JPWO2014168194A1 - Switch - Google Patents

Abstract

In a switch inserted in the DC circuit, a magnetic force change around the circuit is detected by a magnetic sensor. The extraction means extracts a signal in a frequency band from which it is easy to determine “noise due to arc” from the magnetic sensor output. Next, the arc determination means determines whether or not the arc estimation signal output from the extraction means is caused by an arc, and outputs an arc detection signal when it is caused by an arc. The trip unit opens the contact by the arc detection signal. When the probability that the input waveform from the extraction unit at a predetermined time is a waveform caused by an arc is high, the arc determination unit adds a value according to the probability and is a noise waveform other than the arc. When the probability is high, the value corresponding to the probability is deducted. The added points and deducted points are accumulated, and it is determined that an arc has occurred when the number of points is exceeded.

Description

  The present invention relates to a switch that is inserted into a DC power supply line to open and close an electric circuit.

  The DC power obtained by the solar cell is supplied to the load after being converted into AC by the power conditioner.

  During the period from the solar cell to the power conditioner, the state is a direct current state, where a direct current failure such as an arc may occur. The arc itself is also generated in the AC circuit, but the arc generated by the DC has a long duration and causes heat generation. In addition, the circuit and equipment ignite and cause a fire.

  Therefore, the DC electric circuit is provided with a switch so that the circuit can be cut off when an arc is generated or when heat is generated due to the arc.

  For example, Patent Document 1 discloses a switch (circuit breaker with an overheat prevention mounting) provided with an overheat detecting means such as a temperature sensor in the vicinity of a terminal and having a function of preventing a burning accident due to a rise in terminal temperature. ing. Further, for example, Patent Document 2 discloses a switch (circuit breaker) in which a temperature to be compared with a terminal temperature is set to be equal to or lower than an allowable temperature of an electric circuit.

  Further, in Patent Document 3, the period of noise due to arc is detected by a counter, and when there are more than a first predetermined number of periods within a first predetermined time, and further within a second predetermined time, The number of occurrences of the predetermined number of 1 is counted, and it is determined that an arc has occurred when the number of times is within a predetermined range.

JP 62-8419 A Japanese Utility Model Publication 2-75941 JP 2010-134002 A

  However, when a terminal screw is loosened, a gap is created between the terminal of the switch and the electric circuit, and an arc (discharge) occurs, especially when a direct current flows through the switch, compared to when an alternating current flows, The arc may continue to be generated in a state where the magnitude is continuously large without pulsation, and the temperature rises faster than the protective operation by the temperature sensor etc. functions, and the load and the electric circuit may be burned out. is there.

  In addition, the temperature sensor can detect an arc generated at the terminal of the switch, but cannot detect the occurrence of an arc between the terminal and the electric circuit in another device connected to the switch, for example.

  Therefore, a structure for detecting the occurrence of an arc by a factor other than temperature is sought, and as disclosed in Patent Document 3, an attempt is made to detect the occurrence of an arc from noise detected based on voltage fluctuations between electric circuits. Has been made. However, there are various causes of noise generation in the electric circuit and not only due to arcs. Therefore, the arc detection circuit disclosed in Patent Document 3 has many defects that cannot be put into practical use.

  The present invention has been proposed in view of the above-described conventional circumstances, and presents a switch equipped with an arc detection mechanism that can detect an arc quickly without malfunction.

  The present invention is premised on a switch having a power supply side terminal connected to a DC power supply and a load side terminal from which power from the DC power supply is output.

  In the switch, a magnetic force change around the electric circuit is detected by a magnetic sensor. The extraction means extracts a signal in a frequency band from which it is easy to determine “noise due to arc” from the magnetic sensor output. Next, the arc determination means determines whether or not the arc estimation signal output from the extraction means is caused by an arc, and outputs an arc detection signal when it is caused by an arc. The trip unit opens the contact by the arc detection signal.

  The magnetic sensor uses a magnetic core, a Hall element, or a combination of a magnetic core and a Hall element. In addition, a bandpass filter that extracts a predetermined frequency from the output of the magnetic sensor is used as the extraction means. Furthermore, when the probability that the input waveform from the extraction unit at a predetermined time is a waveform caused by an arc is high, the arc determination unit adds a value according to the probability, and a noise waveform other than the arc If the probability is high, the value corresponding to the probability is deducted. The added points and deducted points are accumulated, and it is determined that an arc has occurred when the accumulated value exceeds a predetermined value.

  The arc determining means stores a waveform that serves as a reference of the input waveform from the extracting means in the storage means, compares the reference waveform with the input waveform in a predetermined time unit, and is caused by the arc. When the probability of being a waveform is high, the number of points added according to the probability is given, and when the probability of being a waveform not caused by an arc is high, the number of points deducted according to the probability is given, and the predetermined time unit is added or subtracted sequentially. When this cumulative value reaches a predetermined threshold value, it is determined as an arc.

  According to the present invention, when the probability of an arc-specific waveform is high, a point is added, and when the probability of being a noise waveform other than an arc is high, a point is subtracted. When the cumulative value exceeds a predetermined value, it is determined as an arc. Therefore, even if noise that is not caused by the arc enters the electrical circuit, the switch will not react immediately, and conversely, when the arc is generated frequently, the switch will be shut off reliably. Therefore, the probability that a malfunction occurs will be extremely small. In addition, it is now possible to detect the occurrence of arcs at all connections including remote locations connected to the electric circuit.

  In addition, by identifying the state of defects after the occurrence of arc (noise), large arcs without defects can be quickly interrupted, and small arcs with defects can be interrupted in a few seconds, which can prevent further malfunctions. become.

FIG. 1 is a circuit block diagram showing a configuration of a switch according to an embodiment of the present invention. FIG. 2 is a circuit block diagram showing an example of a specific configuration of the extracting means. FIG. 3 is a circuit block diagram illustrating an example of a specific configuration of the determination unit. FIG. 4 is a perspective view showing the outer shape of the casing of the switch in one embodiment of the present invention. FIG. 5 is a block diagram showing an application example of the switch in one embodiment of the present invention. FIG. 6 is an example of a noise waveform caused by an arc. FIG. 7 is an example of a noise waveform caused by an arc. FIG. 8 is an example of a noise waveform caused by an arc. FIG. 9 is an example of a noise waveform not caused by an arc. FIG. 10 is an example of a noise waveform not caused by an arc.

  FIG. 5 shows an example in which the switch according to the present invention is applied to a DC power source such as a solar power generation system.

  In the photovoltaic power generation system shown in FIG. 5, the DC power output from the solar cell module 2 is supplied to the power conditioner 3 via the switch 1, and the power conditioner 3 converts the DC power into AC power. After being converted into and superposed on the commercial AC power source 5, it is supplied to the load 4.

  1 to 4 show the structure of a switch to which the present invention is applied.

  It has an outer shape as shown in FIG. 4 and is housed in a housing having terminals 41 to 44.

  The terminals 41 and 42 are a pair of power supply side terminals on the positive side and the negative side, respectively. For example, the solar cell module 2 (DC power supply) is connected to the terminals 41 and 42. Further, the terminals 43 and 44 are a pair of load side terminals on the positive side and the negative side, respectively, for example, to which a power conditioner 3 (load) is connected and can output DC power from the solar cell module 2. It is.

  FIG. 1 shows the electrical configuration of the switch.

  The contact 31 is a positive contact, and has one end connected to the terminal 41 via the power line L1 and the other end connected to the terminal 43 via the power line L3. The contact 32 is a negative contact, and one end is connected to the terminal 42 via the power supply line L2, and the other end is connected to the terminal 44 via the power supply line L4.

  The power supply circuit 25 is supplied with the voltage between the power supply lines L3 and L4, that is, the (external) power supply voltage V0 input between the terminals 41 and 42. The internal power supply voltage V1 output from the power supply circuit 25 is supplied to the control circuit 10. Further, the internal power supply voltage V2 output from the power supply circuit 25 is supplied to the trip unit 26.

  The magnetic force sensor 100 is provided on either the power supply line L3 or L4. The magnetic force sensor 100 is constituted by, for example, a coil or a hall element (or a combination of a coil and a hall element) wound around an electric circuit. The output of the magnetic sensor 100 is input to the extraction unit 11, and a signal in a frequency band in which it is easy to determine “noise due to arc” is extracted from the output of the magnetic sensor 100. The signal extracted in this way is input to the arc determination means 12, and when it is determined that the noise is caused by the arc, a point is added, and when it is determined that the noise is other than that, a deduction is made. This addition or deduction is repeated, and when the cumulative value exceeds a predetermined threshold, it is determined as noise and a noise detection signal is output.

  FIG. 2 is a block diagram showing an example of the extracting means 11. As described above, the magnetic force sensor 100 is provided in either the power supply line L1 or the power supply line L2, and is input to the extraction unit 11. Here, the magnetic sensor 100 may be an element that is sensitive to a change in the magnetic field of the electric path, but for example, a coil, a Hall element, or a combination of a core and a Hall element is used.

  In a DC circuit, since there is no current fluctuation, a coil is not normally used. In addition, since the Hall element is also a magnetic sensor, it is not a normal technique to use as arc detection. However, in the present invention, not only the noise caused by the arc but also the noise peculiar to the arc among many types of noise is detected. There is an important factor in the point of detection by the device.

  In the extraction means 11, in-phase noise is removed from the signal from the magnetic force sensor 100 by the instrumentation circuit 111, and then a signal in a specific frequency range (for example, 1 kHz to 100 kHz) is extracted by the band filter 112. The noise caused by the arc spreads over a wide frequency band, but if the waveform pattern is analyzed in the above range, it is easy to find the characteristics caused by the arc. The signal thus extracted is half-wave rectified by the level conversion circuit 113 and input to the arc determination means 12.

  The arc determination unit 12 is provided with a storage unit 121, and the storage unit 121 stores various noise waveforms (basic waveforms) that are predicted to occur in the electric circuit. Furthermore, if the storage means 121 has a high probability of being generated due to an arc with respect to the basic waveform, a positive value (addition point) having a magnitude corresponding to the probability is set to a probability not due to the arc. For a basic waveform having a high value, a negative value (decrease point) having a magnitude corresponding to the probability is added and stored.

  The “basic waveform and added points (deduction points)” do not necessarily have a graphical meaning, but “periodicity ·· UU deduction points UU”, “凪 Ams or more (below) ·· deduction points XX”, “first wave” On the other hand, the next wave is more than double .... addition point YY ", and the next wave is more than half of the first wave .... addition point ZZ. It is an analysis element (frequency, comparison of the magnitude of the first wave and the second wave, etc.) and the corresponding points added or deducted.

  When the input waveform from the level conversion circuit 113 is input to the point assigning means 122 of the arc determination means 12, the input waveform for every predetermined unit time (for example, 50 ms) is stored in the storage means 121. Which basic waveform is matched is determined. Next, the calculation means 123 sequentially adds or subtracts a positive value (addition points) or a negative value (deduction points) of the basic waveform. The added points and deducted points are accumulated, and it is determined that an arc has occurred when a predetermined threshold value is exceeded.

  Here, waveforms characteristic of noise caused by arcs are shown in FIGS. Moreover, the shape of the waveform characteristic of the noise which does not originate in an arc is shown in FIG. 9, FIG.

  As shown in FIG. 6, (1) (a) when there are a plurality of (three in FIG. 6) small waves at the top of the wave, or (b) a wave following a wave having a larger amplitude has a larger amplitude. If it has, the waveform has a high possibility of arcing and has a score. As shown in FIG. 7, (2) a phenomenon that the wave is small but fluctuates at a predetermined height may occur. In this case, points are added a little for each wave. (3) As shown in FIG. 8 (c), even when a large wave continues following a small wave, there is a high possibility that it is an arc, so it has a score.

  On the other hand, as shown in FIG. 9, (4) a regular waveform can be regarded as a waveform generated from, for example, a fluorescent lamp, and has a deduction point. Furthermore, as shown in FIG. 10, (5) when two pairs of waves appear periodically, it can be regarded as a waveform and has a deduction point.

  In addition to the above-described waveforms, there are many characteristic waveforms. A noise waveform caused by an arc has a score, and a waveform not caused by an arc has a deduction. The distribution of points is such that the higher the probability of a wave with a waveform caused by an arc, the higher the positive weight, and the lower the value. Conversely, the higher the probability that the waveform is not caused by the arc, the higher the negative weight, and the lower the value, the smaller the waveform.

  With the above configuration, addition / subtraction is repeated over time with respect to the input waveform. However, when an arc is generated, the addition pattern (target to be added) increases, and the cumulative value becomes the threshold value. When exceeding, it is determined that an arc has occurred, and the calculation means 123 outputs an arc detection signal ARC. The subtraction continues during the period when the arc is not generated, but the calculation is continued as it is so as not to be less than zero.

As described above, when the arc detection signal ARC is output, the tripping unit 26 operates via the OR determination unit 14.
As described above, the waveform input from the extraction unit 11 to the arc determination unit 12 is compared to determine whether or not it is an arc. However, since a large arc heats an electrode and a line rapidly, it is necessary to quickly cut the line, whereas a small arc is not required to be so responsive. Therefore, by adding the following processing, it is possible to ensure the quick disconnection property to a large arc.

  The determination of a big wave is as follows. The number of occurrences of a pulse (arc signal) input from the extraction means 11 to the score giving means 122 of the arc determination means 12 is a predetermined number of times per unit time (for example, 50 times or more in 50 ms), and further, By confirming that the generated intervals are irregular, the noise is caused by the arc, and the number of added points is increased.

  Thus, when a large (strong) arc is generated, the switch can be immediately shut off.

  Then, regardless of whether it is caused by an arc, in the case of small noise, a lot of wrinkles, that is, in a quiet state, occurs between the noise waveforms, whereas in the case of strong noise, there is almost no wrinkle. Therefore, the number and times of wrinkles for a predetermined time (for example, 50 ms) are measured, and the deduction points are increased as the length of wrinkles becomes longer. Specifically, when the voltage input to the score giving means 122 is less than or equal to a predetermined value, the length of the bag is determined by measuring the duration. If the duration is short, the number of points deducted by the kite decreases, and if the duration is long, the number of points deducted increases.

  As a result, even when noise is generated in the signal input from the extracting means 11 to the arc determining means 12, the subsequent wrinkle state is observed and addition / subtraction is performed. As a result, the input noise is large. It is possible to determine whether the noise is caused by an arc, a small arc, or noise that is not caused by an arc, and unnecessary switching of the switch can be prevented.

  As described above, the present invention detects whether or not an arc is generated from the noise pattern indicated by the magnetic change around the electric circuit. Used in combination with methods based on noise detection.

  That is, the temperature sensors 21 to 24 are semiconductor temperature detection elements such as thermistors, and are arranged in the vicinity of the terminals 41 to 44, respectively, so that the temperature of the terminals or the temperature around the terminals can be measured.

  Further, currents corresponding to the measured temperatures T1 to T4 output from the temperature sensors 21 to 24, respectively, are input to the overheat detection circuit 15 and recognized as the measured temperatures T1 to T4, and the overheat detection circuit 15 is set in advance. The overheat detection signal OH is output based on the following conditions.

  The overheat detection circuit 15 generates an overheat detection signal OH if any of the measured temperatures T1 to T4 is equal to or higher than a predetermined temperature (for example, 100 ° C.) set according to the allowable temperature of the electric circuit connected to each terminal. Output.

  The overheat detection circuit 15 preferably sets the overheat detection signal OH to a high level when the overheat state continues for a predetermined time or more.

The reverse connection detection circuit 13 receives the power supply voltage V0, and the reverse connection detection circuit 13 outputs a reverse connection detection signal RC when the polarities of the DC power supplies connected to the terminals 41 and 42 are reversed. The That is, the reverse connection detection circuit 13 detects a reverse connection state in which a power source whose negative side (terminal 42) has a higher potential than the positive side (terminal 41) is connected to the terminals 41 and 42 which are power source side terminals. The reverse connection detection signal RC is output. For example, the reverse connection detection circuit 13 is configured by a photocoupler, and the anode side of the primary side light emitting diode is connected to the terminal 42 (negative side), and the voltage at the terminal 42 is higher than the voltage at the terminal 41. In the reverse connection state, the light emitting diode emits light, the secondary phototransistor is turned on, and the high level reverse connection detection signal RC is output.

  The OR determination unit 14 receives an arc detection signal ARC, an overheat detection signal OH, and a reverse connection detection signal RC, and also receives a control signal CON via a terminal 45. Further, the trip command signal OP output from the OR determination unit 15 is input to the trip unit 26 to open the contacts 31 and 32, thereby preventing DC power from being output from the switch.

  With the above configuration, the OR determination unit 14 drives the trip unit 26 when the arc detection signal ARC is input from the arc determination means 12. The trip unit 26 is driven when any one of the temperature sensors 41 to 44 is higher than a predetermined temperature, or when the voltage on the load side is higher than that on the power source side (when reverse connection is established). Will do.

  As described above, since the arc determination means determines whether or not an arc has occurred using the probability that the noise generated in the electric circuit is caused by the arc as an addition value and the probability that is not caused by the arc as a subtraction value, The probability of is extremely small.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  In the said embodiment, although the case where it used for a solar power generation system was demonstrated as an application example of the switch 1, it is not limited to this. The switch 1 can be widely used for distributed (type) power sources such as small-scale power generation facilities using other natural energy and cogeneration facilities.

  As described above, the present invention is extremely effective in the industry because it can eliminate a failure caused by arc discharge that is likely to occur in a distribution network having a DC power supply.

DESCRIPTION OF SYMBOLS 1 Switch 2 Solar cell module 3 Power conditioner 4 Load 5 Commercial alternating current power supply 100 Magnetic force sensor 11 Extraction means 12 Arc determination means 13 Reverse connection detection circuit 14 OR determination part (logical sum circuit)
15 Overheat detection circuit 21-24 Temperature sensor 25 Power supply circuit 26 Trip unit 31-34 Contact 41-45 Terminal L1-L4 Power supply line

Claims (6)

In a switch having a power supply side terminal connected to a DC power supply and a load side terminal from which power from the DC power supply is output,
A magnetic force sensor for detecting electromagnetic waves around the electric circuit as a magnetic force change;
Extraction means for extracting a signal in a frequency band from which determination of “noise caused by arc” is easy from the magnetic sensor output;
Determining whether the signal output from the extraction means is caused by an arc, and an arc determination means for outputting an arc detection signal when the signal is caused by an arc;
A tripping unit for opening a contact when the arc detection signal is generated;
The switch characterized by having.   The switch according to claim 1, wherein the magnetic sensor is a magnetic core, a semiconductor element capable of detecting electromagnetic waves, or a combination of a magnetic core and a semiconductor element.   The switch according to claim 1 or 2, wherein the extraction means is provided with a bandpass filter that extracts a predetermined frequency from the output of the magnetic force sensor and outputs it to the arc determination means. The arc determination means includes
When there is a high probability that the output of the extraction means at a predetermined time is caused by an arc, the number of points added according to the probability is accumulated, and when there is a high probability that the output is not caused by an arc, a deduction point according to the probability is sequentially accumulated, The switch according to any one of claims 1 to 3, which outputs a signal indicating an arc when the accumulated value reaches a predetermined threshold value.   5. The arc determination unit according to claim 4, wherein the arc determination unit stores a waveform serving as a reference for the determination in a storage unit, and compares the reference waveform with the input waveform to determine the added points and deduct points. Switch.   The switch according to claim 4 or 5, wherein a wrinkle of the input waveform is detected, and a deduction point is determined according to the number of occurrences and the length of the wrinkle in a predetermined time.

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