JP2018100877A - Arc fault detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc fault detection system capable of ensuring an operation on a sound system in a direct current system provided with a reverse flow preventing diode in a branch system by reliably detecting a series or parallel arc fault and separating the faulty part in a DC current system provided with a backflow prevention diode in the branch system.SOLUTION: The arc fault detection system includes: DC current bus line 40 which constitutes a principal line; and branch lines A and B each of which has a solar cell panel 16, 17 connected to the positive bus line P and the negative bus line N therebetween; and backflow prevention diodes 1, 2 which are connected to the respective branch lines to block a current to a direction to the solar cell panel 16, 17 from the positive bus line P. The arc fault detection system also includes: a voltage detection device 3, 4 for detecting a voltage crossing both ends of the diodes 1, 2; a voltage detection device 7, 8 for detecting a line voltage on the positive/negative DC current lines; and a current detection device 5, 6 for detecting a current flowing on the DC current lines. The voltage detection devices 7 and 8 and the current detection devices 5 and 6 are disposed between the diode 1, 2 and the solar cell panel 16, 17.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an arc failure detection system for detecting an arc generated in a branch system or a main system in a DC power generation system such as a solar power generation system or a DC power supply system.

The following are proposed as conventional techniques for detecting an arc in a DC circuit such as a solar power generation system.
For example, in the arc detection means described in Patent Document 1, it is considered that arcing, short-circuiting and disconnection failure occur due to forgetting to tighten screws at the terminal block connected to the solar cell panel, and the output side from the terminal block The fluctuation of the voltage between the wiring and the fluctuation of the current flowing from the terminal block to the output side wiring are simultaneously detected.

Moreover, the arc detection apparatus described in Patent Document 2 has a large number of solar cell panels, such as a mega solar, and is arranged at a plurality of locations, and the switching noise of the inverter of the power conditioner (PCS) is superimposed. It is premised on application to such a DC circuit.
In this arc detection device, the voltage across the DC circuit in which a plurality of solar battery panels are connected in series is detected, and the output is converted into a power spectrum, and then the frequency band corresponding to the switching noise of the inverter is removed and removed. The occurrence of an arc in the DC circuit is determined when the slope of the power spectrum obtained at a plurality of points in the later power spectrum exceeds a predetermined reference value.

In the prior art described in Patent Document 1, in principle, an arc is generated in the vicinity of the terminal block, in other words, in the vicinity of the voltage sensor, and can be detected when the voltage or the like fluctuates. However, particularly in a large-scale photovoltaic power generation system such as a mega solar, since cables are laid for a long distance, arc failures due to cable disconnection or the like may occur in various places.
For this reason, there is almost no sudden voltage fluctuation at the installation position of the voltage sensor in the vicinity of the terminal block, and it is difficult to detect an arc fault occurring in the cable on the solar cell panel side from the terminal block.

The prior art described in Patent Document 2 is a detection method that focuses on the high-frequency component of the voltage generated when an arc is generated, but a failure occurs among a plurality of branch systems (strings) connected to the main system. In order to distinguish and detect the system and the healthy system, it is necessary to be a photovoltaic power generation system with a backflow prevention diode.
However, in the recent mainstream of the photovoltaic power generation system in recent years, PV fuses are used as a safety measure against backflow. According to this type of system, since the detection method described in Patent Document 2 cannot distinguish between a faulty system and a healthy system, it is necessary to stop the entire system when a fault occurs, and it takes a lot of time to identify and recover from a faulty point. It took time and effort.
That is, depending on the configuration of the photovoltaic power generation system, it is difficult to determine the faulty system, and it is difficult to stably continue the photovoltaic power generation.

  In view of the above points, the applicant, as Japanese Patent Application No. 166-16099 (hereinafter referred to as the prior application), facilitates the identification of the branch system and the main system in which the arc failure has occurred, and isolates the failure location from the healthy system. An application has already been filed for an arc fault detection system capable of continuing power supply.

  As shown in FIG. 17, for example, the prior application invention includes an AC power supply system 100, a power conditioner system (PCS) 18, a disconnecting switch 13, a DC bus 40, a voltage detection device 41, a main system, and a DC bus 40 In the system including the branch systems A and B connected between the positive bus P and the negative bus N, the branch systems A and B are paths from the solar cell panels 16 and 17 to the DC bus 40. Current detectors 5 and 6 for detecting the current flowing through each of them, and detecting a series arc fault in each of the branch systems A and B based on the frequency spectrum of the current detection values by these current detectors 5 and 6 It is. In the branch systems A and B, 9 and 10 are disconnecting switches, and 11 and 12 are short-circuiting switches.

Here, the series arc fault refers to an arc fault that occurs on a single DC line, and the following parallel arc fault refers to an arc fault that occurs between positive and negative DC lines.
That is, in the parallel arc fault in each branch system, the current detection value of the branch system where the fault has occurred becomes a unique value due to the inflow of current from the other system, and the voltage detection value of the DC bus 40 is greatly increased. It can be detected by lowering.

  Moreover, the series arc fault of the main system is detected because the current detection values in all the branch systems A and B include a signal component (AC component or vibration component) peculiar to the arc fault. The voltage detection value of the main system is reduced to an arc voltage equivalent value (several tens [V]), and the current detection value in the branch system is detected based on no change compared with the normal state.

Japanese Patent Laying-Open No. 2011-7765 (paragraphs [0031] to [0040], FIGS. 1 to 3 etc.) JP 2014-134445 A (paragraphs [0012] to [0014], FIG. 1 and the like)

Now, as in the case of the branch systems A and B in FIG. 17, when a backflow prevention diode (not shown) for blocking current from the DC bus 40 toward the solar cell panels 16 and 17 is not provided, Parallel arc fault detection and fault system identification are possible.
However, when the above-described backflow prevention diode is provided in the branch system, even if a parallel arc fault occurs in a certain branch system, current does not flow from other healthy systems, and voltage fluctuations cannot be detected. Therefore, there has been a problem that a parallel arc fault cannot be detected.
In domestic photovoltaic power generation systems, a backflow prevention diode is usually attached to the junction box connecting the branch system and the main system, and even in such a system, series and parallel arc faults in the branch system can be detected. It is demanded.

  Therefore, the problem to be solved by the present invention is to reliably detect a series arc fault and a parallel arc fault in a branch system or a main system in a DC system in which a backflow prevention element such as a diode is provided in the branch system, and to isolate the fault location. It is another object of the present invention to provide an arc fault detection system that can continue power supply from a healthy system.

In order to solve the above problems, the invention according to claim 1 is directed to one or a plurality of DC power generators connected between a DC bus forming the main system and a positive bus and a negative bus of the DC bus. A branch system of
In the system in which a backflow prevention element for blocking a current in a direction from the positive bus to the DC power generation facility is connected to the branch system,
A first voltage detection device for detecting a voltage across the backflow prevention element;
A second voltage detection device for detecting a line voltage of a positive and negative DC line between the DC power generation facility and the DC bus;
A current detecting device for detecting an alternating current component and a direct current component of the current flowing through the direct current line;
With
The second voltage detection device and the current detection device are arranged between the backflow prevention element and the DC power generation facility.

  The invention according to claim 2 is the arc fault detection system according to claim 1, wherein in the arc fault detection system provided with a plurality of the branch systems, the parallel arc fault generated on the main system side from the backflow prevention element Is detected based on a change in the voltage detection value by the second voltage detection device in the plurality of branch systems and a change in the current detection value by the current detection device.

  According to a third aspect of the present invention, in the arc fault detection system according to the first aspect, a parallel arc fault that has occurred on the DC power generation facility side from the backflow prevention element provided in each branch system is detected in the branch system. Based on a change in voltage detection value by the first voltage detection device, or a change in voltage detection value by the first and second voltage detection devices in the branch system and a change in current detection value by the current detection device. It is characterized by detecting.

  The invention according to claim 4 is the arc fault detection system according to claim 1, wherein in the arc fault detection system provided with a plurality of the branch systems, a series arc fault generated in the main system is treated as a plurality of the branches. It detects based on the alternating current component of the electric current measured by the said current detection apparatus in a system | strain.

  The invention according to claim 5 is the arc fault detection system according to claim 1, wherein a series arc fault occurring in each branch system is detected by an AC component of a current measured by the current detection device provided in the branch system. It detects based on.

  According to a sixth aspect of the present invention, in the arc fault detection system according to any one of the first to fifth aspects, a disconnecting switch is disposed in the main system, and positive and negative DC lines are provided in the branch system. A short-circuit switch for short-circuiting between them and a disconnecting switch for disconnecting the DC line are arranged.

  According to a seventh aspect of the present invention, in the arc fault detection system according to the sixth aspect, the disconnecting switch and the short-circuiting switch arranged in the branch system include the backflow prevention element and the DC power generation in the branch system. It is characterized by being placed between the facilities.

  The invention according to claim 8 is the arc fault detection system according to claim 6 or 7, wherein the disconnection switch and the short-circuit switch arranged in the branch system generate an arc between the switches. It is characterized by having constituted as an integrated switch by arranging closely in a single case so that it may not.

  The invention according to claim 9 is the arc fault detection system according to any one of claims 1 to 8, wherein the DC bus is connected to an AC power supply system via a power conditioner system. And

  According to the present invention, in a DC system in which a backflow prevention element is provided in each branch system, a series arc fault and a parallel arc fault in the branch system or the main system are reliably detected, and the fault location is separated and protected, and sound The power supply from the grid can be continued.

It is a lineblock diagram of an arc fault detection system concerning an embodiment of the present invention. It is a block diagram of the arc fault detection system which concerns on the modification of embodiment of this invention. It is a block diagram of the arc fault detection system which concerns on the modification of embodiment of this invention. It is a figure which shows the generation | occurrence | production location of the arc in embodiment of this invention. It is a figure which shows the electric current characteristic at the time of generation | occurrence | production of the parallel arc 24. FIG. It is a measurement waveform figure of each detecting device showing a transient phenomenon at the time of generation of parallel arc 24. It is a figure which shows the protection operation | movement after the detection of the parallel arc 24. FIG. It is a figure which shows the electric current characteristic at the time of generation | occurrence | production of the parallel arc 20. FIG. It is a measurement waveform diagram of each detection device showing a transient phenomenon when the parallel arc 20 is generated. It is a figure which shows the protection operation | movement after the detection of the parallel arc 20. FIG. It is a figure which shows the electric current characteristic at the time of generation | occurrence | production of the parallel arc 21. FIG. It is a measurement waveform diagram of each detection device showing a transient phenomenon when the parallel arc 21 is generated. It is a figure which shows the protective operation after the detection of the parallel arc 21. FIG. It is a figure which shows the electric current characteristic at the time of generation | occurrence | production of the parallel arc 23. FIG. It is a measurement waveform figure of each detection device showing a transient phenomenon at the time of generation of parallel arc 23. It is a figure which shows the protection operation | movement after the detection of the parallel arc 23. FIG. It is a block diagram which shows the arc fault detection system which concerns on a prior invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an arc fault detection system according to an embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 17 are denoted by the same reference numerals, and the difference from FIG. 17 will be mainly described below. Needless to say, the number of branch systems connected to the DC bus 40 is not limited to the illustrated example.

  In the branch system A of this embodiment, between the positive side bus P, the negative side bus N and the solar battery panel 16, the backflow prevention diode 1, the voltage detection device 3 for detecting the voltage at both ends thereof, and the integrated switch 14 The voltage detector 7 for detecting the line voltage of the positive and negative DC lines and the current detector 5 for detecting the AC component and the DC component of the current flowing through the DC line are connected. The integrated switch 14 includes a disconnecting switch 9 and a short-circuiting switch 11 connected in close contact with each other and built in a single casing. It is considered that no series arc or parallel arc is generated on or between the wires.

  The configuration of the other branch system B is the same as that of the branch system A. Between the positive bus P, the negative bus N and the solar battery panel 17, the backflow prevention diode 2, the voltage detection device 4, and the integrated switch 15 are provided. The voltage detection device 8 and the current detection device 6 are connected. The integrated switch 15 includes a disconnecting switch 10 and a shorting switch 12.

  2 and 3 are modifications of the present embodiment, and the positions of the voltage detection devices 7 and 8, the current detection devices 5 and 6, and the integrated switches 14 and 15 in the branch systems A and B are shown in FIG. Is different. However, since any of FIGS. 1 to 3 can detect an arc failure based on the same principle, the operation will be described below based on the configuration of FIG.

Considering that arcs cannot be generated in the integrated switch 14, all the series and parallel arcs that can be generated in the main system and the branch system A in FIG. 1 are denoted by reference numerals 19 to 27 in FIG. The arcs 19 and 26 correspond to series arcs, and the arcs 20 to 25 and 27 correspond to parallel arcs.
Here, the series arc 19 and the parallel arcs 20 to 24 are failure cases that may occur in any branch system, but FIG. It should be noted that all of the arcs 19 to 27 do not occur at the same time and are normally generated independently, but for the sake of convenience, all the arcs 19 to 27 are shown in FIG.

Below, each detection method and the protection method which isolate | separates a failure part are demonstrated with respect to four failure cases of the parallel arcs 20, 21, 23, and 24. FIG.
In addition, for the series arc 26 generated in the main system, the AC component peculiar to arc failure is included in the current detection values by the current detection devices 5 and 6 of all the branch systems A and B. Can be detected on the basis.
Further, the series arc 19 generated in the branch system A can be detected based on the AC component peculiar to the arc failure included in the current detection value by the current detection device 5 of the branch system A.
Furthermore, since the parallel arcs 25 and 27 generated in the main system can be handled by the same method as the parallel arc 24 described below, description thereof is omitted here.

FIG. 5 shows current characteristics due to the parallel arc 24 generated in the region from the cathode of the backflow prevention diode 1 to the DC bus 40. In addition, the open / close state of each switch is as shown in FIG.
When this parallel arc 24 is generated, the current from the solar panel 16 flows through a path 28 that returns to the solar panel 16 through the parallel arc 24. On the other hand, the current from the solar battery panel 17 of the other branch system B does not flow to the AC power supply system 100 side but flows through the path 29 passing through the parallel arc 24. Not only in the above example, when the parallel arc 24 is generated, the current from the solar cell panels in all the branch systems is concentrated on the parallel arc 24.

  The reason why the current path is as described above is that the voltage of several hundreds [V] generated between the positive bus P and the negative bus N in the normal state is several tens [V] corresponding to the arc voltage by the parallel arc 24. This is because the PCS 18 is stopped by lowering to the above. When the PCS 18 stops, the load is released as viewed from each solar cell panel, so that the current flowing out from all the solar cell panels is concentrated on the parallel arc 24 having a lower impedance. Current characteristics as shown in FIG.

  Although the details are omitted, not only the parallel arc 24 but also the parallel arcs 25 and 27 are generated on the main system side in FIG. Therefore, by providing current detection devices corresponding to the current detection devices 5 and 6 in all the branch systems, the current flowing through the paths 28 and 29 of FIG. 5 passing through the parallel arc can be detected. Is superimposed with an AC component which is a signal peculiar to an arc failure.

  Further, when the PCS 18 is stopped, the maximum power follow-up control does not function, and the output voltage of the solar cell panel cannot be kept constant. For this reason, when the voltage drop by parallel arc failure arises, a change arises in the operating point of the generated electric power of a solar cell panel. This change in the operating point has a tendency that the current increases with a decrease in voltage in consideration of the current / voltage characteristics of a general solar battery panel. Therefore, an increase in the DC component is detected by all current detection devices. .

  Further, as apparent from the paths 28 and 29 in FIG. 5, even when the parallel arc 24 is generated, a current in the same direction as that in the normal state flows through the backflow prevention diodes 1 and 2. In the voltage detection devices 3 and 4 connected to both ends of the above, a forward voltage drop of about 1 [V] is measured as in the normal state. On the other hand, in the voltage detection devices 7 and 8 that detect the line voltage, the voltage drop (decrease to several hundred [V] to several tens [V]) due to the parallel arc 24 is detected.

The increase in the alternating current component measured by the current detectors 5 and 6 can be detected as a series arc fault according to the above-mentioned prior invention, but the series arc and the parallel arc have different protection methods after detection. It is necessary to detect both separately.
That is, the method of detecting the parallel arc based on the increase of the current AC component cannot be applied, and when paying attention to the waveform measured by the voltage detection devices 3 and 4, it does not change between when the parallel arc is generated and when it is healthy. Therefore, the occurrence of parallel arcs cannot be detected.

On the other hand, in the voltage detection devices 7 and 8 connected between the lines of the branch systems A and B, respectively, a large voltage drop can be detected at the time of a failure, which can be one of failure detection methods. Assuming a case where the power generation amount of the solar cell panels 16 and 17 is remarkably reduced due to an abrupt weather change, it is considered that this can occur even in a healthy state where no parallel arc failure has occurred.
For this reason, if an attempt is made to detect a parallel arc failure by paying attention only to a decrease in the measured voltage by the voltage detection devices 7 and 8, there is a possibility of erroneous detection.

Therefore, in the present embodiment, it is detected that the voltage drop measured by the voltage detection devices 7 and 8 and the direct current component of the current measured by the current detection devices 5 and 6 increase and are in the same direction as when healthy. If it is determined that a parallel arc fault has occurred.
As described above, when the power generation amount of the solar cell panel is significantly reduced, not only the voltage but also the current should be greatly reduced. Therefore, the two changes of the voltage drop measured by the voltage detectors 7 and 8 and the increase of the direct current component measured by the current detectors 5 and 6 are clearly distinguished from the healthy state as a phenomenon that occurs only at the time of the parallel arc failure. Is possible. Therefore, an appropriate threshold value is set for the amount of change in these voltages and currents, and when the state where the line voltage (voltage DC component) is below the threshold value and the current DC component exceeds the threshold value is established, the parallel arc 24 The occurrence can be detected.
As described above, the parallel arcs 25 and 27 on the main grid side can be detected by the same method.

Here, FIG. 6 is a measurement waveform diagram of each detection device showing a transient phenomenon when the parallel arc 24 is generated.
6A and 6B are current AC components included in the waveform measured by the current detectors 5 and 6, respectively, FIGS. 6C and 6D are current DC components, and FIGS. f) is a voltage direct current component included in the measurement waveform by the voltage detection devices 7 and 8, respectively, and FIGS. 6 (g) and 6 (h) are voltage direct current components included in the measurement waveform by the voltage detection devices 3 and 4, respectively.
In order to detect the occurrence of the parallel arc 24 (the same applies to the parallel arcs 25 and 27), based on the detection principle described above, the DC component of the measured current is increased according to FIGS. 6C and 6D, and What is necessary is just to confirm that it is the same direction as the time of healthy, and the DC component of the measurement voltage fell by FIG.6 (e), (f).

Next, FIG. 7 is a diagram illustrating a protective operation after the parallel arc 24 is detected.
As already described, since the current when the parallel arc 24 is generated passes through the paths 28 and 29 in FIG. 5, the arc can be extinguished by interrupting the currents in these paths. That is, when the parallel arc 24 is detected, the disconnecting switches 9 and 10 of the branch systems A and B are turned off from on as shown in FIG. As a result, the current from the solar cell panels 16 and 17 flowing through the parallel arc 24 is interrupted and the parallel arc 24 is extinguished, so that it is possible to isolate the fault location and protect the system. In FIG. 7, 30 indicates the parallel arc after removal.

  Next, FIG. 8 shows current characteristics when the parallel arc 20 is generated between the solar cell panel 16 and the current detection device 5 in the branch system A. A current path flowing through the parallel arc 20 is denoted by reference numeral 31.

Hereinafter, the reason why the current path 31 is generated when the parallel arc 20 is generated will be described.
First, in a healthy state, the line voltage between the branch system A and the main system is almost the same, and is several hundred [V]. At this time, a forward voltage V _{f of} about 1 [V] is generated at both ends of the backflow prevention diode 1. On the other hand, when the parallel arc 20 is generated at the position shown in FIG. 8, the line voltage of the solar cell panel 16 is reduced to about several tens [V], and the backflow prevention diode 1 is turned off. At this time, when viewed from the solar cell panel 16, the parallel arc 20 has the lowest impedance. For this reason, the current when the parallel arc 20 is generated flows out of the solar cell panel 16, passes through the parallel arc 20, and follows a path 31 that returns to the solar cell panel 16.

Next, FIG. 9 is a measurement waveform diagram of each detection device showing a transient phenomenon when the parallel arc 20 occurs.
First, as shown in FIGS. 9 (b), (d), (f), and (h), the current detection device 6 and the voltage detection device 8 installed in the branch system B where no arc is generated, The same waveform is measured. This is because the backflow prevention diode 1 is turned off when the parallel arc 20 is generated.

On the other hand, the measured waveforms in the branch system A in which the parallel arc 20 is generated are as shown in FIGS. 9 (a), (c), (e), and (g). First, as shown in FIG. 9A, the measurement waveform of the alternating current component by the current detection device 5 is the same as that when sound, but this is because current through the parallel arc 20 does not pass through the current detection device 5. This is because the AC signal component peculiar to the arc is not detected.
The measurement waveform of the DC component by the current detection device 5 shown in FIG. 9C becomes zero because the backflow prevention diode 1 is turned off by the parallel arc 20. As shown in FIG. 9 (e), the voltage detection device 7 measures a change in which the line voltage of the solar cell panel 16 decreases to several tens [V] corresponding to the arc voltage. Moreover, as shown in FIG.9 (g), in the voltage detection apparatus 3, the increase in a reverse voltage is measured as a difference of a main voltage and an arc voltage.

Next, a method for detecting the parallel arc 20 from the measured waveforms shown in FIGS.
First, the decrease in the direct current component shown in FIG. 9C to zero and the voltage drop shown in FIG. 9E can occur even in a healthy state due to a sudden change in the amount of solar radiation. Reliable fault detection based on the waveform cannot be expected. Further, the current AC component in FIG. 9A cannot be used for failure detection because it cannot be distinguished from the healthy state.

  Therefore, in this embodiment, the change in the voltage across the backflow prevention diode 1 (measured waveform in FIG. 9G) is used for failure detection. In general, in a large-scale photovoltaic power generation facility such as a mega solar, the main voltage in a healthy state is 200 [V] or more, and the arc voltage is about 50 [V]. For this reason, the increase in the reverse voltage when the parallel arc 20 is generated is 150 [V] or more, which is sufficiently larger than the healthy voltage (about 1 [V]). Therefore, the occurrence of the parallel arc 20 can be detected by setting an appropriate threshold value and detecting the increase in the reverse voltage.

FIG. 10 is a diagram showing a protective operation after detecting the parallel arc 20.
In order to remove the parallel arc 20, a current path having a lower impedance may be generated. Therefore, as shown in FIG. 10, the shorting switch 11 is turned on from off to form the current path 33. Further, by turning off the disconnecting switch 9 from on to off, the failure point is separated and the operation by the sound branch system is continued. In FIG. 10, 32 indicates the parallel arc after removal.

Next, a method for detecting and protecting the parallel arc 21 in the branch system A will be described.
In FIG. 11, reference numeral 34 denotes a current path when the parallel arc 21 is generated. Since the backflow prevention diode 1 is turned off by the parallel arc 21, a signal due to the failure is detected only in the branch system A where the parallel arc 21 is generated.
Hereinafter, a method for detecting the parallel arc 21 will be described with reference to the measurement waveforms of FIGS.

As shown in FIG. 12C, the increase in the direct current component measured by the current detection device 5 is caused by the change in the operating point due to the current / voltage characteristics of the solar cell panel 16, as already described. Further, the increase in the current alternating current component shown in FIG. 12A is due to the current flowing through the parallel arc 21 flowing through the current detection device 5.
Here, FIGS. 12C and 12E are the same as the measurement waveforms (FIGS. 6C and 6E) used when detecting the parallel arc 24 as described above, but in parallel with the parallel arc 24. FIG. Since the protection operation is different from that of the arc 21, it is necessary to detect them separately.

  Therefore, in this embodiment, in addition to FIGS. 12C and 12E, the parallel arc 21 is detected in consideration of the measurement waveform of FIG. 12G (measurement waveform of the voltage DC component by the voltage detection device 3). I tried to do it.

When the parallel arc 21 shown in FIG. 11 is generated, as shown in FIG. 12G, the voltage measured by the voltage detection device 3 becomes 150 [V] or more due to the increase in the reverse voltage, and the parallel arc 24 is generated. This is clearly different from the measured waveform in FIG.
Accordingly, an appropriate threshold value is set for the voltage measured by the voltage detection device 3, and an increase in voltage shown in FIG. 12 (g) is detected, and changes in FIGS. 12 (c) and (e) are detected. In this case, that is, when the measurement waveforms in FIGS. 12C, 12E, and 12G are satisfied under the AND condition, the generation of the parallel arc 21 can be detected.

FIG. 13 shows the protective operation after detecting the parallel arc 21.
The parallel arc 21 can be removed by forming the current path 33 from the solar cell panel 16 by turning the shorting switch 11 from OFF to ON as shown in FIG. Reference numeral 35 denotes a parallel arc after removal.
Next, if the disconnecting switch 9 is turned off from on, the failure point can be separated, the sound system can be protected, and the operation by the sound system can be continued.

Next, FIG. 14 shows a current path when the parallel arc 23 is generated in the branch system A. FIG. 15 is a waveform diagram measured by each detection device showing the transient phenomenon in this case.
When the parallel arc 23 is generated, a current path 36 is formed, and as shown in FIG. 15, in the branch system other than the system in which the failure has occurred (for example, the branch system B), the same waveform as in the normal state is measured. Since these have already been described, detailed description is omitted.
As with the parallel arc 21, the detection of the parallel arc 23 is based on the observation of the three measured waveforms of FIGS. 15C, 15E, and 15G, that is, to distinguish from the parallel arc 24. This is performed according to the AND condition of the three measurement waveforms shown in FIGS. 15 (c), (e), and (g).

FIG. 16 shows the protective operation after the parallel arc 23 is detected.
As is apparent from the path 36 in FIG. 14, only the disconnecting switch 9 needs to be turned off in order to remove and protect the parallel arc 23, but in the present embodiment, a method similar to that when the parallel arc 21 is generated ( (See FIG. 13). That is, as shown in FIG. 16, the short-circuit switch 11 is turned on from off, and the disconnecting switch 9 is turned off to turn off the parallel arc 23 to protect the system. In FIG. 16, reference numeral 37 denotes a parallel arc after removal.

The reason why the above-described method for removing and protecting the parallel arc 23 is employed is as follows.
First, since the measurement waveforms of the detection devices when the parallel arc 21 and the parallel arc 23 are generated are all the same, it is impossible to discriminate and detect parallel arc faults having different occurrence points based on the measurement waveform. For this reason, it is necessary to unify the protection operation of the parallel arcs 21 and 23.
Regarding the parallel arc 23, if the disconnecting switch 9 is turned off from on as described above, the arc can be removed even if the shorting switch 11 is kept off. On the other hand, for the parallel arc 21, the operation of turning on the short-circuit switch 11 from off to in order to remove the arc is essential. Therefore, if the protection operation of the parallel arc 23 is unified with the protection operation when the parallel arc 21 is generated, both the parallel arcs 21 and 23 can be removed and the system can be protected by the common protection operation.

  The present invention includes a solar power generation system, a system in which one or a plurality of branch systems having a DC power generation facility and a backflow prevention diode are connected to the main system, and a series arc fault or parallel generated in the main system or branch system. This is applicable when an arc fault is detected and a protective operation is performed.

1, 2: Backflow prevention diodes 3, 4, 7, 8: Voltage detection device 5, 6: Current detection devices 9, 10, 13: Disconnect switch 11, 12: Short circuit switch 14, 15: Integrated switch 16 and 17: Solar panel 18: PCS (power conditioner)
19, 26: Series arc 20, 21, 22, 23, 24, 25, 27: Parallel arc 28, 29, 31, 33, 34, 36: Current path 30, 32, 35, 37: Parallel arc (after removal)
40: DC bus 100: AC power supply system P: Positive bus N: Negative bus

Claims (9)

A DC bus constituting the main system, and one or a plurality of branch systems having a DC power generation facility connected between a positive bus and a negative bus of the DC bus,
In the system in which a backflow prevention element for blocking a current in a direction from the positive bus to the DC power generation facility is connected to the branch system,
A first voltage detection device for detecting a voltage across the backflow prevention element;
A second voltage detection device for detecting a line voltage of a positive and negative DC line between the DC power generation facility and the DC bus;
A current detecting device for detecting an alternating current component and a direct current component of the current flowing through the direct current line;
With
An arc fault detection system, wherein the second voltage detection device and the current detection device are arranged between the backflow prevention element and the DC power generation facility. The arc fault detection system according to claim 1, wherein the arc fault detection system includes a plurality of the branch systems.
Parallel arc fault that occurred on the main system side from the backflow prevention element,
An arc fault detection system for detecting based on a change in a voltage detection value by the second voltage detection device in a plurality of branch systems and a change in a current detection value by the current detection device. In the arc fault detection system according to claim 1,
A parallel arc fault that occurred on the DC power generation facility side from the backflow prevention element provided in each branch system,
Change in voltage detection value by the first voltage detection device in the branch system, or change in voltage detection value by the first and second voltage detection devices in the branch system, and current detection by the current detection device An arc fault detection system for detecting based on a change in value. The arc fault detection system according to claim 1, wherein the arc fault detection system includes a plurality of the branch systems.
An arc fault detection system for detecting a series arc fault occurring in the main system based on an AC component of a current measured by the current detection devices in a plurality of the branch systems. In the arc fault detection system according to claim 1,
An arc fault detection system for detecting a series arc fault occurring in each branch system based on an AC component of a current measured by the current detection device provided in the branch system. In the arc fault detection system according to any one of claims 1 to 5,
A disconnecting switch is arranged in the main system, and a shorting switch for short-circuiting between positive and negative DC lines and a disconnecting switch for disconnecting the DC line are arranged in the branch system. An arc fault detection system characterized by that. In the arc fault detection system according to claim 6,
An arc fault detection system, wherein a disconnecting switch and a short-circuiting switch arranged in the branch system are arranged between the backflow prevention element and the DC power generation facility in the branch system. In the arc fault detection system according to claim 6 or 7,
As an integrated switch, the disconnecting switch and the short-circuiting switch arranged in the branch system are closely arranged in a single casing so as not to generate an arc between the two switches. An arc fault detection system characterized by comprising. In the arc fault detection system according to any one of claims 1 to 8,
An arc fault detection system, wherein the DC bus is connected to an AC power supply system through a power conditioner system.

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