JPS6236417B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fault section search method when power supply is cut off or a similar fault occurs in a communication transmission system that performs DC series power supply.

FIG. 1 illustrates a general analog coaxial transmission system. In the figure, 1 is a constant current source for power supply,
2 is a transmission line, 31 to 3n', 31' to 3n' are repeaters, 4 is a power separation filter (hereinafter referred to as PSF (Power separation filter)) that separates DC and signals,
5 is a constant voltage diode for supplying a constant voltage to the repeater. Devices for signal relay other than transmission lines, such as repeaters, PSFs, and constant voltage diodes in this example, are called relay devices. Reference numeral 6 denotes a feed turn transformer that transmits only signals and constitutes a loop for direct current. Currently, there are various types of transmission systems, but if you focus only on the power supply circuit, this is basically the type, even if there are some modifications.

Now, in the system shown in Figure 1, if there is some kind of failure, for example, one of the transmission lines 2 is disconnected due to construction work, the power supply from the constant current source 1 is stopped and all repeaters become inoperable. Put it away. As a result, all signals from the repeater are stopped, making it completely impossible to determine the faulty section from the repeater signal. To solve this problem, conventional fault section search methods have been developed, including one that measures the capacitance of the fault section and another that uses a pulse echo tester through the line circuit, but the former requires accurate capacitance measurement. Regarding the latter, it is important to note that line faults exhibiting sufficient insulation resistance to
A transmission system in which the cutoff frequency of the power separator is low has the drawback that the pulses are severely rounded and accuracy cannot be improved.

SUMMARY OF THE INVENTION In view of the above drawbacks, it is an object of the present invention to provide a fault section search method that accurately determines a fault section in a simple and inexpensive manner.

The fault section search method of the present invention is directed to the relay device on the transmitting side of a communication transmission system in which DC series power is supplied via a transmission line to a plurality of relay devices provided with power separators on the input side and output side of the repeater. is constructed by inserting in series a current detection means for detecting a feeding current and turning off a switch element into a feeding system line between the power separator and the repeater on the output side, and the switching element and A series circuit with a resistor is connected between the power supply side of the current detection means and a power supply line on the input side of the repeater of the relay device in the opposite direction, and the power supply is forcibly restarted in the event of a power supply interruption failure. The system is characterized in that it is possible to determine a faulty section by returning the direct current at a repeater immediately before the faulty section.

FIG. 2 shows an embodiment of the present invention, in which relays 71 to 7m operated by the power supply current are connected to the power supply circuit of each repeater on the transmission side (rightward) transmission line in FIG.
and the contacts 81 to 8m and resistance 91 of this relay
This is simply an addition of a circuit that connects the power source side of the relay to the repeater power supply circuit of the receiving side (left-bound) transmission line via a cable length of ~9 m. However, contact 8
1 to 8m is OFF due to relay operation. In addition, the values of the relay current and resistance shall be selected to be appropriate values so that the relay operates even if there is only one relay section (that is, two relays for transmission and reception) after it (on the right side).

In such a configuration, first consider power supply in a normal case. Initially, each relay contact is ON, so when considering the start of power supply, the power supply current is divided into each resistor 91 to 9m, but the relay through which the largest current flows during the transient period when power supply starts is the one at the forefront, i.e. This is relay 71. Therefore, relay 71 operates first, and therefore contact 81 is turned OFF. Next, the relay of the next repeater operates, and in this way, the relays operate one after another until finally all contacts are turned OFF, and power is supplied in the same way as in Fig. 1.

Next, consider failures such as power outages. Generally, when the power supply system is cut off or short-circuited, the constant current source for power supply (1 in FIG. 1) stops power supply to protect the equipment. The fault is now at the repeater 3m.
Let's say it happens after. At this time, if the maintenance personnel discovers that the power supply has been interrupted, they try to forcibly supply power from the constant current power supply. At least up to the repeater 3m-1, the relay operates and power is supplied through the above-described operation. However, with a 3m repeater, no current flows through the relay. Therefore, relay 7m does not operate, and the power supply current remains looped back through resistor 9m. Therefore, if the maintenance person measures the power supply voltage, the voltage V should be V=2m(V _rep +IR)+Ir. However, m is the number of relay sections from the power supply station to this side of the faulty section, I is the supply current, R is the line resistance of one section (one side), and r is the resistance 9
is the resistance value of m. Therefore, the number m of relay sections up to the fault section can be determined from this voltage V. Further, in this state, the repeater is operating normally, so in a system in which the repeater has a supervisory signal oscillator, a normal section can be immediately determined by simply monitoring this signal on the receiving side of the transmission line. That is, it can be seen that the faulty section is one section after the normal section.

Furthermore, when considering a transient period when a fault such as a power cut occurs, a step-like voltage and current is generated from the fault point and propagates left and right. If we pay attention to this step-shaped current, it propagates while the high frequency component is absorbed by the power splitter of each repeater, that is, the rising edge is blunted. That is, the steepest current change is applied to the relay closest to the fault point. Therefore, if the operating time constant of the relay is carefully selected, in the event of a power failure, it is possible to automatically loop before the point of failure. If the power supply voltage at this time is converted into sections and automatically displayed, it is possible to automatically determine the disconnection section.

As described above, according to the present invention, it is possible to determine a disconnection section with a relatively simple configuration, which is extremely useful for streamlining transmission line maintenance, early detection of failure points, and improvement of services through repair. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a general coaxial transmission system, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1... Constant current source for power supply, 2... Transmission line, 31
~3m, 31'~3m'...Repeater, 4...Power separator, 5...Voltage diode, 6...Power loop transformer, 71~7m...Relay, 81~
8m...Relay contact, 91~9m...Resistance.

Claims (1)

[Claims] 1. The relay device on the transmitting side of a communication transmission system that supplies DC series power via a transmission line to a plurality of relay devices provided with power separators on the input side and output side of the repeater A current detecting means for detecting the power supply current and turning off the switch element is inserted in series in the power supply line between the switch and the repeater, and the series circuit of the switch element and the resistor is connected to the current It is connected between the power supply side of the detection means and the power supply system path on the input side of the repeater of the repeater in the opposite direction, and the repeater immediately before the faulty section is connected to the power supply system line on the input side of the repeater of the repeater in the opposite direction, and forcibly restarts the power supply in the event of a power cutoff failure. A fault section search method is characterized in that it is possible to determine a fault section by turning back the DC at.