Arc fault detection method and arc fault detector

Abstract

The present invention provides a fault arc detection method and detector, wherein the fault arc detection method comprises: S11: collecting arc signals in a circuit to be tested within a preset period; S12: determining the number of arc half-waves based on the power frequency in the arc signal; S13: determining whether the arc signal is a fault arc signal according to the magnitude relationship between the number of arc half-waves and a threshold. The technical solution of the present invention is adopted to detect fault arcs based on the magnitude relationship between the number of arc half-waves based on the power frequency and the threshold, so as to achieve early warning, and promptly notify the user to repair the line, thereby achieving preventive protection against electrical fires, taking into account both performance and cost, and being able to be applied on site.

Description

Technical Field

[0001] The present invention generally relates to the field of fire protection technology, and in particular to a fault arc detection method and a fault arc detector. Background Art

[0002] The arc fault detector detects parallel fault arcs caused by line aging and insulation damage, and series fault arcs caused by poor line contact, etc., provides early warning and promptly notifies users to repair these electrical hazards, thereby achieving preventive protection against electrical fires. It is widely used in various scenarios such as indoor lighting lines on higher floors, complex industrial power line locations, residential and industrial and commercial power distribution sites, and other 220Vac low-voltage distribution sites suitable for installation.

[0003] Fault arc detectors need to analyze and detect physical signals generated when an arc occurs in a power line, including sound, light, electricity, etc., among which detecting current signals in power lines is the most commonly used detection method. According to the characteristics of arcs occurring in power systems, the characteristic frequencies of fault arcs are mostly concentrated in the range of 10 to 200 kHz, which puts higher requirements on the signal processing of the fault arc detection device used for fault arc signal detection. In practical applications, fault arc detectors must not only consider performance, but also cost. Therefore, there is an urgent need for a fault arc detection method and a fault arc detector that take into account both performance and cost and can be applied on site.

[0004] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the prior art in the field. Summary of the invention

[0005] In view of one or more of the problems existing in the prior art, the present invention provides a fault arc detection method, comprising:

[0006] S11: collecting arc signals in the circuit to be tested within a preset period;

[0007] S12: Determine the number of arc half-waves based on the power frequency in the arc signal; and

[0008] S13: Determine whether the arc signal is a fault arc signal based on the relationship between the number of arc half-waves and a threshold.

[0009] According to one aspect of the present invention, step S11 comprises the following sub-steps:

[0010] S111: Turn on the arc signal acquisition switch;

[0011] S112: Clearing the arc signal in the storage device;

[0012] S113: collecting arc signals in the circuit to be tested within a preset period, and storing the arc signals in the storage device; and

[0013] S114: After the preset conditions are met, stop collecting arc signals.

[0014] According to one aspect of the present invention, the preset condition includes one or more of the following: the arc signal disappears, the storage device is full, and the switch is closed.

[0015] According to one aspect of the present invention, the arc signal includes a low-frequency arc signal and a high-frequency arc signal, wherein the low-frequency arc signal includes an arc signal with a cut-off frequency below 100 kHz, and the high-frequency arc signal includes an arc signal with a cut-off frequency above 100 kHz.

[0016] According to one aspect of the present invention, step S13 includes: when the number of the arc half-waves is greater than or equal to the threshold, determining that the arc signal is a fault arc signal.

[0017] According to one aspect of the present invention, the step S13 further comprises: when the number of the arc half-waves is less than the threshold, determining that the arc signal is not a fault arc signal.

[0018] According to one aspect of the present invention, the method further includes step S14: when it is determined that the arc signal is a fault arc signal, outputting an alarm prompt.

[0019] The present invention also relates to an arc fault detector, comprising:

[0020] A collection unit is configured to collect arc signals in the circuit to be tested within a preset period;

[0021] a storage unit, electrically connected to the acquisition unit and configured to store the arc signal acquired by the acquisition unit; and

[0022] The processing unit is electrically connected to the acquisition unit and the storage unit respectively, and is configured to execute the arc fault detection method as described above.

[0023] According to one aspect of the present invention, loop two bus communications are supported.

[0024] According to one aspect of the present invention, dual processing units are employed.

[0025] According to one aspect of the present invention, the device further comprises a filtering unit, wherein the filtering unit comprises an RC filter and / or a common mode inductor.

[0026] According to one aspect of the present invention, it further includes a communication interface and / or a wireless communication module.

[0027] By adopting the technical solution of the present invention, the fault arc is detected based on the relationship between the number of arc half-waves based on the industrial frequency and the size of the threshold, so as to realize early warning and promptly notify the user to repair the line, thereby achieving preventive protection against electrical fires, taking into account both performance and cost, and being able to be applied on site. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 A flow chart of a fault arc detection method according to an embodiment of the present invention is shown;

[0030] Figure 2 A flowchart showing the sub-steps of step S11 according to a preferred embodiment of the present invention is shown;

[0031] Figure 3 A schematic diagram of a fault detector according to an embodiment of the present invention is shown;

[0032] Figure 4 A schematic diagram of waveforms of current signals in a power grid when no arc occurs and when an arc occurs is shown according to a preferred embodiment of the present invention;

[0033] Figure 5a to Figure 5i A schematic diagram showing signal waveforms for different alarm situations; and

[0034] Figure 6 A schematic diagram of a fault detector according to a preferred embodiment of the present invention is shown. DETAILED DESCRIPTION

[0035] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is lower in level than the second feature.

[0039] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0040] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0041] The present invention provides a fault arc detection method, which detects fault arcs based on the relationship between the number of arc half-waves based on the industrial frequency and the size of a threshold, so as to achieve early warning and promptly notify the user to repair the line, thereby achieving preventive protection against electrical fires. The method is described in detail below.

[0042] Figure 1 FIG. 1 is a flow chart of a method 10 for detecting an arc fault according to an embodiment of the present invention. Figure 1 As shown, the fault arc detection method 10 includes steps S11 to S13, wherein in step S11, within a preset period, an arc signal in the circuit to be tested is collected; in step S12, the number of arc half-waves based on the power frequency in the arc signal is determined; in step S13, whether the arc signal is a fault arc signal is determined based on the relationship between the number of arc half-waves and a threshold. The steps of the fault arc detection method 10 are described in detail below.

[0043] In step S11, arc signals in the circuit to be tested are collected within a preset period.

[0044] In a preferred embodiment of the present invention, the arc signal in the circuit to be tested is collected, which mainly includes two parts, one part is the arc characteristic signal in the low frequency band (referred to as the low frequency arc signal), and the other part is the arc characteristic signal in the high frequency band (referred to as the high frequency arc signal). Since the low frequency arc signal and the high frequency arc signal occur synchronously in the circuit, a synchronous signal sampling mechanism can be used during sampling. While sampling the low frequency arc signal, a synchronous interrupt is used to capture the high frequency arc signal, so that the AD sampling value of each low frequency arc signal corresponds to a time-synchronized high frequency arc signal characteristic value, thereby realizing high-speed sampling of the arc signal, which is beneficial to improving the sampling efficiency.

[0045] According to a preferred embodiment of the present invention, the low-frequency arc signal may be an arc signal with a cut-off frequency below 100 kHz, and the high-frequency arc signal may be an arc signal with a cut-off frequency above 100 kHz. It should be understood that this embodiment is only used for example and does not constitute a limitation to the present invention. The specific cut-off frequency may be adjusted according to actual conditions, which are all within the protection scope of the present invention.

[0046] Figure 2 The sub-steps of step S11 according to one embodiment of the present invention, namely, the specific process of sampling, are shown below in conjunction with Figure 2 Make an introduction.

[0047] like Figure 2 As shown, the step S11 includes sub-steps S111 to S114.

[0048] In sub-step S111, the arc signal acquisition switch is turned on. In some preferred embodiments, the arc signal acquisition switch can be a physical key switch set on an arc signal acquisition device (such as a fault arc detector, etc.), or a virtual switch set by program software. Before the arc signal in the circuit to be tested needs to be acquired, the arc signal acquisition switch is turned on.

[0049] In sub-step S112, the arc signal in the storage device is cleared. It should be understood that the purpose of this sub-step is to avoid the arc signal data stored in the storage device from interfering with the current arc signal acquisition. When clearing the arc signal, it can be operated by physical buttons, or by program instructions, or it can also be automatically triggered by the processing unit after executing sub-step S111, and the present invention does not limit it. In addition, the present invention does not limit the specific type of the storage device. According to a preferred embodiment of the present invention, the storage device can be, for example, a random access memory (RAM) or a Flash flash memory. It should be noted that in the sub-step S112, clearing the arc signal in the storage device is not a necessary operation. When the storage space of the storage device is not full, the operation of clearing the arc signal in the storage device may not be performed. In addition, S112 can also be executed before S111, that is, as long as the storage space is about to be full, the operation of clearing the arc signal in the storage device is executed, and then the arc signal acquisition starts when the arc signal acquisition condition is met. In this case, the acquisition trigger condition of the arc signal also includes a high-frequency pulse signal detected by the device identified by the program.

[0050] In sub-step S113, arc signals in the circuit to be tested are collected within a preset period, and the arc signals are stored in the storage device.

[0051] According to a preferred embodiment of the present invention, a first-in-first-out data storage and recording method can be adopted. The first-in-first-out data is first stored in a random access memory (RAM). If there is no arc data in the data, the data in the random access memory (RAM) will not be transferred to the Flash memory. On the contrary, if there is arc data in the data, the arc data stored in the random access memory (RAM) will be stored in the Flash memory after a preset period. In some preferred embodiments, the preset period can be less than 50 half waves or less than 100 half waves, wherein the 100 half-wave cycle time is 1s. When storage conditions permit, the acquisition period can be longer. For example, in actual configuration, the continuous sampling time of arc data can reach more than 1 hour, which is related to the storage capacity of the storage device and can be set according to actual conditions, but is at least 15 half waves.

[0052] In sub-step S114, after the preset condition is met, the arc signal collection is stopped. In some preferred embodiments, the preset condition may be that the arc signal in the circuit to be tested disappears, the storage device space is full, or the arc signal collection switch is turned off, or any combination of the above three preset conditions, or other conditions, all of which are within the protection scope of the present invention.

[0053] After the arc signal is collected, the arc signal can be processed and analyzed, which will be described below.

[0054] In step S12, the number of arc half-waves based on the power frequency in the arc signal is determined.

[0055] In some preferred embodiments, the arc characteristic data of the low-frequency arc signal and the high-frequency arc signal in the arc signal may be statistically analyzed to determine the number of arc half-waves based on the industrial frequency (ie, 50 Hz).

[0056] In step S13, it is determined whether the arc signal is a fault arc signal according to the relationship between the number of arc half-waves and a threshold.

[0057] According to a preferred embodiment of the present invention, when the number of arc half-waves based on the power frequency in the collected arc signal is greater than or equal to a threshold, the arc signal is determined to be a fault arc signal; conversely, when the number of arc half-waves is less than the threshold, the arc signal is determined not to be a fault arc signal. In some preferred embodiments, the threshold may be 14 half-waves within 1 second. Figure 4The exemplary case is shown, in which the upper part is a typical signal waveform of the current in the power grid when no arc occurs; the lower part is a typical signal waveform of the current in the power grid when an arc occurs. When the zero point disappears, and a high-frequency peak electrical signal appears at or near the zero point disappearance, the power frequency half-wave current signal that meets these two characteristics is counted as an arc half-wave. In this way, the number of arc half-waves based on the power frequency in the collected arc signal is counted, and by comparing with the threshold, it can be determined whether the arc signal is a fault arc signal. It should be understood that this embodiment is limited to illustrative purposes only and does not constitute a limitation of the present invention.

[0058] According to a preferred embodiment of the present invention, the arc fault detection method 10 further includes step S14 (not shown in the figure), when the arc signal is determined to be an arc fault signal, an alarm prompt is output. The alarm prompt can be an alarm sound, an alarm light, a display screen display, etc. Preferably, it can also be linked with remote monitoring to promptly remind the user to perform maintenance, thereby providing a guarantee for preventive protection against electrical fires.

[0059] In some preferred embodiments of the present invention, the alarm conditions are different for different situations, and the signal waveforms are also different. Figure 5a to Figure 5i Various embodiments are shown in which the low frequency signal and the high frequency signal are separated into two waveforms and displayed in the same figure, such as Figure 5a to Figure 5i As shown, the upper waveform represents the low-frequency signal, the lower waveform represents the high-frequency signal, and the high-frequency signal waveform shows the number of high-frequency signals that appear at the time point synchronized with the low-frequency signal. The following is a detailed description of embodiments under different alarm conditions.

[0060] The first alarm is for overcurrent, refer to Figure 5a , the alarm conditions meet the following conditions:

[0061] 1. The current saturation time of the low-frequency signal half wave is greater than 2.35ms.

[0062] 2. The number of half-waves of the low-frequency signal satisfying the current saturation time > 2.35 ms is ≥ the alarm threshold (eg ALARM1 = 12).

[0063] The second alarm condition meets the following conditions:

[0064] 1. After a valid high-frequency signal appears, check the subsequent 16 half-waves. It should be noted that the valid high-frequency signal refers to a high-frequency signal that appears at or near the zero-point disappearance position. In other words, as long as a high-frequency signal appears at or near the zero-point disappearance position, it can be considered a valid high-frequency signal, regardless of the specific number of high-frequency signals or whether a high-frequency signal appears at the peak of the waveform.

[0065] 2. The zero point disappearance time is within 6.27ms (taking 80 sampling points as an example).

[0066] 3. If any of the following conditions is met, this half-wave can be considered as a suspected fault arc:

[0067] A) The slope of the zero point vanishing position satisfies: the slope of more than 3 points is less than 2 / 3 of the average slope of the zero point vanishing position, reference Figure 5b ,

[0068] B) The slope changes at the zero point disappearance position, for example, there are more than 3 points (including 3) that are greater than a certain threshold (such as the size of 140AD value),

[0069] C) When the above condition B) is not met, the slope of the zero point disappearing position changes, for example, ≥ a certain threshold (for example, 130 AD values), refer to Figure 5c ,

[0070] 4. The half-waves that meet the above conditions will be considered as suspected fault arcs and recorded. When the number of suspected fault arcs ≥ the alarm threshold (for example, ALARM2 = 10), the delay starts, and the delay is 40 half-wave times. When the delay is completed, if the number of suspected fault arcs is still ≥ the alarm threshold (for example, ALARM2 = 10), the alarm state is confirmed and an alarm prompt is output.

[0071] 5. If one of the following conditions is met during the delay period, the alarm status and arc count will be cleared:

[0072] A) If no valid high-frequency signal appears again within 20 half-waves after the first valid high-frequency signal appears, it is considered that the previous suspected fault arc data is caused by misjudgment, the alarm state is cleared, and the number of suspected fault arcs is reset to zero. Figure 5d ,

[0073] B) Within 30 half-waves after the high-frequency signal appears, if one of the following conditions occurs, the alarm status and suspected arc counts are cleared:

[0074] 1) Gradually reduce the half-wave to 10 or more, refer to Figure 5e ,

[0075] 2) There is only one case where the height difference between adjacent half waves is 4 times or more. Figure 5f .

[0076] The third alarm: the sum of the first and second alarm conditions > the alarm threshold (e.g. ALARM3 = 11), refer to Figure 5g , that is, a comprehensive judgment on overcurrent phenomena and suspected arcs.

[0077] The fourth alarm: For example, for the alarm of air conditioning load, refer to Figure 5h , alarm conditions:

[0078] 1. The number of effective high-frequency signal half-waves must be 4 or more within 1 second.

[0079] 2. The difference between the peak values ​​of adjacent waveforms is greater than a certain threshold (e.g. 50AD) three or more times.

[0080] The fifth alarm: For example, an alarm for a vacuum cleaner load, refer to Figure 5i , alarm conditions:

[0081] The number of low-frequency half-waves with valid high-frequency signals on both sides is ≥ the alarm threshold (eg ALARM5=9).

[0082] The sixth alarm: For example, for another type of vacuum cleaner load, the alarm condition is:

[0083] 1. The number of low-frequency half-waves with effective high-frequency signals on both sides is ≥ the alarm threshold (e.g. ALARM6 = 7), refer to Figure 5i ,

[0084] 2. The second alarm waveform + the number of half-waves with effective high-frequency signals on both sides of the half-wave > the alarm threshold (eg ALARM6' = 10).

[0085] The seventh alarm: For example, for capacitor filter type, the alarm condition is:

[0086] 1. The zero point disappearance duration is in the range of [1.18ms, 3.92ms],

[0087] 2. The slope of the zero point vanishing position satisfies: the slopes of more than 3 points are less than half of the average value of the slopes of the zero point vanishing position.

[0088] The above embodiments introduce signal waveforms and alarm conditions under different alarm situations. It can be seen that the alarm conditions and signal waveforms are different for different situations. In practical applications, mastering the alarm conditions and signal waveforms under different situations is helpful to judge faults and achieve early warning, thereby ensuring line safety.

[0089] The present invention also relates to an arc fault detector 200, which is described in detail below.

[0090] Figure 3 FIG. 2 shows a schematic diagram of an arc fault detector 200 according to an embodiment of the present invention. Figure 3As shown, the arc fault detector 200 includes a collection unit 210, a storage unit 220 and a processing unit 230. The collection unit 210 is configured to collect arc signals in the circuit to be tested within a preset period; the storage unit 220 is electrically connected to the collection unit 210 and configured to store the arc signals collected by the collection unit 210; the processing unit 230 is electrically connected to the collection unit 210 and the storage unit 220 respectively, and configured to execute the arc fault detection method 10 as described above.

[0091] Figure 6 A schematic diagram of a fault detector according to a preferred embodiment of the present invention is shown. Figure 6 Provide explanation.

[0092] According to a preferred embodiment of the present invention, the acquisition unit 210 may adopt an arc signal sensor.

[0093] According to a preferred embodiment of the present invention, the fault detector supports remote control and loop two-bus communication. The remote controller transmits communication data to the fault detector via two-bus communication using high / medium or high / medium / low levels, and the fault detector feeds back information to the remote controller by consuming loop current through a controlled current source at a specific medium level, wherein the high level can be defined as a value between 13 and 32V, the medium level can be defined as a value between 5 and 12V, and the low level can be defined as a value less than 3V. It should be understood that the level values ​​in this embodiment are limited to examples and do not constitute a limitation of the present invention.

[0094] According to a preferred embodiment of the present invention, the fault arc detector of the present invention adopts dual processing units, and the two are isolated from each other for communication, which can effectively improve the processing capacity and reduce interference. It should be noted that the specific method of isolating the communication is not limited in the present invention, and it is optional, for example, to be realized by a communication IO isolation circuit. The processing unit can be a central processing unit (CPU), or a microcontroller unit (MCU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The present invention does not limit it, depending on the specific circumstances. In some preferred embodiments, the dual processing units used in the fault arc detector of the present invention can both be microcontroller units (MCU). Compared with other processing units, the use of microcontroller units MCU is cost-effective. The following is an example of using microcontroller units MCU in the processing unit 230.

[0095] The main problem faced by the two-bus communication circuit in the industrial power system is that in the industrial power system, more and more power conversion equipment uses voltage-current converters such as IGBT. The switching characteristics and switching losses of IGBT determine that the switching frequency of IGBT is mostly concentrated between 5kHz and 100kHz. When the IGBT switches, interference signals of the above frequency and its multiples are injected into the power line. The present invention achieves the technical effect of anti-interference by coupling the fault arc detector to the two-bus communication line and setting a filtering unit therein.

[0096] According to a preferred embodiment of the present invention, Figure 6 As shown, the filtering unit can be a common-mode inductor added to the two-bus communication line and the AC mains line, thereby alleviating the problems of two-bus communication anomalies (such as interference) to a certain extent. It should be understood that since the electrical signal strength in the AC mains line is greater than the electrical signal strength in the two-bus communication line, the common-mode inductor in the AC mains line is greater than the common-mode inductor in the two-bus communication line. According to a preferred embodiment of the present invention, the common-mode inductor in the AC mains line can be 22mH, and the common-mode inductor in the two-bus communication line can be several hundred (for example, 100 or 200) uH. It should be understood that in actual operation, the specific size of the common-mode inductor can be appropriately adjusted according to actual conditions.

[0097] In a narrow sense, arc fault detectors are Figure 6 As shown in the upper part, the arc algorithm MCU is the core component of the functional unit capable of analyzing arc faults in the power grid. The generalized arc fault detector (i.e., the arc fault detector of the present invention) not only has the function of analyzing arc faults in the power grid, but also can transmit arc faults to the host computer by means of peripheral communication, and can further improve the detection performance of the arc fault detector itself by means of the powerful analysis function of the host computer. There is a master-slave relationship between the arc algorithm MCU and the two-bus communication MCU, and the master-slave relationship can be defined by itself, that is, the two-bus communication MCU can be the host and the arc algorithm MCU can be the slave, or vice versa. The main function of the two-bus communication MCU is to assist the arc algorithm MCU to better complete arc detection and the transmission of arc information.

[0098] Continue to refer Figure 6 A low-pass filter and a high-pass filter are also provided at the input end of the arc algorithm MCU. The function of the low-pass filter and the high-pass filter is to separate the arc signal in the circuit to be tested, so as to reduce the interference between the low-frequency arc signal and the high-frequency arc signal, which is beneficial to improve the accuracy of the detection result. In some preferred embodiments, the cut-off frequency of the low-pass filter and the high-pass filter is 100kHz. It should be understood that this embodiment is only used for illustration and does not constitute a limitation of the present invention. The cut-off frequency can be appropriately adjusted according to actual conditions.

[0099] According to another preferred embodiment of the present invention, Figure 6 As shown, the filter unit can also be a filter added to the L+ line (refer to the part circled by the dotted line). Compared with using a common mode inductor as the filter unit, the anti-interference effect will be further improved and is not limited by the size of the fault detector. According to a preferred embodiment of the present invention, the filter can be an RC low-pass filter, and other filter types are also within the scope of consideration. The following takes the RC filter as an example for explanation.

[0100] Traditional RC filters cannot be used for L+ loop waveform filtering because the second bus input is connected to the L+ line through a rectifier bridge or a diode. When an interference signal enters through the second bus, the traditional RC filter, for example, only Figure 6R2 and C1 in the circuit are an incomplete filter for the interference signal entering through the two-bus circuit structure, that is, because the rectifier bridge or diode blocks the discharge of the C1 capacitor, when the high, medium and low level of the loop waveform coupled with the interference signal changes, the rising edge speed of the capacitor C1 is significantly higher than the falling edge speed, which will seriously affect the loop communication and cause the interference signal to accumulate on the capacitor C1. In this regard, the solution proposed by the present invention is to use a filter solution with large resistance, small capacitance and matching capacitor discharge resistance, and use a large resistance to reduce the load of the two-bus communication loop and improve the load carrying capacity of the loop. Specifically, it is known that the cutoff frequency of the RC filter is fn=1 / (2π*R*C). If the cutoff frequency of the filter is set to 10kHz (the cutoff frequency is set based on not affecting the loop communication and being able to filter out most of the interference signals coupled by the power equipment), then R2=1MΩ and C1=16pF can be set. In this way, the RC filter cutoff frequency is about 10kHz. The RC charging time constant of the filter is calculated to be τ1=R2*C1. In order to turn the incomplete filter for the two-bus communication into a complete filter, it is only necessary to match the discharge time constant of the filter with the charging time constant.

[0101] To match the charging time with the discharging time, the following can be added: Figure 6 The capacitor discharge resistors R3 and R1 shown in the figure, where R1 is optional, acts as a load of the level in the loop in some detectors to keep the communication waveform from oscillating due to light load, and R3 can also be equivalently placed inside the two-bus communication MCU. Figure 6 As shown, when R1 does not exist in the circuit, and the rectifier bridge or diode reverse impedance and the two-bus communication MCU impedance are approximated to infinity, R3=R2 can achieve the matching of the RC charging time constant and the RC discharging time constant. At this time, the discharge time constant τ2=R3*C1 of the RC filter. Since R2=R3, τ1=τ2. When R1 exists in the circuit, it is only necessary to make (R1+R2) / / R3=R2, and the charging time constant and the discharging time constant of the incomplete filter can also be matched. It should be noted that the RC low-pass filter mentioned in this embodiment is only a special case. For the selection of filter parameters, the present invention is not limited to the case where the charging time constant and the discharging time constant are completely equal. As long as it does not affect the communication and can achieve the expected filtering effect, the matching charging time constant and the discharging time constant can differ by several times, dozens of times or even hundreds of times, depending on the specific situation.

[0102] In addition, for the incomplete filter of the communication signal under the two-bus loop communication mode, a modified filter implemented in a manner that matches the filter charging time constant and the discharge time constant, and a circuit unit that integrates the modified filter into the inside of the MCU chip using the principle of the modified filter, are all within the protection scope of the present invention.

[0103] in addition, Figure 6 The resistors R2, R3, capacitor C1, etc. shown in the figure can be integrated inside the two-bus communication MCU. Figure 6 The controlled current source shown can also be integrated inside the two-bus communication MCU. Figure 6 In the "LDO or MCU with internal LDO" module shown, if the MCU has an internal LDO, the V+ circuit can be directly connected to the two-bus communication MCU, which is within the protection scope of the present invention.

[0104] The above embodiments introduce the specific situation that the filtering unit adopts the filter. In other preferred embodiments, the filtering unit may also adopt the RC filter and the common mode inductor at the same time, which will further enhance the anti-interference capability of the fault detector.

[0105] Continue to refer Figure 6 According to a preferred embodiment of the present invention, the arc fault detector further includes a communication interface and / or a wireless communication module (not shown in the figure). The communication interface may be, for example, a USB interface, an RS485 interface, etc., and the wireless communication interface may be, for example, a WiFi module, a Bluetooth module, an NFC module, a ZigBee module, a 4g or 5g module, etc., which are not limited in the present invention and can be selected according to actual needs.

[0106] In some preferred embodiments, the arc fault detector also includes an expansion interface that can be connected to external devices such as mobile phones, tablets, wearable devices, etc., so as to monitor the detection results of the fault detector more timely. It should be understood that through the communication interface and / or wireless communication module and / or expansion interface, the detection results of the arc fault detector can be transmitted to the user more quickly, so that early warning can be achieved more timely, so that the user can be notified more timely to inspect the line, thereby achieving preventive protection against electrical fires.

[0107] In some preferred embodiments, the arc signal in the circuit to be tested can be collected by the fault detector, stored in a built-in storage device, and the collected arc signal can be processed and analyzed by the built-in processing unit to determine whether there is a fault arc. In other preferred embodiments, the arc signal can also be collected by the fault detector, and transmitted to the host computer via the fire second bus communication and / or communication interface and / or wireless communication module for storage, analysis, processing, etc. In other preferred embodiments, the arc signal collected by the fault detector can also be directly stored in an external storage device, and then uploaded to the host computer through a serial port or other communication method for subsequent analysis and processing, all of which are within the scope of protection of the present invention.

[0108] In some preferred embodiments, the fault arc information data stored in the storage device or transmitted to the host computer by the communication interface and / or the wireless communication module can be used for secondary analysis of the field arc data and self-learning adaptive algorithm adjustment.

[0109] In some preferred embodiments, the adaptive algorithm adjustment parameters based on the application site status fed back by the host computer or through media such as a USB flash drive can be configured into the fault arc detector via fire bus communication or a communication interface (such as an RS485 interface) or wireless communication.

[0110] The present invention further provides a computer-readable storage medium, comprising computer-executable instructions stored thereon, wherein the executable instructions implement the control method 10 as described above when executed by a processor.

[0111] In this article, computer-readable storage medium can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it. In some preferred embodiments, computer-readable storage medium can adopt any combination of one or more computer-readable media. The computer-readable storage medium can be, for example, but not limited to, the form or device of electricity, magnetism, light, or semiconductor, and more specific examples (non-exhaustive list) include: electrical connection with one or more wires, portable computer hard disk, hard disk, random access memory (RAM), non-volatile random access memory (NVRAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination of the above. In addition, the storage medium can be a separate device, or it can be built into the processing unit, and the present invention does not limit this.

[0112] In summary, the arc fault detection method and arc fault detector of the present invention are introduced in detail. The technical solution of the present invention can realize high-speed sampling, data buffering and data storage processing of arc signals. It can realize real-time sampling of arc data and uninterrupted storage of pipelines to ensure that all information when the arc occurs can be accurately recorded, and key arc signals (such as arc faults) can be uploaded to the host computer or remote monitoring system in real time. The arc fault detector adopts loop two-bus communication, dual processing unit architecture, and is compatible with the two-bus communication of fire protection electrical fire detectors. At the same time, considering the electromagnetic interference problem of arc faults applied to industrial occasions, special filtering is performed on the two-bus communication. Based on the characteristics of the two-bus communication frequency and electromagnetic interference in industrial occasions, a feasible filter parameter range is given, and RS485 communication mode and extended wireless function are also provided. Compared with the prior art, the arc fault is detected based on the relationship between the number of arc half-waves based on the industrial frequency and the size of the threshold, so as to achieve early warning, timely notify the user to repair the line, take into account performance and cost, and can be applied on site, so as to achieve preventive protection against electrical fires.

[0113] It should be noted that the fault detector involved in the technical solution of the present invention complies with the national standard GB14287.4-2014 and can be applied to nursing homes, schools, commercial buildings, hotels, factories, warehouses, libraries, offices, family homes, and entertainment venues.

[0114] It should be noted that this specification provides method operation steps as described in the embodiments or schematic diagrams, but more or fewer operation steps may be included based on conventional or non-creative labor. The order of steps listed in the embodiments is only one way of executing the order of many steps and does not represent the only execution order. When the actual system or device product is executed, it can be executed in the order or in parallel according to the method shown in the embodiments or flowcharts.

[0115] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An arc fault detector, comprising: A collection unit is configured to collect arc signals in the circuit to be tested within a preset period; A storage unit, electrically connected to the acquisition unit, configured to store the arc signal acquired by the acquisition unit; and a processing unit, electrically connected to the acquisition unit and the storage unit, respectively, and configured to determine the number of arc half-waves based on the power frequency in the arc signal; and configured to determine whether the arc signal is a fault arc signal according to the relationship between the number of the arc half-waves and a threshold value; The arc fault detector communicates with the remote controller through two buses; the two buses are connected to the two bus L+ line through a rectifier bridge or a diode; the processing unit includes a two bus communication MCU and an arc algorithm MCU, wherein the two bus communication MCU is connected to the two bus L+ line and the arc algorithm MCU, and the arc algorithm MCU is connected to the acquisition unit and the storage unit; the arc fault detector also includes a filtering unit, the filtering unit includes a filter, the filter includes a resistor R2, a capacitor C1 and a resistor R3, one end of the resistor R2 is connected to the two bus L+ line, and the other end is connected to the two bus communication MCU, and one end of the capacitor C1 and the resistor R3, and the other end of the capacitor C1 and the resistor R3 is grounded; the capacitor C1 and the resistor R3 are connected in parallel; the charging time constant and the discharging time constant of the capacitor C1 match. 2 . The arc fault detector according to claim 1 , wherein the filtering unit further comprises a common mode inductor, the common mode inductor is arranged in the two buses and connected to the rectifier bridge. 3 . The arc fault detector according to claim 1 , wherein the arc fault detector further comprises a communication interface and / or a wireless communication module.

4. A fault arc detection method, comprising: S11: collecting arc signals in the circuit to be tested within a preset period; S12: Determine the number of arc half waves based on the power frequency in the arc signal; and S13: determining whether the arc signal is a fault arc signal according to the relationship between the number of arc half-waves and a threshold value, The arc fault detection method is performed by the arc fault detector according to any one of claims 1 to 3.

5. The arc fault detection method according to claim 4, wherein the step S11 comprises the following sub-steps: S111: Turn on the arc signal acquisition switch; S112: Clearing the arc signal in the storage device; S113: collecting arc signals in the circuit to be tested within a preset period, and storing the arc signals in the storage device; and S114: After the preset conditions are met, stop collecting arc signals. 6 . The arc fault detection method according to claim 5 , wherein the preset condition comprises one or more of the following: the arc signal disappears, the storage device is full, and the switch is closed.

7. The fault arc detection method according to claim 4, wherein the arc signal comprises a low-frequency arc signal and a high-frequency arc signal, wherein the low-frequency arc signal comprises an arc signal with a cut-off frequency below 100 kHz, and the high-frequency arc signal comprises an arc signal with a cut-off frequency above 100 kHz.

8. The arc fault detection method according to claim 4, wherein the step S13 comprises: When the number of the arc half-waves is greater than or equal to the threshold, it is determined that the arc signal is a fault arc signal.

9. The arc fault detection method according to claim 4, wherein the step S13 further comprises: When the number of the arc half-waves is less than the threshold, it is determined that the arc signal is not a fault arc signal. 10 . The arc fault detection method according to claim 4 , further comprising step S14 : when it is determined that the arc signal is an arc fault signal, outputting an alarm prompt.

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