, and is supplied with operating currents from the cable landing stations through a feed line of the submarine cable, said submarine equipment comprising:

• a main processing circuit for transmitting communication signals through the submarine cable;
• a power unit for supplying operating power to said main processing circuit;
• a rectifier circuit, connected in series to the feed line, for providing one-way current to said power unit by taking out the operating current from the feed line, regardless of a direction in which the operating current from the cable landing stations is fed;
• and
• a charging/discharging resistor connected in parallel to said rectifier circuit at the input thereof.

Submarine equipment for a submarine cable communication system, which is inserted in a submarine cable connecting a plurality of cable landing stations, and is supplied with operating currents from the cable landing stations through a feed line of the submarine cable, said submarine equipment comprising:

• a main processing circuit for transmitting communication signals through the submarine cable;
• a power unit, connected in series to the feed line, for receiving the operating current from the feed line and for supplying power to said main processing circuit;
• a first nonlinear device, connected in series to said power unit, for preventing a surge current from flowing in a direction opposite to said direction of operating currents;
• a second nonlinear device, connected in parallel to a circuit composed of said first nonlinear device and said power unit connected in series, for bypassing the surge current therethrough;
• and
• a charging/discharging resistor connected in parallel to said second nonlinear device.

A fault locating method for a submarine cable communication system, in which a plurality of cable landing stations are connected to each other by submarine cables with a plurality of submarine equipment inserted in the cable and the submarine equipment is fed with electric power from said landing station via a feed line included in the submarine cable carrying communication signals, said fault locating method comprising the steps of:

• charging an equivalent-capacitor formed between the feed line extending from the landing station to the fault point and sea-water ground, through a charging route consisting of the feed line and charging/discharging resistors each connected in parallel to a nonlinear resistance device of the submarine equipment until the equivalent-capacitor is charged up to a predetermined voltage;
• discharging the charge reversely from the equivalent-capacitor to the landing station through the charging route;
• measuring the capacitance of the equivalent-capacitor;
• and
• locating the fault point of the cable based on the capacitance measured, by using the known capacitance measuring method.