Protection system

Abstract

To protect an AC power system more completely than before.SOLUTION: A protection system (110) for protecting an AC power system (100) includes a compensation reactor (5), a capacitor (6) connected in series with the compensation reactor (5), and a bypass circuit (BP) connected in parallel with at least one of the compensation reactor (5) and the capacitor (6).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] One aspect of the present invention relates to a protection system for protecting an AC power system. [Background technology]

[0002] Various technologies relating to the protection of AC power systems have been proposed. For example, Patent Document 1 listed below discloses a technology aimed at dealing with three-phase short circuit accidents or ground fault accidents. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 5-22468 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present invention is to provide more complete protection for AC power systems than has been possible in the past. [Means for solving the problem]

[0005] A protection system according to one aspect of the present invention is a protection system for protecting an AC power system, and includes a compensation reactor, a capacitor connected in series with the compensation reactor, and a bypass circuit connected in parallel with at least one of the compensation reactor and the capacitor. [Effects of the Invention]

[0006] According to one aspect of the present invention, AC power systems can be protected more completely than ever before. [Brief explanation of the drawings]

[0007] [Figure 1] 1 shows an example of the configuration of a power system according to a reference embodiment. [Figure 2]1 shows an example of the configuration of a power system in a first embodiment. [Figure 3] Simulation models corresponding to the reference embodiment and the first embodiment are shown. [Figure 4] An example of a simulation result obtained in the simulation model of FIG. 3 is shown below. [Figure 5] 10 shows an example of the configuration of a power system in a second embodiment. [Figure 6] 10 shows various configuration examples of a protection system according to a third embodiment. [Figure 7] 10 shows various configuration examples of a protection system according to a third embodiment. [Figure 8] 10 shows an example of the configuration of a power system according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Reference form] Prior to the description of the first embodiment, a reference embodiment will be described. For the sake of convenience, components having the same functions as those described in the reference embodiment will be denoted by the same reference numerals in the following embodiments, and their descriptions will not be repeated. For the sake of brevity, descriptions of matters similar to those in the publicly known art will also be omitted as appropriate.

[0009] Unless otherwise specified, the components and numerical values ​​described in this specification are merely examples. Therefore, for example, unless otherwise specified, the positional relationship and connection relationship of the components are not limited to the examples in the drawings. The term "electrically connected" means "electrically connected" unless there is a contradiction in the content.

[0010] FIG. 1 shows a configuration example of a power system 100R according to a reference embodiment. The power system 100R is an example of the prior art. The power system 100R may be an AC power system. In the reference embodiment, a three-phase AC power system 100R is shown as an example. In FIG. 1, a three-phase electric circuit is shown as a schematic single-line diagram.

[0011] The power system 100R has an AC power source 1. As an example, the power source 1 may be any renewable energy power generation facility (e.g., wind power generation facility). In the reference embodiment, a three-phase AC power source 1 is illustrated. The power source 1 is connected to another power generation facility (not shown) via a power transmission cable 8. Therefore, the power source 1 can be connected to the other power generation facility via an upstream interconnection point P2 shown in FIG. 1 .

[0012] The power system 100R has a main circuit breaker 4 between the power source 1 and the power transmission cable 8. In the example of Fig. 1, the main circuit breaker 4 is disposed at an upstream interconnection point P2 in order to interrupt the current at the upstream interconnection point P2. Fig. 1 illustrates a case in which a three-phase short-circuit fault occurs at a fault point P1 upstream of the upstream interconnection point P2.

[0013] When a fault occurs at the fault point P1, a current flows from the power transmission cable 8 to the main circuit breaker 4. CABLE represents the current flowing from the power transmission cable 8 toward the main circuit breaker 4.

[0014] 1, a power source 1 is connected to a power transmission cable 8 and an electrical facility 12R via a main circuit breaker 4. The electrical facility 12R is, for example, a power receiving facility that receives power from the power source 1.

[0015] Depending on the specifications of the power system, a fairly long power transmission cable may be used. As a result, the power transmission cable may have a relatively large capacitance. Therefore, in the power system, a compensating reactor may be provided to compensate for the capacitance of the power transmission cable. The compensating reactor is also called a shunt reactor.

[0016] As shown in FIG. 1, the power system 100R has a compensating reactor 5 inside the electrical equipment 12R. The compensating reactor 5 may be any type of reactor. In the reference embodiment, the compensating reactor 5 is an iron-core reactor. The reactance of the compensating reactor 5 is set to correspond to the capacitance of the power transmission cable 8. Therefore, the reactance of the compensating reactor 5 is relatively large.

[0017] In the power system 100R, when a fault occurs, the current flowing through the main circuit breaker 4 (hereinafter referred to as i CB 1, the capacitor 6 is connected directly to the compensating reactor 5. The capacitor 6 is a component associated with the compensating reactor 5. Therefore, in this specification, a unit formed by the compensating reactor 5 and the capacitor 6 is referred to as a protection unit UN.

[0018] The compensating reactor 5 may be disposed at any position as long as it can achieve the effect of compensating for leading reactive power at the evaluation point of the power factor, for example. Therefore, the position at which the protection unit UN is disposed is not particularly limited as long as it can achieve the effect. FIG. 1 illustrates a configuration in which the protection unit UN is grounded. However, the protection unit UN according to one embodiment of the present invention does not necessarily have to be grounded (see, for example, FIG. 2, which will be described later).

[0019] The power system 100R further includes a sub-circuit breaker 10 downstream of the main circuit breaker 4 and upstream of the electrical equipment 12R. In the example of Fig. 1, the downstream interconnection point P3 is located downstream of the upstream interconnection point P2. The sub-circuit breaker 10 is disposed at the downstream interconnection point P3 to interrupt the current at the downstream interconnection point P3.

[0020] In Figure 1, i nrepresents the current flowing from the protection unit UN to the main circuit breaker 4. As mentioned above, in the protection unit UN, the compensation reactor 5 and the capacitor 6 are connected in series. Therefore, i n is equal to the current flowing through the compensation reactor 5 and the capacitor 6. In the example of Figure 1, the sub-circuit breaker 10 is connected in series with the protection unit UN. Therefore, i n is equal to the current flowing through the sub-circuit breaker 10.

[0021] When the sub-circuit breaker 10 is in a conducting state, i in the example of FIG. CB is i CABLE and i n The protection unit UN is expressed as the sum of the compensation reactor 5 and the capacitor 6 connected in series to each other. In the protection unit UN, an electrical resonance phenomenon can be generated by the compensation reactor 5 and the capacitor 6 connected in series to each other. Therefore, for example, the protection unit UN can generate a resonance current when a fault occurs in the power system 100R. For this reason, the protection unit UN may be called a resonance unit.

[0022] Therefore, in the reference embodiment, when an accident occurs in the power system 100R, i CB The reactance of the compensating reactor 5 and the capacitance of the capacitor 6 are set so that a zero cross point occurs at i CB The AC component contained in i CB The reactance of the compensating reactor 5 and the capacitance of the capacitor 6 are set so that the reactance is larger than the DC component contained in the compensating reactor 5. In this way, the protection unit UN is provided as a measure against current zero misses in the power system 100R.

[0023] In the power system 100R, a predetermined rated frequency (e.g., 50 Hz or 60 Hz) is set. The rated frequency is also referred to as the fundamental frequency. In order to make the electrical equipment 12R function as a compensating reactor at the fundamental frequency, the reactance of the compensating reactor 5 and the capacitance of the capacitor 6 are generally set so that the resonant frequency of the compensating reactor 5 and the capacitor 6 is lower than the fundamental frequency.

[0024] Therefore, for example, when the sub-circuit breaker 10 is turned on, a subharmonic current having a frequency component lower than the fundamental frequency may flow into the protection unit UN. Then, the subharmonic current may temporarily charge the capacitor 6, causing a magnetization bias in the compensating reactor 5. The magnetization bias in the compensating reactor 5 may lead to core saturation of the compensating reactor 5.

[0025] If the core of the compensating reactor 5 becomes saturated, a subharmonic current may be continuously generated in the compensating reactor 5. The subharmonic current may then cause an overvoltage in the capacitor 6 to occur continuously.

[0026] As described above, in the reference embodiment, continuous overcurrents and overvoltages may occur in the protection unit UN. These continuous overcurrents and overvoltages may adversely affect the electrical equipment 12R. Therefore, some kind of countermeasure against continuous overcurrents and overvoltages is desired.

[0027] [Embodiment 1] As described above, it can be said that the configuration of the reference embodiment has room for improvement in terms of power system protection. Therefore, the inventor of the present application (hereinafter abbreviated as "the inventor") has solved the above-mentioned problems in the reference embodiment. Taking these points into consideration, the first embodiment was newly created.

[0028] Fig. 2 shows an example of the configuration of the power system 100 in the first embodiment. Fig. 2 is a diagram paired with Fig. 1. The power system 100 has a protection system 110 that protects the power system 100. In this respect, the first embodiment differs from the reference embodiment.

[0029] To distinguish it from the electrical equipment 12R in the reference embodiment, the electrical equipment in the first embodiment will be referred to as electrical equipment 12. The protection system 110 in the example of Fig. 2 includes a protection unit UN located within the electrical equipment 12. In the example of Fig. 2, unlike the example of Fig. 1, the capacitor 6 is located upstream of the compensation reactor 5 in the protection unit UN.

[0030] The protection system 110 further includes a bypass circuit BP connected in parallel with at least one of the compensating reactor 5 and the capacitor 6 in the protection unit UN. In Fig. 2, a configuration is illustrated in which the bypass circuit BP is connected in parallel only with the capacitor 6. In the example of Fig. 2, the bypass circuit BP is connected in parallel with the capacitor 6 and in series with the compensating reactor 5.

[0031] The bypass circuit BP may be realized by any electrical component that is considered beneficial for reducing sustained overcurrents and overvoltages in the protection unit UN, or may be realized by a combination of multiple electrical components.

[0032] As an example, the bypass circuit BP may include a bypass circuit breaker 11. The bypass circuit breaker 11 may be any circuit breaker that can be arranged on an electric path in the bypass circuit BP. For the sake of clarity, FIG. 2 illustrates a case in which the bypass circuit BP is configured only by the bypass circuit breaker 11. The turn-on condition of the bypass circuit breaker 11 may be set as appropriate by the designer of the protection system 110. Examples of the turn-on condition of the bypass circuit breaker 11 will be described later.

[0033] In the first embodiment, a case is considered in which the electrical equipment 12 is turned on (the sub-circuit breaker 10 is switched from an interrupted state to a conductive state) when the main circuit breaker 4 is in a conductive state. In the protection system 110, the bypass circuit breaker 11 is turned on in advance before the sub-circuit breaker 10 is turned on. According to the protection system 110, the current flowing from the power source 1 to the electrical equipment 12 bypasses a portion (capacitor 6) of the compensating reactor 5 and capacitor 6 in the protection unit UN. Therefore, it is possible to prevent oscillation at the resonant frequency caused by the compensating reactor 5 and capacitor 6.

[0034] 2, charging of capacitor 6 due to core saturation of compensation reactor 5 can be appropriately avoided compared to power system 100R. In other words, power system 100 can reduce the risk of continuous overcurrent and overvoltage caused by subharmonic oscillations when electrical equipment 12 is turned on compared to power system 100R.

[0035] 2 shows an electrical equipment 90 separate from the electrical equipment 12. In the example of FIG. 2, the electrical equipment 90 is connected to the power source 1 via an upstream interconnection point P4. In the example of FIG. 2, a circuit breaker 91 is disposed at the upstream interconnection point P4 in order to interrupt the current at the upstream interconnection point P4. FIG. 2 illustrates an example in which a three-phase short-circuit fault occurs at a fault point P5 located within the electrical equipment 90 and downstream of the upstream interconnection point P4.

[0036] In the event of a fault within the electrical equipment 90, the circuit breaker 91 is turned off to isolate the electrical equipment 90 from the rest of the power system 100. During the short period from when an accident occurs in the electrical equipment 90 until the circuit breaker 91 is turned off, a momentary drop in the voltage of the power source 1 may occur due to an accident in the electrical equipment 90. This phenomenon is called a momentary voltage drop.

[0037] For example, the voltage of the power system 100 is restored by turning off the circuit breaker 91. In the process of voltage recovery from an instantaneous voltage drop, a transient current may flow from the power source 1 to the electrical equipment 12.

[0038] For this reason, for example, in the above-described embodiment, continuous overcurrent and overvoltage may occur in the protection unit UN even when the instantaneous voltage sag is resolved. However, the protection system 110 of the power system 100 allows a portion of the transient current to flow into the bypass circuit BP. Therefore, the power system 100 can reduce the risk of continuous overcurrent and overvoltage occurring when the instantaneous voltage sag is resolved. In this way, after the instantaneous voltage sag occurs, the bypass circuit breaker 11 may be turned on in preparation for recovery from the instantaneous voltage sag before the circuit breaker 91 is turned off.

[0039] (Verification by simulation) The inventors performed a simulation to verify the effectiveness of the protection system 110. Figure 3 shows a simulation model (hereinafter simply abbreviated as "model") used in the simulation.

[0040] The model 310 in FIG. 3 is a model as a comparative example. The model 310 corresponds to the reference embodiment. Therefore, the model 310 does not have a bypass circuit BP. On the other hand, the model 320 is a model as an example. The model 320 corresponds to the first embodiment. Therefore, the model 320 has a bypass circuit BP (the bypass breaker 11 in the example of FIG. 3).

[0041] 4 shows an example of a simulation result. Graph 410 in FIG. 4 shows the time transition of the current of one of the three phases (e.g., phase A) at the position of sub-breaker 10, obtained as a result of the simulation using model 310. On the other hand, graph 420 shows the time transition of the current of the same phase at the same position, obtained as a result of the simulation using model 320.

[0042] In the simulation, the capacitance XC of the capacitor 6 is set to 0.1 times the reactance XL of the compensation reactor 5. That is, in the simulation, XC / XL is set to 0.1. The rated current in the simulation is set to 600 A (Amperes).

[0043] In the simulation, the sub-circuit breaker 10 is turned on at a predetermined time in both the comparative example and the working example. However, in the working example, the bypass circuit breaker 11 is also turned on at the same time that the sub-circuit breaker 10 is turned on.

[0044] As shown in graph 410, in the comparative example, an overcurrent greater than the rated value occurs continuously for a long period of time after the sub-circuit breaker 10 is turned on. Specifically, in the comparative example, an overcurrent having a magnitude (absolute value) approximately twice the rated value occurs continuously.

[0045] On the other hand, as shown in graph 420, in the example, the magnitude of the current value can be reduced to near the rated value immediately after the sub-circuit breaker 10 is turned on. Note that it has been confirmed by simulation that the trends in the current values ​​of the remaining two of the three phases (e.g., phases B and C) in both the comparative example and the example are similar to those in the example of FIG. was done.

[0046] As described above, the effects of the protection system 110, i.e., the superiority of the first embodiment over the reference embodiment, are also supported by simulation. Thus, according to the first embodiment, it is possible to protect the power system more thoroughly than ever before.

[0047] [Embodiment 2] 5 shows a configuration example of a power system 100 in embodiment 2. The power system 100 in embodiment 2 has a transformer TR that converts the voltage of a power source 1. In this specification, for convenience of explanation, the protection system of embodiment 2 will be referred to as a protection system 110A.

[0048] In the example of FIG. 5, the transformer TR is located outside the electrical equipment 12. The transformer TR is located downstream of the sub-circuit breaker 10 and upstream of the electrical equipment 12. In FIG. 5, a three-phase, three-winding transformer is illustrated as the transformer TR. In the example of FIG. 5, the primary winding of the transformer TR is Y-connected. The power system 100 in FIG. 5 has a neutral point of the three-phase electric circuits. As an example, the neutral point is located at the junction of the Y-connection of the transformer TR.

[0049] One end of the protection unit UN in the protection system 110A is connected to the neutral point. The other end of the protection unit UN is grounded. In this way, the neutral point in the example of FIG. 5 is grounded via the protection unit UN. For this reason, the compensation reactor 5 in the example of FIG. 5 may be referred to as a neutral point compensation reactor. And the capacitor 6 in the example of FIG. 5 may be referred to as a neutral point capacitor.

[0050] By grounding the neutral point via the protection unit UN, it is possible to thoroughly deal with a single-phase ground fault in the power system 100. Specifically, it is possible to effectively prevent a current zero error when a single-phase ground fault occurs. Based on this, FIG. 5 illustrates an example in which a single-phase ground fault occurs at fault point P1.

[0051] 5 illustrates a configuration in which the compensating reactor 5 is grounded and the capacitor 6 is connected to the neutral point. However, as is clear from the description of the first embodiment, the positional relationship between the compensating reactor 5 and the capacitor 6 is not limited to this example. For example, the compensating reactor 5 may be connected to the neutral point and the capacitor 6 may be grounded.

[0052] The protection system 110A also has a bypass circuit BP equivalent to that of the protection system 110 of the first embodiment. Therefore, the second embodiment also provides the same effects as the first embodiment.

[0053] [Embodiment 3] In each of the above-described embodiments, a protection system having a bypass circuit BP configured only by a bypass breaker 11 has been exemplified. However, the configuration of a protection system according to an aspect of the present invention is not limited to this example. In a third embodiment, a variation of the protection system will be described.

[0054] Fig. 6 shows protection systems 110B to 110D according to embodiment 3. First, the protection system 110B in Fig. 6 will be described. The bypass circuit BP in the protection system 110B has a bypass breaker 11 and a resistance element 61 connected in series with the bypass breaker 11.

[0055] The resistor element 61 can attenuate subharmonic currents in the bypass circuit BP, thereby shortening the period during which an overcurrent occurs when the sub-circuit breaker 10 is turned on, for example.

[0056] By appropriately selecting the resistance value of the resistive element 61, the current flowing through the bypass circuit BP can be made sufficiently larger than the current flowing through the capacitor 6 during the period when the bypass breaker 11 is in the conductive state. Therefore, it is preferable that the resistance value of the resistive element 61 is sufficiently larger than the impedance of the capacitor 6. By selecting the resistance value of the resistive element 61 in this way, it becomes possible to more effectively attenuate the subharmonic current.

[0057] Next, a description will be given of a protection system 110C in Fig. 6. The bypass circuit BP in the protection system 110C has a variable resistor 62 instead of the bypass breaker 11. In this way, the bypass circuit BP does not necessarily have to have the bypass breaker 11.

[0058] 6 illustrates a protection system 110C having a bypass circuit BP configured only by a variable resistor 62. In a third embodiment, the variable resistor 62 is an arrester.

[0059] The resistance of an arrester varies depending on the voltage applied to the arrester. Specifically, when the voltage applied to the arrester is below a certain value, the resistance of the arrester is extremely high. On the other hand, when the voltage applied to the arrester exceeds the certain value, the resistance of the arrester decreases rapidly.

[0060] In the protection system 110C, the variable resistor 62 is connected in parallel with the capacitor 6. Therefore, the voltage applied to the variable resistor 62 is equal to the voltage applied to the capacitor 6. Therefore, when the voltage applied to the capacitor 6 exceeds a certain value, the variable resistor 62 transitions from an insulating state (non-conducting state) to a conducting state. Therefore, the protection system 110C can also cause a portion of the current flowing from the power source 1 to the electrical equipment 12 to flow into the bypass circuit BP.

[0061] Next, a description will be given of a protection system 110D in Fig. 6. The bypass circuit BP in the protection system 110D has a saturable reactor 63 instead of the bypass breaker 11. Fig. 6 illustrates the protection system 110D having a bypass circuit BP configured only by the saturable reactor 63.

[0062] In the protection system 110D, the saturable reactor 63 is connected in parallel with the capacitor 6. Therefore, the voltage applied to the saturable reactor 63 is equal to the voltage applied to the capacitor 6. When the voltage applied to the saturable reactor 63 exceeds a certain value, the saturable reactor 63 reaches a saturated state. As a result, the reactance of the saturable reactor 63 decreases rapidly.

[0063] Therefore, when the voltage applied to capacitor 6 exceeds a certain value, saturable reactor 63 transitions from an insulating state to a conducting state. Therefore, protection system 110D can also cause a portion of the current flowing from power source 1 to electrical equipment 12 to flow into bypass circuit BP.

[0064] The protection system 110D may further include a resistive element 61 connected in series with the saturable reactor 63. In this case, similar to the protection system 110B, it becomes possible to more effectively attenuate subharmonic currents.

[0065] Fig. 7 shows protection systems 110E to 110F according to the third embodiment. First, the protection system 110E in Fig. 7 will be described. In the protection system 110E, the bypass circuit BP is connected in parallel only to the compensation reactor 5. That is, in the protection system 110E, the bypass circuit BP is connected in parallel to the compensation reactor 5 and in series to the capacitor 6. In this way, the bypass circuit BP does not necessarily have to be connected in parallel to the capacitor 6.

[0066] The protection system 110E can also cause a portion of the current flowing from the power source 1 to the electrical equipment 12 to flow into the bypass circuit BP. Therefore, the protection system 110E can also protect the power system more completely than ever before.

[0067] Next, a protection system 110F of Fig. 7 will be described. In the protection system 110F, the bypass circuit BP is connected in parallel with both the compensating reactor 5 and the capacitor 6. In this way, the bypass circuit BP does not necessarily have to be connected in parallel with only one of the compensating reactor 5 and the capacitor 6.

[0068] However, when the bypass circuit BP is connected in parallel with both the compensation reactor 5 and the capacitor 6, an excessive current may flow through the bypass circuit BP depending on the configuration of the bypass circuit BP.

[0069] Therefore, as an example, the protection system 110F employs the configuration of the bypass circuit BP in the protection system 110B described above. That is, the bypass circuit BP in the protection system 110F has a bypass breaker 11 and a resistive element 61 connected in series to each other. The resistive element 61 can reduce the value of the current flowing through the bypass circuit BP. Therefore, it is possible to reduce the risk of an excessive current flowing through the bypass circuit BP.

[0070] Additionally, in the protection system 110F, it is preferable to select the resistance value of the resistive element 61 so that the current flowing in the bypass circuit BP is sufficiently larger than the current flowing in the protection unit UN during the period when the bypass breaker 11 is in a conductive state. That is, it is preferable that the resistance value of the resistive element 61 is sufficiently smaller than the impedance of the protection unit UN (the combined impedance of the compensation reactor 5 and the capacitor 6). By selecting the resistance value of the resistive element 61 in this manner, it becomes possible to more effectively attenuate subharmonic currents in the protection system 110F.

[0071] [Embodiment 4] 8 shows an example of the configuration of a power system 100 according to a fourth embodiment. For convenience of explanation, the protection system according to the fourth embodiment is referred to as a protection system 110G. The protection system 110G includes a sensor SR that detects an electrical signal related to a protection unit UN. The protection system 110G also includes a control device 50 that controls a bypass circuit BP based on a value detected by the sensor SR.

[0072] 8, the control device 50 is located outside the electrical equipment 12. However, the control device 50 may be located inside the electrical equipment 12. The location of the control device 50 is arbitrary as long as the control device 50 can acquire the detection value of the sensor SR and control the bypass circuit BP based on the detection value.

[0073] Fig. 8 illustrates an example in which the sensor SR is a current sensor. As in Fig. 2, Fig. 8 also illustrates an example in which the bypass circuit BP is configured only by the bypass breaker 11. Therefore, the control device 50 in the example in Fig. 8 controls the bypass breaker 11 based on the detection value of the sensor SR as a current sensor.

[0074] 8, the sensor SR is located downstream of the sub-circuit breaker 10 and upstream of the electrical equipment 12.

[0075] As an example, the sensor SR may be a digital current sensor that can extract a predetermined frequency component of the current based on the detected value of the current flowing through the protection unit UN. Therefore, for example, a digital current sensor that can extract the frequency component of the subharmonic wave described above can be used as the sensor SR.

[0076] As mentioned above, subharmonic currents can lead to sustained overcurrents and overvoltages, so the control device 50 may turn on the bypass circuit breaker 11 if the sensor SR detects that the current flowing through the protection unit UN contains subharmonic frequency components.

[0077] The control device 50 may also turn on the bypass circuit breaker 11 when the sensor SR detects a current value equal to or greater than a predetermined threshold. The threshold may be set based on, for example, a rated value of the current in the electrical equipment 12. As an example, the threshold may be set to a value twice the rated value.

[0078] The control device 50 may also turn on the bypass circuit breaker 11 when the sensor SR detects that a current value equal to or greater than a predetermined value flows for a predetermined period of time or longer.

[0079] Depending on the specifications of the electrical equipment 12, the bypass circuit breaker 11 may be turned on in advance before the sub-circuit breaker 10 is turned on.

[0080] [Modification] It should be noted that the sensor SR according to one embodiment of the present invention is not limited to a current sensor. For example, the sensor SR may be a voltage sensor that detects a predetermined voltage. As an example, the sensor SR may detect the voltage applied to the capacitor 6 as the predetermined voltage. Therefore, the position of the sensor SR is not limited to the example of FIG. 8. In this example, the "voltage applied to the capacitor 6" refers to the voltage between the two terminals of the capacitor 6.

[0081] In a modified example, the control device 50 controls the bypass breaker 11 based on the detection value of the sensor SR serving as a voltage sensor. As an example, the sensor SR may be a digital voltage sensor that can extract a predetermined frequency component of the voltage applied to the capacitor 6 based on the detection value of the voltage. The control device 50 may turn on the bypass breaker 11 when the sensor SR detects that the voltage applied to the capacitor 6 includes a subharmonic frequency component.

[0082] The control device 50 may also turn on the bypass circuit breaker 11 when the sensor SR detects a voltage value equal to or greater than a predetermined threshold. The threshold may be set based on, for example, the rated voltage value of the electrical equipment 12.

[0083] The control device 50 may also turn on the bypass circuit breaker 11 when the sensor SR detects that a state has occurred in which a voltage value equal to or greater than a predetermined value has been applied for a predetermined period of time or longer.

[0084] A predetermined voltage detected by the sensor SR as a voltage sensor is applied to the capacitor 6. It should be noted that the sensor SR is not limited to the voltage detected by the sensor SR. For example, the sensor SR may be a voltage sensor that detects the voltage to ground of the capacitor 6. Therefore, the sensor SR as a voltage sensor may be located at the position of the sensor SR in FIG.

[0085] [Software implementation example] The functions of the protection systems 110 to 110G (hereinafter referred to as "devices" for convenience) can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly the control device 50).

[0086] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0087] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0088] Some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of one aspect of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0089] The processes described in the above embodiments are performed by AI (Artificial Intelligence). In this case, the AI ​​may be executed by the control device, or may be executed by another device (for example, an edge computer or a cloud server).

[0090] 〔summary〕 A protection system according to a first aspect of the present invention is a protection system for protecting an AC power system, and includes a compensation reactor, a capacitor connected in series with the compensation reactor, and a bypass circuit connected in parallel with at least one of the compensation reactor and the capacitor.

[0091] In a protection system according to a second aspect of the present invention, in the first aspect, the bypass circuit may include a circuit breaker.

[0092] A protection system according to a third aspect of the present invention is based on the second aspect, and the bypass circuit may further include a resistive element connected in series with the circuit breaker.

[0093] In the protection system according to a fourth aspect of the present invention, in any one of the first to third aspects, the bypass circuit may have a variable resistor.

[0094] In a protection system according to a fifth aspect of the present invention, in the fourth aspect, the variable resistor may be an arrester.

[0095] In a protection system according to a sixth aspect of the present invention, in any one of the first to fifth aspects, the bypass circuit may include a saturable reactor.

[0096] In a protection system according to a seventh aspect of the present invention, in any one of the first to sixth aspects, the bypass circuit may be connected in parallel with the capacitor and in series with the compensation reactor.

[0097] In a protection system according to an eighth aspect of the present invention, in any one of the first to sixth aspects, the bypass circuit may be connected in parallel with the compensation reactor and in series with the capacitor.

[0098] In a protection system according to a ninth aspect of the present invention, in any one of the first to sixth aspects, the bypass circuit may be connected in parallel with both the compensation reactor and the capacitor.

[0099] A protection system according to aspect 10 of the present invention, in any one of aspects 1 to 9, may further include a current sensor that detects a current flowing through a protection unit constituted by the compensation reactor and the capacitor, and a control device that controls the bypass circuit based on a detection value of the current sensor.

[0100] In a protection system according to an eleventh aspect of the present invention, in any one of the first to tenth aspects, the protection system may further include a voltage sensor that detects the voltage applied to the capacitor, and a control device that controls the bypass circuit based on the detected value of the voltage sensor.

[0101] A protection system according to a twelfth aspect of the present invention, in any one of the first to tenth aspects, may further include a voltage sensor that detects the voltage to ground of the capacitor, and a control device that controls the bypass circuit based on the detected value of the voltage sensor.

[0102] [Additional Notes] One aspect of the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of one aspect of the present invention. [Explanation of symbols]

[0103] 1 power supply 4 Main circuit breaker 5 Compensation reactor 6 Capacitors 10 Sub-circuit breaker 11 Bypass circuit breaker (bypass circuit breaker) 12 Electrical Equipment 50 Control device 61 Resistor element 62 Variable resistor (arrester) 63 Saturable reactor 100 Power system 110~110G Protection System BP bypass circuit UN Conservation Unit SR sensor (current sensor, voltage sensor)

Claims

1. A protection system for protecting an AC power system, comprising: a compensating reactor; a capacitor connected in series with the compensation reactor; a bypass circuit connected in parallel with at least one of the compensation reactor and the capacitor.

2. The protection system of claim 1 , wherein the bypass circuit comprises a circuit breaker.

3. The protection system of claim 2 , wherein the bypass circuit further comprises a resistive element connected in series with the circuit breaker.

4. The protection system of claim 1 , wherein the bypass circuit comprises a variable resistor.

5. The protection system of claim 4 , wherein the variable resistor is an arrester.

6. The protection system of claim 1 , wherein the bypass circuit includes a saturable reactor.

7. The protection system of claim 1 , wherein the bypass circuit is connected in parallel with the capacitor and in series with the compensation reactor.

8. The protection system of claim 1 , wherein the bypass circuit is connected in parallel with the compensation reactor and in series with the capacitor.

9. The protection system of claim 1 , wherein the bypass circuit is connected in parallel with both the compensation reactor and the capacitor.

10. a current sensor for detecting a current flowing through a protection unit constituted by the compensation reactor and the capacitor; The protection system according to claim 1 , further comprising: a control device that controls the bypass circuit based on a detection value of the current sensor.

11. a voltage sensor that detects a voltage applied to the capacitor; The protection system according to claim 1 , further comprising: a control device that controls the bypass circuit based on a detected value of the voltage sensor.

12. a voltage sensor for detecting a voltage to ground of the capacitor; The protection system according to claim 1 , further comprising: a control device that controls the bypass circuit based on a detected value of the voltage sensor.

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