Arc detection device, arc detection method, and arc detection program

Abstract

An arc detection device (10) detects an arc generated in a power supply cable (31) from which power is supplied from a PV (30), and comprises a current acquisition unit (11) and a dangerous-state determination unit (12). The current acquisition unit (11) acquires the current flowing through the cable (31). The dangerous-state determination unit (12) determines, in accordance with the amount of variation in the current acquired by the current acquisition unit (11), whether the state is one in which an arc having a high degree of danger is predicted to occur.

Description

Arc detection device, arc detection method, and arc detection program

[0001] The present invention relates to, for example, an arc detection device, an arc detection method, and an arc detection program connected to a cable supplied from a power supply facility such as solar power generation or wind power generation.

[0002] In a conventional solar power generation system, the electric power generated by a solar cell is supplied to a power transmission network via a power conditioning system (hereinafter referred to as PCS (Power Conditioning System)) including a DC-AC converter or the like. In such a solar power generation system, an arc may occur due to a failure in a circuit or the like within the system. When an arc occurs, the portion where the arc occurs becomes high in temperature and may cause a fire or the like. Therefore, the solar power generation system detects the occurrence of an arc by measuring the alternating current of the arc using a current sensor.

[0003] For example, in Patent Document 1, every time a stepwise increase in current is detected, a current pulse is generated, and this current pulse is integrated by a first tracking circuit having a first long time constant and a second tracking circuit having a second short time constant to generate first and second tracking signals respectively. When the second tracking signal decreases by a selected ratio of the first tracking signal, a charging pulse having a value that is a function of the amplitude of the most recent stepwise increase is generated, and when the time decay accumulation value of the charging pulse reaches a predetermined value, an arc fault detection device that gives an indication of an arc fault is disclosed.

[0004] Japanese Patent Application Laid-Open No. 2000-105265 (Patent No. 4870252)

[0005] However, the above conventional arc fault detection device has the following problems. That is, in the arc fault detection device disclosed in the above publication, by tracking the amplitude of the stepwise change in the current generated by the arc fault, the sensitivity of the envelope detection type arc fault detector for low current arcs is increased without sacrificing the response time to more dangerous arc faults at high currents.

[0006] However, with this configuration, while it is possible to determine whether an arc is dangerous after it has occurred, it is difficult to predict the occurrence of high-current, highly dangerous arcs. Furthermore, conventionally, when detecting arcs, frequency analysis of the alternating current flowing through the cable was performed, and if a certain amount of frequency peak was detected between 10 kHz and 100 kHz, it was determined that an arc had occurred.

[0007] However, because the frequency peaks in that frequency band include noise frequencies, there was a risk of many false detections. Furthermore, in order to suppress the occurrence of false detections as much as possible, it was necessary to take measures such as setting a high threshold value for judgment or detecting arcs while checking and comparing the arc status of other panels. The object of the present invention is to provide an arc detection device, an arc detection method, and an arc detection program that can accurately detect the occurrence of high-risk arcs that occur in cables to which power is supplied from power supply equipment.

[0008] (Means for solving the problem) The arc detection device according to the first invention is an arc detection device for detecting arcs that occur in a power supply cable to which power is supplied from a power supply facility, and comprises a current acquisition unit and a hazardous state determination unit. The current acquisition unit acquires the current flowing through the cable. The hazardous state determination unit determines, according to the amount of fluctuation in the current acquired by the current acquisition unit, whether or not a state in which the occurrence of a highly hazardous arc is predicted is present.

[0009] Here, for example, in order to accurately detect highly dangerous arcs that occur when power is supplied from a power supply facility via a cable, it is determined whether or not the conditions are such that the occurrence of a dangerous arc is predicted based on the amount of fluctuation in the current flowing through the cable. Here, the power supply facility includes, for example, renewable energy facilities such as solar power generation facilities, wind power generation facilities, and geothermal power generation facilities.

[0010] The current acquisition unit may be configured to measure the current flowing through the cable, or it may be configured to acquire the measurement result of the current flowing through the cable from a current measuring instrument. This allows for the detection of fluctuations in the current flowing through the cable that occur as a precursor to arcing before an arc actually occurs, and if the amount of fluctuation is large, it can be determined that a dangerous arc is likely to occur. As a result, it is possible to accurately detect the occurrence of highly dangerous arcs in cables to which power is supplied from power supply equipment.

[0011] The arc detection device according to the second invention is the same as the arc detection device according to the first invention, wherein the danger state determination unit determines that if the amount of current fluctuation acquired by the current acquisition unit exceeds a predetermined threshold, it is a state in which the occurrence of a highly dangerous arc is predicted. This makes it possible to determine whether or not an arc is highly dangerous depending on whether or not the amount of current fluctuation flowing through the cable exceeds a predetermined threshold.

[0012] The arc detection device according to the third invention is an arc detection device according to the first or second invention, further comprising a detection unit for detecting the presence or absence of an arc. This makes it possible to determine whether or not a highly dangerous arc is occurring in accordance with the amount of fluctuation in the current flowing through the cable mentioned above, and to determine whether or not an actual arc is occurring.

[0013] The arc detection device according to the fourth invention is the arc detection device according to the third invention, wherein the detection unit detects the presence or absence of an arc based on the fluctuation frequency of the current acquired by the current acquisition unit. Here, the fluctuation frequency refers to the frequency obtained from the FFT (Fast Fourier Transform) analysis results. This makes it possible to determine the presence or absence of a highly dangerous arc corresponding to the amount of fluctuation of the current flowing through the cable, and to determine the actual presence or absence of an arc by detecting the fluctuation frequency of that current.

[0014] The arc detection device according to the fifth invention is an arc detection device according to the third invention, further comprising a first control unit that controls the power supply from the power supply equipment to the downstream side to shut off when the hazardous condition determination unit determines that a state in which the occurrence of a highly dangerous arc is predicted is observed, and the detection unit detects the occurrence of an arc. This makes it possible to prevent damage or failure of the cable by shutting off the power supplied from the power supply equipment to the downstream side via the cable when the occurrence of a highly dangerous arc is predicted.

[0015] The arc detection device according to the sixth invention is an arc detection device according to the third invention, further comprising a first threshold adjustment unit that, when the hazardous state determination unit determines that a state in which the occurrence of a highly hazardous arc is predicted is observed, adjusts the value of the determination threshold used in the detection unit to lower it. As a result, when the occurrence of a highly hazardous arc is predicted, the occurrence of a highly hazardous arc can be easily detected by lowering the value of the determination threshold in the detection unit.

[0016] The arc detection device according to the seventh invention is an arc detection device according to the third invention, wherein the hazardous state determination unit determines that the occurrence of a high-risk arc is not predicted, the detection unit detects the occurrence of an arc, and when the number of detections exceeds a predetermined number, the power supply from the power supply equipment to the downstream side is shut off. As a result, in the case of a low-risk arc, the power is not shut off immediately, but rather the power supply is shut off only after the occurrence of an arc is actually detected and the number of detections exceeds a predetermined number.

[0017] The arc detection device according to the eighth invention is an arc detection device according to the third invention, further comprising a second threshold adjustment unit that, when the hazardous state determination unit determines that the occurrence of a highly hazardous arc is not expected, adjusts the value of the determination threshold used in the detection unit to increase it. As a result, when the occurrence of a highly hazardous arc is not expected, adjusting the value of the determination threshold in the detection unit to increase it makes it more difficult to detect the occurrence of a low-hazardous arc, while only detecting the occurrence of a highly hazardous arc.

[0018] The arc detection device according to the ninth invention is an arc detection device according to the first or second invention, and is placed between a power supply facility and a power conditioner that converts the DC power supplied from the power supply facility into AC power. By placing the arc detection device on the cable connecting the power supply facility and the power conditioner that converts the DC power supplied from the power supply facility into AC power, the occurrence of highly dangerous arcs can be detected with high accuracy.

[0019] The arc detection device according to the tenth invention is an arc detection device according to the first or second invention, and is located inside a power conditioner that converts DC power supplied from a power supply facility into AC power. By placing the arc detection device inside the power conditioner that converts DC power supplied from a power supply facility into AC power, it is possible to detect the occurrence of highly dangerous arcs with high accuracy.

[0020] The arc detection device according to the eleventh invention is an arc detection device according to the first or second invention, and the power supply equipment is renewable energy equipment. As a result, by installing this arc detection device on renewable energy equipment such as solar power generation equipment, wind power generation equipment, and geothermal power generation equipment, it is possible to detect the occurrence of highly dangerous arcs with high accuracy.

[0021] The arc detection device according to the twelfth invention is an arc detection device for detecting arcs generated in a power supply cable to which power is supplied from a power supply facility, and comprises a voltage acquisition unit and a hazardous state determination unit. The voltage acquisition unit acquires the voltage applied to the cable. The hazardous state determination unit determines whether or not a state in which the generation of a highly hazardous arc is predicted is present, according to the fluctuation range of the waveform showing the voltage acquired by the voltage acquisition unit.

[0022] Here, for example, in order to accurately detect highly dangerous arcs that occur when power is supplied from a power supply facility via a cable, it is determined whether or not the occurrence of a dangerous arc is predicted based on the fluctuation range of the waveform indicating the voltage related to the cable. Here, the power supply facility includes, for example, renewable energy facilities such as solar power generation facilities, wind power generation facilities, and geothermal power generation facilities.

[0023] The voltage acquisition unit may be configured to measure the voltage applied to the cable, or it may be configured to acquire the measurement result of the voltage applied to the cable from a voltage measuring instrument. This allows for the detection of the amplitude of the waveform indicating the voltage applied to the cable, which occurs as a precursor to arcing before arcing occurs. If the amplitude of the amplitude is large, it can be determined that a dangerous arc is likely to occur. As a result, the occurrence of highly dangerous arcs in cables supplied with power from power supply equipment can be detected with high accuracy.

[0024] The 13th invention relates to an arc detection method using an arc detection device for detecting arcs occurring in a power supply cable supplied with power from a power supply facility. The current acquisition unit of the arc detection device acquires the current flowing through the cable, and the danger state determination unit of the arc detection device determines, according to the amount of current fluctuation acquired in the current acquisition step, whether or not a state is expected in which the occurrence of a highly dangerous arc is predicted.

[0025] Here, for example, in order to accurately detect highly dangerous arcs that occur when power is supplied from a power supply facility via a cable, it is determined whether or not the conditions are such that the occurrence of a dangerous arc is predicted based on the amount of fluctuation in the current flowing through the cable. Here, the power supply facility includes, for example, renewable energy facilities such as solar power generation facilities, wind power generation facilities, and geothermal power generation facilities.

[0026] The acquisition of current may involve measuring the current flowing through the cable, or obtaining the measurement result from a current meter. This allows for the detection of fluctuations in the current flowing through the cable, which occur as a precursor to arc formation, and if the fluctuation is large, it can be determined that a dangerous arc is likely to occur. As a result, the occurrence of highly dangerous arcs in cables supplied with power from power supply equipment can be detected with high accuracy.

[0027] The arc detection program according to the 14th invention is an arc detection program for an arc detection device that detects arcs occurring in a power supply cable supplied with power from a power supply facility, wherein the current acquisition unit of the arc detection device acquires the current flowing through the cable, and the dangerous state determination unit of the arc detection device causes a computer to execute an arc detection method that determines whether or not a state in which the occurrence of a highly dangerous arc is predicted is in accordance with the amount of fluctuation of the current acquired in the current acquisition step.

[0028] Here, for example, in order to accurately detect highly dangerous arcs that occur when power is supplied from a power supply facility via a cable, it is determined whether or not the conditions are such that the occurrence of a dangerous arc is predicted based on the amount of fluctuation in the current flowing through the cable. Here, the power supply facility includes, for example, renewable energy facilities such as solar power generation facilities, wind power generation facilities, and geothermal power generation facilities.

[0029] The acquisition of current may involve measuring the current flowing through the cable, or it may involve obtaining the measurement result of the current flowing through the cable from a current measuring instrument. This allows for the detection of fluctuations in the current flowing through the cable that occur as a precursor to arc formation before an arc actually occurs, and if the amount of fluctuation is large, it can be determined that a dangerous arc is likely to occur.

[0030] As a result, it is possible to accurately detect the occurrence of highly dangerous arcs in cables that receive power from power supply equipment.

[0031] (Effects of the Invention) The arc detection device according to the present invention can accurately detect the occurrence of highly dangerous arcs in cables to which power is supplied from power supply equipment.

[0032] A block diagram showing the configuration of an arc detection device according to one embodiment of the present invention, arranged in a junction box installed between a PV and a power conditioner. A control block diagram showing the configuration of the arc detection device of Figure 1. (a) is a graph showing the arc generation time when the amount of current fluctuation acquired by the current acquisition unit of the arc detection device of Figure 2 is small. (b) is a graph showing the arc generation time when the amount of current fluctuation acquired by the current acquisition unit of the arc detection device of Figure 2 is large. (a) is a graph showing the FFT analysis result (relationship between frequency and voltage) when no arc is detected by the arc frequency detection unit of the arc detection device of Figure 2. (b) is a graph showing the FFT analysis result (relationship between frequency and voltage) when an arc is detected by the arc frequency detection unit of the arc detection device of Figure 2. A flowchart showing the processing flow of the arc detection method implemented by the arc detection device of Figure 2. A block diagram showing the configuration of an arc detection device according to another embodiment of the present invention, arranged inside a power conditioner that converts DC power supplied from a PV into AC power. A control block diagram showing the configuration of an arc detection device according to yet another embodiment of the present invention. (a) and (b) are graphs illustrating the principle by which the arc detection device in Figure 7 determines the presence or absence of a high-risk arc based on the fluctuation range of the voltage waveform. (a) and (b) are figures showing the average values ​​and fluctuation ranges of voltage, current, and inter-arc voltage before and after arc generation, as shown in Figures 8(a) and 8(b).

[0033] (Embodiment 1) An arc detection device 10 according to one embodiment of the present invention will be described below with reference to Figures 1 to 5. In this embodiment, unnecessary detailed explanations may be omitted. For example, detailed explanations of already well-known matters and redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art. Furthermore, the applicant provides the accompanying drawings and the following explanation so that those skilled in the art can fully understand the present invention, and does not intend to limit the subject matter described in the claims by means of these.

[0034] (1) System configuration including arc detection device 10 As shown in Figure 1, the arc detection device 10 according to this embodiment is installed in a junction box 20 located between a plurality of PVs (Photovoltaics) (solar power generation equipment) 30 and a power conditioner 40, and acquires the current flowing through the cable 31 supplied from the plurality of PVs 30 to the power conditioner 40 to predict the occurrence of a high-risk arc. More specifically, the arc detection device 10 determines whether or not a high-risk arc is predicted to occur in accordance with the amount of fluctuation in the current flowing through the cable 31.

[0035] The detailed configuration of the arc detection device 10 will be described in detail later. The PV (photovoltaic power generation equipment) 30 converts sunlight into electricity and supplies DC power to the power conditioner 40 via cables 31 and 32, as shown in Figure 1. The power conditioner 40 converts the DC power supplied from the PV 30 via cables 31 and 32 into AC power and supplies the AC power to the load 50.

[0036] The load 50 is a general appliance that consumes power and receives power from the power conditioner 40. Specifically, the load 50 is, for example, various electrical appliances used in homes such as air conditioners, microwave ovens, and televisions, as well as machinery and lighting equipment such as air conditioners and lighting fixtures used in commercial and industrial facilities. Here, when the power conditioner 40 performs switching-type voltage conversion, it is controlled to change the switching period in order to maintain the output voltage.

[0037] In this case, if the load 50 is sufficiently large, the voltage is stabilized by the filter that smooths the switching frequency. On the other hand, if the load 50 is light, it becomes slower than the switching frequency, and the filter that smooths the switching frequency cannot absorb it, leaving ripple, which causes the voltage and current to become unstable. Furthermore, if the load 50 is light, the power energy supplied from PV30 is not consumed, creating a condition where arcs, which are highly dangerous as described later, are likely to occur.

[0038] (2) Configuration of the Arc Detection Device 10 As shown in Figure 2, the arc detection device 10 of this embodiment includes a current acquisition unit 11, a dangerous state determination unit 12, an arc frequency detection unit (detection unit) 13, a threshold adjustment unit (first threshold adjustment unit, second threshold adjustment unit) 14, a control unit (first control unit) 15, and an output unit 16. The current acquisition unit 11 measures and acquires the current flowing through the cable 31 connecting the PV 30 and the power conditioner 40.

[0039] The hazardous state determination unit 12 determines whether or not a state is expected in which a high-risk arc is likely to occur, based on the amount of current fluctuation acquired by the current acquisition unit 11. The hazardous state determination unit 12 determines that a state is expected in which a high-risk arc is likely to occur if the amount of current fluctuation acquired by the current acquisition unit 11 exceeds a predetermined threshold. The arc frequency detection unit 13 detects whether or not an arc has actually occurred based on the current fluctuation frequency acquired by the current acquisition unit 11.

[0040] Here, the fluctuating frequency refers to the frequency obtained from the FFT (Fast Fourier Transform) analysis results. The threshold adjustment unit (first threshold adjustment unit, second threshold adjustment unit) 14 adjusts the threshold value used for determination in the arc frequency detection unit 13 to decrease when the hazardous state determination unit 12 determines that a state in which the occurrence of a high-risk arc is predicted. Conversely, the threshold adjustment unit 14 adjusts the threshold value used for determination in the arc frequency detection unit 13 to increase when the hazardous state determination unit 12 determines that a state in which the occurrence of a high-risk arc is not predicted.

[0041] When it is determined in the risk state determination unit 12 that a state is predicted in which an arc with a high risk level will occur, the control unit (first control unit) 15 controls to cut off the power supply from the PV 30 to the downstream side. Further, when it is determined in the risk state determination unit 12 that a state in which the occurrence of an arc with a high risk level is not predicted, and an arc is detected in the arc frequency detection unit 13, the control unit 15 controls to delay the time for cutting off the power supply from the PV 30 to the downstream side. The output unit 16 converts the determination result of the occurrence of an arc with a high risk level in the arc detection device 10 into a binary signal and outputs it.

[0042] <Prediction of occurrence of high-risk arc> Here, as shown in FIG. 3(a), when the amount of change in the current flowing through the cable 31 is a small value of, for example, about 780 mA (the load 50 is above a predetermined value), the arc generation time is about 280 msec.

[0043] On the other hand, as shown in FIG. 3(b), when the amount of change in the current flowing through the cable 31 is a large value of, for example, about 1.59 A (the load 50 is a light load), the arc generation time becomes as long as about 2.45 sec. For example, when the capacity of the power conditioner 40 is 3.6 Kw, the power generation voltage setting of the PV 30 is 450 V, and the power generation current setting of the PV 30 is 8 A, when it is determined that a high-risk arc has occurred (≈ light load), the AC load resistance (voltage is AC 100 V) is 18.0 Ω.

[0044] On the other hand, when it is determined that a high-risk arc has not occurred (≈ not a light load), the AC load resistance (voltage is AC 100 V) is 16.7 Ω. That is, when conditions other than the current load resistance (current) are the same, as shown in FIGS. 3(a) and 3(b), the occurrence of an arc with a long generation time and a high risk level is determined by the magnitude of the amount of change in the current.

[0045] Next, the following factors may cause the arc generated in the cable 31 to continue. That is, the arc stops occurring when the energy supply to the arc is insufficient. Therefore, when the power supplied from the PV 30 ≤ the power consumption of the power conditioner 40, the power conditioner 40 consumes almost all of the power supplied from the PV 30. As a result, the energy supply to the arc is insufficient, and the arc generation time is short (the generated arc is small).

[0046] On the other hand, when the power supplied from the PV 30 > the power consumption of the power conditioner 40, the consumption on the power conditioner 40 side is small. Therefore, the energy supply to the arc becomes excessive, and the arc generation time becomes long (the generated arc is large). At this time, when the power supplied from the PV 30 ≤ the power consumption of the power conditioner 40, since the AC (alternating current) load resistance is small, the current value flowing through the cable 31 is likely to be stable.

[0047] On the other hand, when the power supplied from the PV 30 > the power consumption of the power conditioner 40, since the AC (alternating current) load resistance is large, the current value flowing through the cable 31 is unstable and the amount of variation is likely to increase. Therefore, when the current flowing through the cable 31 is unstable (excessive power supply), an arc with a high degree of danger is likely to continue to occur in the cable 31.

[0048] In the arc detection device 10 of the present embodiment, as shown in FIG. 3(b), in order to predict the occurrence of an arc with a long generation time and a high degree of danger, the current acquisition unit 11 detects the variation and the amount of variation of the current flowing through the cable 31 that occurs at a stage before the arc occurs. The dangerous state determination unit 12 determines whether or not it is a state in which the occurrence of an arc with a high degree of danger is predicted according to the detected amount of variation of the current.

[0049] Furthermore, after determining whether or not the occurrence of a highly dangerous arc is predicted in the arc detection device 10, the arc frequency detection unit 13 detects whether or not an arc has actually occurred based on the fluctuation frequency of the current detected in the current acquisition unit 11. Specifically, if no arc has occurred, as shown in Figure 4(a), no frequency peaks are detected in the frequency band of section A (10 kHz to 100 kHz).

[0050] On the other hand, when an arc occurs, a certain amount of frequency peaks are detected in the frequency band of portion A (10 kHz to 100 kHz), as shown in Figure 4(b). Therefore, in the arc detection device 10 of this embodiment, the arc frequency detection unit 13 detects whether or not a certain amount of frequency peaks are detected in the frequency band of portion A (10 kHz to 100 kHz) shown in Figure 4(b), thereby determining whether or not an arc has actually occurred.

[0051] This means that, compared to conventional methods that detect the occurrence of an arc by determining whether a certain amount of frequency peaks are detected in a predetermined frequency band, the current method determines whether the occurrence of a high-risk arc is predicted, and then detects the occurrence of an arc by detecting frequency peaks in the predetermined frequency band. This prevents many false detections caused by picking up noise frequencies in that frequency band. Furthermore, in the arc detection device 10 of this embodiment, there is no need to set a high threshold for determination or to check and compare the arc status of other PV panels to detect arcs in order to avoid false detections.

[0052] <Arc Detection Method> The arc detection method implemented by the arc detection device 10 of this embodiment will be explained below using the flowchart shown in Figure 5.

[0053] In other words, in the arc detection device 10, in step S11, the current acquisition unit 11 detects the current flowing through the cable 31 (continuous monitoring) (current acquisition step). Next, in step S12, the danger state determination unit 12 determines whether the amount of current fluctuation detected in step S11 is greater than or equal to a predetermined threshold. If the amount of current fluctuation is greater than or equal to the predetermined threshold, the device proceeds to step S13; if it is less than the predetermined threshold, the device proceeds to step S16.

[0054] Next, in step S13, since it was determined in step S12 that the amount of current fluctuation was above a predetermined threshold, the danger state determination unit 12 determines that the occurrence of a high-risk arc is predicted and determines the danger level to be high. Next, in step S14, since it was determined in step S13 that the danger level is high, the arc frequency detection unit 13 detects the presence or absence of a frequency peak (arc frequency) in a predetermined frequency band. If the arc frequency detection unit 13 detects an arc frequency, the process proceeds to step S15. On the other hand, if the arc frequency detection unit 13 does not detect an arc frequency, it is determined that no arc has occurred, and the process returns to step S11 and the subsequent processing is repeated.

[0055] Next, in step S15, since it was determined in step S14 that an arc frequency was detected, the control unit 15 controls the power supply from the power supply equipment (PV30) to be immediately shut off. On the other hand, in step S16, since it was determined in step S12 that the amount of current fluctuation was less than a predetermined threshold, the danger state determination unit 12 determines that the occurrence of a high-risk arc is not predicted and determines the danger level to be low.

[0056] Next, in step S17, since the risk level was determined to be low in step S16, the arc frequency detection unit 13 detects the presence or absence of a frequency peak (arc frequency) in a predetermined frequency band. If the arc frequency detection unit 13 detects an arc frequency, the process proceeds to step S18. On the other hand, if the arc frequency detection unit 13 does not detect an arc frequency, it is determined that no arc has occurred, and the process returns to step S11, repeating the subsequent steps.

[0057] Next, in step S18, since it was determined in step S17 that an arc frequency was detected, albeit with a low degree of danger, the control unit 15 determines whether the arc frequency has been detected more than a predetermined threshold number of times. If it is determined that the number of times the arc frequency has been detected is greater than or equal to the predetermined threshold, it is determined that the system is dangerous because the arc detection time is long, even though the degree of danger is low, and the system proceeds to step S15, where the control unit 15 controls the system to shut off the power supply from the power supply equipment (PV30).

[0058] On the other hand, if the number of arc frequency detections is determined to be below a predetermined threshold, the system determines that the risk is low and the arc detection time is short, and therefore it is not dangerous. The system then returns to step S11 and repeats the subsequent processing. This allows for improved safety by shutting off the power supply after detecting a large arc once, when the occurrence of a high-risk arc is predicted. Conversely, if the occurrence of a high-risk arc is not predicted (i.e., only low-risk arcs are predicted), the system can avoid frequent power supply interruptions in low-risk situations by shutting off the power supply after a few cycles (a few seconds) of small arcs.

[0059] <Main Features> As shown in Figure 1, the arc detection device 10 of this embodiment is a device for detecting arcs that occur in a power supply cable 31 to which power is supplied from a PV 30, and as shown in Figure 2, it comprises a current acquisition unit 11 and a dangerous state determination unit 12. The current acquisition unit 11 acquires the current flowing through the cable 31. The dangerous state determination unit 12 determines whether or not a state in which the occurrence of a highly dangerous arc is predicted is in accordance with the amount of fluctuation of the current acquired by the current acquisition unit 11.

[0060] This allows for the detection of fluctuations in the current flowing through cable 31, which occur as a precursor to arc formation before an arc actually occurs. If the fluctuation is large, it can be determined that a dangerous arc is likely to occur. As a result, it is possible to accurately detect the occurrence of highly dangerous arcs in cable 31, which is supplied with power from power supply equipment such as PV30.

[0061] [Other Embodiments] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention. (A) In the above embodiment, examples of the present invention were described as the arc detection device 10 and the arc detection method. However, the present invention is not limited thereto.

[0062] For example, the present invention may be implemented as an arc detection program that causes a computer to execute the arc detection method described above. This arc detection program is stored in a memory (storage unit) mounted on the arc detection device, and the CPU reads the arc detection program stored in the memory and causes the hardware to execute each step. More specifically, the same effect as above can be obtained by the CPU reading the arc detection program and executing the steps described above. Furthermore, the present invention may be implemented as a recording medium that stores the arc detection program.

[0063] (B) In the above embodiment, an example was described in which the arc detection device 10 is located in a junction box 20 installed between the PV 30 and the power conditioner 40. However, the present invention is not limited thereto. For example, as shown in Figure 6, the arc detection device 110 may be installed in a power conditioner 140 that converts the DC power supplied from the PV 30 into AC power.

[0064] (C) In the above embodiment, an example was given in which the occurrence of a highly dangerous arc is predicted based on the amount of fluctuation in the current flowing through the cable from which power is supplied from the solar power generation equipment (PV30). However, the present invention is not limited thereto.

[0065] For example, the system may be configured to determine whether or not a highly dangerous arc is predicted based on the fluctuation range of the waveform indicating the voltage across the cable to which power is supplied from the solar power generation equipment (PV30). Specifically, for example, as shown in Figure 7, the arc detection device 210 may include a voltage acquisition unit 211 that measures and acquires the voltage across the cable.

[0066] For example, as shown in Figure 8(a), when a highly dangerous arc occurs, it can be seen that the voltage fluctuates along with the current flowing through the cable 31. In this case, the arc is present for a long time, indicating a high level of danger. At this time, as shown in Figure 9(a), the voltage fluctuation range before the arc occurred was 45.3V, and the current fluctuation range was 3.33A.

[0067] On the other hand, as shown in Figure 8(b), when a low-risk arc occurs, the fluctuations in the current and voltage flowing through the cable 31 are small. In this case, the duration of the arc is also short, indicating a low level of danger. At this time, as shown in Figure 9(b), the voltage fluctuation range before arc generation is 9.3V and the current fluctuation range is 0.67A, which are smaller than the fluctuation ranges shown in Figure 9(a).

[0068] Therefore, in the arc detection device 210 of this embodiment, the voltage acquisition unit 211 acquires the voltage applied to the cable 31. The danger state determination unit 12 determines whether or not a state in which the occurrence of a highly dangerous arc is predicted is present, based on the amount of voltage fluctuation detected by the voltage acquisition unit 211. This allows for the detection of voltage fluctuations applied to the cable 31 that occur as a precursor to arc occurrence before the arc actually occurs, and if the amount of fluctuation is large, it can be determined that a state in which the occurrence of a dangerous arc is predicted is present. As a result, similar to the embodiment 1 described above, the occurrence of highly dangerous arcs that occur in the cable 31 to which power is supplied from a power supply equipment such as a PV 30 can be detected with high accuracy.

[0069] (D) In ​​the above embodiment, an example was described in which the arc detection device 10 is provided in a junction box 20 located between the PV 30 and the power conditioner 40. However, the present invention is not limited thereto. For example, the arc detection device may be provided inside the power conditioner.

[0070] (E) In the above embodiment, an example was given in which the occurrence of a highly dangerous arc is predicted according to the amount of current fluctuation, and whether or not an arc actually occurred is determined based on the frequency of the current fluctuation. However, the present invention is not limited thereto. For example, the present invention may be configured to only predict the occurrence of a highly dangerous arc according to the amount of current fluctuation, without determining whether or not an arc actually occurred based on the frequency of the current fluctuation.

[0071] (F) In the above embodiment, as shown in Figure 1, an example was described in which an arc detection device 10 is arranged on each of the multiple cables 31 connected to the multiple PVs 30. However, the present invention is not limited thereto. For example, an arc detection device may be arranged on a single cable connected to a single renewable energy facility such as a single PV.

[0072] (G) In the above embodiment, an example was given in which the occurrence of a highly dangerous arc is predicted based on the amount of fluctuation in the current flowing through the cable to which power is supplied from the solar power generation equipment (PV30). However, the present invention is not limited thereto. For example, the configuration may determine whether the occurrence of a highly dangerous arc is predicted based on the amount of fluctuation in the current flowing through the cable to which power is supplied from other renewable energy equipment such as wind power generation or geothermal power generation equipment, in addition to solar power generation equipment.

[0073] (H) In the above embodiment, an example was given in which an arc was determined based on the current fluctuation frequency. However, the present invention is not limited thereto. For example, a configuration may be used in which the voltage difference and current across the arc generation site are detected without using the current fluctuation frequency to determine whether an arc was actually generated.

[0074] <Note> The arc detection device according to the first invention is an arc detection device for detecting arcs that occur in a power supply cable to which power is supplied from a power supply facility, and comprises: a current acquisition unit that acquires the current flowing through the cable, and a dangerous state determination unit that determines whether or not the occurrence of a highly dangerous arc is predicted according to the amount of fluctuation of the current acquired by the current acquisition unit.

[0075] The arc detection device according to the second invention is the arc detection device according to the first invention, wherein the danger state determination unit determines that if the amount of current fluctuation acquired by the current acquisition unit exceeds a predetermined threshold, it is a state in which the occurrence of a highly dangerous arc is predicted. The arc detection device according to the third invention is the arc detection device according to the first or second invention, further comprising a detection unit for detecting the presence or absence of an arc.

[0076] The arc detection device according to the fourth invention is the arc detection device according to the third invention, wherein the detection unit detects the presence or absence of an arc based on the fluctuation frequency of the current acquired by the current acquisition unit. The arc detection device according to the fifth invention is the arc detection device according to the third invention, further comprising a first control unit that controls the power supply from the power supply equipment to the downstream side to shut off when the hazardous state determination unit determines that a state in which the occurrence of a highly hazardous arc is predicted is present, and the detection unit detects the occurrence of an arc.

[0077] The arc detection device according to the sixth invention is the arc detection device according to the third invention, further comprising a first threshold adjustment unit that adjusts the value of the threshold used for determination in the detection unit to lower it when the danger state determination unit determines that a state in which the occurrence of a highly dangerous arc is predicted is observed. The arc detection device according to the seventh invention is the arc detection device according to the third invention, when the danger state determination unit determines that a state in which the occurrence of a highly dangerous arc is not predicted is observed, and the detection unit detects the occurrence of the arc, and the number of detections exceeds a predetermined number, the power supply from the power supply equipment to the downstream side is shut off.

[0078] The arc detection device according to the eighth invention is an arc detection device according to the third invention, further comprising a second threshold adjustment unit that adjusts the value of the threshold used for determination in the detection unit to increase when the danger state determination unit determines that the occurrence of a high-risk arc is not expected. The arc detection device according to the ninth invention is an arc detection device according to any one of the first to eighth inventions, and is arranged between the power supply equipment and a power conditioner that converts the DC power supplied from the power supply equipment into AC power.

[0079] The arc detection device according to the tenth invention is an arc detection device according to any one of the first to ninth inventions, and is located inside a power conditioner that converts DC power supplied from the power supply equipment into AC power. The arc detection device according to the eleventh invention is an arc detection device according to any one of the first to tenth inventions, and the power supply equipment is renewable energy equipment.

[0080] The arc detection device of the present invention has the effect of being able to accurately detect the occurrence of highly dangerous arcs that occur in cables to which power is supplied from power supply equipment, and is therefore widely applicable to electrical equipment, including renewable energy equipment such as solar power generation equipment.

[0081] 10 Arc detection device 11 Current acquisition unit 12 Dangerous state determination unit 13 Arc frequency detection unit (detection unit) 14 Threshold adjustment unit 15 Control unit 16 Output unit 20 Junction box 30 PV (Photovoltaic power generation equipment) 31, 32 Cable 40 Power conditioner 50 Load 110 Arc detection device 140 Power conditioner 210 Arc detection device 211 Voltage acquisition unit

Claims

1. An arc detection device for detecting arcs occurring in a power supply cable from which power is supplied from a power supply facility, comprising: a current acquisition unit for acquiring the current flowing through the cable; and a hazardous condition determination unit for determining whether or not a state in which the occurrence of a highly dangerous arc is predicted is present, according to the amount of fluctuation of the current acquired by the current acquisition unit.

2. The arc detection device according to claim 1, wherein the dangerous state determination unit determines that if the amount of current fluctuation obtained by the current acquisition unit exceeds a predetermined threshold, it is a state in which the occurrence of a highly dangerous arc is predicted.

3. The arc detection device according to claim 1 or 2, further comprising a detection unit for detecting the presence or absence of an arc.

4. The arc detection device according to claim 3, wherein the detection unit detects the presence or absence of an arc based on the fluctuation frequency of the current acquired by the current acquisition unit.

5. The arc detection device according to claim 3, further comprising a first control unit that controls the power supply to the downstream side from the power supply equipment when the hazardous state determination unit determines that a state in which the occurrence of a highly hazardous arc is predicted is present, and the detection unit detects the occurrence of an arc.

6. The arc detection device according to claim 3, further comprising a first threshold adjustment unit that adjusts the value of the threshold used for determination in the detection unit to lower the value of the threshold used in determination when the danger state determination unit determines that a state in which the occurrence of a high-risk arc is predicted is present.

7. The arc detection device according to claim 3, wherein the hazardous state determination unit determines that a state in which the occurrence of a high-risk arc is not predicted, the detection unit detects the occurrence of the arc, and when the number of detections exceeds a predetermined number, the power supply from the power supply equipment to the downstream side is shut off.

8. The arc detection device according to claim 3, further comprising a second threshold adjustment unit that adjusts the value of the determination threshold used in the detection unit to increase when the danger state determination unit determines that the occurrence of a high-risk arc is not predicted.

9. The arc detection device according to claim 1 or 2, which is positioned between the power supply equipment and a power conditioner that converts the DC power supplied from the power supply equipment into AC power.

10. An arc detection device according to claim 1 or 2, which is located inside a power conditioner that converts DC power supplied from the power supply equipment into AC power.

11. The arc detection device according to claim 1 or 2, wherein the power supply equipment is renewable energy equipment.

12. An arc detection device for detecting arcs occurring in a power supply cable from which power is supplied from a power supply facility, comprising: a voltage acquisition unit for acquiring the voltage applied to the cable; and a hazardous state determination unit for determining whether or not a state in which the occurrence of a highly dangerous arc is predicted, according to the fluctuation range of the waveform showing the voltage acquired by the voltage acquisition unit.

13. An arc detection method using an arc detection device for detecting arcs occurring in a power supply cable supplied with power from a power supply facility, wherein the current acquisition unit of the arc detection device acquires the current flowing through the cable, and the danger state determination unit of the arc detection device determines, according to the amount of fluctuation of the acquired current, whether or not a state in which the occurrence of a highly dangerous arc is predicted.

14. An arc detection program for an arc detection device that detects arcs occurring in a power supply cable supplied with power from a power supply facility, wherein the current acquisition unit of the arc detection device acquires the current flowing through the cable, and the danger state determination unit of the arc detection device determines, according to the amount of fluctuation in the acquired current, whether or not the occurrence of a highly dangerous arc is predicted, and causes a computer to execute an arc detection method.

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