Method, apparatus, and system for detecting arc energy

Abstract

Provided is a method for detecting arc energy, said method comprising: detecting the current of a cable; detecting the voltage of the cable; determining the generation of an arc; calculating the amount of decrease in voltage from the point in time at which the arc was generated; and calculating the arc energy on the basis of the current and the amount of decrease in voltage.

Description

Method, apparatus and system for detecting the energy of an arc

[0001] The present invention relates to a method, apparatus and system for detecting the energy of an arc that occurs when a cable breaks.

[0002] A method for determining whether an arc has occurred based on the frequency characteristics of a current is known. In this method, a current sensor measures the current in a cable. The components of the measured current in the arc frequency band (e.g., several tens of kHz) are analyzed using FFT (Fast Fourier Transform). The occurrence of an arc is determined based on the level of the frequency characteristics obtained.

[0003] International Publication No. WO2017 / 149859

[0004] However, in order to accurately determine not only the occurrence of an arc but also the effects of the arc, it is necessary to detect the energy of the arc. As shown in Fig. 7, the energy of the arc is represented by the product of the voltage Va at a portion 101 in the cable 100 where the arc has occurred due to a break and the current Ia flowing through that portion. In detail, as shown in Fig. 8, before the arc occurs, the voltage Va at the portion 101 is zero, and therefore the arc energy is zero. After the cable is broken at the portion 101 due to an arc, the current Ia is zero, and therefore the arc energy is also zero. The product of the voltage Va and the current Ia during the transient occurrence of the arc indicates the magnitude of the arc energy.

[0005] Therefore, by detecting the voltage Va and current Ia during arc generation, the arc energy can be calculated with high accuracy. However, when detecting the energy of an arc generated by a cable break, it is difficult to predict the location of the cable break. In particular, when the cable is installed over a wide area, it is not easy to detect the voltage at the cable break. An object of the present invention is to accurately detect the energy of an arc generated when a cable breaks.

[0006] A first aspect of the present invention is a method for detecting the energy of an arc that occurs when a cable connected to a power source is broken, the method comprising: detecting a current in the cable; detecting a voltage in the cable; determining whether an arc has occurred; calculating a voltage decrease from the time the arc occurred; and calculating the energy of the arc based on the voltage decrease and the current.

[0007] A device according to a second aspect of the present invention is a device for detecting the energy of an arc that occurs when a cable connected to a power source is broken. The device according to this aspect includes a current sensor, a voltage sensor, and a computer. The current sensor detects the current in the cable. The voltage sensor detects the voltage in the cable. The computer acquires the current and voltage. The computer determines the occurrence of an arc. The computer calculates the decrease in voltage from the time the arc occurred. The computer calculates the energy of the arc based on the decrease in voltage and the current.

[0008] A system according to a third aspect of the present invention includes a power supply, a cable, and an arc energy detection device. The cable is connected to the power supply. The arc energy detection device is connected to the cable. The arc energy detection device includes a current sensor, a voltage sensor, and a computer. The current sensor detects the current in the cable. The voltage sensor detects the voltage in the cable. The computer acquires the current and voltage. The computer determines the occurrence of an arc. The computer calculates the voltage decrease from the time the arc occurred. The computer calculates the energy of the arc based on the voltage decrease and the current.

[0009] According to the present invention, it is possible to accurately detect the energy of an arc that occurs when a cable is broken.

[0010] Fig. 1 is a schematic diagram showing the configuration of a power supply system according to an embodiment; Fig. 2 is a block diagram showing the configuration of an arc energy detection device; Fig. 3 is a diagram showing a current waveform and a voltage waveform when an arc occurs; Fig. 4 is a diagram showing a current waveform and an inverted voltage waveform when an arc occurs; Fig. 5 is a diagram showing the configuration of a power supply system according to a modified example; Fig. 6 is a diagram showing a method for calculating arc energy according to a modified example; Fig. 7 is a diagram showing a method for calculating theoretical arc energy; Fig. 8 is a diagram showing a method for calculating theoretical arc energy.

[0011] A method for calculating arc energy according to an embodiment will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a power supply system 1 according to the embodiment. As shown in Fig. 1, the power supply system 1 includes a power source 2, a power conditioner 3, a cable 4, and a power interruption device 5.

[0012] The power source 2 supplies power. The power source 2 includes, for example, a solar panel 6. The solar panel 6 generates power using sunlight. The power source 2 supplies the power generated by the solar panel 6. The power conditioner 3 controls the power generated by the power source 2. The power conditioner 3 converts the power generated by the power source 2 and supplies it to an electrical device or a battery. The cable 4 connects the power source 2 and the power conditioner 3. The cable 4 includes a first cable 4A and a second cable 4B. For example, the first cable 4A is connected to the positive terminal of the power source 2, and the second cable 4B is connected to the negative terminal of the power source 2.

[0013] The power cutoff device 5 switches between connecting and disconnecting the power source 2 and the cable 4 in response to a command from the power conditioner 3. The power cutoff device 5 includes, for example, a relay 7. The relay 7 is switchable between an on state and an off state. When the relay 7 is in the on state, it connects the power source 2 to the cable 4. When the relay 7 is in the off state, it disconnects the power source 2 from the cable 4.

[0014] The power conditioner includes an arc energy detection device 8. The arc energy detection device 8 detects the occurrence of an arc in the cable 4 and detects the energy of the arc that has occurred. FIG. 2 is a block diagram showing the configuration of the arc energy detection device 8. As shown in FIG. 2, the arc energy detection device 8 includes a current sensor 11, a voltage sensor 12, and a detection circuit 13.

[0015] The current sensor 11 is connected to the first cable 4A. The current sensor 11 detects the current input to the power conditioner. The current sensor 11, that is, the current sensor 11, detects current waveform data indicating the waveform of the current flowing through the first cable 4A. The voltage sensor 12 is connected to the first cable 4A and the second cable 4B. The voltage sensor 12 detects the voltage between the first cable 4A and the second cable 4B.

[0016] The detection circuit 13 includes an amplifier 14, a filter 15, and a microcomputer 16. The amplifier 14 amplifies the current waveform data detected by the current sensor 11. The filter 15 extracts components of the arc frequency band from the amplified current waveform data.

[0017] Microcomputer 16 includes an A / D conversion unit 21, an FFT unit 22, an arc determination unit 23, an arc energy calculation unit 24, and an interruption control unit 25. A / D conversion unit 21, FFT unit 22, arc determination unit 23, and arc energy calculation unit 24 are each realized by processing by microcomputer 16. A / D conversion unit 21 performs A / D conversion on the current waveform data in the arc frequency band that has passed through filter 15. FFT unit 22 performs a fast Fourier transform on the converted current waveform data to calculate the power spectrum of the current waveform data for each frequency component.

[0018] The arc determination unit 23 determines whether an arc has occurred based on the power spectrum of the current waveform data. For example, the arc determination unit 23 determines whether an arc has occurred when the power spectrum of the current waveform data is equal to or greater than a predetermined power threshold.

[0019] The arc energy calculation unit 24 calculates the energy of the arc based on the current detected by the current sensor 11 and the voltage detected by the voltage sensor 12. FIG. 3 is a diagram showing the waveform of the current I1 and the waveform of the voltage V1 when an arc occurs. The arc determination unit 23 determines that an arc has occurred at time T1 shown in FIG. 3. The arc energy calculation unit 24 calculates the decrease ΔV in the voltage V1 from the time T1 when the arc occurs. For example, the arc energy calculation unit 24 calculates the decrease ΔV in the voltage V1 from the time T1 when the arc occurs by inverting the waveform of the voltage V1 after the time T1 when the arc occurs.

[0020] The arc energy calculation unit 24 calculates the energy of the arc based on the decrease ΔV in the voltage V1 after the arc generation time T1 and the current I1. As shown by hatching in Fig. 4, the arc energy calculation unit 24 calculates the product of the decrease ΔV in the voltage V1 after the arc generation time T1 and the current I1 as the arc energy Ea.

[0021] The cutoff control unit 25 determines, based on the energy of the arc, whether to cut off the power from the power source 2 to the cable 4. For example, if the energy of the arc is equal to or greater than a predetermined energy threshold, the cutoff control unit 25 determines to cut off the power from the power source 2 to the cable 4. In that case, the cutoff control unit 25 controls the power cutoff device 5 to cut off the power to the cable 4.

[0022] According to the method for calculating arc energy of this embodiment described above, the arc energy is calculated based on the decrease ΔV in the voltage V1 input from the cable 4 to the arc energy detection device 8 after the time T1 at which the arc occurs. When an arc occurs, the voltage V1 input to the arc energy detection device 8 decreases by the voltage at the portion of the cable 4 where the arc occurred. Therefore, the decrease ΔV in the voltage V1 after the time T1 at which the arc occurred can be considered to correspond to the voltage at the portion of the cable 4 where the arc occurred. Therefore, even if the position of the break in the cable 4 cannot be identified, the arc energy can be detected with high accuracy.

[0023] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0024] The configuration of the power supply system 1 is not limited to that of the above embodiment and may be modified. For example, the power source 2 may include a generator other than the solar panel 6. Alternatively, the power source 2 may be a commercial power source 2.

[0025] The configuration of the arc energy detection device 8 is not limited to that of the above embodiment and may be modified. For example, Fig. 5 is a diagram showing the configuration of a power supply system 1 according to a modified example. As shown in Fig. 5, the arc energy detection device 8 may be separate from the power conditioner 3.

[0026] The method for calculating the arc energy is not limited to that of the above embodiment and may be modified. FIG. 6 is a diagram showing a method for calculating the arc energy according to a modified example. For example, after an arc occurs, it may take a certain amount of time for the arc determination unit 23 to detect the arc. In this case, as shown in FIG. 6 , the arc energy calculation unit 24 may estimate the time T1 when the arc occurred to be a predetermined time ΔT before the time T2 when the arc occurrence was determined.

[0027] According to the present invention, it is possible to accurately detect the energy of an arc that occurs when a cable is broken.

[0028] 2: Power supply 4: Cable 5: Power cutoff device 6: Solar panel 8: Arc energy detection device 11: Current I1 sensor 12: Voltage sensor 16: Microcomputer

Claims

1. A method for detecting the energy of an arc that occurs when a cable connected to a power source is broken, comprising: detecting a current in the cable; detecting a voltage in the cable; determining the occurrence of the arc; calculating a decrease in the voltage from the time the arc occurred; and calculating the energy of the arc based on the decrease in voltage and the current.

2. The method according to claim 1, further comprising estimating the occurrence of the arc to be a predetermined time before the occurrence of the arc is determined.

3. The method of claim 1, further comprising controlling a power interruption device connected to the cable to interrupt power to the cable if the energy of the arc is equal to or greater than a predetermined threshold.

4. The method of claim 1, wherein the power source comprises a solar panel.

5. A device connected to a cable connected to a power source for detecting the energy of an arc that occurs when the cable is broken, the device comprising: a current sensor that detects the current in the cable; a voltage sensor that detects the voltage in the cable; and a computer that acquires the current and the voltage, wherein the computer determines the occurrence of the arc, calculates the amount of voltage decrease from the time the arc occurred, and calculates the energy of the arc based on the amount of voltage decrease and the current.

6. The device according to claim 5, wherein the computer estimates the time when the arc occurred to be a predetermined time before the time when the arc occurred.

7. The device according to claim 5, wherein the computer controls a power cut-off device connected to the cable to cut off power to the cable when the energy of the arc is equal to or greater than a predetermined threshold.

8. The device of claim 5, wherein the power source includes a solar panel.

9. A system comprising: a power source; a cable connected to the power source; and an arc energy detection device connected to the cable, wherein the arc energy detection device includes a current sensor that detects a current in the cable; a voltage sensor that detects a voltage in the cable; and a computer that acquires the current and the voltage, wherein the computer determines the occurrence of the arc; calculates a decrease in the voltage from the time the arc occurred; and calculates the energy of the arc based on the decrease in voltage and the current.

10. The system according to claim 9, wherein the computer estimates the time when the arc occurred to be a predetermined time before the time when the arc occurred.

11. The system of claim 9, further comprising a power cutoff device connected to the cable, wherein the computer controls the power cutoff device to cut off power to the cable when the energy of the arc is equal to or greater than a predetermined threshold.

12. The system of claim 9, wherein the power source includes a solar panel.

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