CN110824320B - Direct current arc fault detection method and device - Google Patents
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Abstract
The invention discloses a direct current arc fault detection method. The method comprises the steps of sampling current of a protected direct-current line, converting a sampled current signal into a voltage signal through a transfer function between the current and the voltage, extracting characteristic quantity of preset frequency band components in the voltage signal, detecting direct-current arc faults by using the characteristic quantity of the extracted voltage, arranging a terminal unit which is connected with a load in parallel and at least comprises a capacitor element at the tail end of the protected direct-current line, and reducing the impedance of the protected line in the preset frequency band by using the terminal unit so as to enhance the identification degree of the arc signals. The invention also discloses a direct current arc fault detection device. The invention can reduce the impedance of the protected line in the preset frequency band by the terminal unit, enhance the recognition degree of the arc signal and carry out accurate and safe arc detection on the direct current line with a load with larger inductance.
Description
Technical Field
The invention relates to a direct current arc fault detection method, and belongs to the technical field of arc fault detection.
Background
With the development of power electronic technology, the direct current power supply technology has more and more technical and economic advantages, and has good development prospect under the background of energy revolution. In addition, dc power supply is widely used and plays an indispensable role in important fields, such as large-scale dc photovoltaic power generation systems, aircraft power supply systems, automobile systems, and dc power transmission systems. The emergence and rapid development of direct current loads (such as LED lamps, electric vehicles, data and computing centers, etc.), the requirements of end users for high reliability and high quality power are increasing, the demand of people for direct current power distribution is also becoming more and more obvious, and direct current power supply has a great prospect.
However, in the dc power supply system, there are also phenomena such as dielectric breakdown, loosening of metal joints, aging of elements, or biting by animals, which may cause a dc arc fault in the system, thereby causing a fire hazard. The direct current arc has no periodic zero crossing point characteristic of the alternating current arc, once the direct current arc is generated, the direct current arc is difficult to extinguish by itself, and the direct current arc has more harm than the alternating current arc. Therefore, the reliable direct current arc fault detection technology has important significance for ensuring the safe and reliable operation of the direct current power supply system.
In a direct current power supply system, the types of direct current loads are diversified, the arc characteristics of the direct current loads have larger difference, particularly, the inductance of the direct current motor loads is larger, the high-frequency signal of the arc current in a loop can be filtered and attenuated, and the larger the inductance is, the more the attenuation is serious, the unobvious high-frequency signal characteristic of the arc current signal can be caused, and the detectability is not realized.
In the existing direct current arc fault detection technology, arc current signal waveforms are mainly collected, time domain characteristics or frequency domain characteristics of high-frequency components of preset frequency bands (or called characteristic frequency bands) in signals are calculated by using analysis methods such as FFT, HHT and wavelets, and fault arcs are judged according to the extracted time domain or frequency domain characteristics. However, in a loop with a large inductance of the load, due to the filter characteristic of the inductance, the arc current high-frequency signal is attenuated by filtering, so that the time domain characteristic and the frequency domain characteristic variation of the arc current are not obvious, and the arc signal and the background noise cannot be distinguished. In addition, the harmonic content in the DC load is generally large, and is difficult to distinguish together with the aliasing of the low-frequency components of the arc current. Therefore, any existing analysis method based on arc current time-frequency domain characteristics cannot effectively detect the direct-current arc fault under the load with large inductance.
Chinese patent CN201710512191.3 "a method and process for detecting low voltage series dc arc by using parallel capacitor current" detects series dc arc fault by using the variation rate and the variation of spectral area of the parallel capacitor current. The patent has the following defects for detecting the direct current arc fault under the load with larger inductance: firstly, the parallel connection of capacitors in an inductive load loop may cause LC or LCL resonant current, which results in the instability of a loop system and even damages to loop equipment; secondly, for a multi-branch load, each branch needs to be connected with a capacitor in parallel, and the current of each capacitor needs to be measured, so that the system cost is increased.
Disclosure of Invention
The invention aims to solve the technical problem that the existing direct current arc fault detection technology based on time-frequency analysis cannot perform arc detection on a direct current line with a load with large inductance, and provides a direct current arc fault detection method which can perform accurate and safe arc detection on the direct current line with the load with large inductance.
The invention specifically adopts the following technical scheme to solve the technical problems:
a method for detecting DC arc fault includes sampling current of protected DC line, converting sampled current signal to voltage signal by transfer function between current and voltage, carrying out characteristic quantity extraction on preset frequency band component in voltage signal, carrying out DC arc fault detection by utilizing characteristic quantity of extracted voltage, setting a terminal unit containing at least one capacitance element and being parallel to load at tail end of protected DC line, using said terminal unit to reduce impedance of protected line in preset frequency band so as to raise identification degree of arc signal.
Preferably, the terminal unit is a capacitive circuit.
Preferably, the terminal unit is a resistor and capacitor series circuit.
Preferably, the terminal unit is a network formed by connecting a capacitor in parallel with a series circuit of a resistor and a capacitor.
Preferably, the transfer function is an equivalent circuit model between the current I and the voltage U of the protected line, and is
Wherein Z is the termination unit impedance, ZoIs the load impedance and L is the protected line inductance.
Preferably, the capacitive element C in the terminal unit is configured according to the inductance L of the protected line and the upper and lower limits of the preset frequency band, and the value range is
In the formula f1、f2The lower limit and the upper limit of the preset frequency band are set, and L is the inductance of the protected line.
Preferably, the lower limit f of the preset frequency band1At 40kHz, the upper limitf2100kHz was taken.
Preferably, the characteristic quantity is a spectral energy of a preset frequency band component in the voltage signal.
The following technical scheme can be obtained according to the same invention concept:
a direct current arc fault detection device comprises a characteristic extraction module and a fault detection module, wherein the characteristic extraction module is used for extracting characteristic quantity of a preset frequency band component in a voltage signal converted from a current sampling signal in a protected direct current line; the protection circuit is characterized by further comprising a terminal unit for reducing the impedance of the protected line in a preset frequency band, wherein the terminal unit is arranged on the load side behind the sampling point of the protected direct current line and is connected with the load in parallel.
Preferably, the terminal unit is a capacitive circuit.
Preferably, the terminal unit is a resistor and capacitor series circuit.
Preferably, the terminal unit is a network formed by connecting a capacitor in parallel with a series circuit of a resistor and a capacitor.
Preferably, the transfer function is an equivalent circuit model between the current I and the voltage U of the protected line, and is
Wherein Z is the termination unit impedance, ZoIs the load impedance and L is the protected line inductance.
Preferably, the capacitive element C in the terminal unit is configured according to the inductance L of the protected line and the upper and lower limits of the preset frequency band, and the value range is
In the formula f1、f2The lower limit and the upper limit of the preset frequency band are set, and L is the inductance of the protected line.
Preferably, the lower limit f of the preset frequency band1Taking 40kHz, the upper limit f2100kHz was taken.
Preferably, the characteristic quantity is a spectral energy of a preset frequency band component in the voltage signal.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
on the basis of the existing direct current arc fault detection technology based on time-frequency analysis, the impedance of a protected line in a preset frequency band is reduced and the recognition degree of an arc signal is enhanced by utilizing a terminal unit which is arranged at the tail end of the protected direct current line and is connected with a load in parallel and at least comprises a capacitive element; and further, the voltage characteristic converted according to the transfer function between the current and the voltage is adopted to replace the traditional current characteristic, so that accurate and safe arc detection is realized on a direct current line with a load with large inductance.
The technical scheme of the invention has simple implementation mode and low implementation cost; and furthermore, a terminal unit at least comprising a capacitive element can select proper parameters, so that the detection of the arc voltage signal in the inductive load circuit is realized, and meanwhile, the circuit has a certain inhibiting effect on aliasing low-frequency and high-frequency noise components in the arc voltage signal.
Drawings
FIG. 1 is a schematic circuit diagram of a prior art;
FIG. 2 is a U/I amplitude-frequency characteristic diagram of 12mH and 33mH resistance-inductance load parallel terminal units;
FIG. 3 is a circuit schematic of the method of the present invention;
FIG. 4 is a schematic circuit diagram of a first embodiment of the present invention;
FIG. 5 is a circuit schematic of a second embodiment of the present invention;
FIG. 6 is a circuit schematic of a third embodiment of the present invention;
FIG. 7 is a diagram showing the U/I amplitude-frequency characteristics of the resistive-inductive load parallel termination unit.
Detailed Description
The principle of the existing direct current arc detection technology is shown in fig. 1, an arc fault protection breaker (AFDD) firstly performs sampling measurement on the current of a protected line, then performs time-frequency domain analysis on the current signal obtained by sampling, and judges whether direct current occurs according to the time-frequency domain characteristicsAn arc fault, and timely opening the circuit when an arc fault is detected. However, when the dc load in the circuit has a large inductance, such as a 2.5kW dc brush motor, the armature inductance reaches 33mH, and a single inductance filter can be formed in the load loop due to the load inductance, so the arc current signal in the loop is also affected by the inductance filtering. In the figure, L is the equivalent inductance of the protected line, Z0Is the load impedance.
The transfer function of the circuit shown in fig. 1 is:
now, for two inductive loads with inductance of 12mH and 33mH, the U/I amplitude-frequency characteristic comparison analysis is performed through the above transfer function, as shown in fig. 2, G _12mH is the amplitude-frequency characteristic of the inductive load line impedance of 12mH, and G _33mH is the amplitude-frequency characteristic of the inductive load line impedance of 33 mH. In the figure, the impedance gain of the line of an inductive load of 33mH is larger than that of 12mH at the frequency point of 1kHz, the impedance gain values of the two inductive loads are different by about 8.5 dB, namely about 2.66 times at the frequency point of 40kHz, the impedance gains of the two inductive loads are both more than 69.5dB, and the impedance gain of each frequency point in the line is larger as the frequency point is higher, namely the inductance of the load contained in the line is larger. The larger the line impedance gain, the more significant the filter blocking effect on the ac component. Therefore, in a loop containing an inductive load, the problem that the arc high-frequency signal is attenuated by inductive filtering exists, the arc high-frequency signal is more seriously attenuated by filtering when the inductance is larger, and even the frequency spectrum of the arc current signal is not obviously changed.
According to the relevant literature data of the direct current arc fault detection, the existing direct current arc detection technology mostly utilizes the frequency band of 40 KHz-100 kHz in the direct current arc current high-frequency signal to detect the direct current arc fault. However, since the circuit including the inductive load has the signal attenuation problem, the frequency band signal cannot be effectively detected for the arc fault in the circuit including the inductive load by the arc current. In addition, the direct current arc current also has the defects that the direct current arc voltage is easily influenced by external factor interference, the aliasing variation with the background noise signal is relatively small, and the variation cannot be distinguished in serious conditions.
Aiming at the defect that the existing direct current arc fault detection technology based on time-frequency analysis is difficult to carry out arc detection on a direct current line with a load with larger inductance, the invention adopts the technical scheme that a terminal unit which is arranged at the load side behind the sampling point of the protected direct current line and is connected with the load in parallel and at least comprises a capacitive element is utilized to reduce the impedance of the protected line in a preset frequency band and enhance the recognition degree of an arc signal; the traditional current characteristics are further replaced by the voltage characteristics converted according to the transfer function between the current and the voltage, so that accurate and safe arc detection is realized on a direct-current line with a load with large inductance; and furthermore, a terminal unit can select proper parameters, so that the detection of the arc voltage signal in the inductive load circuit is realized, and meanwhile, the circuit has a certain inhibiting effect on aliasing low-frequency and high-frequency noise components in the arc voltage signal.
The dc arc fault detection device of the present invention is shown in fig. 3, and includes a feature extraction module for performing feature extraction on a frequency component of a preset frequency band in a sampling signal on a line side of a protected dc line, and a fault detection module for performing dc arc fault detection using the extracted features; the device also comprises a terminal unit used for reducing the impedance of the protected line in a preset frequency band and enhancing the identification degree of the arc signal, wherein the terminal unit at least comprises a capacitor element, and the terminal unit is arranged on the load side behind the sampling point of the protected direct current line and is connected with the load in parallel. As shown in fig. 3, after a current signal at the line side of the protected line collected by the current transformer passes through the band-pass filter, only a frequency signal of a characteristic frequency band is retained, then the characteristic extraction module extracts characteristics therefrom, the fault detection module performs dc arc fault detection by using the extracted characteristics, outputs a detection result, and controls a switch in the line according to the detection result.
The direct current arc current contains harmonic components generated by a load, and is more easily influenced by external factor interference compared with direct current arc voltage, and has the defects of relatively small aliasing variation with background noise signals, incapability of distinguishing direct current arc signal variation even in serious conditions and the like. The arc voltage signal can avoid aliasing influence of background noise and load harmonic signals on the arc detection signal, and improve the discrimination of arc detection, so preferably, the sampling signal is a voltage sampling signal obtained by converting the current sampling signal through a transfer function between current and voltage.
In order to further reduce the influence of the inductive load on the filtering attenuation of the characteristic frequency band sampling signal and effectively suppress the high-frequency noise and higher harmonics in the sampling signal, preferably, the capacitive element in the terminal unit is configured according to the inductance L of the protected line and the upper and lower limits of the preset frequency band, and the value range is
In the formula f1、f2The lower limit and the upper limit of the preset frequency band are set, and L is the inductance of the protected line.
Preferably, the lower limit f of the preset frequency band1Taking 40kHz, the upper limit f2100kHz was taken.
The capacitive terminal unit can adopt a capacitor circuit C consisting of one or more capacitors, an RC series circuit formed by serially connecting a capacitor and a resistor, or an RC network formed by parallelly connecting a capacitor circuit and an RC circuit; in view of the fact that the resistor can perform a damping function in the circuit, the LCL resonance in the loop caused by the parallel capacitor can be avoided, and the resonance current can be suppressed, therefore, it is preferable that the capacitive termination unit is formed by connecting at least one capacitor and at least one resistor.
The characteristics may be various time-frequency characteristics used in the prior art, and preferably, the spectrum energy of a preset frequency band in the sampling signal is used.
To facilitate understanding of the public, the technical solution of the present invention is further described in detail by the following specific examples.
The first embodiment,
As shown in fig. 4, the dc arc fault detection apparatus of this embodiment includes a capacitor C, a damping resistor Rd, a current transformer, a band-pass filter, a feature extraction module, and a fault detection module, where the capacitor C and the damping resistor Rd are connected in series to form a terminal unit, and a line load in this embodiment is a resistive load. As shown in fig. 4, a capacitor C is connected in series with a damping resistor Rd and then connected in parallel to the end (load side) of a protected line as a terminal unit, a current transformer measures the current of the protected line, a current signal measured by the current transformer is provided to a band-pass filter, the band-pass filter retains a 40-100 kHz frequency band signal in the current signal and provides the signal to a feature extraction module, the feature extraction module converts the current signal into a voltage signal through a transfer function between the current and the voltage, then obtains a voltage signal frequency spectrum through fourier transform, and performs energy calculation on the 40-100 kHz frequency band in the voltage signal frequency spectrum, or the feature extraction module obtains a current signal frequency spectrum through fourier transform, and performs energy calculation on the 40-100 kHz frequency band in the current frequency spectrum, and then converts the current spectrum energy into voltage spectrum energy through the transfer function between the current and the voltage, and the fault detection module judges the arc fault according to the frequency spectrum energy, and when the calculated frequency spectrum energy variable quantity exceeds a preset threshold value, the fault detection module judges that the protected line has the direct current arc fault, outputs an alarm state signal and triggers an auxiliary signal of an electric switch breaking loop. If the load is 2.5kW of direct current brush motor, the armature equivalent inductance can be measured by related instruments to be about 33mH, the equivalent inductance of the circuit is generally very small, and the equivalent inductance of dozens of meters of the circuit is uH grade, and 10uH can be taken. And determining the capacitance value of the terminal unit according to a configuration method that the resonance frequency of an LCL filter consisting of the capacitor of the terminal unit, the equivalent inductor of the load and the inductor of the preceding line is configured in the preset frequency band. Since the line inductance value is generally much lower than the load equivalent inductance value, the capacitance value of the terminal unit may also be determined according to a configuration method in which the resonant frequency of the LC filter composed of the capacitor of the terminal unit and the preceding line inductance is configured within the preset frequency band.
When taking L ═ 0.01uH, Lo ═ 33mH, fres ═ 100kHz,
resonating at LCLThe point configuration method, the capacitance C can be represented by the formula
Is solved to obtain
According to the LC resonance point configuration method, the capacitance C can be represented by the formula
Is solved to obtain
The results are the same for both configuration methods.
The damping resistance Rd is generally obtained from the capacitance impedance at the resonance point, i.e.
In the formula, k can be taken by comprehensively considering loss and attenuation degree of a resonance point.
Wherein, the transfer function G between the current I and the voltage U in the protected line is:
where Zo is the load impedance, C is the capacitance element in the termination unit, Rd is the damping resistance in the termination unit, and L is the line inductance.
The voltage spectrum energy calculation formula is as follows:
the voltage spectrum energy calculation formula can also be:
the voltage spectrum energy calculation formula can also be:
where n is the total number of spectral points in each band in the voltage spectrum, fnIs the magnitude of a voltage spectrum point.
The voltage spectrum energy calculation method is not limited to the above three calculation methods.
Example two:
the resonance oscillation of the LCL filter is mainly caused by the harmonic excitation in the current, when the harmonic current of the load in the loop is small and the line itself has a certain equivalent impedance, which has a certain damping effect, so as to prevent the resonance oscillation of the LCL filter from being caused by the excitation, in this case, the dc arc fault detection apparatus shown in fig. 5 may be adopted, which includes a capacitor C, a current transformer, a band-pass filter, a feature extraction module, and a fault detection module, and the line load in this embodiment is a resistance-inductance load. As shown in fig. 5, a capacitor C is connected in parallel to the end (load side) of the protected line as a capacitive terminal unit, a current transformer measures the current of the protected line, a current signal measured by the current transformer is provided to a band pass filter (a signal filtering unit in the figure), the band pass filter retains a 40KHz to 100KHz frequency band signal in the current signal and provides the signal to a feature extraction module, the feature extraction module converts the current signal into a voltage signal through a transfer function between current and voltage, then obtains a voltage signal frequency spectrum through fourier transform, and performs energy calculation on the 40KHz to 100KHz frequency band in the voltage signal frequency spectrum, or the feature extraction module obtains the current signal frequency spectrum through fourier transform, performs energy calculation on the 40KHz to 100KHz frequency band in the current frequency spectrum, and then converts the current spectrum energy into voltage spectrum energy through the transfer function between current and voltage, and the fault detection module judges the arc fault according to the frequency spectrum energy, and when the calculated frequency spectrum energy variable quantity exceeds a preset threshold value, the fault detection module judges that the protected line has the direct current arc fault, outputs an alarm state signal and triggers an auxiliary signal of an electric switch breaking loop.
The transfer function H between the current I and the voltage U in the protected line is as follows:
where Zo is the equivalent impedance of the load.
The calculation method of the capacitance C and the calculation of the spectral energy are the same as those in the first embodiment, and are not described again.
Example three:
this embodiment is another form of the dc arc fault detection apparatus of the present invention, as shown in fig. 6, which includes a capacitor C, RdCdThe circuit comprises a damping branch circuit, a current transformer, a band-pass filter, a feature extraction module and a fault detection module, wherein the circuit load in the embodiment is a resistance-inductance load, and a capacitor CdThe function of the resistor is to reduce the current value flowing through the resistor so as to reduce the damping loss. As shown in fig. 6, the damping branch route RdAnd CdIn series, capacitors C and RdCdThe damping branch circuits are connected in parallel and then connected in parallel to the tail end (load side) of a protected circuit as a capacitive terminal unit, a current transformer measures the current of the protected circuit, a current signal measured by the current transformer is provided to a band-pass filter, the band-pass filter reserves a 40 KHz-100 KHz frequency band signal in the current signal and provides the signal to a characteristic extraction module, the characteristic extraction module converts the current signal into a voltage signal through a transfer function between the current and the voltage, then a voltage signal frequency spectrum is obtained through Fourier transform, energy calculation is carried out on the 40 KHz-100 KHz frequency band in the voltage signal frequency spectrum, or the characteristic extraction module obtains a current signal frequency spectrum through the Fourier transform, energy calculation is carried out on the 40 KHz-100 KHz frequency band in the current frequency spectrum, and then the current spectrum energy is converted into voltage spectrum energy through the transfer function between the current and the voltage, and the fault detection module judges the arc fault according to the frequency spectrum energy, and when the calculated frequency spectrum energy variable quantity exceeds a preset threshold value, the fault detection module judges that the protected line has the direct current arc fault, outputs an alarm state signal and triggers an auxiliary signal of an electric switch breaking loop.
The transfer function H between the current I and the voltage U in the protected line is as follows:
in the formula ZoIs the equivalent impedance of the load.
The calculation method of the capacitance C and the calculation of the spectral energy are the same as those in the first embodiment, and are not described again.
Fig. 7 shows a comparison of U/I amplitude-frequency characteristics of a 33mH resistive-inductive load connected in parallel with a terminal unit having a capacitor of 0.22uf and a non-terminal unit, where G _ L is the load line impedance amplitude-frequency characteristic of the non-terminal unit, and G _ LCL is the line impedance amplitude-frequency characteristic of the resistive-inductive load connected in parallel with the terminal unit having a capacitor of 0.22 uf. As can be seen from the amplitude-frequency characteristic curve of the graph, the line impedance gain of the G _ LCL connected in parallel with the termination unit having a capacitance of 0.22uf is smaller than that of the G _ L not connected in parallel with the termination unit at a frequency point of 2.7kHz or higher; at the frequency point of 40kHz, the impedance gain after the parallel connection of the terminal units is 25dB, and is 50dB lower than that of the impedance gain of the non-parallel connection terminal units; the higher the frequency point is, the larger the difference in impedance gain value between the two is, and the impedance gain difference reaches a maximum at the resonance point. Therefore, after the terminal unit containing the capacitor is connected in parallel, the impedance of the protected circuit in a preset frequency band is greatly reduced, so that the amplitude of the arc signal is enhanced to return to a measurable range, the recognition degree of the arc signal is enhanced, and the influence of an inductive load on the filtering attenuation of the arc signal is reduced or eliminated.
Claims (16)
1. A DC arc fault detection method comprises the steps of sampling current of a protected DC line, converting a sampled current signal into a voltage signal through a transfer function between the current and the voltage, extracting characteristic quantity of a preset frequency band component in the voltage signal, and detecting DC arc faults by using the extracted characteristic quantity of the voltage.
2. The direct current arc fault detection method of claim 1, wherein the termination unit is a capacitive circuit.
3. The direct current arc fault detection method of claim 1, wherein the termination unit is a resistor and capacitor series circuit.
4. The dc arc fault detection method of claim 1, wherein the termination unit is a capacitor in parallel with a series circuit of a resistor and a capacitor.
5. The method of claim 1, wherein the transfer function is an equivalent circuit model between the current I and the voltage U of the protected line, and is
Wherein Z is the termination unit impedance, ZoIs the load impedance and L is the protected line inductance.
6. The method according to claim 1, wherein the capacitive element in the terminal unit is configured according to the inductance L of the line to be protected and the upper and lower limits of the preset frequency band, and the value range is
In the formula f1、f2The lower limit and the upper limit of the preset frequency band are set, and L is the inductance of the protected line.
7. The method according to claim 6, wherein the lower limit f of the predetermined frequency band is1Taking 40kHz, the upper limit f2100kHz was taken.
8. The method according to claim 1, wherein the characteristic quantity is a spectral energy of a predetermined frequency band component in the voltage signal.
9. A direct current arc fault detection device comprises a characteristic extraction module and a fault detection module, wherein the characteristic extraction module is used for extracting characteristic quantity of a preset frequency band component in a voltage signal which is formed by converting a current sampling signal in a protected direct current line through a transfer function between current and voltage; the protection circuit is characterized by further comprising a terminal unit which is used for reducing the impedance of the protected circuit in a preset frequency band and at least comprises a capacitor element, wherein the terminal unit is arranged on the load side behind the sampling point of the protected direct current circuit and is connected with the load in parallel.
10. The dc arc fault detection device of claim 9, wherein the termination unit is a capacitive circuit.
11. The dc arc fault detection device of claim 9, wherein the termination unit is a resistor and capacitor series circuit.
12. The dc arc fault detection device of claim 9, wherein the termination unit is a capacitor in parallel with a series circuit of a resistor and a capacitor.
13. The dc arc fault detection device of claim 9, wherein the transfer function is an equivalent circuit model between the current I and the voltage U of the protected line, and is
Wherein Z is the termination unit impedance, ZoIs the load impedance and L is the protected line inductance.
14. The direct current arc fault detection device of claim 9, said termination unitThe capacitance element C is configured according to the inductance L of the protected line and the upper and lower limits of the preset frequency band, and the value range is
In the formula f1、f2The lower limit and the upper limit of the preset frequency band are set, and L is the inductance of the protected line.
15. The dc arc fault detection device of claim 14, wherein the lower limit f of the predetermined frequency band is set1Taking 40kHz, the upper limit f2100kHz was taken.
16. The dc arc fault detection device according to claim 9, wherein the characteristic quantity is a spectral energy of a predetermined frequency band component in the voltage signal.
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| CN113437940B (en) * | 2021-06-25 | 2022-07-05 | 合肥工业大学 | Device and method for positioning series arc fault under condition of parallel connection of multiple photovoltaic branches |
| CN113866572B (en) * | 2021-09-06 | 2024-05-28 | 西安理工大学 | DC fault arc detection and positioning method under multi-power electronic device access condition |
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