Power grid protection system

Abstract

The present invention is a power grid protection system (100) for protecting a power grid (50) comprising a voltage line (56) through which a current supplied from a transformer secondary-side facility flows, and a grounded neutral line (55), said power grid protection system (100) comprising a circuit breaker (11) installed in the voltage line (56), and a commutator (12) that connects the voltage line (56) and the neutral line (55) on the transformer secondary-side facility side from the breaker (11). When an abnormality occurs in the voltage line (56) due to a short-circuit accident or a ground fault accident, the accident current flowing through the voltage line (56) is commutated to the neutral line (55) via the commutator (12).

Description

[Technical Field]

[0001] The present disclosure relates to a power system protection system that protects a power system when an abnormality occurs due to a short-circuit fault or a ground fault. [Background Art]

[0002] Conventionally, in a power system that supplies power transformed by substation equipment to a load, a mechanical circuit breaker has been used to protect the power system when an abnormality occurs due to a short-circuit fault or a ground fault. However, with mechanical circuit breakers, current interruption is not completed until the arc generated when the current is interrupted is extinguished, so current interruption takes time and the spread range of the fault becomes large.

[0003] Patent Document 1 discloses a power system protection system that protects a power system when an abnormality occurs due to a short-circuit fault or a ground fault. The power system protection system disclosed in Patent Document 1 includes a power switch, a bridge circuit installed on the load side relative to the power switch, and a contactor installed on the load side relative to the bridge circuit. The power system protection system disclosed in Patent Document 1 includes a magnetically driven switch, and when an abnormality due to a short-circuit fault or a ground fault occurs, the magnetically driven switch closes to commutate the fault current to a neutral line. The apparatus disclosed in Patent Document 1 commutates the fault current to the neutral line, thereby preventing the fault current from flowing to the location where the short-circuit fault or ground fault occurs without using a circuit breaker that interrupts the fault current, and can suppress an increase in the spread range of the fault. [Prior Art Document] [Patent Document]

[0004] [Patent Document 1] Japanese National Publication of International Patent Application No. Hei 8-508154 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] However, the power system protection system disclosed in Patent Document 1 does not allow fault current to flow to the short-circuit location by commutating the fault current to the neutral wire. However, even after commutating the fault current, the short-circuit location does not become current-free. Therefore, simply commutating the fault current is not enough to open the contactor and disconnect the short-circuit location. Consequently, the power system protection system disclosed in Patent Document 1 could not disconnect the short-circuit location and resume power transmission unless the fault current was interrupted by another device after commutation. For this reason, the device disclosed in Patent Document 1 had the problem of taking time from the occurrence of a fault to the resumption of power transmission.

[0006] This disclosure is made in view of the above and aims to provide a power system protection system that shortens the time from the occurrence of an abnormality due to a short-circuit or ground fault to the resumption of power transmission to the load. [Means for solving the problem]

[0007] To solve the aforementioned problems and achieve the objectives, the power system protection system according to this disclosure is a power system protection system that protects a power system comprising a voltage line through which current supplied from the secondary side equipment of a substation flows, and a grounded neutral line, and comprises a circuit breaker installed on the voltage line and a commutator that connects the voltage line and the neutral line on the secondary side equipment of the substation beyond the circuit breaker. When an abnormality occurs in the voltage line due to a short circuit or ground fault, the power system protection system commutates the fault current flowing in the voltage line to the neutral line via the commutator. [Effects of the Invention]

[0008] According to this disclosure, it is possible to obtain a power system protection system that shortens the time from the occurrence of an anomaly due to a short-circuit or ground fault to the resumption of power transmission to the load. [Brief explanation of the drawing]

[0009] [Figure 1] Diagram showing the configuration of the power grid protection system according to Embodiment 1. [Figure 2]Functional block diagram of the control unit of the power grid protection system according to Embodiment 1 [Figure 3] Schematic diagram of the circuit breaker tripping mechanism of the power grid protection system according to Embodiment 1 [Figure 4] A diagram showing the tripping characteristics of the circuit breaker of the power grid protection system according to Embodiment 1. [Figure 5] A flowchart showing the operation flow of electromagnetic tripping of a circuit breaker in a power grid protection system according to Embodiment 1. [Figure 6] This diagram shows a state in which an abnormality occurs due to a short-circuit fault or ground fault in a branch circuit of the power system that is the target of protection by the power system protection system according to Embodiment 1. [Figure 7] This figure shows the state in which the semiconductor switch of the commutator in the power grid protection system according to Embodiment 1 is turned ON. [Figure 8] This figure shows the state in which the semiconductor switch of the commutator in the power grid protection system according to Embodiment 1 is turned off. [Figure 9] This figure shows a first example of the progression of fault current during an abnormality caused by a short-circuit or ground fault in the power system protection system according to Embodiment 1. [Figure 10] This figure shows a second example of the progression of fault current during an abnormality caused by a short-circuit or ground fault in the power system protection system according to Embodiment 1. [Figure 11] Schematic diagram of a current-limiting unit of a circuit breaker in a power grid protection system according to a modified example of Embodiment 1. [Figure 12] Diagram showing the configuration of the power grid protection system according to Embodiment 2. [Figure 13] Diagram showing the configuration of the power grid protection system according to Embodiment 3. [Figure 14] This figure shows the configuration of the control unit of the power grid protection system according to Embodiment 4. [Figure 15] This figure shows the hardware configuration of the control unit of the power grid protection system according to Embodiments 1 to 4. [Modes for carrying out the invention]

[0010] Hereinafter, the power system protection system according to the embodiment will be described in detail with reference to the drawings.

[0011] Embodiment 1. Fig. 1 is a diagram showing the configuration of the power system protection system according to Embodiment 1. The power system protection system 100 according to Embodiment 1 is a system that protects a power system 50 that supplies power transformed by substation equipment to a load 53. The power system 50, which is a target to be protected by the power system protection system 100, includes a transformer 51 serving as secondary equipment of the substation equipment, a voltage line 56, and a neutral line 55. The transformer 51 steps down power supplied from unillustrated primary equipment of the substation equipment and supplies the power to the voltage line 56. The voltage line 56 has a main system 52 connected to the transformer 51, a plurality of branch paths 54 branching from the main system 52 and connected to each load 53, and a grounding wire 58 connecting each load 53 and a ground 57. The power system protection system 100 includes a plurality of circuit breakers 11, a converter 12 installed upstream of the plurality of circuit breakers 11, a control device 13 having a control unit 80 that controls the circuit breakers 11 and the converter 12, and a relay 14 and an instrument transformer 15 installed on each of the circuit breakers 11. The circuit breakers 11 include a main circuit breaker 111 installed in the main system 52 and lower circuit breakers 112 provided in each branch path 54. The power system 50 and the power system protection system 100 constitute a DC power distribution system that supplies DC power to the load 53.

[0012] The circuit breakers 11 and the converter 12 included in the power system protection system 100 are installed on the same switchboard.

[0013] The commutator 12 includes a plurality of semiconductor switches 121 connected in series or parallel, and connects the main trunk system 52 and the neutral wire 55. By connecting the plurality of semiconductor switches 121 in parallel, the current that can be passed through the commutator 12 can be increased. Further, by connecting the plurality of semiconductor switches 121 in series, the withstand voltage of the commutator 12 can be increased. The main circuit breaker 111 and the subordinate circuit breaker 112 are mechanical circuit breakers. The relay 14 transmits an abnormality detection signal to the control unit 80 when a fault current larger than the rated current flows upon occurrence of an abnormality caused by a short-circuit fault or a ground fault. The instrument transformer 15 reduces the voltage and current of the current flowing through the main trunk system 52 or the branch path 54 and outputs the resulting current.

[0014] Figure 2 is a functional block diagram of the control unit of the power system protection system according to the first embodiment. The control unit 80 includes: an abnormality detection signal receiving unit 81 that receives an abnormality detection signal output when the relay 14 detects the occurrence of an abnormality caused by a short-circuit fault or a ground fault; a commutation completion detection unit 82 that detects completion of commutation based on the magnitude of the current output by the instrument transformer 15; a semiconductor switch control unit 83 that controls the semiconductor switch 121 of the commutator 12; and a circuit breaker control unit 84 that controls the circuit breaker 11.

[0015] Figure 3 is a schematic configuration diagram of a tripping mechanism of the circuit breaker of the power system protection system according to the first embodiment. The circuit breaker 11 includes a tripping mechanism 40 comprising: a heating resistor 31; a bimetal 32 attached to the heating resistor 31; an electromagnet 33 having a fixed iron core 331 and a movable iron core 332; a tripping rod 34 fixed to the movable iron core 332; a molded case 35; and a common tripping shaft 37 rotatably supported inside the molded case 35 by a support arm 36. The tripping mechanism 40 further includes a latch 38 protruding from the common tripping shaft 37, and a roller trigger 39 engaged with the latch 38. The tripping mechanism 40 of the circuit breaker 11 is of a thermal electromagnetic type that performs thermal tripping by the bimetal 32 and electromagnetic tripping by the electromagnet 33.

[0016] When an overcurrent flows, the Joule heating generated in the heating resistor 31 causes the temperature of the bimetal 32 to rise, causing the bimetal 32 to bend in the direction of arrow A, and the common tripping shaft 37 to rotate in the direction of arrow B. As the common tripping shaft 37 rotates in the direction of arrow B, the engagement between the latch 38 and the roller trigger 39 is released, and the circuit breaker 11 trips.

[0017] Furthermore, if a large current such as a short-circuit current flows as an overcurrent, current flows through the movable core 332, and the movable core 332 is attracted to the fixed core 331. At this time, the tripping rod 34 fixed to the movable core 332 contacts a projection provided on the common tripping shaft 37, causing the common tripping shaft 37 to rotate in the direction of arrow B. As the common tripping shaft 37 rotates in the direction of arrow B, the engagement between the latch 38 and the roller trigger 39 is released, and the circuit breaker 11 trips. The circuit breaker 11 used as the lower circuit breaker 112 is equipped with a detection unit (not shown) that detects fault current flowing due to a short-circuit or ground fault, and the circuit breaker 11 detects the occurrence of a fault itself and performs an electromagnetic tripping operation. The circuit breaker 11 used as the main circuit breaker 111 is not equipped with a detection unit that detects fault current flowing due to a short-circuit or ground fault, and performs an electromagnetic tripping operation when it receives a trip command output from the circuit breaker control unit 84. Alternatively, a circuit breaker 11 equipped with a detection unit (not shown) that detects fault currents flowing due to a short-circuit or ground fault may be used as the main circuit breaker 111. In this case, the control unit 80 can be configured without the circuit breaker control unit 84.

[0018] Figure 4 shows the tripping characteristics of the circuit breaker in the power system protection system according to Embodiment 1. When the magnitude of the overcurrent is less than or equal to current I1, the circuit breaker 11 performs thermal tripping using a bimetallic strip, and when the magnitude of the overcurrent exceeds current I1, it performs electromagnetic tripping using an electromagnet. Thermal tripping is performed by transferring Joule heat generated in the heating resistor 31 to the bimetallic strip 32, and therefore the operating time is longer than that of electromagnetic tripping.

[0019] Figure 5 is a flowchart illustrating the operation flow of the electromagnetic tripping of a circuit breaker in a power system protection system according to Embodiment 1. In step S1, a short-circuit or ground fault occurs and a fault current flows. In step S2, current flows through the movable core 332 and the electromagnetic tripping is initiated. In step S3, the tripping rod 34 fixed to the movable core 332 rotates the common tripping shaft 37, performing a tripping latch operation that releases the engagement between the latch 38 and the roller trigger 39. In step S4, the roller trigger 39 rotates due to the tripping latch operation, and a movable contact (not shown) begins to separate from a fixed contact (not shown). At this time, an arc is generated between the movable contact and the fixed contact. In step S5, the movable contact moves to a preset position, completing the separation between the movable contact and the fixed contact, and the arc is stretched. In step S6, the stretched arc is extinguished, completing the interruption of the current. In the above operation, the time from when a short-circuit or ground fault occurs until the contacts begin to separate in step S4 is the contact opening time.

[0020] Figure 6 shows a state in which an abnormality occurs due to a short-circuit fault or ground fault in a branch of the power system protected by the power system protection system according to Embodiment 1. Note that only a part of the power system protection system 100 is shown in Figure 6, and the relay 14 and instrument transformer 15 are not shown. When an abnormality occurs due to a short-circuit fault or ground fault in one of the branch lines 54, current flows without passing through the load 53, and a fault current 22, which is larger than the rated current 21, flows through the branch line 54 where the short-circuit fault or ground fault abnormality occurred. When the relay 14 detects the fault current 22, it notifies the control unit 80 of the occurrence of an abnormality due to a short-circuit fault or ground fault. In addition, the lower circuit breaker 112 installed in the branch line 54 where the short-circuit fault or ground fault abnormality occurred detects the short-circuit fault or ground fault and performs an electromagnetic trip operation.

[0021] When the control unit 80 is notified of an abnormality due to a short-circuit or ground fault, it outputs a command to the commutator 12 to turn on the semiconductor switch 121. For example, when the control unit 80 detects that the circuit breaker 11 has opened due to a short-circuit or ground fault, it outputs a command to the commutator 12 to turn on the semiconductor switch 121. Figure 7 shows the state in which the semiconductor switch of the commutator of the power system protection system according to Embodiment 1 is turned on. Note that Figure 7 shows only a part of the power system protection system 100, and the relay 14 and instrument transformer 15 are not shown. The commutator 12 is turned on when it is commutating the fault current to the neutral wire 55 (not shown in Figure 7) and at least when it detects that the circuit breaker 11 has occurred a short-circuit or ground fault. For example, the commutator 12 is turned on when it is commutating the fault current to the neutral wire 55 and at least when it detects that the circuit breaker 11 has opened. Because the semiconductor switch 121 operates faster than a mechanical switch, even if the control unit 80 outputs commands to the commutator 12 and the lower circuit breaker 112 simultaneously, the operation to turn on the semiconductor switch 121 of the commutator 12 occurs before the tripping operation of the lower circuit breaker 112. In other words, by the time the tripping operation of the lower circuit breaker 112 occurs, the semiconductor switch 121 of the commutator 12 is already turned on, the fault current 22 has been commutated to the neutral line 55, and the current flowing through the branch line 54 is smaller than the fault current 22. For this reason, no arc is generated, or only a weak arc is generated, during the tripping operation of the lower circuit breaker 112. Therefore, deterioration of the lower circuit breaker 112 due to the tripping operation can be suppressed.

[0022] After the lower circuit breaker 112 has finished tripping, the control unit 80 turns off the semiconductor switch 121 of the commutator 12. Figure 8 shows the state in which the semiconductor switch of the commutator of the power system protection system according to Embodiment 1 is turned off. Note that Figure 8 shows only a part of the power system protection system 100, and the relay 14 and instrument transformer 15 are not shown. Since the lower circuit breaker 112 installed in the branch line 54 where an abnormality due to a short circuit or ground fault has occurred is in the tripped state, no current flows through the branch line 54 where the abnormality due to a short circuit or ground fault has occurred. As a result, the rated current 21 flows only through the branch line 54 and the main system 52 where no abnormality due to a short circuit or ground fault occurred.

[0023] Furthermore, it is preferable that the time from when the relay 14 detects the fault current until a command to turn on the semiconductor switch 121 of the commutator 12 is output is less than 1 / 4 cycle of the frequency of the current flowing through the power system 50. Figure 9 is a diagram showing a first example of the transition of fault current when an abnormality occurs due to a short-circuit fault or ground fault in the power system protection system according to Embodiment 1. In Figure 9, the solid line shows the current flowing through the circuit breaker 11 installed in the main system 52 or branch line 54 where an abnormality has occurred due to a short-circuit fault or ground fault, the dashed line shows the current flowing through the semiconductor switch 121 of the commutator 12, and the dashed line shows the current flowing through the circuit breaker when the fault current is interrupted in a power system protection system that interrupts the fault current with a mechanical circuit breaker. In the first example shown in Figure 9, the time from when the relay 14 detects the fault current until a command to turn on the semiconductor switch 121 of the commutator 12 is output is 1 / 4 cycle or more of the frequency of the current flowing through the power system 50. If an abnormality occurs due to a short circuit or ground fault at time t11, at time t12a, the lower circuit breaker 112 detects the occurrence of the short circuit or ground fault and starts tripping by electromagnetic tripping. At time t12b, the control unit 80 outputs a command to the commutator 12 to turn on the semiconductor switch 121. As a result, from time t12b onward, the current flowing through the semiconductor switch 121 increases, while the current flowing through the lower circuit breaker 112 decreases. At time t13, the tripping operation of the lower circuit breaker 112 is completed. The instrument transformer 15, detecting that no current is flowing through the lower circuit breaker 112, notifies the control unit 80 that the commutation of the fault current is complete. As a result, at time t14, the control unit 80 outputs a command to the commutator 12 to turn off the semiconductor switch 121. As a result, from time t14 onward, the current flowing through the semiconductor switch 121 decreases. At time t15, when the current increases, the operation to turn off the semiconductor switch 121 is completed. Because the lower circuit breaker 112 is tripped, even if the semiconductor switch 121 of the commutator 12 is turned off, no current flows to the location where the short-circuit or ground fault malfunction occurred.

[0024] As shown in Figure 9, if the time from when the relay 14 detects the fault current until the command to turn on the semiconductor switch 121 of the commutator 12 is output is 1 / 4 cycle or more of the frequency of the current flowing through the power system 50, the current flowing through the lower circuit breaker 112 will reach its maximum before the commutation of the fault current begins. Therefore, if the time from when the relay 14 detects the fault current until the command to turn on the semiconductor switch 121 of the commutator 12 is output is 1 / 4 cycle or more of the frequency of the current flowing through the power system 50, a circuit breaker with the same breaking capacity as the lower circuit breaker of a power system protection system without a commutator must be used as the lower circuit breaker.

[0025] Figure 10 shows a second example of the transition of fault current when an abnormality occurs due to a short-circuit fault or ground fault in the power system protection system according to Embodiment 1. In Figure 10, the solid line shows the current flowing through the circuit breaker 11 installed in the main system 52 or branch line 54 where an abnormality has occurred due to a short-circuit fault or ground fault, the dashed line shows the current flowing through the semiconductor switch 121 of the commutator 12, and the dashed line shows the current flowing through the circuit breaker when the fault current is interrupted in a power system protection system that interrupts the fault current with a mechanical circuit breaker. When an abnormality occurs due to a short-circuit fault or ground fault at time t1, at time t2, the lower circuit breaker 112 detects the occurrence of the short-circuit fault or ground fault and starts tripping by electromagnetic tripping. The control unit 80 also outputs a command to the commutator 12 to turn on the semiconductor switch 121. Therefore, from time t2 onward, the current flowing through the semiconductor switch 121 increases, while the current flowing through the lower circuit breaker 112 decreases. At time t3, the tripping operation of the lower circuit breaker 112 is completed. The instrument transformer 15, detecting that no current is flowing through the lower circuit breaker 112, notifies the control unit 80 that the commutation of the fault current is complete. At time t4, the control unit 80 outputs a command to the commutator 12 to turn off the semiconductor switch 121. As a result, the current flowing through the semiconductor switch 121 decreases from time t4 onward. At time t5, when the current increases, the operation to turn off the semiconductor switch 121 is completed. Because the lower circuit breaker 112 has tripped, even if the semiconductor switch 121 of the commutator 12 is turned off, no current flows to the location where the short-circuit or ground fault anomaly occurred. As a result, power transmission is normally resumed in branch lines 54 other than the branch line 54 where the short-circuit or ground fault anomaly occurred. In the power system protection system 100 according to Embodiment 1, the maximum current flowing through the lower circuit breaker 112 is smaller than the maximum current flowing through the lower circuit breaker in a power system protection system without a commutator. Therefore, a smaller circuit breaker with a lower breaking capacity can be used compared to a power system protection system without a commutator.

[0026] The commutator 12 can consolidate the breaking capacities of the individual circuit breakers 11, and by changing the number of commutators 12 in parallel and series, the overall breaking capacity of the power system protection system 100 can be easily adjusted. Furthermore, since high-breaking-capacity circuit breakers 11 are not required in the power system protection system 100, the number of circuit breaker models 11 can be reduced by standardizing the models of the circuit breakers 11. By standardizing the models of the circuit breakers 11, the selection of circuit breaker models 11 becomes unnecessary, and the panel design can be standardized. In addition, when increasing the breaking capacity of the power system protection system 100, it is not necessary to replace all the circuit breakers 11, but only the number of commutators 12 in parallel and series needs to be adjusted, so the overall breaking capacity of the power system protection system 100 can be easily increased.

[0027] In the above explanation, an example was given of an abnormality occurring in the branch line 54 due to a short circuit or ground fault. However, if an abnormality occurs in the main circuit 52 due to a short circuit or ground fault, when the relay 14 installed in the main circuit 52 detects the occurrence of the abnormality due to a short circuit or ground fault, the control unit 80 can trip the main circuit breaker 111 and turn on the semiconductor switch 121 of the commutator 12, thereby commutating the fault current and disconnecting the short circuit.

[0028] Furthermore, if multiple power systems 50 are provided corresponding to each phase of a three-phase AC power system, the control unit 80 can, in the case of a two-phase short circuit, turn on the semiconductor switches 121 of the commutators 12 of the power systems 50 corresponding to the two phases where the short-circuit fault occurred, and in the case of a three-phase short circuit, turn on the semiconductor switches 12 of the commutators 12 of the power systems 50 corresponding to the three phases, thereby commutating the fault current and isolating the short-circuit location only in the phase where the short-circuit fault occurred.

[0029] Since the semiconductor switch 121 operates faster than a mechanical switch, the power system protection system 100 according to Embodiment 1 can prevent fault current from flowing to the fault location faster than when using a mechanical circuit breaker, thereby preventing the fault from spreading to a wider area. Furthermore, after the fault current has been commutated, the location where the short-circuit fault occurred can be isolated by interrupting the rated current at the lower circuit breaker 112 installed in the branch line 54 where the fault due to a short-circuit fault or ground fault occurred. The main circuit breaker 111 and the lower circuit breaker 112 do not need to interrupt the fault current, and only need to interrupt the rated current, so the power system protection system 100 can be miniaturized by using small circuit breakers with low breaking capacity. Furthermore, because the main circuit breaker 111 and the lower circuit breaker 112 do not interrupt the fault current, it is easy to comply with the protective coordination specified in IEC 60947-1, Coordination of the components of the motor circuit, type 2, a standard set by the International Electrotechnical Commission, which states that "there shall be no damage except for slight welding of the electromagnetic switches, and they shall remain usable without replacement."

[0030] Furthermore, the semiconductor switch 121 of the commutator 12 is normally in the off state and is only turned on when an abnormality occurs due to a short circuit or ground fault, so there is no need to provide cooling equipment.

[0031] The power system protection system 100 according to Embodiment 1 can interrupt the current flowing to the location of the anomaly at the circuit breaker 11 installed in the main system 52 or branch line 54 where the anomaly due to a short circuit or ground fault occurred, after the commutation of the fault current is completed. Therefore, power supply to the load 53 can be resumed in a short time after the anomaly due to a short circuit or ground fault occurs.

[0032] In the above explanation, a commutator 12 using a semiconductor switch 121 was given as an example, but the commutator 12 can also be configured using a mechanical switch that can operate at a speed faster than 1 / 4 cycle of the frequency of the current flowing through the power system 50.

[0033] Furthermore, the circuit breaker 11 may be equipped with a current-limiting unit that limits the fault current that flows when a short-circuit or ground fault occurs. Figure 11 is a schematic diagram of a current-limiting unit of a circuit breaker in a power system protection system according to a modified example of Embodiment 1. The current-limiting unit 60 comprises a grid 61 installed around a fixed contact 72 provided on a fixed contact 71, and a projection 62 provided on the fixed contact 71. The grid 61 is composed of a plurality of insulating members arranged at narrow intervals. When a fault current flows when a short-circuit or ground fault occurs, an electromagnetic repulsive force acts between the movable contact 73 and the fixed contact 71, causing the movable contact 73 to rotate in the direction of arrow C, which causes the movable contact 74 provided on the movable contact 73 to separate from the fixed contact 72, and an arc is generated between the movable contact 74 and the fixed contact 72 as shown by line X in Figure 11. The arc generated between the movable contact and the fixed contact is attracted to the grid 61 as shown by line Y in Figure 11, forcibly reducing the arc spot and narrowing the arc column. Subsequently, as shown by line Z in Figure 11, the arc spot of the fixed contact 72 is rapidly commutated to the projection 62, and the arc is cooled by the grid 61. Then the circuit breaker 11 body trips, and the interruption is completed.

[0034] If the circuit breaker 11 is equipped with a current limiting unit 60, the control unit 80 may detect the automatic opening of the current limiting unit 60 and issue an ON command to the commutator 12. In this case, it is possible to turn on the commutator 12 at an earlier timing compared to when the opening of the circuit breaker 11 is detected, and the time required for commutation and interruption can be shortened due to the effect of the current limiting unit 60.

[0035] Embodiment 2. Figure 12 shows the configuration of the power system protection system according to Embodiment 2. The power system protection system 100 according to Embodiment 2 differs from the power system protection system 100 according to Embodiment 1 in that the control unit 80 is provided on the commutator 12. Other than this, it is the same as the power system protection system 100 according to Embodiment 1, so redundant explanations are omitted.

[0036] In the power system protection system 100 according to Embodiment 2, since the control unit 80 is located in the commutator 12, the signal line connecting the control unit 80 and the semiconductor switch 121 is short, and the delay in transmitting commands to turn the semiconductor switch 121 on or off from the control unit 80 to the semiconductor switch 121 is small. Therefore, the time required from the occurrence of an abnormality due to a short circuit or ground fault to the commutation of the fault current can be shortened.

[0037] Embodiment 3. Figure 13 shows the configuration of the power system protection system according to Embodiment 3. The power system protection system 100 according to Embodiment 3 differs from the power system protection system 100 according to Embodiment 1 in that the control unit 80 is provided on the relay 14. The control unit 80 is provided on the relay 14 installed in the main system 52 or branch line 54 of the voltage line 56 where a short circuit or ground fault is considered to be highly likely to occur. In Embodiment 3, the control unit 80 is provided on the relay 14 installed in the main system 52. Other than this, it is the same as the power system protection system 100 according to Embodiment 1, so redundant explanations are omitted.

[0038] In the power system protection system 100 according to Embodiment 3, since the control unit 80 is located on the relay 14, the signal line connecting the control unit 80 and the relay 14 is short, and the delay in transmitting the fault detection signal from the relay 14 to the control unit 80 is small. Therefore, the time required from the occurrence of an abnormality due to a short circuit or ground fault to the commutation of the fault current can be shortened.

[0039] Embodiment 4. Figure 14 shows the configuration of the control unit of the power system protection system according to Embodiment 4. The power system protection system 100 according to Embodiment 4 differs from the power system protection system 100 according to Embodiment 1 in that the control unit 80 includes a commutation count storage unit 85. Other than this, it is the same as the power system protection system 100 according to Embodiment 1, so redundant explanations are omitted.

[0040] The commutation count storage unit 85 stores the number of times a command to turn on the semiconductor switch 121 has been output to the commutator 12.

[0041] If an abnormality occurs due to a short circuit or ground fault and fault current flows through the voltage line 56, a large current exceeding the rated current will flow, which may cause deterioration of the main circuit 52 and branch lines 54, deterioration of loads 53, and deterioration of circuit breakers 11, relays 14, and instrument transformers 15, etc.

[0042] When a fault current is interrupted by a mechanical circuit breaker, the arc generated during the current interruption leaves traces such as melting of a portion of the circuit breaker's contacts, making it possible to retrospectively recognize that the fault current was interrupted by the circuit breaker. Therefore, users of power system protection systems using mechanical circuit breakers can discover traces of the fault current during maintenance of the power system protection system, even if it is not immediately after an abnormality caused by a short circuit or ground fault, and replace voltage lines 56, etc. In contrast to this, the embodiment 4 In the power system protection system 100 related to this, the commutator 12 commutates the fault current to the neutral line 55, so the circuit breaker 11 does not interrupt the fault current, and no trace of the fault current remains in the circuit breaker 11. However, in the embodiment 4 In the power system protection system 100, the number of times a command to turn on the semiconductor switch 121 is output to the commutator 12 is stored in the commutation count storage unit 85. Therefore, the user of the power system protection system 100 can retrospectively recognize that an abnormality has occurred in the voltage line 56 due to a short circuit or ground fault by checking the number stored in the commutation count storage unit 85. 4 Users of the power system protection system 100 can detect traces of fault current during maintenance of the power system protection system 100 and replace voltage lines 56, etc., even if it is not immediately after a short-circuit or ground fault occurs.

[0043] Figure 15 shows the hardware configuration of the control unit of the power system protection system according to Embodiments 1 to 4. The control unit 80 is realized by a computer system comprising a processor 91 that performs various processes, a memory 92 which is the main memory, and a storage device 93 that stores information.

[0044] The processor 91 may be a computing device such as an arithmetic unit, microprocessor, microcomputer, CPU (Central Processing Unit), or DSP (Digital Signal Processor). The memory 92 may be a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). The storage device 93 stores a program for executing the process of controlling the commutator 12 and the circuit breaker 11.

[0045] The above computer system realizes the functions of the control unit 13 by having the processor 91 read programs corresponding to the processing of each component, stored in the storage device 93, into the memory 92 and execute them. The memory 92 is also used as temporary memory for each process executed by the processor 91. The programs executed by the processor 91 may be provided stored on a storage medium or provided via a network.

[0046] The configurations shown in the above embodiments are merely examples of the content, and can be combined with other known technologies. It is also possible to omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of Symbols]

[0047] 11 Circuit breaker, 12 Commutator, 13 Control device, 14 Relay, 15 Instrument transformer, 21 Rated current, 22 Fault current, 31 Heating resistor, 32 Bimetal, 33 Electromagnet, 34 Tripping rod, 35 Molded case, 36 Support arm, 37 Common tripping shaft, 38 Latch, 39 Roller trigger, 40 Tripping mechanism, 50 Power system, 51 Transformer, 52 Main system, 53 Load, 54 Branch line, 55 Neutral wire, 56 Voltage line, 57 Ground, 58 Grounding wire, 60 Current limiting unit, 61 Grid, 62 Projection, 71 Fixed contact, 72 Fixed contact, 73 Movable contact, 74 Movable contact, 80 Control unit, 81 Anomaly detection signal receiver, 82 Commutation completion detection unit, 83 Semiconductor switch control unit, 84 Circuit breaker control unit, 85 Commutation count memory unit, 91 Processor, 92 Memory, 93 Storage device, 100 Power system protection system, 111 Main circuit breaker, 112 Lower circuit breakers, 121 Semiconductor switch, 331 Fixed core, 332 Movable core.

Claims

1. A power system protection system that protects a power system comprising a voltage line through which current supplied from the secondary side equipment of a substation flows, and a grounded neutral line, A circuit breaker installed on the aforementioned voltage line, The circuit breaker is further equipped with a commutator that connects the voltage line and the neutral line on the secondary side of the substation equipment. A power system protection system characterized in that, when an abnormality occurs in the voltage line due to a short-circuit fault or a ground fault, the fault current flowing through the voltage line is commutated to the neutral line via the commutator.

2. The power system protection system according to claim 1, characterized in that the commutator is turned ON when the circuit breaker detects the occurrence of a short-circuit fault or a ground fault when commutating the fault current to the neutral line.

3. The power system protection system according to claim 2, characterized in that the commutator is turned ON when it detects that the circuit breaker has opened when commutating the fault current to the neutral line.

4. The power system protection system according to claim 2, characterized in that the commutator starts commutating the fault current to the neutral wire before the circuit breaker opens.

5. The power system protection system according to claim 1, characterized in that the commutator commutates the fault current to the neutral line within a time of less than 1 / 4 cycle of the frequency of the current flowing through the voltage line after an abnormality due to the short-circuit fault or the ground fault occurs in the voltage line.

6. The voltage line comprises a main system connected to the secondary equipment of the substation and a plurality of branch lines branching off from the main system. The circuit breaker comprises a main circuit breaker installed in the main circuit and lower circuit breakers installed in each of the branch lines. The power system protection system according to claim 1, characterized in that the commutator connects the main circuit and the neutral line on the secondary equipment side of the substation equipment side, rather than on the main circuit breaker side.

7. The power system protection system according to claim 1, characterized in that the commutator comprises a plurality of semiconductor switches connected in parallel or in series.

8. The power system protection system according to claim 1, further comprising a commutation completion detection unit for detecting when the commutation of the fault current to the neutral wire has been completed.

9. The power system protection system according to claim 1, characterized in that it includes a control unit that controls the commutator and the circuit breaker.

10. The system includes a relay that monitors the current flowing through the aforementioned voltage line. The power system protection system according to claim 9, characterized in that the control unit is provided in the relay.

11. The power system protection system according to claim 1, characterized in that the commutator has a commutation count storage unit that stores the number of times the commutator has commutated the fault current to the neutral wire.

12. The power system protection system according to any one of claims 1 to 11, characterized in that the circuit breaker and the commutator are installed in the same substation.

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