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

Abstract

The present invention provides an arc detection device capable of accurately detecting the occurrence of highly dangerous arcs in cables supplied with power from power supply equipment. [Solution] The arc detection device 10 is a device for detecting arcs that occur in a power supply cable 31 to which power is supplied from 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 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.

Description

Technical Field

[0004] , , , , ,

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

Background Art

[0002] In a conventional solar power generation system, electric power generated by solar cells 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 and 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 temperature, and there is a risk of causing 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, a current pulse is generated every time a stepwise increase in current is detected, 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.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional arc fault detection device described above has the following problems. In other words, the arc fault detection device disclosed in the above publication increases the sensitivity of the envelope detection type arc fault detector to low-current arcs without sacrificing reaction time to high-current and more dangerous arc faults by tracking the amplitude of the step-like change in current generated by the arc fault.

[0006] However, with this configuration, while it was possible to determine whether an arc was dangerous after it had occurred, it was difficult to predict the occurrence of high-current, highly dangerous arcs. Furthermore, conventionally, when detecting arcs, the 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 included noise frequencies, there was a risk of many false detections. Furthermore, in order to suppress the occurrence of false detections as much as possible, measures such as setting a high threshold value for judgment or detecting arcs while checking and comparing the arc status of other panels were necessary. 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 highly dangerous arcs in cables supplied with power from power supply equipment. [Means for solving the problem]

[0008] The arc detection device according to the first invention is an arc detection device for detecting arcs generated in a power supply cable supplied with power 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, based on the amount of fluctuation in the current acquired by the current acquisition unit, whether or not a state is expected in which the generation of a highly hazardous arc is predicted.

[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, power supply facilities include, 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, which occur as a precursor to arc formation, before an arc actually occurs. 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 that receive power 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 allows for determining whether an arc is highly dangerous based on whether the fluctuation in the current 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 whether or not an arc is generated. This allows for the determination of whether or not a high-risk arc is occurring in accordance with the fluctuation amount of current flowing through the aforementioned cable, as well as the determination of whether or not an arc is actually 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 fluctuating frequency refers to the frequency obtained from the FFT (Fast Fourier Transform) analysis results. This allows for the determination of whether or not a high-risk arc is occurring, based on the fluctuation amount of the current flowing through the aforementioned cable, and by detecting the frequency of that current fluctuation, it is possible to determine whether or not an actual arc is occurring.

[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 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. This allows for the prevention of cable damage or malfunction 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 a dangerous state determination unit determines that a state in which the occurrence of a highly dangerous arc is predicted is in which case it adjusts the value of the determination threshold used in the detection unit to lower it. This allows for easy detection of high-risk arcs by lowering the threshold value used for determination in the detection unit when the occurrence of a high-risk arc is predicted.

[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 a state in which the occurrence of a highly hazardous 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 the occurrence of an arc with a low risk level, without immediately interrupting the power supply, it is possible to interrupt the power supply after the occurrence of the arc is actually detected and the detection count reaches a predetermined number or more.

[0017] The arc detection device according to the eighth invention is the arc detection device according to the third invention, and further includes a second threshold adjustment unit that adjusts to increase the value of the determination threshold used in the detection unit when it is determined in the risk state determination unit that the occurrence of an arc with a high risk level is not predicted. As a result, when the occurrence of an arc with a high risk level is not predicted, by adjusting to increase the value of the determination threshold in the detection unit, it becomes difficult to detect the occurrence of an arc with a low risk level, and only the occurrence of an arc with a high risk level can be detected.

[0018] The arc detection device according to the ninth invention is the arc detection device according to the first or second invention, and is arranged between a power supply facility and a power conditioner that converts DC power supplied from the power supply facility into AC power. As a result, by arranging the arc detection device on the cable connecting between the power supply facility and the power conditioner that converts DC power supplied from the power supply facility into AC power, the occurrence of an arc with a high risk level can be detected with high accuracy.

[0019] The arc detection device according to the tenth invention is the arc detection device according to the first or second invention, and is arranged inside a power conditioner that converts DC power supplied from the power supply facility into AC power. As a result, by arranging the arc detection device inside the power conditioner that converts DC power supplied from the power supply facility into AC power, the occurrence of an arc with a high risk level can be detected with high accuracy.

[0020] The arc detection device according to the eleventh invention is the arc detection device according to the first or second invention, and the power supply facility is a renewable energy facility. Thus, for example, by installing this arc detection device on renewable energy facilities such as solar power generation facilities, wind power generation facilities, and geothermal power generation facilities, it is possible to accurately detect the occurrence of arcs with a high degree of danger.

[0021] The arc detection device according to the twelfth invention is an arc detection device that detects an arc occurring in a power supply cable supplied with power from a power supply facility, and includes a voltage acquisition unit and a dangerous state determination unit. The voltage acquisition unit acquires the voltage applied to the cable. The dangerous state determination unit 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 fluctuation range of the waveform indicating the voltage acquired by the voltage acquisition unit.

[0022] Here, for example, in order to accurately detect a highly dangerous arc that occurs when power is supplied from a power supply facility via a cable, it is determined whether or not it is a state in which the occurrence of a dangerous arc is predicted according to 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 may be configured to acquire the measurement result of the voltage applied to the cable from a voltage measuring device. Thereby, the fluctuation range of the waveform indicating the voltage applied to the cable, which occurs as a sign of arc generation before the arc occurs, is detected, and when the fluctuation range is large, it can be determined that it is a state in which the occurrence of a dangerous arc is predicted. As a result, it is possible to accurately detect the occurrence of a highly dangerous arc occurring in the cable supplied with power from the power supply facility.

[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 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, power supply facilities include, 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 be a process of measuring the current flowing through the cable, or it may be a process of 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, which occur as a precursor to arc formation, before an arc actually occurs. 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 that receive power from power supply equipment.

[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, power supply facilities include, 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 be a process of measuring the current flowing through the cable, or it may be a process of 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, which occur as a precursor to arc formation, before an arc actually occurs. 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. [Effects of the Invention]

[0031] According to the arc detection device of the present invention, it is possible to accurately detect the occurrence of highly dangerous arcs in cables to which power is supplied from power supply equipment. [Brief explanation of the drawing]

[0032] [Figure 1] A block diagram showing a configuration in which an arc detection device according to one embodiment of the present invention is placed in a junction box installed between a PV and a power conditioner. [Figure 2] A control block diagram showing the configuration of the arc detection device in Figure 1. [Figure 3] (a) is a graph showing the arc generation time when the current fluctuation amount obtained in the current acquisition section of the arc detection device in Figure 2 is small. (b) is a graph showing the arc generation time when the current fluctuation amount obtained in the current acquisition section of the arc detection device in Figure 2 is large. [Figure 4](a) is a graph showing the FFT analysis results (relationship between frequency and voltage) when no arc is detected in the arc frequency detection section of the arc detection device shown in Figure 2. (b) is a graph showing the FFT analysis results (relationship between frequency and voltage) when an arc is detected in the arc frequency detection section of the arc detection device shown in Figure 2. [Figure 5] A flowchart showing the processing flow of the arc detection method performed by the arc detection device in Figure 2. [Figure 6] A block diagram showing 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. [Figure 7] A control block diagram showing the configuration of an arc detection device according to yet another embodiment of the present invention. [Figure 8] (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. [Figure 9] (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). [Modes for carrying out the invention]

[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 details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. Furthermore, the applicant provides the accompanying drawings and the following description so that those skilled in the art may fully understand the present invention, and not intends to limit the subject matter described in the claims.

[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. It acquires the current flowing through the cable 31 supplied from the plurality of PVs 30 to the power conditioner 40 and predicts 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 based on 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 more detail later. The PV (photovoltaic) system 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 PV30 via cables 31 and 32 into AC power and supplies the AC power to the load 50.

[0036] Load 50 consists of general electrical appliances that consume power and receive power from the power conditioner 40. Specifically, Load 50 includes, for example, various electrical appliances used in homes such as air conditioners, microwave ovens, and televisions, as well as machinery and lighting equipment used in commercial and industrial facilities such as air conditioners and lighting fixtures. In this case, 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 stabilizes due to 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, when the load of 50 is light, the electrical energy supplied from PV30 is not consumed, creating a condition where a highly dangerous arc is likely to occur, as described later.

[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 PV30 and the power conditioner 40.

[0039] The hazardous condition 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 condition 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 fluctuation frequency of the current 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] The control unit (first control unit) 15 controls the power supply from PV30 to the downstream side to shut off when the hazardous condition determination unit 12 determines that a state in which the occurrence of a high-risk arc is predicted. Furthermore, when the hazardous condition determination unit 12 determines that a state in which the occurrence of a high-risk arc is not predicted, and the arc frequency detection unit 13 detects the occurrence of an arc, the control unit 15 controls the power supply from PV30 to the downstream side to delay the time it takes to shut off the power supply. The output unit 16 converts the determination result of the arc detection device 10 regarding the occurrence of a high-risk arc into a binary signal and outputs it.

[0042] <Prediction of high-risk arc occurrences> Here, as shown in Figure 3(a), when the fluctuation in the current flowing through the cable 31 is a small value, 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 Figure 3(b), when the fluctuation in the current flowing through cable 31 is a large value, for example, about 1.59A (indicating a light load), the arc generation time becomes longer, approximately 2.45 seconds. For example, if the capacity of power conditioner 40 is 3.6 kW, the generating voltage setting of PV30 is 450 V, and the generating current setting of PV30 is 8 A, then when it was determined that a high-risk arc was occurring (≒ light load), the AC load resistance (voltage is AC100 V) was 18.0 Ω.

[0044] On the other hand, when it was determined that no high-risk arcs were generated (i.e., not a light load), the AC load resistance (voltage AC100V) was 16.7Ω. In other words, assuming all other conditions are the same except for the current load resistance (current), the occurrence of arcs that last longer and are more dangerous, as shown in Figures 3(a) and 3(b), is determined by the magnitude of the current fluctuation.

[0045] Next, the following are possible factors that may cause the arc that occurred in cable 31 to persist. In other words, arc generation ceases when there is insufficient energy supply to the arc. Therefore, when the power supplied from PV30 is less than or equal to the power consumption of power conditioner 40, the power conditioner 40 consumes almost all of the power supplied from PV30, resulting in insufficient energy supply to the arc and a short arc generation time (small arc generation).

[0046] On the other hand, if the power supplied from PV30 is greater than the power consumption of power conditioner 40, the power consumption on the power conditioner 40 side is low, resulting in an excess of energy supplied to the arc, and thus the arc generation time will be longer (the generated arc will be larger). In this case, if the power supplied from PV30 is less than or equal to the power consumption of the power conditioner 40, the AC load resistance is small, and the current flowing through cable 31 tends to be stable.

[0047] On the other hand, if the power supplied from PV30 is greater than the power consumption of the power conditioner 40, the AC load resistance is large, so the current flowing through cable 31 is unstable and prone to large fluctuations. Therefore, if the current flowing through cable 31 is unstable (excessive power supply), highly dangerous arcs are likely to continuously occur in cable 31.

[0048] In the arc detection device 10 of this embodiment, as shown in Figure 3(b), in order to predict the occurrence of a long-duration, high-risk arc, the current acquisition unit 11 detects fluctuations in the current flowing through the cable 31 and the amount of these fluctuations in the stage before the arc occurs, and the danger state determination unit 12 determines, based on the detected amount of current fluctuation, whether or not a state in which the occurrence of a high-risk arc is predicted is present.

[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 is generated, no frequency peaks are detected in the frequency band of section A (10kHz to 100kHz), as shown in Figure 4(a).

[0050] On the other hand, when an arc occurs, a certain amount of frequency peak is detected in the frequency band of section A (10kHz to 100kHz), 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 peak is detected in the frequency band of portion A (10kHz to 100kHz) shown in Figure 4(b), thereby detecting whether or not an arc has actually occurred.

[0051] This method, compared to conventional methods that detect the occurrence of an arc based on whether a certain amount of frequency peaks are detected in a predetermined frequency band, allows for detection of the occurrence of an arc by first determining whether a high-risk arc is predicted, and then detecting the frequency peaks in the predetermined frequency band. This prevents the detection of many false positives 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 judgment or to detect arcs while checking and comparing the arc status of other PV panels in order to avoid false detections.

[0052] <Arc detection method> The arc detection method performed by the arc detection device 10 of this embodiment can be described below using the flowchart shown in Figure 5.

[0053] In other words, in step S11, the arc detection device 10 detects the current flowing through the cable 31 (continuous monitoring) (current acquisition step). Next, in step S12, the hazardous condition 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 process proceeds to step S13; otherwise, the process 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 the risk level was determined to be high in step S13, 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, repeating the subsequent steps.

[0055] Next, in step S15, since it was determined in step S14 that an arc frequency was detected, the control unit 15 controls the system to immediately shut off the power supply from the power supply equipment (PV30). 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 or not the arc frequency has been detected more than a predetermined threshold number of times. If it is determined that the number of arc frequency detections exceeds a predetermined threshold, the system determines that the system is dangerous even if the risk level is low, because the arc detection time is long, and 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 risk level is low and the arc detection time is short, so it is determined that there is no danger, and the process returns to step S11 and the subsequent processing is repeated. This allows for enhanced safety by shutting off the power supply upon detection of a large arc if a highly dangerous arc is anticipated. On the other hand, if the occurrence of a high-risk arc is not predicted (and only a low-risk arc is predicted), the power supply can be shut off when a small arc lasts for several cycles (several seconds), thus avoiding frequent power outages in low-risk situations.

[0059] <Key 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 PV30, 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 present, according to the amount of fluctuation in the current acquired by the current acquisition unit 11.

[0060] This allows for the detection of fluctuations in the current flowing through the cable 31, which occur as a precursor to arc formation before an arc actually occurs. 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 high-risk arcs in the cable 31 to which power is supplied 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 embodiments, 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 the memory (storage unit) of the arc detection device. The CPU reads the arc detection program stored in memory and instructs the hardware to execute each step. More specifically, the same effect as described above can be achieved 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 storing an 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 within a power conditioner 140 that converts the DC power supplied from the PV30 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 amplitude 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 related to 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 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 arc generation 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 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 across cable 31 that occur as a precursor to arc formation before the arc actually occurs. If the amount of fluctuation is large, it can be determined that a dangerous arc is likely to occur. As a result, similar to Embodiment 1 described above, it is possible to accurately detect the occurrence of high-risk arcs in the cable 31 to which power is supplied from power supply equipment such as PV30.

[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 installed 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 system may only predict the occurrence of a high-risk arc based on the amount of current fluctuation, and may not determine 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 placed on each of the multiple cables 31 connected to the multiple PVs 30. However, the present invention is not limited thereto. For example, the configuration may involve an arc detection device being placed on a single cable connected to a single renewable energy facility such as a PV system.

[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 from which power is supplied from the solar power generation equipment (PV30). However, the present invention is not limited thereto. For example, the system may be configured to determine whether or not a high-risk arc is predicted based on fluctuations in the current flowing through cables supplied with power from other renewable energy facilities such as wind power generation and geothermal power generation, in addition to solar power generation facilities.

[0073] (H) In the above embodiment, an example was given in which it was determined whether or not an arc actually occurred based on the fluctuation frequency of the current. However, the present invention is not limited thereto. For example, the configuration may determine whether or not an arc has actually occurred by detecting the voltage difference and current across the arc generation site, without using the current fluctuation frequency.

[0074] <Note> The arc detection device according to the first invention is: An arc detection device for detecting arcs that occur in power supply cables supplied with power from power supply equipment, A current acquisition unit that acquires the current flowing through the aforementioned cable, A dangerous state determination unit determines whether or not a state in which the occurrence of a highly dangerous arc is predicted is present, based on the amount of current fluctuation obtained in the current acquisition unit. It is equipped with.

[0075] The arc detection device according to the second invention is the arc detection device according to the first invention, The hazardous condition determination unit determines that if the amount of current fluctuation acquired by the current acquisition unit exceeds a predetermined threshold, it is a condition in which the occurrence of a highly dangerous arc is predicted. The arc detection device according to the third invention is an arc detection device according to the first or second invention, It also includes a detection unit that detects whether or not an arc is occurring.

[0076] The arc detection device according to the fourth invention is the arc detection device according to the third invention, The detection unit detects whether or not an arc is occurring based on the fluctuation frequency of the current acquired by the current acquisition unit. The arc detection device according to the fifth invention is an arc detection device according to the third invention, The system further includes a first control unit that, when the hazardous condition determination unit determines that a state in which the occurrence of a highly dangerous arc is predicted is present, and the detection unit detects the occurrence of an arc, controls the system to shut off the power supply from the power supply equipment to the downstream side.

[0077] The arc detection device according to the sixth invention is an arc detection device according to the third invention, The system further includes a first threshold adjustment unit that, when the hazardous condition determination unit determines that a state in which the occurrence of a highly dangerous arc is predicted is present, adjusts the value of the determination threshold used in the detection unit to lower it. The arc detection device according to the seventh invention is an arc detection device according to the third invention, If the hazard determination unit determines that a state in which the occurrence of a high-risk arc is not predicted, 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, The system further includes a second threshold adjustment unit that, when the hazardous state determination unit determines that the occurrence of a high-risk arc is not predicted, adjusts the value of the determination threshold used in the detection unit to increase it. The arc detection device according to the ninth invention is an arc detection device according to any one of the first to eighth inventions, It is positioned between the aforementioned 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 10th invention is an arc detection device according to any one of the 1st to 9th inventions, It is located inside a power conditioner that converts DC power supplied from the aforementioned power supply equipment into AC power. The arc detection device according to the 11th invention is an arc detection device according to any one of the first to tenth inventions, The aforementioned power supply equipment is a renewable energy facility. [Industrial applicability]

[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. [Explanation of Symbols]

[0081] 10 Arc detection device 11 Current acquisition section 12 Hazardous Condition Determination Unit 13. Arc frequency detection unit (detection unit) 14. Threshold adjustment section 15 Control Unit 16 Output section 20 junction boxes 30 PV (Solar 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 section

Claims

1. An arc detection device for detecting arcs that occur in power supply cables supplied with power from power supply equipment, A current acquisition unit that acquires the current flowing through the aforementioned cable, A dangerous state determination unit determines whether or not a state in which the occurrence of a highly dangerous arc is predicted is present, based on the amount of current fluctuation obtained in the current acquisition unit. An arc detection device equipped with the following features.

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

3. It further includes a detection unit for detecting whether or not an arc is occurring. The arc detection device according to claim 1 or 2.

4. The detection unit detects whether or not an arc is occurring based on the fluctuation frequency of the current acquired by the current acquisition unit. The arc detection device according to claim 3.

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

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

7. If the hazardous condition determination unit determines that a state in which the occurrence of a high-risk arc is not predicted, 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. The arc detection device according to claim 3.

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

9. The following 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: The arc detection device according to claim 1 or 2.

10. Located inside the power conditioner that converts DC power supplied from the aforementioned power supply equipment into AC power, The arc detection device according to claim 1 or 2.

11. The aforementioned power supply equipment is a renewable energy facility. The arc detection device according to claim 1 or 2.

12. An arc detection device for detecting arcs that occur in power supply cables supplied with power from power supply equipment, A voltage acquisition unit that acquires the voltage applied to the aforementioned cable, A danger state determination unit determines whether or not a state in which the occurrence of a high-risk arc is predicted is present, based on the fluctuation range of the waveform showing the voltage acquired by the voltage acquisition unit. An arc detection device equipped with the following features.

13. An arc detection method using an arc detection device that detects arcs occurring in power supply cables supplied with power from power supply equipment, The current acquisition unit of the arc detection device acquires the current flowing through the cable, The danger state determination unit of the arc detection device determines, based on the acquired amount of current fluctuation, whether or not a state is in which the occurrence of a highly dangerous arc is predicted. Arc detection method.

14. An arc detection program for an arc detection device that detects arcs occurring in power supply cables supplied with power from power supply equipment, The current acquisition unit of the arc detection device acquires the current flowing through the cable, The danger state determination unit of the arc detection device determines, based on the acquired amount of current fluctuation, whether or not a state is in which the occurrence of a highly dangerous arc is predicted. An arc detection program that instructs a computer to perform an arc detection method.

Images