JPS6236416B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for locating a point of failure when power supply is cut off or a similar failure occurs in a communication transmission system that performs DC series power supply.

FIG. 1 shows an example of the Anarod 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, and 4
is a power separator (hereinafter referred to as
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, although there may be some variations.

Now, in the system shown in Figure 1, if there is some kind of disconnection, for example, one of the transmission lines 2 is disconnected due to construction, etc., the power supply from the constant current source 11 etc. is stopped and all intermediate power supply operations are stopped. Stop. Therefore, since no information is obtained through the relay device, it is not possible to determine not only the location of the failure but also the disconnection between which relay devices.

In order to solve these problems, various methods for determining fault sections have been proposed.
Both methods only determine the faulty section and cannot determine the fault location. Conventionally, in order to determine the fault location, the fault section is first determined, the faulty transmission line 2 is cut off at a repeater installation station (hereinafter referred to as a relay station) adjacent to the fault location, and the pulse echo is transmitted from there. A method is used in which the fault location is located using a tester. However, since the introduction of solid-state electronic repeaters, the reliability of repeaters has improved dramatically, and relay stations are not only unmanned, but are also often installed underground (inside manholes) due to their transmission characteristics. It's summery. These relay stations are often located on main roads, and attempting to enter a manhole to locate a fault point is often impossible during the day due to the need for traffic regulations, and therefore it takes time to locate the fault. This has the disadvantage that the recovery of the transmission line function is delayed, which in turn affects the quality of the communication service.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to simply,
The object of the present invention is to provide a fault point locating method that immediately locates a fault point from a power supply station without having to go to an underground relay station or the like.

The failure point locating method of the present invention is a communication transmission system in which the relay device on the transmitting side supplies DC series power via a transmission line to a plurality of relay devices each having a power separator on the input side and the output side of the relay device. It is constructed by inserting in series a current detection means for detecting a power supply current and disconnecting it from the first and second switch elements in a power supply system path between the power separator and the repeater on the output side, A series circuit of the first switch element and a resistor is connected between the connection point of the current detection means and the repeater and a power supply line on the input side of the repeater of the repeater in the opposite direction, and A signal input side of the repeater on the transmitting side is coupled to the transmitter via a switch element, and a pulse echo from the repeater adjacent to the fault point to the fault point is observed via the power-supplied repeater. It is characterized by making it possible to locate the point of failure.

FIG. 2 representatively shows a relay device in an embodiment of the present invention, and a relay 7m (m= 1, 2, . As long as the section adjacent to the repeater is normal, relay 7m will operate due to the power supply current, opening contact 8m and making it appear equivalent to Figure 1, but in addition, the output side of repeater 3m and A hybrid coil H is inserted at the intermediate point between PSF4 and between the input side of repeater 3m' and PSF4, and furthermore, this hybrid coil H is connected to the balanced wiring network BNW.
And one terminal is terminated. Further, one terminal of each of the hybrid coils H on the side of repeaters 3m and 3m' is connected by a contact 10m which is opened by the operation of a relay 7m. However, contacts 8m and 10m are OFF due to relay operation. In addition, the value of the current and resistance of the relay is such that even if there is one relay section after it (on the right side) (i.e., there are two
An appropriate value shall be selected so that the relay will operate even if there is only a repeater).

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 9m resistor, but the relay through which the largest current flows during the transient period of power supply start is the one at the forefront, that is, 71. be. Therefore, relay 71 operates first, and therefore contact 81 is turned OFF. Next, the relay 82 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 repeater 3 (m-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. In other words, because a disconnection fault has occurred, repeater 3 is automatically or manually disconnected.
The power supply becomes a loop at m, 3m'. In this state, the maintenance person connects the pulse sending section of the pulse echo tester to the input of the transmitting amplifier at the cable or sending end from the location where the power feeding device is located, and connects the receiving section of the pulse echo tester to the output of the receiving amplifier. . The output pulse waveform of the pulse echo tester is selected so that it passes through the relay transmission line normally, taking into account the section length of the relay transmission line to be measured, the repeater interval, the upper and lower frequency limits of the repeater, the repeater overload point, etc. It shall be.

If pulses are sent to the transmitting side of the relay transmission line in this way, they will be relayed one after another at each repeater, and finally reach the repeater 3m immediately before the faulty section.
reaches the output side of. However, as mentioned above, the output side of repeater 3m and the input side of repeater 3m' are connected through the hybrid coil and contact 10m (in other repeaters, contact 10i is connected).
(absolutely not). The hybrid coil on the output side of repeater 3m has an infinite amount of attenuation between the output of repeater 3m and the input of repeater 3m' in an ideal balanced state. It is assumed that the balance of the transmission line is unbalanced, and that there is leakage equivalent to the attenuation of the transmission line in one repeater section. If this amount of attenuation is NdB, the output pulse of repeater 3m receives N+3dB of attenuation, reaches the input of repeater 3m', is interrupted in the receiving transmission line, and returns to the receiving point of the pulse echo tester. . However, 3dB is the loss of the hybrid coil on the 3m' side of the repeater.

On the other hand, the pulse output from the 3m repeater has a loss of 3dB to the downstream transmission line.
It propagates to the railway line side. However, since the line is disconnected, the pulse propagated through the line is reflected with a reflection coefficient of approximately 1, but the loss of the hybrid coil for the reflected wave is only 3 dB, and the loss at the contact point 1 is only 3 dB.
The reflected pulse is transmitted via 0m towards repeater 3m'. In this way, one pulse is eventually received after a certain time T from the time when the pulse was sent out from the pulse echo tester, and then a short time △
Another pulse will be received after t. If this situation is drawn on a cathode ray tube, an image like that shown in Figure 3 will be obtained. From this image, T, △t
By finding , it is possible to find the position of the repeater immediately before the point of failure and the position from this position of the repeater to the point of failure. The method for determining this is well known, so it will be omitted here, but in an echo pulse tester, the time from the trigger input to the start of the sweep is made variable, and the image is moved to an arbitrary location by manipulating the delay time. By replacing time with distance, distance can now be directly connected. In FIG. 3, the leftmost pulse is the sending pulse, the middle pulse is the return pulse at the repeater, and the rightmost pulse is the reflected pulse on the line. The undershoot in the middle and rightmost pulses is due to the direct current cut, but there is no particular problem. The reason why the height of the middle pulse, that is, the folded pulse at the repeater, and the rightmost pulse, that is, the reflected pulse at the fault point, is different is that even if the reflection coefficient at the fault point is 1, the height is different from the middle point between the next repeater and the next repeater. This is an example of what happened because the failure point is a little far away and the amount of attenuation in the round trip to the failure point is greater than the amount of attenuation N of the folded pulse described above.

As described above, according to the present invention, fault positions can be easily and accurately located, which greatly contributes to maintenance and service.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a general coaxial cable transmission system, Fig. 2 is a circuit diagram showing an embodiment of the present invention,
FIG. 3 is a waveform diagram showing an example of an image obtained by the pulse echo tester in FIG. 2. 1... Constant current power supply for power supply, 2... Transmission line, 3
1, 31', 32, 32', 3n, 3n', 3m3
m'...Repeater, 4...PSF, 5...Voltage diode, 71,7m...Relay, 81,8m,1
0m...Contact that is disconnected due to relay operation, H...
...Hybrid coil, BNW...Balanced wiring network,
T: Pulse round trip propagation time from the test station to the relay station immediately before the fault section, Δt: Pulse round trip propagation time from the relay station immediately before the fault section to the fault point.

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 a power supply current and turning off the first and second switch elements is inserted in series in a power supply line between the switch and the repeater, and the first switch element and the second switch element are connected to each other. A series circuit with a resistor is connected between the connection point of the current detection means and the repeater and a feed line on the input side of the repeater of the repeater in the opposite direction, and the current is transmitted via the second switch element. The signal output side of the repeater on the side and the signal input side of the repeater on the receiving side are connected, and the pulse echo from the repeater adjacent to the failure point to the failure point is transmitted through the relay device that is supplied with power. A fault point locating method is characterized in that the fault point can be located by observing the fault point.