DC Cable Monitoring System in Photovoltaic Power Generation Equipment

Abstract

Provided is a DC cable monitoring system in a solar power generation facility that can determine whether an abnormality in a DC cable to be monitored is due to theft or a defect such as a failure. 【Solution means】A resistance value measuring means 20 capable of measuring the resistance value of a DC cable 6 connecting an aggregation unit 4 that aggregates DC power generated by a solar cell unit 3 and a power conditioner 5, and based on the normal resistance value NR of the DC cable 6, an abnormal resistance value setting means 30 for setting a first lower limit value L1 as the lower limit value of the normal resistance value and a second lower limit value L2 having a resistance value smaller than the first lower limit value L1, and when the resistance value of the DC cable 6 is equal to or less than the first lower limit value L1 and equal to or more than the second lower limit value L2 during cable monitoring, it is determined that a cut has occurred in the DC cable 6, and when it is less than the second lower limit value L2, it is determined that a defect other than a cut has occurred in the DC cable 6. It is equipped with an abnormal state determination means 50.

Description

Technical Field

[0001] The present invention relates to a DC cable monitoring system in a photovoltaic power generation facility. More specifically, the present invention relates to a DC cable monitoring system in a photovoltaic power generation facility that can determine whether an abnormality in a DC cable to be monitored is caused by theft (cutting) or a defect such as a failure.

Background Art

[0002] Conventionally, for example, a technique as disclosed in Patent Document 1 is known.

[0003] <Patent Document 1> Japanese Patent Application Laid-Open No. 2016-131470 Patent Document 1 states that “to provide an abnormality detection system for a photovoltaic power generation facility that can surely detect abnormalities such as theft even at night with a low cost and a simple system configuration” is an issue, “In an abnormality detection system for a photovoltaic power generation facility including a lower unit that aggregates DC power generated by a solar cell unit and an upper unit that aggregates the DC power collected by the lower unit, the lower units are connected in parallel to the upper unit, and a measuring device for measuring impedance is provided in each wiring cable connecting each of these lower units and the upper unit. Further, upstream of each of these measuring units, a determination unit for detecting the abnormality based on the measurement result during non-generation of the solar cell unit is provided. In the measuring device, as the impedance, the combined impedance aggregated for each of all the lower units connected in parallel to the upper unit is measured.” An abnormality detection system for a photovoltaic power generation facility is described (in the abstract column of the same document).

[0004] Also, in paragraph 0030 of the same document, “(ST3) In the determination unit 12, the resistance values (R1 to R3) of the electric circuits aggregated for each lower unit are stored in advance as initial setting values. The determination unit 12 compares ··· omitted in the middle ···, and if Z1 = 1 / (1 / R1 + 1 / R2 + 1 / R3), it makes a normal determination (a determination that it is in a "normal state" without theft, failure, etc.), and here, it ends the abnormal detection routine. It is described that, in paragraph 0031 of the same, “(ST4) In cases other than Z1 = 1 / (1 / R1 + 1 / R2 + 1 / R3), it is an abnormal determination and a warning display is performed.” It is described.

[0005] That is, according to the technology described in this Patent Document 1, it is understood that it is possible to determine whether the electric circuit (wiring cable) to be determined is in a "normal state" without theft, failure, etc., or in an abnormal state.

[0006] However, in the technology described in this Patent Document 1, it is not possible to determine whether the abnormal state is due to theft or due to a failure or the like.

[0007]

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The problem to be solved by the present invention is to provide a DC cable monitoring system in a photovoltaic power generation facility that can determine whether an abnormality in a DC cable to be monitored is due to theft or due to a defect such as a failure.

Means for Solving the Problems

[0010] In order to solve the above problems, the DC cable monitoring system in the photovoltaic power generation facility of the present invention is A solar cell unit, an aggregation unit that aggregates the DC power generated by this solar cell unit, a power conditioner that converts the DC power from this aggregation unit into AC, In a solar power generation facility including a DC cable that connects the aggregation unit and the power conditioner, resistance value measuring means capable of measuring the resistance value of the DC cable connecting the aggregation unit and the power conditioner, abnormal resistance value setting means for setting, based on the normal resistance value of the DC cable measured by this resistance value measuring means, a first lower limit value as the lower limit value of the normal resistance value and a second lower limit value that is a resistance value smaller than this first lower limit value, During cable monitoring, when the resistance value of the DC cable measured by the resistance value measuring means is equal to or less than the first lower limit value and equal to or greater than the second lower limit value, it is determined that a cut has occurred in the DC cable, and when it is less than the second lower limit value, it is determined that a malfunction other than a cut has occurred in the DC cable, abnormal state determination means, characterized by comprising.

[0011] Since it has the above configuration, the following operational effects can be obtained according to the DC cable monitoring system in this solar power generation facility.

[0012] The resistance value measuring means can measure the resistance value of the DC cable connecting the aggregation unit and the power conditioner. The abnormal resistance value setting means sets, based on the normal resistance value of the DC cable measured by the resistance value measuring means, a first lower limit value as the lower limit value of the normal resistance value and a second lower limit value that is a resistance value smaller than this first lower limit value. During cable monitoring, the following determination is made by the abnormal state determination means. (a) When the resistance value of the DC cable measured by the resistance value measuring means is equal to or less than the first lower limit value and equal to or greater than the second lower limit value, it is determined that a cut has occurred in the DC cable. (b) When the resistance value of the DC cable measured by the resistance value measuring means is less than the second lower limit value, it is determined that a problem other than disconnection has occurred in the DC cable.

[0013] Therefore, according to the DC cable monitoring system in this photovoltaic power generation facility, it is possible to determine whether the abnormality of the DC cable to be monitored is due to theft (disconnection) or a problem such as a failure (for example, a problem such as a connection cable ground fault or an accident due to flooding). Since the countermeasures in the case where the abnormality of the DC cable is due to theft are different from the countermeasures in the case of a problem such as a failure, according to the present invention, appropriate countermeasures can be taken.

[0014] In addition, in order to solve the above problems, the DC cable monitoring system in the photovoltaic power generation facility of the present invention is a solar cell unit, a plurality of aggregation units that aggregate the DC power generated by this solar cell unit, a power conditioner that aggregates the DC power from these plurality of aggregation units, in a photovoltaic power generation facility including a plurality of DC cables that connect the plurality of aggregation units and the power conditioner respectively, resistance value measuring means capable of measuring the resistance value of the entire plurality of DC cables connecting each aggregation unit and the power conditioner, abnormal resistance value setting means for setting a first lower limit value as the lower limit value of the normal resistance value and a second lower limit value that is a resistance value smaller than the first lower limit value, based on the normal resistance value of the entire DC cable measured by this resistance value measuring means, abnormal state determination means for determining that a disconnection has occurred in the DC cable when the resistance value of the entire DC cable measured by the resistance value measuring means is less than or equal to the first lower limit value and greater than or equal to the second lower limit value during cable monitoring, and determining that a problem other than disconnection has occurred in the DC cable when it is less than the second lower limit value, characterized by comprising.

[0015] Since it has the above configuration, the following operational effects can be obtained according to the DC cable monitoring system in this photovoltaic power generation facility.

[0016] The resistance value measuring means can measure the resistance value of the entire DC cable connecting the aggregation unit and the power conditioner. Based on the normal resistance value of the entire DC cable measured by the resistance value measuring means, the abnormal resistance value setting means sets a first lower limit value as the lower limit value of the normal resistance value and a second lower limit value that is a resistance value smaller than the first lower limit value. During cable monitoring, the abnormal state determination means makes the following determination. (a) When the resistance value of the entire DC cable measured by the resistance value measuring means is less than or equal to the first lower limit value and greater than or equal to the second lower limit value, it is determined that a break has occurred in the DC cable. (b) When the resistance value of the entire DC cable measured by the resistance value measuring means is less than the second lower limit value, it is determined that a problem other than a break has occurred in the DC cable.

[0017] Therefore, according to the DC cable monitoring system in this photovoltaic power generation facility, it is possible to determine whether the abnormality of the DC cable to be monitored is due to theft (break) or a problem such as a failure (for example, a problem such as a connection cable ground fault or an accident due to flooding, etc.). Since the countermeasures in the case where the abnormality of the DC cable is due to theft are different from those in the case of a problem such as a failure, appropriate countermeasures can be taken according to the present invention.

[0018] In the DC cable monitoring system in this photovoltaic power generation facility, furthermore, When the abnormality determination means determines that a disconnection has occurred in the DC cable, an alarm for disconnection occurrence indicating that the DC cable has been disconnected is transmitted. When it is determined that a problem other than disconnection has occurred in the DC cable, an alarm transmission means for transmitting an alarm for problem occurrence indicating that a problem has occurred in the DC cable 6 can be provided. With this configuration, the alarm transmission means can issue an alarm indicating that an abnormality has occurred in the DC cable to be monitored and whether the abnormality is due to theft (disconnection) or a problem (for example, a problem such as a connection cable ground fault or an accident due to flooding or the like).

[0019] In this DC cable monitoring system for a solar power generation facility, at least the resistance value measuring means, the abnormality determination means, and the alarm transmission means are incorporated in the power conditioner. Furthermore, a management device is provided at a location separated from the power conditioner and wirelessly receives the disconnection occurrence alarm or the problem occurrence alarm from the alarm transmission means. This management device can be configured to transmit the above alarm to a predetermined notification destination. With this configuration, it becomes possible to immediately take appropriate measures in response to the problem for the cable in which the problem has occurred.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of a DC cable monitoring system for a solar power generation facility according to the present invention will be described with reference to the drawings. In each figure, the same parts or corresponding parts are denoted by the same reference numerals.

[0022] As shown in FIG. 1, the DC cable monitoring system 1 in the photovoltaic power generation facility of this embodiment is a solar cell unit 3, a plurality of aggregation units 4 that aggregate the DC power generated by this solar cell unit 3, a power conditioner 5 that aggregates the DC power from these plurality of aggregation units 4, and a plurality of DC cables 6 that connect the plurality of aggregation units 4 and the power conditioner 5 respectively, and is applicable to the photovoltaic power generation facility 2. Note that, as will be described later, it is also applicable when there is only one DC cable 6 instead of a plurality of DC cables.

[0023] As also shown in FIG. 2, the DC cable monitoring system 1 in the photovoltaic power generation facility of this embodiment is resistance value measuring means 20 capable of measuring the resistance value of the entire plurality of DC cables 6T connecting each aggregation unit 4 and the power conditioner 5, abnormal resistance value setting means 30 that sets, based on the normal resistance value NRT of the entire DC cable 6T measured by this resistance value measuring means 20, a first lower limit value L1T as the lower limit value of the normal resistance value and a second lower limit value L2T that is a resistance value smaller than this first lower limit value, and abnormal state determination means 50 that, when monitoring the cable, determines that a cut has occurred in one or more of the DC cables 6 when the resistance value of the entire DC cable 6T measured by the resistance value measuring means 20 is less than or equal to the first lower limit value L1T and greater than or equal to the second lower limit value L2T, and determines that a problem other than a cut has occurred in one or more of the DC cables 6 when it is less than the second lower limit value L2T.

[0024] This system 1 further When the abnormality determination means 50 determines that a disconnection has occurred in the DC cable 6, the disconnection occurrence alarm CA indicating that the DC cable 6 has been disconnected is transmitted. When it is determined that a problem other than disconnection has occurred in the DC cable 6, the alarm transmission means 60 transmits a problem occurrence alarm FA indicating that a problem has occurred in the DC cable 6.

[0025] In this system 1, The resistance value measuring means 20, the abnormality determination means 50, and the alarm transmission means 60 are configured as a unit 110 and incorporated in the power conditioner 5 (see FIG. 1).

[0026] This system 1 further includes a management device 100 that is installed at a location separated from the power conditioner 5 and wirelessly receives the disconnection occurrence alarm CA or the problem occurrence alarm FA from the alarm transmission means 60. This management device 100 transmits the above alarm to a predetermined notification destination 200.

[0027] With the above configuration, the following operational effects can be obtained according to the DC cable monitoring system in this photovoltaic power generation facility.

[0028] The resistance value measuring means 20 can measure the resistance value of the entire DC cable 6T connecting the aggregation unit 4 and the power conditioner 5.

[0029] Based on the normal resistance value NRT of the entire DC cable 6T measured by the resistance value measuring means 20 by the abnormal resistance value setting means 30, a first lower limit value L1T as the lower limit value of the normal resistance value and a second lower limit value L2T that is a resistance value smaller than the first lower limit value L1T are set.

[0030] During cable monitoring, the abnormality determination means 50 makes the following determination.

[0031] (a) When the resistance value RT of the entire DC cable 6T measured by the resistance value measuring means 20 is equal to or less than the first lower limit value L1T and equal to or greater than the second lower limit value L2T, it is determined that a break has occurred in one or more of the DC cables 6.

[0032] (b) When the resistance value RT of the entire DC cable 6T measured by the resistance value measuring means 20 is less than the second lower limit value L2T, it is determined that a problem other than a break has occurred in one or more of the DC cables 6.

[0033] Therefore, according to the DC cable monitoring system in this photovoltaic power generation facility, it is possible to determine whether the abnormality of the DC cable 6 to be monitored is due to theft (cutting) or a problem such as a failure (for example, a problem such as a connection cable ground fault or an accident due to flooding).

[0034] Since the countermeasures in the case where the abnormality of the DC cable 6 is due to theft are different from those in the case of a problem such as a failure, appropriate countermeasures can be taken according to this system.

[0035] The DC cable monitoring system in this photovoltaic power generation facility further includes the alarm transmitting means 60. Therefore, the alarm transmitting means 60 can issue an alarm indicating that an abnormality has occurred in the DC cable 6 to be monitored and whether the abnormality is due to theft (cutting) or a problem such as a failure. That is, an alarm for the occurrence of a cut CA or an alarm for the occurrence of a problem FA can be transmitted.

[0036] In addition, in this photovoltaic power generation facility's DC cable monitoring system, at least a resistance value measurement means 20, an abnormal state determination means 50, and an alarm transmission means 60 are incorporated into the power conditioner 5. Further, a management device 100 is installed at a location separated from the power conditioner 5. This management device 100 wirelessly receives a disconnection occurrence alarm CA or a malfunction occurrence alarm FA from the alarm transmission means 60 and transmits these alarms to a predetermined notification destination 200. Therefore, it becomes possible to immediately take appropriate measures corresponding to the problem for the cable 6 in which the problem has occurred.

[0037] This will be further described in detail below. The solar cell unit 3 can be composed of a known group of solar panels. Each aggregation unit 4 can be composed of a known appropriate aggregation unit, for example, a known junction box.

[0038] Each solar cell unit 3 and the aggregation unit 4 are connected by a known DC cable 3c. The DC power generated by the solar cell unit 3 is aggregated to each aggregation unit 4 through this DC cable 3c. This DC cable 3c is a thinner cable compared to the DC cable 6.

[0039] The power conditioner 5 can be composed of a known appropriate power conditioner. In this embodiment, it is composed of a central type power conditioner.

[0040] Each aggregation unit 4 and the power conditioner 5 are connected by a known DC cable 6, and the DC power from each aggregation unit 4 is aggregated to the power conditioner 5 through this DC cable 6. This DC cable 6 is a thicker cable compared to the DC cable 3c.

[0041] Both the DC system cable 3c and the DC system cable 6 have a current flow of approximately 0V after sunset. However, since the DC system cable 6 is thicker than the DC system cable 3c, it is more likely to be a target for theft compared to the DC system cable 3c. Even if the DC system cable 3c is cut (stolen), the measured resistance value of the DC system cable 6 will change. Therefore, according to this system, as a result, even when the DC system cable 3c is stolen, it can be detected.

[0042] The power of the power conditioner 5 will be supplied to a predetermined facility through the AC system cable 5c and the associated equipment 7. Since an AC voltage of approximately 380 - 600V is applied to the AC system cable 5c except during a power outage, it is not likely to be a target for theft.

[0043] In FIG. 2, 6(1), 6(2), ··· 6(n) are the aforementioned DC system cables 6. Relays 21(1 - n) are respectively connected to these DC system cables 6, and a resistance value measuring device 24 is connected via the relays 21(1 - n). Note that 6f is the terminal of the cable 6, and 6b is the connection terminal block.

[0044] 22 is a PCS input voltage measuring means for measuring the input voltage to the power conditioner 5. By being connected to an appropriate location of the power conditioner 5, it measures the input voltage to the power conditioner 5.

[0045] 23 is a relay operation control means for controlling the operation of the above - mentioned relays 21(1 - n). It inputs the measurement result from the PCS input voltage measuring means 22, and when the measured voltage nV becomes approximately 0 (that is, when power generation by the solar cell unit 3 becomes approximately 0 due to sunset), it sequentially operates the above - mentioned relays 21(1 - n) to sequentially connect each DC system cable 6(1 - n) to the resistance value measuring device 24, and issues a relay operation signal to each relay 21(1 - n) to cause the resistance value measuring device 24 to measure the resistance values R(1 - n) of each DC system cable 6(1 - n).

[0046] Due to the operation of the relays 21(1~n), the resistance values R(1~n) of the DC cables 6(1~n) sequentially measured by the resistance measuring device 24 are sequentially sent from the resistance measuring device 24 to the control unit 81. The control unit 81 accumulates these resistance values R(1~n) and determines the cumulative value as the resistance value RT of the entire plurality of DC cables 6.

[0047] Prior to cable monitoring, the abnormal resistance value setting means 30 is based on the normal resistance value NRT of the resistance value RT of the entire plurality of DC cables 6 measured by the resistance measuring means 20, and sets a first lower limit value L1T as the lower limit value of the normal resistance value and a second lower limit value L2T which is a resistance value smaller than the first lower limit value L1T. These first lower limit value L1T and second lower limit value L2T are stored in the storage unit 41 via, for example, the transmission and reception means 71, 72, and the control unit 81 described later.

[0048] Specifically, for example, when the normal resistance value NRT of the resistance value RT of the entire plurality of DC cables 6 measured by the resistance measuring means 20 is 6 MΩ, based on this 6 MΩ, the first lower limit value L1T as the lower limit value of the normal resistance value is set to, for example, 5 MΩ, and the second lower limit value L2T which is a resistance value smaller than the first lower limit value L1T is set to, for example, 100 Ω. As described above, these values are stored in the storage unit 41.

[0049] During cable monitoring (at sunset), due to the operation of the relays 21(1~n), the resistance values R(1~n) of the DC cables 6(1~n) sequentially measured by the resistance measuring device 24 are accumulated by the control unit 81, and the cumulative value is determined as the resistance value RT of the entire plurality of DC cables 6 and sent to the abnormal state determination means 50.

[0050] The abnormal state determination means 50 determines that a break has occurred in one or more of the DC cables 6 when the resistance value RT of the entire DC cable 6 is less than or equal to the first lower limit value L1T set by the abnormal resistance value setting means 30 and greater than or equal to the second lower limit value L2T, and determines that a problem other than a break has occurred in the DC cable 6 when it is less than the second lower limit value L2T.

[0051] For example, when the resistance value RT of the entire DC cable 6 is 5 MΩ, the abnormal state determination means 50 determines that the DC cable 6 is disconnected, and when it is 0 Ω, it determines that a problem other than disconnection has occurred in the DC cable 6. This determination signal is sent to the alarm transmission means 60(61) and is sent to the management device 100 of this system 1 via the transmission / reception means 71.

[0052] Upon receiving the determination signal from the abnormal state determination means 50, when the abnormal state determination means 50 determines that the DC cable 6 is disconnected, the alarm transmission means 60 transmits a disconnection occurrence alarm CA indicating that the cable has been disconnected, and when it is determined that a problem other than disconnection has occurred in the DC cable 6, it transmits a problem occurrence alarm FA indicating that a problem has occurred in the cable 6.

[0053] In this embodiment, the above-described resistance value measurement means 20, abnormal state determination means 50, alarm transmission means 61(60), and transmission / reception means 71 are configured as a unit 110 and incorporated into the power conditioner 5 (see FIG. 1). The management device 100 includes unit identification information providing means 10, and the unique unit identification information UI for each provided unit 110 by this unit identification information providing means 10 is stored in the storage unit 41 via the transmission / reception means 71, 72, and the control unit 81. The signal from the alarm transmission means 61 is sent to the transmission / reception means 72 provided in the management device 100 of this system 1 via the transmission / reception means 71 together with the unit identification information UI (that is, the identification information of the unit to which the cable 6 where disconnection or a problem has occurred is connected). Both of these transmission / reception means 71 and 72 can be configured by known transmission / reception means operable in a wireless communication environment (including a wireless LAN and Wi-Fi environment).

[0054] The unit 110 is provided with control means (for example, an MCU) 81 for controlling the above-described respective means 22, 23, 24, 50, 61, 71 within the unit 110.

[0055] The management device 100 can be configured as a known personal computer including a control means (e.g., CPU) for controlling each means of the device 100, and input means (not shown) such as a keyboard and a mouse, a display (not shown), etc.

[0056] When the management device 100 receives the unit identification information UI(1~n) and the malfunction occurrence warning FA (or disconnection occurrence warning CA) from the unit 110, it transmits these warnings to a predetermined notification destination (e.g., a failure response department, a theft response department, etc.) 200. Thereby, it becomes possible to immediately take appropriate measures corresponding to the problem for the cable in which the problem has occurred.

[0057] The cable monitoring operation as described above is repeated, for example, until the measured voltage by the voltage measuring means 22 becomes a predetermined voltage of 0 or more due to sunrise.

[0058] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and can be appropriately modified within the scope of the gist of the present invention. For example, in the above embodiment, the case where there are a plurality of power conditioners 5 has been described, but it is also applicable to the case of a single one. Similarly, it is also applicable when there is one cable 6. In this case, in the above embodiment, The resistance value measuring means 20 is configured to measure the resistance value of a single DC cable 6 connecting the aggregation unit (4) and the power conditioner (5), The abnormal resistance value setting means 30 is configured to set a first lower limit value L1 as the lower limit value of the normal resistance value and a second lower limit value L2 which is a resistance value smaller than the first lower limit value L1, based on the normal resistance value NR of the DC cable 6 measured by the resistance value measuring means 20. When monitoring the cable, if the resistance value of the DC cable 6 measured by the resistance value measuring means 20 is less than or equal to the first lower limit value L1 and greater than or equal to the second lower limit value L2, the abnormal state determination means 50 determines that a break has occurred in the DC cable 6. When the resistance value is less than the second lower limit value L2, the abnormal state determination means 50 determines that a problem other than a break has occurred in the DC cable 6. By adopting such a configuration, it is applicable.

Explanation of Signs

[0059] 3: Solar cell unit 4: Aggregation unit 5: Power conditioner 5 6: DC cable 20: Resistance value measuring means 30: Abnormal resistance value setting means 50: Abnormal state determination means

Claims

1. A solar cell unit (3); An aggregation unit (4) that aggregates the DC power generated by this solar cell unit (3); A power conditioner (5) that converts the DC power from this aggregation unit (4) into AC; In a solar power generation facility (2) comprising a DC cable (6) that connects the aggregation unit (4) and the power conditioner (5), A resistance value measuring means (20) capable of measuring the resistance value of the DC cable (6) connecting the aggregation unit (4) and the power conditioner (5) and the equipment connected to this DC cable (6); An abnormal resistance value setting means (30) that sets a lower limit value (L2), which is a resistance value smaller than the normal resistance value, based on the normal resistance value (NR) of the DC cable (6) measured by this resistance value measuring means (20) and the equipment connected to this DC cable (6); When monitoring the cable, when the resistance value of the DC cable (6) measured by the resistance value measuring means (20) and the equipment connected to this DC cable (6) is less than the lower limit value (L2), an abnormal state determining means (50) that determines that a problem other than disconnection has occurred in the DC cable (6); An alarm transmitting means (60) that transmits a malfunction occurrence alarm (FA) indicating that a problem other than disconnection has occurred in the DC cable (6) when the abnormal state determining means (50) determines that a problem other than disconnection has occurred in the DC cable (6); At least the resistance value measuring means (20), the abnormal state determining means (50), and the alarm transmitting means (60) are incorporated in the power conditioner (5); Furthermore, a management device (100) is provided at a location separated from the power conditioner (5) and wirelessly receives the malfunction occurrence alarm (FA) from the alarm transmitting means (60); This management device (100) is characterized in that it transmits the above alarm to a predetermined notification destination (200), and is a DC cable monitoring system in a solar power generation facility.

2. A solar cell unit (3); A plurality of aggregation units (4) that aggregate the DC power generated by this solar cell unit (3); A power conditioner (5) that aggregates the DC power from these plurality of aggregation units (4); In a photovoltaic power generation facility (2) including a plurality of DC cables (6) that connect the plurality of aggregation units (4) and the power conditioner (5) in parallel with each other, resistance value measuring means (20) capable of measuring the total resistance value obtained by summing the individual resistance values of the plurality of DC cables (6) connecting each aggregation unit (4) and the power conditioner (5) and the devices connected to this DC cable (6); abnormal resistance value setting means (30) that sets a lower limit value (L2T), which is a resistance value smaller than the normal resistance value, based on the normal resistance value (NRT) of the entire DC cable (6) and the devices connected to this DC cable (6) measured by this resistance value measuring means (20); when monitoring the cable, when the total resistance value of the DC cable (6) and the devices connected to this DC cable (6) measured by the resistance value measuring means (20) is less than the lower limit value (L2T), abnormal state determination means (50) that determines that a problem other than a break has occurred in the DC cable (6); alarm transmission means (60) that transmits a failure occurrence alarm (FA) indicating that a problem other than a break has occurred in the DC cable (6) when the abnormal state determination means (50) determines that a problem other than a break has occurred in the DC cable (6); at least the resistance value measuring means (20), the abnormal state determination means (50), and the alarm transmission means (60) are incorporated in the power conditioner (5); furthermore, a management device (100) is provided at a location separated from the power conditioner (5) and wirelessly receives the failure occurrence alarm (FA) from the alarm transmission means (60); This management device (100) is characterized in that it transmits the above alarm to a predetermined notification destination (200). A DC cable monitoring system in a photovoltaic power generation facility.

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