Abstract:
A submarine cable power feeding system includes N (N is an integer of 2 or larger) main submarine cables extending from the land in the offshore direction, N-stage (N is an integer of 2 or larger) submarine feed branching devices, and first to Nth (N is an integer of 2 or larger) sub submarine cables. Each submarine feed branching device is connected to the main submarine cable to receive constant-voltage power from a constant-voltage feed unit. Each sub submarine cable connects the Nth-stage submarine feed branching device, connected to the Nth main submarine cable, to the adjacent submarine feed branching device through submarine repeaters, thereby receiving power from a constant-current feed unit. Each constant-current feed unit is built in the submarine feed branching device. The submarine feed branching devices and the submarine repeaters are arranged in a matrix on a plane.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a submarine cable power feeding system and, more particularly, to a submarine cable power feeding system for feeding power to submarine repeaters connected to submarine cables arranged in a matrix on a plane.  
           [0002]    Hitherto, this kind of submarine cable power feeding system for submarine cable devices is used in order to feed power one or a plurality of submarine repeaters from a land power supply through a feed line serving as a submarine cable. The repeaters are connected in series on the sea bottom. For example, a method for feeding power to a plurality of submarine repeaters connected in series from a land direct current (DC) constant-current power supply through a feed line as a submarine cable is disclosed in an article “KAITEI DOUJIKU KEIBURU TSUSHIN HOUSHIKI (submarine coaxial cable communication system)” by Seiichi Shimura, page 182, published on Mar. 25, 1979.  
           [0003]    However, the above conventional systems have the following problems.  
           [0004]    In the case of constant-current power feed, it is impossible under land-based power feeding control to branch a feed line serving as a submarine cable to expand the arrangement of submarine repeaters in a matrix on a plane. The reason is as follows. Loads on branch cables vary depending on the number of submarine repeaters connected after branching the feed line as the submarine cable, the current consumption of each submarine repeater, and the length of the feed line as the submarine cable, so that currents of the respective feed lines as the branch submarine cables are different from each other. Thus, predetermined power cannot be supplied to each repeater.  
           [0005]    Constant-voltage parallel power feed and alternating-current (AC) power feed are not included in the existing technique for the submarine cable system. The constant-voltage parallel power feed and the AC power feed have the following problems.  
           [0006]    For the constant-voltage power feed, a feed line as a submarine cable can be branched. However, it is necessary to extend the range of input voltages in a power supply unit of each submarine repeater. The reason is as follows. As a cable connecting the submarine repeaters becomes longer, terminal voltages of the respective submarine repeaters are not equivalent to each other due to a voltage drop caused by the resistance of the cable. It is necessary to fabricate a power supply unit of each submarine repeater in accordance with the specifications for the maximum input voltage.  
           [0007]    For the AC power feed, since voltage can be freely changed, land power feeding systems often use the AC power feed. However, a submarine cable has a single-wire structure. The power efficiency of single-wire AC power feed is low. Accordingly, long-distance power transmission cannot be realized. Furthermore, in case where the long-distance power transmission is to be carried out by the AC power feed, the transmission frequency has to be lowered in order to improve the transmission efficiency. For this purpose, each of the repeaters require a transformer which transforms the AC voltage at a low frequency so that the voltage corresponding to the circuit of each repeaters is transformed. This results in an increase in the size of the submarine repeater. Thus the AC power feed is not suitable for use in devices disposed on the sea bottom.  
         SUMMARY OF THE INVENTION  
         [0008]    It is an object of the present invention to provide a submarine cable power feeding system in which a feed line as a submarine cable is branched so that the matrix arrangement of submarine repeaters can be expanded on a plane.  
           [0009]    Another object of the present invention is to provide a submarine cable power feeding system in which a feed line as a submarine cable can be easily extended or shortened and a submarine repeater can be easily added or removed at any time.  
           [0010]    According to the present invention, a submarine cable power feeding system includes arrangements extending from the land in the longitudinal direction, the arrangements for feeding constant-voltage power to submarine feed branching devices ( 10  or  10   a ) connected in the longitudinal direction with constant-voltage feed lines ( 2  and  2   a ), and arrangements extending in the lateral direction, the arrangements for feeding constant-current power with constant-current feed lines ( 3 ,  3   a , and  3   b ) connecting the submarine feed branching devices ( 10  or  10   a ) in the lateral direction. According to the present invention, the arrangements in the longitudinal direction are combined with the arrangements in the lateral direction. Consequently, the arrangement of devices such as submarine repeaters ( 20 ) requiring power feed can be expanded to an unlimited extent in a matrix on a plane. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a block diagram of the configuration of a submarine cable power feeding system according to the present invention;  
         [0012]    [0012]FIG. 2 is a block diagram of the configuration of a submarine feed branching device ( 10 ) in FIG. 1;  
         [0013]    [0013]FIG. 3 is a block diagram of the configuration of a submarine feed branching device ( 10   a ) in FIG. 1; and  
         [0014]    [0014]FIG. 4 is a block diagram of the configuration of a submarine repeater ( 20 ) in FIG. 1.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    An embodiment of the present invention will now be described in detail hereinbelow with reference to the drawings.  
         [0016]    [0016]FIG. 1 is a block diagram of the configuration of a submarine feed branching device according to the present invention. Referring to FIG. 1, constant-voltage feed units  1  and  1   a  are disposed on the land. The constant-voltage feed units  1  and  1   a  supply constant-voltage power to submarine feed branching devices  10  through constant-voltage feed lines  2  and  2   a , respectively The respective submarine feed branching devices  10  convert the constant-voltage power into negative (−) constant-current power and positive (+) constant-current power and then feed the constant-current power to submarine repeaters  20  through constant-current feed lines  3 ,  3   a , and  3   b . Each submarine feed branching device  10  feeds power to the next-stage submarine feed branching device  10  or b 1   a  through the constant-voltage feed line  2  or  2   a.    
         [0017]    Each submarine feed branching device b 1   a  converts the constant-voltage power into negative (−) constant-current power and positive (+) constant-current power and then supplies the constant-current power to the submarine repeaters  20  through the constant-current feed line  3   a . Each submarine feed branching device boa supplies the constant-voltage power to a plurality of stages, namely, the submarine feed branching devices  10  or boa through the constant-voltage feed line  2  or  2   a . Each submarine repeater  20  receives the constant-current power from the submarine feed branching device  10  or b 1   a , or another submarine repeater  20  through the constant-current feed line  3 ,  3   a , or  3   b . Each submarine repeater  20  converts the constant-current power into constant-voltage power and then supplies the constant-voltage power to an observation unit  4 .  
         [0018]    [0018]FIG. 2 shows the details of the submarine feed branching device  10  shown in FIG. 1. Referring to FIG. 2, the submarine feed branching device  10  comprises a negative (−) constant-current power supply unit  6 , a positive (+) constant-current power supply unit  7 , and underwater connectors  5 . The negative constant-current power supply unit  6  generates negative (−) constant-current power from the constant-voltage power supplied. The positive (+) constant-current power supply unit  7  generates positive (+) constant-current power from the constant-voltage power supplied. Each underwater connector  5  connects to the constant-voltage feed line  2  or the constant-current feed line  3 . Each underwater connector  5  is detachable undersea.  
         [0019]    [0019]FIG. 3 shows the details of the submarine feed branching device  10   a  shown in FIG. 1. Referring to FIG. 3, the submarine feed branching device  10   a  comprises the negative (−) constant-current power supply unit  6 , the positive (+) constant-current power supply unit  7 , a feed distribution unit  8  for feeding the constant-voltage power to two or more portions, and the underwater connectors  5 . Each underwater connector  5  connects to the constant-voltage feed line  2   a  or the constant-current feed line  3   a . Each underwater connector  5  is detachable undersea.  
         [0020]    [0020]FIG. 4 shows the details of the submarine repeater  20  shown in FIG. 1. Referring to FIG. 4, the submarine repeater  20  comprises a constant-current DC/DC converter  9  and the underwater connectors S. The constant-current DC/DC converter  9  converts the constant-current power into constant-voltage power and then outputs the converted power to a feed line  11  for the observation unit. Each underwater connector  5  connects to the constant-current feed line  3  or the observation-unit feed line  11 . Each underwater connector  5  is detachable undersea.  
         [0021]    The configuration of the system according to the present embodiment has been described in detail. The constant-voltage feed unit and the observation unit in the diagram are well-known to those skilled in the art. These units are not directly related to the present invention. Accordingly, the detailed configurations thereof are omitted.  
         [0022]    The operation of the submarine cable power feeding system in FIG. 1 will now be described. The constant-voltage feed unit  1  is disposed on the land. The constant-voltage feed unit  1  supplies constant-voltage power to the submarine feed branching device  10  in the first stage through the constant-voltage feed line  2 . The submarine feed branching device  10  can allow the same current to flow through loads connected in series. The loads are the characteristics of the constant-current power feed. The submarine feed branching device  10  utilizes an advantage in that power supply circuits of the respective submarine repeaters can be uniformed with a simple construction. In order to supply power to the submarine repeaters  20  over a long distance, the submarine feed branching device  10  converts constant-voltage power into negative (−) constant-current power and positive (+) constant-current power. Thus, the constant-current power is supplied to the submarine repeaters  20  through the constant-current feed line  3 . FIGS. 2 and 3 show the polarities of the constant-current power feed at this time. Each submarine repeater  20  receives the constant-current power, converts the power into constant-voltage power, and then supplies the constant-voltage power to the observation unit  4 .  
         [0023]    The constant-voltage feed line  2  serves as the characteristics of the constant-voltage power feed. The submarine feed branching device  10  utilizes an advantage in that the constant-voltage feed line  2  can be extended by connection without disconnection. The submarine feed branching device  10  feeds constant-voltage power supplied from the constant-voltage feed unit  1  to the second-stage device  10  through the constant-voltage feed line  2 . Furthermore, the submarine feed branching device  10  is connected to the third-stage device  10  and the third-stage device is then connected to the fourth-stage device  10 , resulting in an extension of the power feeding system. Consequently, the submarine feed branching devices  10  are arranged in the longitudinal direction with respect to the land.  
         [0024]    For the connection, the devices  10  of the necessary number can be added when required. It is unnecessary to initially set a voltage to a high level. Accordingly, constant-voltage feed components can be economically realized. The constant-voltage power feed has the following problem. In parallel connection, the respective submarine feed branching devices  10  do not have the same terminal voltage due to a voltage drop caused by the resistance of the cable. However, the constant-voltage feed line  2  is shorter than the constant-current feed line  3  connecting the submarine repeaters  20  and the number of submarine feed branching devices  10  is smaller than that of submarine repeaters  20 . Therefore, it is unnecessary to set a voltage to a high level. Accordingly, the influence on the devices is small.  
         [0025]    The submarine feed branching device  10  is connected to the submarine feed branching device  10   a  to arrange more submarine feed branching devices  10  in two directions. In other words, the feed line can be easily branched using the characteristics of the constant-voltage power feed. The submarine feed branching devices  10   a  can be arranged instead of the submarine feed branching devices  10 .  
         [0026]    The submarine feed branching devices  10  and  10   a  can be freely connected to each other anywhere the constant-voltage feed line  2  or  2   a  can be connected to the device. The negative (−) constant-current power and the positive (+) constant-current power are supplied from each of the submarine feed branching devices  10  and  10   a  to the submarine repeaters  20 . The submarine repeaters  20  are connected in the lateral direction. For the connection of the submarine repeaters  20 , a circuit can also be constructed with seawater or cable returns.  
         [0027]    The constant-voltage feed unit  1   a  is disposed at a distance from the constant-voltage feed unit  1  for the redundancy of the submarine feed branching device  10  depending on the connecting state of the submarine repeaters  20 . In the same way as the foregoing case, the constant-voltage feed unit  1   a  feeds power to constant-voltage power to the first-stage submarine feed branching device  10  through the constant-voltage feed line  2   a . The constant-voltage feed units  1  and  1   a  are similarly connected through the submarine feed branching devices  10  and  10   a , and the submarine repeaters  20 . Thus, the power feeding system can be expanded in a wide range.  
         [0028]    [0028]FIG. 2 is the block diagram showing one example of the configuration of the submarine feed branching device  10  according to the present embodiment. Referring to FIG. 2, the submarine feed branching device  10  comprises the four underwater connectors  5 , the negative (−) constant-current power supply unit  6 , and the positive (+) constant-current power supply unit  7 . The constant-voltage feed units  1  and  1   a  are disposed on the land. Constant-voltage power is supplied from the constant-voltage feed unit  1  or  1   a , or the submarine feed branching device  10  or  10   a  to each underwater connector  5  through the constant-voltage feed line  2  or  2   a . The negative (−) constant-current power supply unit  6  converts the supplied constant-voltage power into constant-current power and then supplies the power to the submarine repeaters  20  through the underwater connector  5  and the constant-current feed line  3 . In this instance, the constant-current feed line  3   a  or  3   b , or another constant-current feed line further connected is used in some cases. Similarly, the positive (+) constant-current power supply unit  7  supplies constant-current power through the underwater connector  5 .  
         [0029]    When the constant-voltage power feed is further extended, constant-voltage power can be supplied to the next-stage submarine feed branching device  10  or  10   a  through the underwater connector  5  and the constant-voltage feed line  2 . Since the underwater connectors  5  are used, the power feeding system can be expanded and be branched at any time.  
         [0030]    [0030]FIG. 3 is the block diagram showing one example of the configuration of the submarine feed branching device  10   a  according to the present embodiment. Referring to FIG. 3, the submarine feed branching device  10   a  is constructed by adding the feed distribution unit  8  and one underwater connector  5  to the configuration of the submarine feed branching device  10  shown in FIG. 2. The feed distribution unit  6  distributes the constant-voltage power feed. The underwater connector  5  can supply power to the next-stage submarine feed branching device  10  or  10   a . Power feed to a plurality of stages can be realized by preparing a plurality of underwater connectors  5 .  
         [0031]    [0031]FIG. 4 is the block diagram showing one example of the configuration of the submarine repeater  20  according to the present embodiment. Referring to FIG. 4, the submarine repeater  20  comprises three underwater connectors  5  and the constant-current DC/DC converter  9 . The constant-current DC/DC converter  9  receives constant-current power from the submarine feed branching device  10  or  10   b  through the constant-current feed line  3  and the underwater connector  5 . The constant-current DC/DC converter  9  converts the constant-current power into constant-voltage power. After the conversion, in order to supply the constant-voltage power to the observation unit  4 , the constant-voltage power is supplied to the observation-unit feed line  11 .  
         [0032]    As mentioned above, according to the present embodiment, the constant-voltage power feeding arrangements in the longitudinal direction with respect to the land are combined with the constant-current power feeding arrangements in the lateral direction. Accordingly, the arrangement of devices such as submarine repeaters ( 20 ) requiring power feed can be expanded to an unlimited extent in a matrix on a plane. According to the present embodiment, various connections of the submarine feed branching devices  10   a  can be realized. In other words, the submarine feed branching device  10   a  can be connected to the constant-voltage feed unit  1  or  1   a  disposed on the land. The submarine feed branching devices  10   a  can also be connected in series.  
         [0033]    The constant-voltage power supply unit can be constructed with direct current or alternating current.  
         [0034]    As mentioned above, according to the present invention, the following advantages can be obtained.  
         [0035]    Voltage can be distributed in the constant-voltage power feeding arrangement. The power supply circuits of the submarine repeaters can be formed with the same simple construction in the constant-current power feeding arrangement. The constant-voltage power feeding arrangements can be combined with the constant-current power feeding arrangements. Accordingly, the feed line serving as the submarine cable can be branched and the arrangement of the submarine repeaters can be expanded in a matrix on a plane.  
         [0036]    In the case of the constant-voltage power feed, power corresponding to connected loads is output. Accordingly, the extension of the feed line serving as the submarine cable and the additional installation of the submarine repeater can be easily performed later.  
         [0037]    In the parallel connection, when a new submarine feed branching device is connected, it is unnecessary to disconnect the feed line. Accordingly, the power feeding system can be extended in the offshore direction without temporarily stopping the power feed supplied from the land.