JPH09233004A - Feeding path changeover circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a feeding path to other cables on the occurrence of a fault in a cable. SOLUTION: An optical cable TRUNK (BRANCH1, BRANCH2) is connected respectively to a terminal A, (B, C). A relay K1 is activated by supplying a negative current to the circuit from the BRANCH1 while the BRANCH2 is kept open and the TRUNK connects to ground. Thus, the BRANCH2 is disconnected from the circuit and connects to ground. Then a positive current is supplied from the TRUNK to feed power to both ends of optical cables connected to the TRUNK and the BRANCH1. Then a relay K3 is active by supplying a negative current to the circuit from the BRANCH2 while the TRUNK is kept open and the BRANCH1 connects to ground to disconnect the TRUNK and to connect the BRANCH1 and BRANCH2 to ground at a ground E2. Thus, power is fed to each line from one side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply path switching circuit for switching a power supply path to a repeater or a branching device provided on a transmission line in a long distance optical transmission system such as an optical submarine cable transmission system.

[0002]

2. Description of the Related Art The optical submarine cable system enables large-capacity long-distance digital transmission due to the low loss property and wide band property of optical fibers. Since it can accommodate a plurality of optical fibers, it can be branched in the sea in units of optical fiber pairs to connect a plurality of grounds. Therefore, regardless of the point-to-point configuration, a multi-point configuration connecting three or more landing stations can be realized. An example of the configuration of such an optical submarine cable system is shown in FIG.

In FIG. 5, T1 to T6 are terminal stations (landing stations) installed on land, and 1 to 5 are landing stations T1 to T6.
It is an optical submarine cable that connects between the two. C1 to C13 are optical repeaters inserted in the optical submarine cables 1 to 5 at intervals of, for example, several tens of km, and BU1 to BU4 are signals transmitted to one optical submarine cable in the sea. It is a branching unit (BU: Branching Unit). As shown, in this example, the landing station T1
The main optical submarine cable 1 is installed between the optical submarine cable 1 and the T4, and the branching device BU inserted in the optical submarine cable 1
1 to BU4 to other landing stations T2, T3, T5 and T
The optical submarine cables 2 to 5 are branched to 6 respectively. With such a configuration, transmission between landing stations is possible.

Each of the optical repeaters C1 to C13 and the branching units BU1 of the optical submarine cable system configured as described above.
BU4 must be supplied with power from the power feeding devices of the landing stations T1 to T6. This power supply is performed using the copper tube of optical submarine cable and tensile strength piano wire,
There are two types of power feeding methods, a single-end feeding method in which power is fed from only one terminal station feeding apparatus and a both-end feeding method in which power is fed from two terminal station feeding apparatuses. In the case of roads, the both-end feeding method is usually adopted.

The broken line in FIG. 5 shows an example of such a power feeding path. In this example, landing stations T1 and T
The optical repeaters C1, C2, C4, C6, C9, C10 provided in the main optical submarine cable 1 connecting
C13 and the branching units BU1 to BU4 are fed by a double-end feeding method in which the landing station T1 side has a positive polarity (+) and the landing station T4 side has a negative polarity (−). In addition, the optical submarine cable 2 is grounded to seawater through an electrode provided on the casing of the branching device BU1, and a negative (-) power supply voltage is applied from the landing station T2, whereby the optical submarine cable is The optical repeater C3 inserted in 2 is fed by one end by the landing station T2. Similarly, the optical submarine cable 3 between the branching device BU2 and the landing station T3, the branching device BU3 and the landing station T5.
The optical submarine cable 4 between the landing stations and the optical submarine cable 5 between the branching device BU4 and the landing station T6 are also fed at one end by each landing station. The grounding in seawater with the polarity as described above is to prevent the electrode itself from being decomposed and corroded by the electrolytic reaction.

In the optical submarine cable system configured as described above, if a failure occurs in a part of the optical submarine cables, another optical submarine cable is used to secure a communication path, and each branch device BU Is provided with a power supply path switching circuit for switching the power supply path. Since the branching device BU is installed on the seabed or the like, this power feeding path switching circuit is realized by a highly reliable element such as a vacuum relay that operates by a power feeding current.

FIG. 6 shows an example of such a power feeding path switching circuit. In this figure, A, B and C are terminals to which an optical cable is connected, and the cable is a terminal station via an optical repeater. It is connected to the power supply device. Further, E is a ground terminal connected to seawater as described above. K1 and K2 are relays for high voltage such as a vacuum relay, and k1 and k2 are contacts of the relay K1 and the relay K2, respectively. It should be noted that each contact of the relay is connected to the "1" side in the initial state, and is switched to the "2" side by the operation of the relay.

When the system is started up using such a power supply path switching circuit, first, the terminal station connected to the terminal A side is grounded and the terminal station connected to the terminal C side is left open. . In addition, a negative feed voltage is applied from a terminal connected to the terminal B side. Then, by gradually increasing the power supply voltage, a current flows in the relay K1 in proportion to the power supply voltage, and when this current becomes equal to or more than the moving current of the relay K1, the contact k1 is switched to the “2” side. And terminal C
Is grounded to seawater via terminal E. Next, a positive power supply voltage is supplied from the terminal station connected to the terminal A side. Therefore, the cable connected to the terminal A and the cable connected to the terminal B are fed at both ends from the terminal station connected to the terminal A and the terminal station connected to the terminal B. Further, in this state, by applying a negative power supply voltage from the terminal connected to the terminal C, a power supply current flows from the ground to the terminal C side via the terminal E and the relay contact k1 and is connected to the terminal C. The cable provided is supplied to one end of the cable by the terminal station connected to the terminal C.

When the terminal A side is first grounded and the terminal C side is negative and the power supply voltage is increased, the relay K2
Is operated and its contact k2 changes from "1" side in the figure to "2"
Then, the terminal B is connected to the terminal E and grounded. Therefore, it is possible to have both-end power feeding from the terminal A side and the terminal C side and one-end power feeding from the ground to the terminal B side. In this way, the power feeding method can be controlled depending on how the voltage is supplied at the time of start-up.

In the state of both-end power feeding from the terminal A side and the terminal B side and one-end power feeding from the ground through the terminal E to the terminal C side as described above, the terminal B side is provided. It is assumed that the optical submarine cable connected to the power supply fails and the power supply current stops flowing. At this time, relay K
1, the power supply current stops flowing, and the contact k1 of the relay K1
Returns to the "1" side, and one end of the relay K2 and the terminal C are connected. As a result, a current flows from the terminal A side to the terminal C side, and the relay K2 operates to enter the both-end power supply state in which power is supplied from the terminal A side and the terminal C side. At this time, the terminal B is grounded via the terminal E.

Further, as described above, in the state of both-end power feeding from the terminal A side and the terminal C side, and one-end power feeding from the ground through the terminal E to the terminal B side, the terminal C is fed.
Even when a failure occurs in the optical submarine cable connected to the side, the power feeding path is switched in the same manner as above.

In such a power feeding path switching circuit of FIG. 6, both-end power feeding from the terminal A side and the terminal B side,
In the state of single-end power feeding from the terminal E side to the terminal C side, the potentials near the terminals C, E and the contact k1 are almost zero.
Although it is [V], the potentials near the terminals A and B and the relay K2 are potentials other than 0 [V]. Therefore, when the power supply current stops flowing due to a failure on the terminal A side or the terminal B side, the contact k1 of the relay K1 returns to the "1" side, but at this time, arc discharge occurs at the contact k1. Contact failure may occur. Therefore, there is also proposed a power supply path switching circuit that prevents such switching in the high voltage application state (Japanese Patent Laid-Open No. 63-18902).
No. 5).

[0013]

According to the conventional feed line switching circuit shown in FIG. 6, when the optical submarine cable connected to the terminal B fails, and when the optical submarine cable connected to the terminal C is used. When a failure occurs, the power supply path can be switched to ensure communication between other optical submarine cables, but power cannot be supplied between the terminal B side and the terminal C side, and the terminal cannot be supplied. When a failure occurs in the cable connected to the A side, it is impossible to connect the terminals B and C even if switching is performed.

Therefore, the present invention provides a method for supplying power to any of the three cables connected to the branching unit BU so that a failure occurs in one cable. Another object is to provide a power supply path switching circuit capable of securing a power supply path for the other two cables.

[0015]

In order to achieve the above object, a power feeding path switching circuit of the present invention has first, second and third terminals respectively connected to a power feeding path and respective anodes. First and second zener diodes connected to the first terminal, a cathode of the first zener diode and the second terminal, and the first zener diode to the second zener diode connected to the second terminal. Connected between the first relay that operates only by the current flowing in the direction of the terminal and the cathode of the second Zener diode and the third terminal, and from the second Zener diode to the third terminal. A second relay that operates only by a current flowing in the direction of, and a third relay that is connected between the second terminal and the third terminal and has a lower sensitivity than other relays. A self-holding type fourth relay connected between the second terminal and ground by the operation of the second relay; and a third terminal and ground by the operation of the first relay. Fifth self-holding type connected between
And the third terminal is disconnected from the circuit by the operation of the first relay and connected to the fifth relay, and the second terminal is connected by the operation of the second relay to the circuit. Connected to the fourth relay, the first terminal is disconnected from the circuit and grounded by the operation of the third relay, and the second terminal is grounded, and the fourth relay Is a circuit for disconnecting the second terminal from the circuit, and a circuit for operating the fifth relay to disconnect the third terminal from the circuit.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

A. First Embodiment FIG. 1 shows a first embodiment of the power feeding path switching circuit of the present invention. In this figure, A, B, and C are terminals of this power supply path switching circuit, and the optical submarine cables are connected to these terminals, respectively, as described above. Here, the optical cable connected to the terminal A is called TRUNK, the optical cable connected to the terminal B is called BRANCH1, and the optical cable connected to the terminal C is called BRANCH2. K
Reference numerals 1 to K5 are first to fifth relays including vacuum relays and the like, and k1, k2, k3-1, k3-2, k4-1,
k4-2, k5-1 and k5-2 are contacts of the relays K1 to K5, respectively. Each contact of these relays is in a state as shown in the figure in an initial state where no current is flowing. As shown in the figure, the reason that all paths are connected in the initial state is to enable an insulation test or the like.

Further, D1 to D7 are Zener diode groups, and as shown in the figure, D1 and D3 are Zener diode groups in which four Zener diodes are connected in series, and D2, D4, D6 and D7 are three Zener diode groups. Zener diode group in which Zener diodes are connected in series, D5
Is a Zener diode group in which 8 Zener diodes are connected in series, 4 each in the reverse direction,
R1 and R2 are resistors. Further, E1 to E4 are ground terminals connected to seawater via the casing of the power feeding path switching circuit as described above. The number of elements forming each Zener diode group varies depending on the operating voltage of the relay and the Zener voltage.

Here, the Zener diode groups D2 and D4 are connected in parallel to the relays K1 and K2, respectively, because both ends of the relays K1 and K2 when a current flows from the terminal A side to the terminal B or C side. This is to limit the voltage applied to the relay and to prevent the relay from operating due to the current in the opposite direction.
The Zener diode groups D6 and D7 are connected in parallel to the relays K4 and K5, respectively, because the relays K4 (K5) are connected to both ends of the relay K4 (K5) when a current flows from the ground terminal E3 (E4) to the terminal B (C). The applied voltage is limited and the terminal B (C) to the ground terminal E3 (E4)
This is to prevent the relay K4 (K5) from operating when a current flows through it.

Further, the Zener diode group D5 connected in series in the direction of different polarities is connected in parallel to the series circuit of the relay K3 and the resistor R2 when the current of the relay K3 flows in any direction. However, it is for the purpose of making it work, and for limiting the voltage applied to both ends thereof. Furthermore, the resistor R2 is connected to the relay K3.
Are connected in series in order to divide the voltage determined by the Zener diode group D5 and divide the voltage applied to the relay K3. Also, relay K
The resistor R1 is connected in parallel to the series circuit of the resistor 3 and the resistor R2 in order to divert the current flowing through the relay K3 and reduce the sensitivity of the relay.

As an example of the resistance values of the resistors R1 and R2, assuming that the resistance value of the winding of each relay is RL, R1 = 3RL (1) R2 = (1/2) RL (( 2) can be set. In this case, relay K3 and resistor R2
The combined resistance of the circuit consisting of the series circuit and the resistance R1 connected in parallel with the series circuit has a value equal to the winding resistance RL of the relay.

The zener voltage per zener diode element is Vz, and the voltage and current at which each relay operates are Vc and Ic, respectively. It is assumed that the following relationship holds between the Zener voltage Vz and the operating voltage Vc of the relay. 2Vz <Vc <3Vz (3) When the relay K3 operates, the contact k3-1 needs to be disconnected from the circuit before the contact k3-2 is connected to the ground terminal E2. Note that this is a normal operation in a relay having two circuit contacts.

A-1. Start-up procedure during normal operation When starting up the system using the power supply path switching circuit configured in this way, each terminal station cooperates to apply the power supply voltage, and various power supply methods are used to connect the optical cable. Power can be supplied to the optical repeater group and the branching device itself which are inserted therein. An example of the starting method will be described below.

A-1.1. TRUNK-BRANCH1
When the TRUNK on the energizing terminal A side and the BRANCH1 on the terminal B side are fed at both ends and the BRANCH2 on the terminal C side is fed at one end, first, at the terminal station connected to the terminal C, the terminal C (BRANCH2) is opened. , The terminal A (TRUNK) is grounded at the terminal station connected to the terminal A. Then, a negative voltage is gradually applied from the terminal station connected to the terminal B (BRANCH1). As a result, from the grounded terminal A (TRUNK) side to the terminal B (BR
ANCH1) side, a current path passing through a Zener diode group D1, a parallel circuit of a relay K1 and a Zener diode group D2, a Zener diode group D3, a parallel circuit of a relay K2 and a Zener diode group D4, a relay K3 and a resistor R.
2, the current starts to flow through the resistor R1 and the current path passing through the parallel circuit of the Zener diode group D5. At this time, since the parallel circuit of the relay K2 and the Zener diode group D4 and the parallel circuit of the relay K3 and the resistor R2, the resistor R1 and the Zener diode group D5 are connected in series, the current flowing in the path passing therethrough is The current is smaller than the current flowing through the relay K1. Therefore, the relay K1 operates first, and its contact k1 is switched to the "2" side. As a result, the BRANC connected to the terminal C
H2 is separated from this circuit, and the terminal E is also connected via the parallel circuit of the Zener diode group D7 and the relay K5.
4 is grounded.

Next, a positive voltage is supplied from the terminal station connected to the terminal A (TRUNK). Also, a negative voltage is supplied from the terminal connected to the terminal C. As a result, the terminal E4
Current flows from the relay K5 to the terminal C (BRANCH2) through the parallel circuit of the relay K5 and the Zener diode group D7, the relay K5 operates, and the contact k5-1 causes the BRANCH
2 from other branches (TRUNK and BRANCH1)
While being heavily separated, the contact k5-2 causes the relay K5 to be in a self-holding state. From the above, the terminal A (T
RUNK) side and the terminal B (BRANCH1) side, the state of both-end power feeding and the terminal C (BRANCH)
It is in the state of single-end power feeding on the 2) side.

A-1.2. TRUNK-BRANCH2
Energization Contrary to the above, TRUNK of terminal A and BRAN of terminal C
When CH2 and the BRANCH1 of the terminal B are fed at both ends and the one end is fed, the above-mentioned TRUNK-BRANCH is used.
In the case of one-energization, by reversing the terminal B (BRANCH1) and the terminal C (BRANCH2), the state of both-end power feeding from both the terminal A (TRUNK) side and the terminal C (BRANCH2) side , Terminal B (BR
It can be in a state of single-end power feeding on the ANCH1) side.

A-1.3. BRANCH1, BRANC
H2 energization First, terminal A (TRUNK) is opened and terminal B is
(BRANCH1) is grounded. And terminal C
A forward current (negative current) is applied from (BRANCH2). As a result, the terminal B, the contact k2, and the contact k4-
1, a parallel circuit of a relay K3 and a resistor R2, a resistor R1 and a Zener diode group D5, a contact k5-1, a contact k1,
The current path passing through the terminal C, the terminal B, the contact k2, the contact k4-1, the parallel circuit of the relay K1 and the Zener diode group D2, the Zener diode group D1, the Zener diode group D3, the relay K2 and the Zener diode group D4. A current starts to flow through two current paths of the parallel circuit, the contact k5-1, the contact k1, and the current path passing through the terminal C. here,
Since, for example, the Zener diode group D1 is inserted in the current path passing through the parallel circuit of the relay K1 and the Zener diode group D2 and the parallel circuit of the relay K2 and the Zener diode group D4, almost no current flows. Therefore, the relay K3 operates, the contact k3-1 is first switched, and TRUNK is disconnected, and the contact k3-
2 causes BRANCH1 and BRANCH2 to be grounded at terminal E2. Therefore, a current flows through the BRANCH2 through the ground E2, the contact k3-2, the relay K3 and the resistor R2, the resistor R1, and the parallel circuit of the Zener diode group D5, the contact k5-1, the contact k1, and the terminal C.
That is, BRANCH2 is supplied with one end.

Next, a forward current (negative current) is applied from BRANCH1. This current is applied to the contacts k2 and k4-1.
And k3-2 to the ground terminal E2. Therefore, the BRANCH1 is also fed with one end.
In this state, even if a positive current flows from the TRUNK side, the current flows to the ground terminal E1 through the contact k3-1,
There is no change in the above conditions.

A-2. Procedure for restarting after a failure If a failure occurs on the line, each terminal station can restart the system and restart the system by avoiding the failed optical cable. For example, in a system that is normally supplied with power as shown in FIG. 5, when a failure occurs at any part of the optical cable, the power supply path is changed to avoid the path where the failure has occurred and to restart the system. Can be launched. It should be noted that there are various kinds of obstacles such as an open obstacle in which the cable is cut and current cannot flow and a shunt obstacle in which the cable is grounded to seawater.

A-2.1. Rebooting at the time of failure of BRANCH Assuming that a failure occurs in BRANCH2, the restarting operation is analyzed. Note that when a failure occurs in BRANCH1, it can be handled in the same way. In Figure 2, B
An equivalent circuit when a failure occurs in RANCH2 is shown.
First, it is assumed that each terminal station (relay station) uses a current source to supply power to the corresponding cable. In the state shown in the figure, since a failure has occurred in BRANCH2, TR
A current source CC _T of the terminal station on the UNK side and a current source CC ₁ of the terminal station on the BRANCH 1 side are used. A diode is inserted in parallel with each current source as shown in the figure.

Further, the impedance between the terminal C of BRANCH2 and the ground is Z ₂ , TRUNK and the current source CC _T.
The impedance of the cable between Z _T and BRANC
The impedance of the cable between H1 and the current source CC ₁ is Z ₁ . Then, it is assumed that Z _T and Z ₁ are impedances sufficiently larger than Z ₂ . If this assumption does not hold, the current I ₁ flowing through the relay K1 increases and the current flowing through the other relays decreases, so that the restart is easier.

In such a state, the magnitude of the current flowing from the current source CC _T on the TRUNK side is I _T , BRA
The magnitude of the current flowing through the current source CC ₁ on the NCH1 side is I _B1 , and the magnitude of the current flowing from BRANCH2 to the ground is I _B2 . If Ic is the current at which each relay operates, I ₁ is the current flowing through the relay K1, I ₂ is the current flowing through the relay K2, and I ₃ is the current flowing through the relay K3 and the parallel circuit of the resistor R2 and the resistor R1. The following relational expression holds for the current of. However, Ic> I ₁ > 0, Ic
_{> I 2> 0, (4/3} ) Ic> I 3> - (4/3) Ic
Suppose that holds. _{I 1 · RL + I 3 ·} RL-I 2 · RL = 0 ··· (4) I T = I 1 + I 2 ··· (5) I B1 = I 1 -I 3 ··· (6)

By solving the above equations (4) to (6) using the above equations (1) and (2), the following equations (7) to (9) are obtained. _{I 1 = (1/3) I T} + (1/3) I B1 ··· (7) I 2 = (2/3) I T - (1/3) I B1 ··· (8) I 3 _{= (1/3) I T - (} 2/3) I B1 ··· (9)

After the above preparation, an example of the restarting procedure will be shown below. (1) A current of I _T = Ic flows from the constant current source CC _T on the TRUNK side. Since I _B1 = 0, the current I at this time is I
₁ , I ₂ and I ₃ are given by the following formulas (7) to (9): I ₁ = (1/3) Ic, I ₂ = (2/3) Ic, I ₃ = (1/3) Ic Become.

(2) Next, a current of I _B1 = 2Ic is supplied from the constant current source CC ₁ on the BRANCH 1 side. The currents I ₁ , I ₂ and I _{3 at} this time are similarly I ₁ = Ic, I ₂ = 0, I ₃ = −Ic. Here, since I ₁ = Ic, the relay K1 operates, the contact k1 is switched to the "2" side, and the TRU
The power supply line between NK and BRANCH1 rises, and BRA
NCH2 is disconnected from the system. Although I ₃ = −Ic, the current flowing through the relay K3 is (2/3) I.
Since it is c, the relay K3 does not operate.

(3) Subsequently, the current from the BRANCH1 side is increased to a regular value. (4) Increase the current from the TRUNK side to a regular value. By the procedure described above, it is possible to disconnect the BRANCH 2 in which a failure has occurred and to start power supply at both ends between the TRUNK-BRANCH 1.

It is clear that this procedure is effective even when an open failure occurs on the BRANCH2 side. However, the current values of I ₁ , I ₂ , and I ₃ are different from those in the above case. Therefore, this startup procedure can be applied to all failures on the BRANCH2 side including open failures.

A-2.2. Restart of TRUNK in case of shunt failure Analyze the restarting operation assuming that a shunt failure in which TRUNK is shorted to seawater occurs. FIG. 3 shows an equivalent circuit when a shunt failure occurs in TRUNK. It is assumed here that the impedances Z ₁ and Z ₂ are sufficiently larger than Z _T. Also, BRANCH
It is assumed that the current source of the terminal station on the one side can reverse the polarity.

(1) A reverse current of magnitude Ic, I _B1 = -Ic, flows from the BRANCH 1 side. That is, in FIG. 3, in the terminal station on the BRANCH 1 side, the switch for switching the current source is connected to the “1” side and the constant current source CC ₁₁ is connected to the BRA.
Connected to NCH1, the magnitude Ic from the constant current source CC ₁₁
The current of is sent to the BU side. At this time, the voltage applied to the relay K1 is 3V in the forward direction of the Zener diode group D2.
Since this is d (Vd is the forward voltage drop of one Zener diode), this relay does not operate. The total voltage applied to relays K2 and K3 is also 3V.
Since it becomes d, almost no current flows, and these relays do not operate.

(2) Next, a current of magnitude (3/2) Ic from the constant current source CC ₂ of the terminal station on the BRANCH 2 side, I _B2 =
Flow (3/2) Ic. As a result, in the above (1), all the current Ic flowing from the BRANCH1 side flows to the BRANCH2 side, and the current of (1/2) Ic flows through the relay K2. Each current I at this time
₁ , ₁ , ₂ and I ₃ are as follows. I ₁ = 0, I ₂ = (1/2) Ic, I ₃ = Ic In this case, neither relay operates. Note that I
₃ = Ic, but relay K as in the above case
The current flowing through 3 is (2/3) Ic, and the relay K3 does not operate.

(3) Subsequently, the power supply current I _B1 from the BRANCH1 side is increased to I _B1 =-(3/2) Ic. As a result, all the current I _B2 flowing through BRANCH2 is B
The supply current I _B1 from the RANCH1 side is used to supply the currents I ₁ , I ₂ , and I ₃ as follows. I ₁ = 0, I ₂ = 0, I ₃ = (3/2) Ic Here, since the current flowing through the relay K3 becomes equal to Ic, the relay K3 operates. As a result, the contact point k3-1
Causes TRUNK to be disconnected, and contact k3-2 causes B
RANCH1 and BRANCH2 are grounded at the ground terminal E2.

(4) The current I _B2 supplied from the BRANCH2 side is increased to a regular value. (5) BRANCH
At the terminal station on the 1st side, the changeover switch is switched to the "2" side, and the regular power supply current with the polarity reversed is supplied from the current source CC ₁₂ . As a result, BRANCH1 is connected to the ground terminal E2.
From will be one end fed by the feed path to the current source CC _12, also, BRANCH2 is a current source CC ₂ of the through circuit consisting of the relay K3 and resistors R1, R2 from the ground terminal E2 BRANCH2 side end station Power is supplied to one end by a current path reaching the end.

A-2.3. Rebooting when TRUNK has an open failure Even when an open failure occurs in which the cable on the TRUNK side is disconnected, the above-mentioned A-2.2. A restart procedure similar to that of can be used. In this case, the above-mentioned A-2.2. In (2), BRANCH2
From I _B2 = (3/2) Ic, the relay K3 operates. Therefore, the above-mentioned A-2.2. The procedure of (3) can be omitted.

A-2.4. Rebooting at the time of failure other than shunt or open of TRUNK When a failure other than shunt or open failure occurs on the TRUNK side, the above-mentioned A-2.2. The same procedure as can be used. In this case, depending on the grounding impedance at the fault point, the A-2.2. When the relay K3 operates in (2) in the procedure of (3)
In some cases, the relay K3 may operate, but in any case, as described above, the faulty TRUNK is disconnected and the BRANCH1 and BR are
ANCH2 can be launched.

B. Other Embodiments FIG. 4 shows another embodiment of the present invention. This embodiment is the same as the first embodiment shown in FIG.
The values of 1 and R2 are R1 = 2RL and R2 = RL, and the Zener voltage V per element of the Zener diode is
z is a voltage slightly higher than the operating voltage Vc of each relay. By doing so, the number of Zener diodes can be reduced as compared with the case of the first embodiment described above. By reducing the number of components in this way, the reliability can be further improved and the branching device BU can be downsized. The operation of the circuit and the startup method in the embodiment shown in FIG. 4 are similar to those in the case of the first embodiment described above, and therefore detailed description thereof will be omitted.

The circuit diagrams in the respective embodiments shown in FIGS. 1 and 4 only show the basic circuit, and in order to perform the minute current measurement and the capacitance measurement, the nodes are connected to each other. It is necessary to connect with high resistance.

[0046]

According to the present invention, it is possible to arbitrarily supply power to an optical cable connected to any one of the three terminals, and even if a failure occurs in the cable, A power supply path switching circuit that can secure a power supply path for another cable can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of a power supply path switching circuit of the present invention.

FIG. 2 is a BRANC according to the first embodiment of the present invention.
It is an equivalent circuit at the time of H failure.

FIG. 3 is a TRUNK according to the first embodiment of the present invention.
It is an equivalent circuit at the time of failure.

FIG. 4 is a diagram showing a configuration of another embodiment of a power feeding path switching circuit of the present invention.

FIG. 5 is a diagram showing an example of an optical submarine cable transmission system.

FIG. 6 is a diagram showing an example of a conventional power supply path switching circuit.

[Explanation of symbols]

 1-5 optical submarine cables A, B, C terminals BU branching device C1-C13 optical repeaters D1-D7 Zener diode groups E1-E4 grounding terminals K1-K5 relays k1-k5-2 relay contacts R1-R2 resistances T1-T6 Landing station

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Asakawa 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo International Telegraph and Telephone Corporation (72) Naoki Norimatsu 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo No. International Telegraph and Telephone Corporation (72) Inventor Hitoshi Nishikawa 2-3-2 Nishishinjuku, Shinjuku-ku, Tokyo Kadydi Submarine Cable System Co., Ltd.

Claims (1)

[Claims] 1. A first and a second connected to a power feeding path, respectively.
And a third terminal, first and second Zener diodes whose anodes are both connected to the first terminal, and connected between the cathode of the first Zener diode and the second terminal A first relay that operates only by a current flowing from the first zener diode in the direction of the second terminal, and is connected between the cathode of the second zener diode and the third terminal, A second relay that operates only by a current flowing from the second zener diode in the direction of the third terminal; and a second relay that is connected between the second terminal and the third terminal, A third relay having a low sensitivity; a self-holding fourth relay connected between the second terminal and ground by the operation of the second relay; and the first relay. A self-holding type fifth relay connected between the third terminal and the ground by the operation of the first relay, the third terminal being disconnected from the circuit by the operation of the first relay. The second terminal is connected to the fifth relay, the second terminal is disconnected from the circuit by the operation of the second relay, and is connected to the fourth relay, and the first terminal is connected by the operation of the third relay. Is disconnected from the circuit and grounded, the second terminal is grounded, the second terminal is disconnected from the circuit by the operation of the fourth relay, and the third terminal is disconnected by the operation of the fifth relay. A power supply path switching circuit, characterized in that the terminal is separated from the circuit.