Power transmission system, method for controlling a power transmission system

Abstract

We provide a power transmission system and control method that can flexibly respond to failures while keeping costs down. [Solution] The system includes a power transmission terminal section having a plurality of first circuit breakers capable of interrupting power transmission, a first section having a plurality of first cable lines to which one end of each of the plurality of first circuit breakers is connected and capable of transmitting power transmission through the plurality of first circuit breakers, a second section having a second cable line corresponding to each of the plurality of first cable lines and transmitting power transmission transmitted by the plurality of first cable lines, intermediate electrical equipment having a plurality of disconnectors capable of opening and closing the connection between the other end of each of the plurality of first cable lines and one end of each of the plurality of second cable lines, and a plurality of switches capable of opening and closing the connection between the connection points of the other end of each of the plurality of first cable lines and one end of each of the plurality of second cable lines, a power receiving terminal section having a plurality of second circuit breakers capable of interrupting power transmission received from the other end of each of the plurality of second cable lines, and a control unit configured to detect faults and capable of controlling the opening and closing of each of the plurality of disconnectors and the plurality of switches.

Description

Technical Field

[0001] Embodiments of the present invention relate to a power transmission system and a method for controlling the power transmission system.

Background Art

[0002] As a method for transporting electric power from an offshore wind power plant, long-distance submarine cable power transmission is known. The power transmission method of submarine cable power transmission is roughly classified into a DC type and an AC type.

[0003] The DC power transmission method is to arrange converters that convert alternating current to direct current at the power transmission end and the power reception end for power transmission. Since the DC power transmission method does not generate reactive power, it has the characteristic that the restriction on the power transmission distance is small. On the other hand, the cost required for the converter becomes an issue.

[0004] The AC power transmission method is to convert the electric power generated by the generator in the windmill of the offshore wind power plant into commercial frequency alternating current by a power conditioner and transmit it using an AC cable. The AC power transmission method has a restriction on the power transmission distance due to reactive power. On the other hand, a converter for converting alternating current to direct current is not required.

[0005] The AC power transmission method may use a reactor to compensate for the reactive power generated in the AC cable. In particular, in a power transmission line where the power transmission distance is about 100 km or more, in addition to the substations or transformer substations at the power transmission end and the power reception end, additional reactors may be provided in the middle of the cable line. The additional reactors installed in the middle of the cable line may be protected by a switching device, or may be protected by a configuration in which the connection is switched via a busbar cable. Also, the cable line may be protected by a circuit breaker. Thus, the reactors installed in the middle of the cable line and the associated switching devices may be arranged on an offshore platform. In the following description, the reactors and switching devices arranged in the middle of the cable line are referred to as "intermediate electrical equipment". Also, a section of the cable line separated by the intermediate electrical equipment is referred to as a "section".

[0006] Cable lines may contain multiple circuits. Methods have been proposed for efficient and flexible power transmission from offshore, including the use of transformers with multiple secondary windings and the presence of junction boxes underwater.

[0007] In the event of a fault in a power transmission line installed on the seabed, the fault can be resolved using circuit breakers located at both ends of the section. Because seabed cables are not susceptible to lightning strikes, their failure rate is lower than that of overhead power transmission lines. However, once a fault occurs in a seabed cable, it is highly likely to be a permanent failure. Considering these characteristics, there is a need to reduce costs by appropriately combining electrical equipment. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent No. 10,374,398 [Patent Document 2] British Patent Specification No. 2586799 [Overview of the project] [Problems that the invention aims to solve]

[0009] Thus, conventional power transmission systems and their control methods have challenges in fault response and cost reduction, especially when installed on the seabed. The power transmission system and its control method in this embodiment were developed to solve these problems, and aim to provide a power transmission system and its control method that can respond flexibly to faults while keeping costs down. [Means for solving the problem]

[0010] The power transmission system of the embodiment comprises: a power transmission terminal section having a plurality of first circuit breakers capable of interrupting power transmission; a first section having a plurality of first cable lines to which one end of each of the plurality of first circuit breakers is connected, and capable of transmitting power transmission through the plurality of first circuit breakers via the plurality of first cable lines; a second section having a second cable line corresponding to each of the plurality of first cable lines, and transmitting power transmission transmitted by the plurality of first cable lines via the plurality of second cable lines; intermediate electrical equipment having a plurality of disconnectors capable of opening and closing the connection between the other end of each of the plurality of first cable lines and one end of each of the plurality of second cable lines; a plurality of switches capable of opening and closing the connection between the connection points of the other end of each of the plurality of first cable lines and one end of each of the plurality of second cable lines; a power receiving terminal section having a plurality of second circuit breakers capable of interrupting power transmission received from the other end of each of the plurality of second cable lines; and a control unit configured to detect faults occurring in the first section and the second section, and capable of controlling the opening and closing of each of the plurality of disconnectors and the plurality of switches. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing the configuration of the power transmission system according to the first embodiment. [Figure 2] This figure shows the normal circuit state of the power transmission system according to the first embodiment. [Figure 3] This flowchart shows the control operation of the power transmission system according to the first embodiment. [Figure 4] This diagram shows the process of accident removal after an accident occurs in the power transmission system according to the first embodiment. [Figure 5] This diagram shows the power transmission system according to the first embodiment after the fault has been cleared. [Figure 6] This is a block diagram showing the configuration of the power transmission system according to the second embodiment. [Figure 7] This figure shows the normal circuit state of the power transmission system according to the second embodiment. [Figure 8]This figure shows the power transmission system after fault removal according to the second embodiment. [Modes for carrying out the invention]

[0012] (Configuration of the first embodiment) The power transmission system of the first embodiment will be described in detail below with reference to the drawings. In the following description, common functional components will be denoted by the same reference numerals, and redundant explanations will be omitted. Figure 1 is a block diagram showing the configuration of the power transmission system 100 according to the first embodiment.

[0013] The power transmission system 100 shown in Figure 1 is, for example, a power transmission means that transmits AC power from a generator G to a busbar B. The power transmission system 100 has a power transmission terminal 11 that receives power from the generator G and a power receiving terminal 12 that supplies power to the busbar B. Between the power transmission terminal 11 and the power receiving terminal 12 are the first to third sections 31, 32, and 33, a first intermediate equipment 21 located between the first and second sections 31 and 32, and a second intermediate equipment 22 located between the second and third sections 32 and 33.

[0014] Sections 1 to 31 to 33 are power transmission means having multiple cable lines. In the example shown in Figure 1, sections 1 to 31 to 33 each have four cable lines. That is, sections 1 to 31 to 33 each have cable lines 1 to 41a to 41d, 42a to 42d, and 43a to 43d, respectively.

[0015] The first intermediate electrical equipment 21 connects the first cable line 41a in the first section 31 and the first cable line 42a in the second section 32 in a way that allows for interruption, and includes intersection disconnectors 51a and 52a connected in series. Similarly, the first intermediate electrical equipment 21 connects the second to fourth cable lines 41b to 41d and the second to fourth cable lines 42b to 42d in a way that allows for interruption, and includes intersection disconnectors 51b and 52b, intersection disconnectors 51c and 52c, and intersection disconnectors 51d and 52d connected in series, respectively.

[0016] Further, the first intermediate electrical equipment 21 includes a line disconnecting switch 61ab capable of opening and closing the interconnection between the connection points of the sectionalizing circuit breakers 51a and 52a and the connection points of the sectionalizing circuit breakers 51b and 52b. Similarly, the first intermediate electrical equipment 21 includes a line disconnecting switch 61bc capable of opening and closing the interconnection between the connection points of the sectionalizing circuit breakers 51b and 52b and the connection points of the sectionalizing circuit breakers 51c and 52c. Further, the first intermediate electrical equipment 21 includes a line disconnecting switch 61cd capable of opening and closing the interconnection between the connection points of the sectionalizing circuit breakers 51c and 52c and the connection points of the sectionalizing circuit breakers 51d and 52d.

[0017] A reactor (not shown) may be connected between the sectionalizing circuit breakers 51a and 52a via a reactor disconnecting switch (not shown). Similarly, a reactor (not shown) may be connected between the sectionalizing circuit breakers 51b and 52b, between the sectionalizing circuit breakers 51c and 52c, and between the sectionalizing circuit breakers 51d and 51d via a reactor disconnecting switch (not shown). That is, the first intermediate electrical equipment 21 can dispose reactors in the AC transmission line together with circuit breakers and switches.

[0018] The second intermediate electrical equipment 22 includes series-connected sectionalizing circuit breakers 53a and 54a for cut-off connection between the first cable line 42a in the second section 32 and the first cable line 43a in the third section 33. Similarly, the second intermediate electrical equipment 22 includes series-connected sectionalizing circuit breakers 53b and 54b, sectionalizing circuit breakers 53c and 54c, and sectionalizing circuit breakers 53d and 54d for cut-off connection between the second to fourth cable lines 42b to 42d and the second to fourth cable lines 43b to 43d, respectively.

[0019] Further, the second intermediate electrical equipment 22 includes an inter-line switching device 62ab capable of opening and closing the mutual connection between the connection points of the inter-section circuit breakers 53a and 54a and the connection points of the inter-section circuit breakers 53b and 54b. Similarly, the second intermediate electrical equipment 22 includes an inter-line switching device 62bc capable of opening and closing the mutual connection between the connection points of the inter-section circuit breakers 53b and 54b and the connection points of the inter-section circuit breakers 53c and 54c. Further, the second intermediate electrical equipment 22 includes an inter-line switching device 62cd capable of opening and closing the mutual connection between the connection points of the inter-section circuit breakers 53c and 54c and the connection points of the inter-section circuit breakers 53d and 54d.

[0020] A reactor (not shown) may be connected between the inter-section circuit breakers 53a and 54a via a reactor switching device (not shown). Similarly, reactors (not shown) may be connected between the inter-section circuit breakers 53b and 54b, between the inter-section circuit breakers 53c and 54c, and between the inter-section circuit breakers 53d and 54d via reactor switching devices (not shown). That is, the second intermediate electrical equipment 22 can dispose reactors in the AC transmission line together with circuit breakers and switches.

[0021] The inter-line switching devices 61ab, 61bc, 61cd and the inter-line switching devices 62ab, 62bc, 62cd may be constituted by circuit breakers, or may be constituted by disconnectors. Further, they may be constituted by a combination of a circuit breaker and a disconnector.

[0022] The power transmission terminals 11 include circuit breakers 71a to 71d for protecting the power transmission of the first to fourth cable lines 41a to 41d of the first section 31. Similarly, the power reception terminals 12 include circuit breakers 72a to 72d for protecting the power transmission of the first to fourth cable lines 43a to 43d of the third section 33. The above-described inter-section circuit breakers, inter-line switching devices, and circuit breakers are controlled to be opened and closed by a control unit 80. The control unit 80 is a functional element capable of detecting an accident in the power transmission system 100 and performing protection control.

[0023] Figure 2 shows the normal circuit state of the power transmission system according to the first embodiment. In Figure 2, closed states of disconnectors, switches, circuit breakers, etc. are represented by black circles, and open states are represented by white circles.

[0024] As shown in Figure 2, in the normal mode embodiment of the power transmission system 100, circuit breaker 71a, intersection disconnectors 51a and 52a, intersection disconnectors 53a and 54a, and circuit breaker 72a are in the closed state (connected state). Similarly, in the normal mode embodiment of the power transmission system 100, circuit breakers 71b to 71d, intersection disconnectors 51b and 52b, intersection disconnectors 51c and 52c, intersection disconnectors 51d and 52d, intersection disconnectors 53b and 54b, intersection disconnectors 53c and 54c, intersection disconnectors 53d and 54d, and circuit breakers 72b to 72d are in the closed state (connected state). Therefore, the first to third sections 31 to 33 are connected in series, and the generator G and the busbar B are connected.

[0025] On the other hand, the inter-circuit switching devices 61ab, 61bc, 61cd and 62ab, 62bc, 62cd are all in the open (disconnected) state. Therefore, the first cable lines 41a, 42a, 43a, the second cable lines 41b, 42b, 43b, the third cable lines 41c, 42c, 43c, and the fourth cable lines 41d, 42d, 43d are in an independent state from each other. In other words, the generator G and the busbar B are connected by four independent and parallel cable lines.

[0026] In the example shown in Figure 2, four parallel cable lines are configured under normal conditions, but this is not the only configuration. The control unit 80 may control some of the four cable lines to a disconnected state (stopped state) depending on the power transmitted from the generator G to the busbar B. By increasing or decreasing the number of parallel cable lines in this way, power transmission losses can be reduced.

[0027] (Operation of the first embodiment) Next, the operation of the power transmission system 100 of the first embodiment will be described in detail with reference to Figures 3 to 5. Figure 3 is a flowchart showing the control operation of the power transmission system according to the first embodiment. Figure 4 shows the accident removal process after an accident occurs in the power transmission system according to the first embodiment. Figure 5 shows the state after the accident removal in the power transmission system according to the first embodiment.

[0028] The control unit 80 is configured to detect faults in the power transmission system 100 (S200). If no fault is detected (No. in S200), the power transmission system 100 continues to transmit power (S210).

[0029] Now, let's assume that a ground fault occurs in the second cable line 42b of the second section 32, as shown in Figure 4. When the control unit 80 detects the fault (Yes in S200), the control unit 80 controls the circuit breaker 71b at the power transmission terminal 11 and the circuit breaker 72b at the power receiving terminal 12 to open them. Through this operation, the first cable lines 41b, 42b, and 43b are disconnected from the power transmission system 100 and the ground fault is eliminated (S220).

[0030] Since the inter-circuit switching devices 61ab and 62ab are in the open state, even if a ground fault occurs in the second cable line 42b, one of the four sets of cable lines provided in the second section 32, the fault in the second cable line 42b can be eliminated simply by opening the circuit breakers 71b and 72b that protect both ends of the second cable lines 41b, 42b, and 43b at the transmission terminal 11 and the receiving terminal 12. At this time, the amount of power that the power transmission system 100 can transmit will decrease compared to before the fault, so the control unit 80 may issue a power generation limiting command to the generator G.

[0031] The control unit 80 determines whether or not power transmission can be continued based on the fault location by controlling the circuit breakers 71b and 72b (S230).

[0032] If the determination results in the inability to continue power transmission (No. in S230), for example, if the power transmission capacity becomes insufficient due to the removal of the second cable line 42b, the control unit 80 controls the generator G to stop power transmission by the power transmission system 100 (S240).

[0033] If the determination indicates that power transmission can be continued (Yes in S230), the control unit 80 calculates the optimal route that minimizes losses while excluding the faulty line and ensures that each line does not exceed its power transmission limit (S250). In the example shown in Figure 4, the control unit calculates a route that minimizes losses when only the second cable line 42b, where the ground fault occurred, is excluded, and ensures that the remaining cable lines do not exceed their power transmission limits.

[0034] The control unit 80 controls the inter-section disconnectors, inter-circuit switches, and circuit breakers to configure the calculated path (S260). For example, the control unit 80 controls the circuit breakers 71a~71d and 72a~72d to the open state to stop the power supply, and then controls the inter-section disconnectors and inter-circuit switches to open and close according to the calculation result.

[0035] Figure 5 shows the state of the power transmission system 100 controlled by the control unit 80 based on the calculation results. In the example shown in Figure 5, the power transmission system 100 of the embodiment has the following states: inter-section disconnectors 51a, 52a and 53a, 54a, inter-section disconnectors 51b and 54b, inter-section disconnectors 51c, 52c, 53c, 54 and inter-section disconnectors 51d, 52d, 53d, 54d are in a closed state, inter-section disconnectors 52b and 53b are in an open state, inter-line switching devices 61ab, 62ab and inter-line switching devices 61bc, 62bc are in a closed state, and inter-line switching devices 61cd, 62cd are in an open state. In other words, the inter-section disconnectors 52b and 53b are opened, excluding the second cable line 42b from the power transmission system 100, and the fourth cable lines 41d, 42d, and 43d are excluded from the first to third cable lines.

[0036] With this configuration, in Section 2 32, power is transmitted using the three lines excluding the faulty second cable line 42b, while in Section 1 31 and Section 32, power is transmitted using all four lines. More specifically, the capacity of the power transmission paths for the first cable lines 41a, 42a, 43a, the second cable lines 41b, 43b, and the third cable lines 41c, 42c, 43c is increased, and the fourth cable lines 41d, 42d, 43d are made unaffected by the other three cable lines.

[0037] Subsequently, the control unit 80 controls circuit breakers 71a-71d and 72a-72d to the closed state and resumes power transmission (S270). In the example shown in Figure 5, all circuit breakers 71a-71d and 72a-72d are controlled to the closed state, but this is not the only example. If the calculation results indicate that it is not necessary to close any of the circuit breakers 71a-71d and 72a-72d that were tripped to clear the fault, they may remain in the open state instead of being closed.

[0038] According to the power transmission system 100 of this embodiment, even in the event of an accident, the first intermediate electrical equipment and the second intermediate electrical equipment can use disconnectors to open the section where the accident occurred while continuing to transmit power using the cable section where the accident did not occur. Therefore, power transmission losses can be reduced. In addition, the first intermediate electrical equipment and the second intermediate electrical equipment do not require circuit breakers for accident removal, and relatively inexpensive disconnectors or switchgear are sufficient, thus eliminating the cost of circuit breakers and reducing the overall cost required for the power transmission system.

[0039] (Configuration of the second embodiment) Next, the power transmission system of the second embodiment will be described in detail. Figure 6 is a block diagram showing the configuration of the power transmission system according to the second embodiment. In the following description, components and operations common to the first embodiment will be indicated with the same reference numerals, and redundant explanations will be omitted.

[0040] The power transmission system 101 shown in Figure 6 is a power transmission means that transmits AC power from the generator G to the busbar B, similar to the power transmission system 100 of the first embodiment. The power transmission system 101 has a power transmission terminal 13 that receives power from the generator G and a power receiving terminal 14 that supplies power to the busbar B. Between the power transmission terminal 13 and the power receiving terminal 14 are the first and second sections 34, 35 and the intermediate electrical equipment 23 which is located between the first and second sections 34, 35.

[0041] Sections 34-35 of the first and second sections have multiple cable lines. In the example shown in Figure 6, sections 34-35 of the first and second sections each have four cable lines. That is, sections 34-35 of the first and second sections each have the first to fourth cable lines 44a-44d and 45a-45d.

[0042] The intermediate electrical equipment 23 connects the first cable line 44a in the first section 34 and the first cable line 45a in the second section 35 in a way that allows for interruption, and includes intersection disconnectors 55a and 56a connected in series. Similarly, the intermediate electrical equipment 23 connects the second to fourth cable lines 44b to 44d and the second to fourth cable lines 45b to 45d in a way that allows for interruption, and includes intersection disconnectors 55b and 56b, intersection disconnectors 55c and 56c, and intersection disconnectors 55d and 56d connected in series, respectively.

[0043] Furthermore, the intermediate electrical equipment 23 includes an inter-circuit switch 63ab capable of opening and closing the connection between the connection points of inter-section disconnectors 55a and 56a and inter-section disconnectors 55b and 56b. Similarly, the intermediate electrical equipment 23 includes an inter-circuit switch 63bc capable of opening and closing the connection between the connection points of inter-section disconnectors 55b and 56b and inter-section disconnectors 55c and 56c. In addition, the intermediate electrical equipment 23 includes an inter-circuit switch 63cd capable of opening and closing the connection between the connection points of inter-section disconnectors 55c and 56c and inter-section disconnectors 55d and 56d.

[0044] A reactor (not shown) may be connected between intersection disconnectors 55a and 56a via a reactor switching device (not shown). Similarly, a reactor (not shown) may be connected between intersection disconnectors 55b and 56b, between intersection disconnectors 55c and 56c, and between intersection disconnectors 55d and 56d via a reactor switching device (not shown).

[0045] The inter-circuit switching devices 63ab, 63bc, and 63cd may be composed of disconnectors or circuit breakers. Alternatively, they may be composed of a combination of disconnectors and circuit breakers.

[0046] The power transmission terminal 13 is equipped with circuit breakers 73a to 73d that protect the power transmission of the first to fourth cable lines 44a to 44d of the first section 34. Similarly, the power receiving terminal 14 is equipped with circuit breakers 74a to 74d that protect the power transmission of the first to fourth cable lines 45a to 45d of the second section 35. The opening and closing of the inter-section disconnectors, inter-line switching devices, and circuit breakers described above are controlled by the control unit 81. The control unit 81 is a functional element that can detect and protect against faults in the power transmission system 101.

[0047] Figure 7 shows the normal circuit state of the power transmission system 101 according to the second embodiment. In Figure 7, closed states of disconnectors, switchgear, circuit breakers, etc. are represented by black circles, and open states are represented by white circles.

[0048] As shown in Figure 7, in the normal mode of the power transmission system 101, circuit breaker 73a, inter-section disconnectors 55a and 56a, and circuit breaker 74a are in the closed state (connected state). Similarly, in the normal mode of the power transmission system 101, circuit breaker 73b, inter-section disconnectors 55b and 56b, and circuit breaker 74b are in the closed state (connected state). On the other hand, inter-circuit switching devices 63ab and 63bc are in the open state (disconnected state). That is, the first cable lines 44a and 45a and the second cable lines 44b and 45b are connected in series in parallel to each other, connecting the generator G and the busbar B.

[0049] Furthermore, in the normal mode embodiment of the power transmission system 101, circuit breaker 73c, intersection disconnectors 55c and 56c, and circuit breaker 74c are in the open (disconnected) state. Similarly, in the normal mode embodiment of the power transmission system 101, circuit breaker 73d, intersection disconnectors 55d and 56d, and circuit breaker 74d are in the open (disconnected) state. And the inter-circuit switching device 63cd is in the open (disconnected) state. That is, the third cable lines 44c and 45c and the fourth cable lines 44d and 45d are disconnected from each other.

[0050] Thus, in the second embodiment, the power transmission system 101 transmits power with only a portion (two) of the four cable lines connected, because the power transmitted during normal operation is smaller than that of the power transmission system 100 in the first embodiment. In the example shown in Figure 7, two of the four cable lines are configured in parallel during normal operation, but this is not the only configuration. The control unit 81 may disconnect (stop) three or fewer of the four cable lines depending on the power transmitted from the generator G to the busbar B. By increasing or decreasing the number of parallel cable lines in this way, power transmission losses can be reduced.

[0051] (Operation of the second embodiment) The operation of the power transmission system 101 in the second embodiment is the same as the operation of the power transmission system 100 in the first embodiment shown in Figure 3, except for the opening and closing control of the circuit breakers, inter-section disconnectors, and inter-line switching devices by the control unit. That is, since the power transmission system 101 in the second embodiment has only two sections and it is not possible to control the system to exclude a specific cable line from the power transmission system using inter-section disconnectors, the system performs control to exclude the section between the circuit breaker at the power transmission terminal and the circuit breaker at the power receiving terminal from the power transmission system.

[0052] The control unit 81 controls the inter-section disconnectors, inter-circuit switches, and circuit breakers to configure the calculated path. For example, the control unit 81 controls the circuit breakers 73a-73d and 74a-74d to the open state to stop the power supply, and then controls the inter-section disconnectors and inter-circuit switches to open and close according to the calculation result.

[0053] Figure 8 shows the state of the power transmission system 101 after fault removal according to the second embodiment. As shown in Figure 8, assume that a ground fault occurs in the second cable line 45b of the second section 35.

[0054] In the example shown in Figure 8, the power transmission system 101 of the embodiment has the following configurations: inter-section disconnectors 55a, 56a and inter-section disconnectors 55d, 56d are in a closed state; inter-section disconnectors 55b, 56b and inter-section disconnectors 55c, 56c are in an open state; inter-circuit switching devices 63ab, 63bc, 63cd are in an open state; circuit breakers 73a, 73d, 74a, 74d are in a closed state; and circuit breakers 73b, 73c, 74b, 74c are in an open state. In other words, instead of excluding the second cable lines 44b and 45b, which include the fault location, from the power transmission system 101, the fourth cable lines 44d and 45d are connected as power transmission lines.

[0055] With this configuration, power transmission under normal conditions is performed using two lines, the first cable lines 44a, 45a and the second cable lines 44b, 45b shown in Figure 7. After a failure, the system switches to power transmission using two lines, for example, the first cable lines 44a, 45a and the fourth cable lines 44d, 45d shown in Figure 8. In other words, by replacing the cable lines disconnected due to the failure with cable lines that were open under normal conditions, it is possible to maintain the number of power transmission lines.

[0056] The power transmission system 101 of the second embodiment can reduce power transmission losses because it can open the section where a fault has occurred using inter-section disconnectors and inter-circuit switching devices of the intermediate electrical equipment, and continue power transmission using the cable section where no fault has occurred. The intermediate electrical equipment does not require circuit breakers for fault removal, eliminating the cost of circuit breakers and reducing the cost required for the power transmission system.

[0057] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0058] 11, 13... Power transmission terminals, 12, 14... Power receiving terminals 21...First intermediate electrical equipment, 22...Second intermediate electrical equipment, 23...Intermediate electrical equipment 31-33…Sections 1-3, 34-35…Sections 1-2 41a~41d, 42a~42d, 43a~43d, 44a~44d, 45a~45d... Cable lines 1 to 4 51a~51d, 52a~52d, 53a~53d, 54a~54d, 55a~55d, 56a~56d...Intersection disconnector 61ab, 61bc, 61cd, 62ab, 62bc, 62cd, 63ab, 63bc, 63cd… Inter-circuit switching devices 71a~71d, 72a~72d, 73a~73d, 74a~74d... Circuit breakers 80, 81… Control Unit 100, 101… Power transmission system B...Bus line G... Generator

Claims

1. A power transmission terminal section having multiple first circuit breakers capable of interrupting the power transmission, A first section having a plurality of first cable lines to which one end of each of the plurality of first circuit breakers is connected, and capable of transmitting the power transmitted through the plurality of first circuit breakers via the plurality of first cable lines, A second section having a plurality of second cable lines corresponding to each of the plurality of first cable lines, and transmitting the power transmitted by the plurality of first cable lines via the plurality of second cable lines, An intermediate electrical installation comprising: a plurality of disconnectors capable of opening and closing the connection between the other end of each of the plurality of first cable lines and one end of each of the plurality of second cable lines; and a plurality of switches capable of opening and closing the connection between the connection points between the other end of each of the plurality of first cable lines and one end of each of the plurality of second cable lines; A power receiving terminal section having a plurality of second circuit breakers capable of interrupting the transmission power received from the other end of each of the plurality of second cable lines, A control unit is configured to detect accidents occurring in the first and second sections, and to control the opening and closing of each of the plurality of disconnectors and the plurality of switches. A power transmission system equipped with this system.

2. The power transmission system according to claim 1, characterized in that the intermediate electrical equipment is provided with reactors at the electrical connection points of each of the plurality of disconnectors and the plurality of switches.

3. The control unit, If an accident occurs in any of the above-mentioned multiple first cable lines and multiple second cable lines, Controlling the opening and closing of the plurality of first circuit breakers and the plurality of second circuit breakers to exclude the cable line in which the fault was detected from the plurality of first cable lines and the plurality of second cable lines. The power transmission system according to claim 1, characterized by the following:

4. The control unit, The power transmission path that minimizes the power transmission loss for the entire set of first and second cable lines is calculated. Controlling the opening and closing of each of the multiple disconnectors and the multiple switches to realize the power transmission path obtained as a result of the above calculation. The power transmission system according to claim 3, characterized by the above.

5. The power transmission system according to claim 3, characterized in that the control unit can transmit power through some of the multiple first cable lines and the multiple second cable lines in place of the cable line in which the fault was detected.

6. A control method for controlling the power transmission system described in claim 1, The system detects faults in the plurality of first cable lines and the plurality of second cable lines. The cable line in which the fault was detected is excluded from the plurality of first cable lines and the plurality of second cable lines. The power transmission path that minimizes the power transmission loss for the entire set of first and second cable lines is calculated. The power transmission path obtained as a result of the calculation is configured by controlling the opening and closing of each of the aforementioned multiple disconnectors and the aforementioned multiple switches. A control method characterized by the following.

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