Electrical equipment and arc detection method and device thereof

Abstract

The embodiment of the present application provides an electric device and an arc detection method and device thereof, the method comprising: sampling a current signal of a resistive load to obtain a sampling signal; amplifying the sampling signal to a range in which an arc detection device can distinguish between an arc critical point voltage and a reference voltage; and determining whether an arc exists by comparing a processed value of the amplified sampling signal with a preset value. The embodiment of the present application can improve the accuracy of arc detection, and is simple to implement and low in cost.

Description

Technical Field

[0001] The present application relates to the technical field of arc detection, and in particular to an electrical device and an arc detection method and device thereof. Background Art

[0002] Arcing refers to the phenomenon that when the voltage exceeds the tolerance of air, the air is ionized and becomes a conductor, generating an arc. The high temperature generated by the arcing may bring many hazards. For example, the arcing may damage the equipment (such as melting or breaking the parts), or even cause a fire. Therefore, arcing detection is of great significance.

[0003] In the current existing technology, arc detection is to convert the time domain detection signal after sampling, amplification, analog-to-digital conversion, etc. into a frequency domain signal or a pulse signal, and then determine whether an arc occurs based on the frequency domain signal or the pulse signal obtained after the conversion. Since part of the real signal will be lost in the process of converting the time domain detection signal into the frequency domain signal or the pulse signal, this affects the accuracy of the existing arc detection scheme. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide an electrical device and an arc detection method and device thereof to improve the accuracy of arc detection.

[0005] To achieve the above objectives, on the one hand, an embodiment of the present application provides an arc detection method, comprising:

[0006] Sampling the current signal of the resistive load to obtain a sampling signal;

[0007] Amplifying the sampling signal to a range where the arc detection device can distinguish between the arc critical point voltage and the reference voltage;

[0008] The presence of arcing is determined by comparing the processed value of the amplified sampling signal with the preset value.

[0009] Preferably, before determining whether arcing exists according to comparing the processed value of the amplified sampled signal with the preset value, the method further includes:

[0010] Performing a DC bias on the amplified sampling signal;

[0011] Correspondingly, the determining whether arcing exists according to comparing the sampled signal processing value after amplification and the preset value includes: determining whether arcing exists according to the sampled signal processing value after DC bias and the preset value including the DC bias amount.

[0012] Preferably, before determining whether arcing exists according to comparing the processed value of the amplified sampled signal with the preset value, the method further includes:

[0013] Performing inversion processing on the negative half-cycle signal of the amplified sampling signal;

[0014] Correspondingly, the determining whether arcing exists according to comparing the processed value of the sampled signal after amplification and the preset value includes: determining whether arcing exists according to the processed value of the sampled signal after inversion processing and the preset value.

[0015] Preferably, the determining whether there is arcing according to comparing the processed value of the amplified sampled signal with the preset value comprises one of the following methods:

[0016] Determine whether there is an arc according to the comparison of the amplified sampling signal and the reference voltage range;

[0017] Determine whether there is arcing according to the comparison slope and the preset slope range, wherein the slope is the slope of the amplified current sampling signal and the slope of the sampling signals several times before the current sampling signal;

[0018] The existence of arcing is determined based on the comparison difference and the preset difference range, wherein the difference is the difference between the amplified current sampling signal and the sampling signals several times before the current sampling signal.

[0019] Preferably, the determining whether arcing exists according to comparing the amplified sampling signal and the reference voltage range comprises:

[0020] When the resistive load is in operation, if N continuously collected voltage sampling values ​​are all within the reference voltage range, it is confirmed that an arc is detected; wherein N is a preset first quantity threshold.

[0021] Preferably, the method further comprises:

[0022] When arcing is detected M times continuously, an arcing alarm is issued and / or the resistive load is disconnected from the power supply; wherein M is a preset second quantity threshold.

[0023] Preferably, the method further comprises:

[0024] It is determined whether the resistive load is in an operating state.

[0025] Preferably, the confirming whether the resistive load is in a running state comprises:

[0026] When R voltage sampling values ​​collected continuously are all greater than a preset voltage threshold, it is confirmed that the resistive load is in an operating state; wherein R is a preset third quantity threshold.

[0027] Preferably, the step of confirming whether the resistive load is in operation further comprises:

[0028] When S continuously collected voltage sampling values ​​are all within the reference voltage range, it is confirmed that the load is in a stopped state, and the counts of M and N therein are cleared; wherein S is a preset fourth quantity threshold.

[0029] Preferably, the reference voltage range is obtained in advance according to the following method:

[0030] When the resistive load is not started, the current signal of the resistive load is sampled to obtain a sampling signal, and the reference voltage range is determined according to the sampling signal.

[0031] Preferably, the voltage value of the arc critical point voltage is obtained in advance according to the following method:

[0032] The minimum duration T of zero load current during the arcing process to be identified is predetermined;

[0033] According to the formula Determine the phase of the voltage at the critical point of arcing;

[0034] According to the formula U A =U0sinθ determines the voltage value of the arc critical point voltage;

[0035] Among them, θ is the phase angle of the arc critical point voltage, T0 is the AC voltage period, U A is the voltage value of the arc critical point voltage, and U0 is the peak value of the AC voltage.

[0036] Preferably, the step of sampling the current signal of the resistive load to obtain a sampling signal; and amplifying the sampling signal to a range in which the arc detection device can distinguish between an arc critical voltage and a reference voltage includes:

[0037] Obtaining the current signal of the resistive load and converting it into a corresponding voltage signal, and amplifying the voltage signal to a range in which the arc detection device can distinguish between the arc critical voltage and the reference voltage; or,

[0038] The current signal of the resistive load is obtained, the current signal is amplified and the amplified current signal is converted into a corresponding voltage signal, so that the arc detection device can distinguish between the arc critical point voltage and the reference voltage range.

[0039] On the other hand, an embodiment of the present application further provides an arc detection device, comprising:

[0040] A sampling and amplification module and a signal processing module connected to the signal output end of the sampling and amplification module; wherein,

[0041] A sampling and amplification module, used for sampling the current signal of the resistive load to obtain a sampling signal, and amplifying the sampling signal to a range in which the signal processing module can distinguish between the arc critical point voltage and the reference voltage;

[0042] The signal processing module is used to determine whether arcing exists based on the comparison and amplification of the sampled signal processing value and the preset value.

[0043] Preferably, the arc detection device further comprises:

[0044] A DC bias module, used for performing a DC bias on the sampling signal amplified by the sampling and amplifying module; the signal input end of the DC bias module is connected to the signal output end of the sampling and amplifying module, and the signal output end of the DC bias module is connected to the signal input end of the signal processing module;

[0045] Correspondingly, the signal processing module is used to determine whether arcing exists according to the sampled signal processing value after DC bias and the preset value including the DC bias amount.

[0046] Preferably, the arc detection device further comprises:

[0047] A full-wave rectifier module, used for inverting the negative half-cycle signal of the amplified sampling signal; the signal input end of the full-wave rectifier module is connected to the signal output end of the sampling and amplification module, and the signal output end of the full-wave rectifier module is connected to the signal input end of the signal processing module;

[0048] Correspondingly, the signal processing module is used to determine whether arcing exists according to the sampled signal processing value after inversion processing and the preset value.

[0049] Preferably, the sampling and amplification module includes a signal sampling module and an amplification module, and the signal output end of the signal sampling module is connected to the signal input end of the amplification module; wherein the signal sampling module is used to sample the current signal of the resistive load to obtain a sampling signal; and the amplification module is used to amplify the sampling signal to a range where the signal processing module can distinguish between the arc critical point voltage and the reference voltage.

[0050] Preferably, the signal processing module includes an analog-to-digital conversion module and a processor, the signal input end of the analog-to-digital conversion module is connected to the signal output end of the amplification module, and the signal output end of the analog-to-digital conversion module is connected to the signal input end of the processor; accordingly, the sampling and amplification module is used to amplify the sampling signal to a range where the analog-to-digital conversion module can distinguish between the arc critical point voltage and the reference voltage.

[0051] Preferably, the signal processing module determines whether arcing exists by comparing the amplified sampled signal processing value and the preset value, including one of the following methods:

[0052] Determine whether there is an arc according to the comparison of the amplified sampling signal and the reference voltage range;

[0053] Determine whether there is arcing according to the comparison slope and the preset slope range, wherein the slope is the slope of the amplified current sampling signal and the slope of the sampling signals several times before the current sampling signal;

[0054] The existence of arcing is determined based on the comparison difference and the preset difference range, wherein the difference is the difference between the amplified current sampling signal and the sampling signals several times before the current sampling signal.

[0055] Preferably, the signal processing module determines whether arcing exists according to comparing the amplified sampling signal with a preset reference voltage range, including:

[0056] When the load is in working state, when N continuously collected voltage sampling values ​​are all within the reference voltage range, it is confirmed that an arc is detected; wherein N is a preset first quantity threshold.

[0057] Preferably, the arc detection device also includes: an alarm and / or load disconnection device, which is used to issue an arc alarm and / or disconnect the load from the power supply when the signal processing module detects arcing M times continuously; wherein M is a preset second quantity threshold.

[0058] Preferably, the signal processing module is also used to determine whether the resistive load is in an operating state.

[0059] Preferably, the signal processing module confirms whether the resistive load is in a running state, including:

[0060] When R voltage sampling values ​​continuously collected by the analog-to-digital conversion module are all greater than a preset voltage threshold, the signal processing module confirms that the resistive load is in an operating state; wherein R is a preset third quantity threshold.

[0061] Preferably, the signal processing module confirms whether the resistive load is in a running state, and further includes:

[0062] When the S voltage sampling values ​​continuously collected by the analog-to-digital conversion module are all within the reference voltage range, the signal processing module confirms that the load is in a stopped state and clears the counts of M and N therein; where S is a preset fourth quantity threshold.

[0063] Preferably, the voltage value of the arc critical point voltage is obtained in advance according to the following method:

[0064] The minimum duration T of the load current being zero during the arcing process to be identified is predetermined;

[0065] According to the formula Determine the phase of the voltage at the critical point of arcing;

[0066] According to the formula UA =U0sinθ determines the voltage value of the arc critical point voltage;

[0067] Among them, θ is the phase angle of the arc critical point voltage, T0 is the AC voltage period, U A is the voltage value of the arc critical point voltage, and U0 is the peak value of the AC voltage.

[0068] Preferably, the amplification module and the DC bias module are implemented by an isolation operational amplifier.

[0069] Preferably, the signal sampling module includes a current transformer.

[0070] Preferably, the resistive load comprises an electric heating element.

[0071] On the other hand, an embodiment of the present application further provides an electric device, the electric device comprising:

[0072] Power supply side,

[0073] a resistive load connected to the power supply terminal, and,

[0074] An arc detection device is arranged between the power supply terminal and the resistive load.

[0075] Preferably, the electrical equipment includes an electric water heater, and the resistive load includes an electric heating element of the electric water heater.

[0076] It can be seen from the technical solutions provided by the above embodiments of the present application that after the arc detection solution of the embodiment of the present application samples the current signal of the resistive load to obtain the sampled signal, the sampled signal can be amplified to the extent that the arc detection device can distinguish between the arc critical point voltage and the reference voltage range, so that the arc detection device can directly determine whether there is an arc in the time domain by comparing the amplified sampled signal processing value and the preset value, thereby improving the accuracy and anti-interference ability of arc detection. Moreover, compared with the prior art, the embodiment of the present application also avoids the problem of partial real signal loss caused by converting the time domain signal into a frequency domain signal or a pulse signal, which is conducive to further improving the accuracy of arc detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. In the drawings:

[0078] Figure 1This is a structural block diagram of an electrical device in one embodiment of the present application;

[0079] Figure 2 This is a principle block diagram of an arc detection device in one embodiment of the present application;

[0080] Figure 3 This is a principle block diagram of an arc detection device in another embodiment of the present application;

[0081] Figure 4 This is a circuit schematic diagram of an arc detection device in one embodiment of the present application;

[0082] Figure 5 This is a circuit schematic diagram of an arc detection device in another embodiment of the present application;

[0083] Figure 6 This is a principle block diagram of an arc detection device in another embodiment of the present application;

[0084] Figure 7 This is a circuit schematic diagram of an arc detection device in another embodiment of the present application;

[0085] Figure 8 This is a method flow chart of an arc detection method in one embodiment of the present application;

[0086] Fig. 9 A waveform diagram of a voltage signal and a voltage amplified signal in one embodiment of the present application;

[0087] Fig.10 Schematic diagram of waveforms of a voltage signal, a voltage amplified signal, and a voltage amplified signal after DC bias in one embodiment of the present application;

[0088] Fig.11 This is a waveform diagram of a voltage signal obtained after full-wave rectification in one embodiment of the present application;

[0089] Fig.12 A schematic diagram of voltage changes when arcing occurs in one embodiment of the present application (without DC bias);

[0090] Fig.13 Schematic diagram of voltage variation when arcing occurs in one embodiment of the present application (with DC bias). DETAILED DESCRIPTION

[0091] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0092] Studies have shown that electrical equipment with resistive loads (especially pure resistive loads) is prone to arcing under conditions such as poor contact. Specifically, when there is poor contact or a small circuit-breaking gap at a certain position where the resistive load is connected, a voltage is easily formed between the contacts on both sides, and this voltage follows the change of the sine wave waveform. When the voltage gradually increases and reaches a certain voltage point (i.e., the breakdown voltage point), the air is broken down to ionize the air molecules, thereby forming an arc current (i.e., arcing). The high temperature generated by the arc current can further intensify the ionization effect, thereby forming a path; when the voltage reaches the peak of the sine wave and then slowly decreases, as the voltage decreases, the arc and the path will be disconnected at a certain voltage point (i.e., the disconnection voltage point) and last for a period of time; thereafter, as the voltage increases again, when the voltage reaches the breakdown voltage point again, it will break down the air again to form an arc and a path, and when the voltage decreases from the peak value to the disconnection voltage point again, the arc and the path will be disconnected again and last for a period of time, and this is repeated.

[0093] In order to accurately detect whether there is arcing in the resistive load, the corresponding electrical equipment can be improved in the implementation of the present application. Figure 1 As shown, in some embodiments of the present application, the improved electrical equipment may include: a power supply end, a resistive load connected to the power supply end, and an arc detection device connected between the power supply end and the resistive load. The power supply end can be used as a power supply interface; the arc detection device can be used to detect whether the resistive load has an arc. The electrical equipment may be any resistive load device. For example, in some exemplary embodiments, the electrical equipment may be an electric water heater, etc.; accordingly, when the electrical equipment is an electric water heater, the resistive load may be an electric heating element (such as a heating rod, etc.) of the electric water heater.

[0094] In some embodiments of the present application, the arc detection device described in this embodiment may include a sampling and amplification module and a signal processing module connected to the signal output end of the sampling and amplification module. The sampling and amplification module may be used to sample the current signal of the resistive load to obtain a sampling signal, and amplify the sampling signal to a range where the signal processing module can distinguish between the arc critical point voltage and the reference voltage; the signal processing module may be used to determine whether an arc exists based on the comparison of the amplified sampling signal processing value and the preset value.

[0095] In one embodiment of the present application, Figure 2 As shown, preferably, the sampling and amplification module may include a signal sampling module and an amplification module. Wherein, the signal output end of the signal sampling module is connected to the signal input end of the amplification module; the signal sampling module is used to sample the current signal of the resistive load to obtain a sampling signal; the amplification module is used to amplify the sampling signal to the signal processing module to be able to distinguish between the arc critical point voltage and the reference voltage range. For example, in one embodiment, the signal sampling module can be implemented by a current transformer and a sampling resistor, and the amplification module can be implemented by an amplification circuit or an integrated amplifier (such as an operational amplifier). In another embodiment of the present application, the sampling and amplification module can also be implemented by a current transformer and a sampling resistor with an amplification function. Wherein, the current transformer with an amplification function can be implemented in the form of multiple groups of windings, for example. In this case, the current sensor can be used to obtain the current signal of the resistive load and amplify it, and the sampling resistor can be used to convert the amplified current signal into a corresponding voltage signal, so that the arc detection device can distinguish between the arc critical point voltage and the reference voltage range.

[0096] In some embodiments of the present application, the signal processing module can be implemented in many ways to determine whether there is an arc according to the comparison of the amplified sampling signal processing value and the preset value. Specifically, for example, it can be determined whether there is an arc according to the comparison of the amplified sampling signal and the reference voltage range; it can also be determined whether there is an arc according to the comparison slope and the preset slope range, and the slope is the slope between the amplified current sampling signal and the sampling signals several times before the current sampling signal; it can also be determined whether there is an arc according to the comparison difference and the preset difference range, and the difference is the difference between the amplified current sampling signal and the sampling signals several times before the current sampling signal, and so on. Among them, the processing value can be directly obtained, or the slope calculation, the difference calculation, etc. are performed. Therefore, compared with the prior art, the present application amplifies the sampling signal to the arc detection device can distinguish the arc critical point voltage and the reference voltage range, and has the characteristics of high arc detection accuracy and strong anti-interference ability.

[0097] In an exemplary embodiment, the determination of whether there is an arc based on the comparison of the amplified sampling signal and the reference voltage range may include, for example: when the resistive load is in operation, if the N voltage sampling values ​​collected continuously are all within the reference voltage range, it is confirmed that an arc is detected; wherein N is a preset first quantity threshold, which can be determined according to needs, experiments or experience, preferably, N≥2. It can be seen that in the process of judging suspected arcing and the above-mentioned judgment of arcing, the premise of continuous sampling point judgment is emphasized, so as to avoid misjudgment caused by judgment based on a single sampling point. This judgment based on continuous sampling points can actually be regarded as a judgment of the duration of arcing. For example, for the above-mentioned judgment of suspected arcing, the N voltage sampling values ​​collected continuously by the analog-to-digital conversion module are all within the reference voltage range, which can be considered that the voltage sampling values ​​output by the analog-to-digital conversion module in the continuous sampling period of N Δt are all within the reference voltage range.

[0098] In some embodiments of the present application, the signal processing module may be an analog-to-digital conversion module and a processor. Accordingly, the signal input end of the analog-to-digital conversion module is connected to the signal output end of the amplification module, and the signal output end of the analog-to-digital conversion module is connected to the signal input end of the processor; accordingly, the amplification module is used to amplify the sampling signal to a range where the analog-to-digital conversion module can distinguish between the arc critical point voltage and the reference voltage. In other embodiments of the present application, if the processor itself is integrated with an analog-to-digital conversion function, the signal processing module may also be such a processor integrated with an analog-to-digital conversion function.

[0099] After sampling the current signal of the resistive load to obtain the sampled signal, the arc detection scheme of the embodiment of the present application can amplify the sampled signal to the extent that the arc detection device can distinguish between the arc critical point voltage and the reference voltage range, so that the arc detection device can directly determine whether there is an arc in the time domain based on the comparison of the amplified sampled signal processing value and the preset value, thereby improving the accuracy and anti-interference ability of arc detection. Moreover, compared with the prior art, the embodiment of the present application also avoids the problem of partial loss of real signals caused by converting time domain signals into frequency domain signals or pulse signals, which is conducive to further improving the accuracy of arc detection. In addition, compared with the prior art, the arc detection scheme of the embodiment of the present application eliminates the processing process of converting time domain signals into frequency domain signals or pulse signals, and the scheme is simple and easy to implement.

[0100] In one embodiment of the present application, under normal conditions, when the applied electric field strength is increased to exceed the tolerance range of the air, the air is ionized to become a conductor and the corresponding voltage when the arc is formed can be referred to as the breakdown point voltage. Correspondingly, in the arc state, when the applied electric field strength is weakened to be insufficient to break through the air, the air is terminated from ionization and the arc is disconnected. The voltage corresponding to the disconnection point voltage can be referred to as the disconnection point voltage. Therefore, since the breakdown point voltage and the disconnection point voltage are both the dividing points of the critical state of arcing, they can be collectively referred to as the critical point voltage of arcing.

[0101] In one embodiment of the present application, in general, the voltage signal obtained by the sampling and amplification module is a voltage signal that changes according to a sine wave, which has a peak value and a valley value (for example, the peak value can be 250mV, and the valley value can be -250mV). In theory, the reference voltage range corresponds to the voltage point corresponding to when the load current is zero, but because the signal voltage value of the critical point voltage is small, and because of signal jitter and external interference, the critical point voltage cannot be distinguished from the interference signal near the zero point, so signal amplification is required; in order to improve the system's own fault tolerance and facilitate the detection of arcing, the present embodiment needs to set the allowable deviation of the reference voltage, that is, the reference voltage range. The setting standard of the reference voltage range is to be able to cover the interference signal near the zero point after amplification, and to be able to distinguish the arcing critical point voltage outside the reference voltage range.

[0102] In one embodiment of the present application, after the analog-to-digital conversion module is specified (for example, for a processor with a built-in analog-to-digital conversion module, when the processor is selected, the analog-to-digital conversion module is also determined), the resolution of the analog-to-digital conversion module is determined accordingly. In this case, in order to enable the analog-to-digital conversion module to distinguish between the arc critical point voltage and the reference voltage range, the sampling signal needs to be fully amplified. In some cases, it is even allowed to amplify the signal to a distorted state, or, if necessary, the signal portion that exceeds the allowable input voltage value of the analog-to-digital conversion module is clamped.

[0103] The above-mentioned ability to distinguish can be understood as follows: the resolution ability of the analog-to-digital conversion module is limited. If the amplification factor is not enough, the analog-to-digital conversion module may mistakenly believe that the collected arc critical point voltage is the sampling signal voltage value corresponding to the load current being zero, and thus cannot be distinguished from the reference voltage range; in this case, for example Fig.12As shown, when the voltage changes from the disconnection point voltage to the zero point voltage, and then from the zero point voltage to the breakdown point voltage, regardless of whether arcing occurs, the analog-to-digital conversion module will identify the voltage value in this stage as the sampling signal voltage value corresponding to the load current being zero (unless the voltage value is greater than the arcing critical point voltage). In this way, effective arcing detection and judgment cannot be performed subsequently. Therefore, it is necessary to amplify the voltage signal at least to the range where the analog-to-digital conversion module can distinguish between the arcing critical point voltage and the reference voltage.

[0104] Considering uncertain factors such as actual interference and voltage fluctuation, the reference voltage range (0±Δu) can be set in advance according to actual test data and calculation results to determine whether arcing occurs. Among them, ±Δu is the allowable deviation (if the DC bias V is added after amplification, the reference voltage range can be V±Δu).

[0105] like Fig. 9 As shown, ① is the voltage waveform before amplification, ② is the waveform after amplification, and the points corresponding to t1 and t2 are arc critical points. Assume that the arc duration to be identified is Δt=t2-t1, Δt≥T, and T is the minimum duration of zero load current during the arc process to be identified. In an exemplary embodiment, the value of T can be set according to the US UL standard; in other embodiments, the value of T can be set according to actual conditions, so this application does not limit this.

[0106] Ideally, the two arc critical points are symmetrical with respect to point 0. Based on T, the arc critical point voltage and the corresponding phase θ that the analog-to-digital conversion module can identify can be theoretically calculated. Specifically:

[0107] Assuming the power grid AC cycle is T0, according to the formula The phase angle corresponding to the minimum arcing critical point voltage can be determined as Therefore, the arc critical point voltage that needs to be identified and distinguished is U A =U0sinθ; where U0 is the peak value of the voltage waveform before amplification.

[0108] Obviously, if U A ≤Δu, the signal needs to be amplified. In order to facilitate identification and distinction, the amplification factor needs to satisfy N≥Δu / U A , that is, it is considered that under this magnification factor N, the analog-to-digital conversion module can distinguish between the arc critical point voltage and the zero-crossing point voltage.

[0109] If the amplification factor exceeds the sampling level extreme value of the analog-to-digital conversion module (e.g., the sampling level range is 0-3.3V, the corresponding maximum value is 3.3V, and the minimum value is 0V), it is necessary to additionally clamp the part exceeding the sampling level extreme value. The amplified arc critical point voltage must at least meet U b =N*U A Under the premise of appropriate magnification, for example, the magnification factor can be set as Δu / U according to experience. A Preferably, if the amplitude of the amplified signal exceeds the sampling level limit, clamping processing is required.

[0110] In an exemplary embodiment, according to the relevant US UL safety standard, the constant T can be set to 0.00042s, and the mains frequency is 50Hz, then its period T0 = 0.02s, so that Correspondingly, U A =U0sinθ=0.555*sin0.021π=0.0366V.

[0111] Obviously, 0.036<0.15 (that is, U min <Δu)), so it needs to be magnified. In the case of, although the larger N is, the smaller the test error is, considering the asymmetry and interference of two adjacent critical points in actual situations, an amplifier module with amplification capacity of more than 5 times can be selected to leave enough margin for the test. There are many options for isolation op amps, and their amplification factors are also varied. Generally, isolation op amps have their own output active bias voltage. Assuming that the allowable deviation Δu is 0.1V, the reference voltage range can be set to 1.65±0.1V when a DC bias of 1.65 is used.

[0112] It should be noted that the above-mentioned method of setting the reference voltage range is only an example and should not be regarded as a limitation of the present application. In other embodiments of the present application, the reference voltage range can also be set from the perspective of power or the like.

[0113] refer to Figure 3 As shown, in another embodiment of the present application, the arc detection device may further include a DC bias module, which may be used to perform DC bias on the sampling signal amplified by the sampling and amplifying module; the signal input end of the DC bias module is connected to the signal output end of the sampling and amplifying module, and the signal output end of the DC bias module is connected to the signal input end of the signal processing module; accordingly, the signal processing module may determine whether an arc exists based on the sampled signal processing value after DC bias and a preset value including a DC bias amount. Of course, in this case, the preset reference voltage range should also be the reference voltage range obtained when DC bias is performed. In this way, the reference voltage range is raised according to the DC bias, for example Fig.13 As shown, it can be ensured that the entire arc waveform is within the detectable range of the processor, so that the arc in the negative half cycle can also be detected. Fig.13 Middle,U d , U0 and U j They represent the disconnection point voltage, the zero-crossing point voltage and the breakdown point voltage respectively, Δt represents the sampling period of the analog-to-digital conversion module, and T=t2-t1 is the time period that needs to be judged whether there is arcing.

[0114] refer to Figure 4 As shown, in one embodiment of the present application, the signal sampling module may include a current transformer L2, a resistor R1 and a resistor R9. Such a signal sampling module has a simple and reliable structure and low implementation cost. Among them, the current transformer L2 can be used to collect the current signal of the resistive load, and the resistor R1 can be used to convert the current signal collected by the current transformer L2 into a corresponding voltage signal. Among them, the two ends of the primary side of the current transformer L2 (i.e., end 3 and end 4) are used as input ends for connecting the loop of the resistive load; the two ends of the secondary side of the current transformer L2 (i.e., end 1 and end 2) are used as output ends; the resistor R1 is connected across the two ends of the secondary side of the current transformer L2, one end of the resistor R9 is connected to the two ends of the secondary side of the current transformer L2, and the other end of the resistor R9 is connected to the amplification module to provide the converted voltage signal to the amplification module for processing. Of course, in other embodiments of the present application, the signal sampling module can also be implemented in other ways, for example, the current transformer therein can be replaced by a current sensor such as a Hall sensor.

[0115] Combination Figure 4 As shown, in an exemplary embodiment of the present application, the amplification module may be, for example, an operational amplifier. Figure 4 In the embodiment, the in-phase input terminal of the operational amplifier serving as the amplification module is connected to the resistor R9 of the signal sampling module to receive the voltage signal provided by the signal sampling module; the output terminal of the operational amplifier is connected to the DC bias module according to the capacitor C3 to provide the amplified voltage signal to the DC bias module for processing.

[0116] Combination Figure 4 As shown, in an exemplary embodiment of the present application, the DC bias module may include a resistor R25, one end of the resistor R25 is used as an input end, and is respectively connected to a DC bias voltage ( Figure 4 The UP end shown in the figure) and the output end of the amplifier module are used to perform DC bias processing on the amplified voltage signal output by the amplifier module; the other end of the resistor R25 is connected to the processor as an output end to provide the DC biased voltage signal to the analog-to-digital conversion module of the processor for processing.

[0117] In another exemplary embodiment of the present application, the amplification module and the DC bias module may also be directly implemented according to an isolated operational amplifier, for example Figure 5 As shown, the VINN pin is the input terminal of the isolation operational amplifier U5; the VOP pin is the output terminal of the isolation operational amplifier U5, and the VOP pin can be connected to the processor through the resistor R10. The use of this isolation operational amplifier not only simplifies the circuit structure, but also eliminates the measurement error caused by the ground loop, which is conducive to further improving the accuracy of arc detection.

[0118] In one embodiment of the present application, the processor includes but is not limited to a microcontroller unit (MCU) (such as a single-chip microcomputer, etc.), a digital signal processor (DSP), a programmable logic device (PLD), etc. Figure 4 As shown, in an exemplary embodiment, the processor may include an MCU of model PIC30F210, and the second pin of the MCU of model PIC30F210 is used as a signal input terminal and connected to the output terminal of the DC bias module. Figure 5 As shown, in another exemplary embodiment, when the amplification module and the DC bias module are implemented according to an isolation operational amplifier, the second pin of the MCU of model PIC30F210 can be connected to the output end of the isolation operational amplifier.

[0119] refer to Figure 6 As shown, in another embodiment of the present application, the arc detection device may further include a full-wave rectifier module, which may be used to perform inversion processing on the negative half-cycle signal of the amplified sampling signal; the signal input end of the full-wave rectifier module is connected to the signal output end of the sampling and amplifying module, and the signal output end of the full-wave rectifier module is connected to the signal input end of the signal processing module; accordingly, the signal processing module may determine whether an arc exists based on the sampling signal processing value after the inversion processing and the preset value.

[0120] Similar to the above-mentioned DC bias module, the purpose of adding a full-wave rectifier module is to flip the negative half-cycle signal of the voltage signal amplified by the amplifier module to the positive half-cycle (for example Fig.11 As shown), it can be ensured that the waveform of the entire arc is within the detectable range of the processor, so that the arc in the negative half cycle can also be detected.

[0121] Combination Figure 7As shown, in an exemplary embodiment, the full-wave rectifier module can be, for example, a single-phase full-wave rectifier module, which can include a diode D1, a diode D2 and a resistor R25, wherein the diode D1 and the diode D2 are connected in series with the resistor R25 after being reverse-parallel connected; one end of the resistor R25 is connected to the output end of the amplification module to receive the amplified voltage signal output by the amplification module; the other end of the resistor R25 is connected to the input end of the processor to provide the flipped voltage signal to the analog-to-digital conversion module of the processor for processing.

[0122] It should be noted that, in some cases, some processors have an internal integrated analog-to-digital conversion module, so there is no need to consider the issue of setting up an analog-to-digital conversion module. In other cases, when the processor does not have an internal integrated analog-to-digital conversion module, an independent analog-to-digital conversion module can be added, and the analog-to-digital conversion module can convert the voltage analog signal provided by the amplification module, the DC bias module or the full-wave rectification module into a corresponding voltage digital signal, and provide it to the processor for processing.

[0123] In one embodiment of the present application, the arc detection device may further include an alarm and / or load disconnection device; which may be used to issue an arc alarm and / or disconnect the load from the power supply when the signal processing module detects arcing M times in succession, so as to avoid or reduce the damage of arcing to electrical equipment; wherein M is a preset second quantity threshold. The arc alarm may be a text alarm, a voice alarm, and / or an optical signal alarm, etc. The load disconnection device may be, for example, a controllable switch (such as a resistor) connected in series to the circuit of the resistive load. Figure 2 , Figure 3 or Figure 6 shown) and so on.

[0124] It is necessary to point out that the above-mentioned arc detection method is more practical when the resistive load is in the running state. Therefore, in one embodiment of the present application, before obtaining the current signal of the resistive load, the signal processing module can also determine whether the resistive load is in the running state. For example, when the R voltage sampling values ​​continuously collected by the analog-to-digital conversion module are all greater than the preset voltage threshold, it can be confirmed that the resistive load is in the running state; wherein R is the preset third quantity threshold; and when the S voltage sampling values ​​continuously collected by the analog-to-digital conversion module are all within the reference voltage range, it can also be confirmed that the load is in the stopped state, and the counts of M and N therein are cleared to prepare for the next count; wherein S is the preset fourth quantity threshold.

[0125] It should be noted that when the above arc detection device adopts a DC bias module, accordingly, before determining whether an arc exists by comparing the amplified voltage signal with the preset reference voltage range, it may also include: a step of DC biasing the amplified voltage signal. In an exemplary embodiment, the voltage signal obtained after the DC bias may be as follows: Fig.10 Correspondingly, the determination of whether arcing exists based on the comparison of the amplified voltage signal and the preset reference voltage range may be based on the DC biased voltage signal and the preset reference voltage range.

[0126] For the convenience of description, the above device is described in various units according to their functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0127] refer to Figure 8 As shown, in one embodiment of the present application, the arc detection method of the arc detection device may include the following steps:

[0128] S801, obtain the current signal of the resistive load and sample it to obtain a sampling signal. In an exemplary embodiment, the voltage signal obtained after conversion can be as follows: Fig.10 As shown by the solid line in .

[0129] S802, amplify the sampling signal to a range where the arc detection device can distinguish between the arc critical point voltage and the reference voltage. In an exemplary embodiment, the voltage signal obtained after amplification can be as follows: Fig.10 As shown by the dotted line in .

[0130] S803: Determine whether there is arcing by comparing the processed value of the amplified sampled signal with the preset value. If there is arcing, execute step S804; otherwise, jump to execute step S801.

[0131] S804. When arcing is detected M times continuously, an arcing alarm is issued and / or the load is disconnected from the power supply; wherein N wherein M is a preset second quantity threshold; wherein N wherein M is a preset second quantity threshold, which can be specifically determined according to standards, experiments or experience.

[0132] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the method embodiment, since it is basically similar to the device embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the device embodiment.

[0133] It should also be noted that the terms "comprises", "includes" or any other variants thereof are intended to cover non-exclusive inclusion, so that a method, device or apparatus including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such method, device or apparatus. In the absence of further restrictions, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the method, device or apparatus including the element.

[0134] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. An arc detection method, characterized in that: include: Sampling the current signal of the resistive load to obtain a sampling signal; according to The sampling signal is amplified by an amplification factor of so that the arc detection device can distinguish the arc critical point voltage and the reference voltage range; wherein, is the magnification, is the allowable deviation of the reference voltage, is the voltage value of the critical point voltage of arcing; the critical point voltage of arcing includes the breakdown point voltage and the disconnection point voltage; the breakdown point voltage is the sampling signal voltage corresponding to the arcing when the applied electric field strength is enhanced to exceed the tolerance range of air, so that the air is ionized to become a conductor and the arc is formed; the disconnection point voltage is the sampling signal voltage corresponding to the arcing when the applied electric field strength is weakened to be insufficient to break through the air, so that the air stops ionizing and the arc is disconnected; Determining whether there is arcing according to comparing the processed value of the sampled signal after amplification with the preset value; determining whether there is arcing according to comparing the processed value of the sampled signal after amplification with the preset value includes one of the following methods: Determine whether there is an arc according to the comparison of the amplified sampling signal and the reference voltage range; Determine whether there is arcing according to the comparison slope and the preset slope range, wherein the slope is the slope of the amplified current sampling signal and the slope of the sampling signals several times before the current sampling signal; The existence of arcing is determined based on the comparison difference and the preset difference range, wherein the difference is the difference between the amplified current sampling signal and the sampling signals several times before the current sampling signal.

2. The arc detection method according to claim 1, characterized in that: Before determining whether there is arcing according to the comparison and amplification of the sampled signal processing value and the preset value, the method further includes: Applying a DC bias to the amplified sampling signal; Correspondingly, the determining whether arcing exists according to comparing the sampled signal processing value after amplification and the preset value includes: determining whether arcing exists according to the sampled signal processing value after DC bias and the preset value including the DC bias amount.

3. The arc detection method according to claim 1, characterized in that: Before determining whether there is arcing according to the comparison and amplification of the sampled signal processing value and the preset value, the method further includes: Performing inversion processing on the negative half-cycle signal of the amplified sampling signal; Correspondingly, the determining whether arcing exists according to comparing the processed value of the sampled signal after amplification and the preset value includes: determining whether arcing exists according to the processed value of the sampled signal after inversion processing and the preset value.

4. The arc detection method according to claim 1, characterized in that: The method of determining whether there is an arc according to comparing the amplified sampling signal and the reference voltage range includes: When the resistive load is in operation, if N continuously collected voltage sampling values ​​are all within the reference voltage range, it is confirmed that an arc is detected; wherein N is a preset first quantity threshold.

5. The arc detection method according to claim 4, characterized in that: Also includes: When arcing is detected M times continuously, an arcing alarm is issued and / or the resistive load is disconnected from the power supply; Wherein M is a preset second quantity threshold.

6. The arc detection method according to claim 4, characterized in that: The method further comprises: It is determined whether the resistive load is in an operating state.

7. The arc detection method according to claim 6, characterized in that: The step of confirming whether the resistive load is in a running state includes: When R voltage sampling values ​​collected continuously are all greater than a preset voltage threshold, it is confirmed that the resistive load is in an operating state; wherein R is a preset third quantity threshold.

8. The arc detection method according to claim 7, characterized in that: The step of confirming whether the resistive load is in a running state further includes: When S continuously collected voltage sampling values ​​are all within the reference voltage range, it is confirmed that the load is in a stopped state, and the counts of M and N therein are cleared; wherein S is a preset fourth quantity threshold.

9. The arc detection method according to any one of claims 1 to 8, characterized in that: The reference voltage range is obtained in advance according to the following method: When the resistive load is not started, the current signal of the resistive load is sampled to obtain a sampling signal, and the reference voltage range is determined according to the sampling signal.

10. The arc detection method according to any one of claims 1 to 8, characterized in that: The voltage value of the arc critical point voltage is obtained in advance according to the following method: The minimum duration T of the load current being zero during the arcing process to be identified is predetermined; According to the formula Determine the phase of the voltage at the critical point of arcing; According to the formula Determine the voltage value of the arc critical point voltage; in, is the phase angle of the arc critical point voltage, is the AC voltage cycle, is the voltage value of the arc critical point voltage, is the peak value of the AC voltage.

11. The arc detection method according to any one of claims 1 to 8, characterized in that: The current signal of the resistive load is sampled to obtain a sampling signal; according to The sampling signal is amplified by an amplification factor of , so that the arc detection device can distinguish the arc critical point voltage and the reference voltage range includes: Obtain the current signal of the resistive load and convert it into the corresponding voltage signal. amplifying the voltage signal by an amplification factor of , so that the arc detection device can distinguish between the arc critical voltage and the reference voltage range; or, Obtain the current signal of the resistive load according to The current signal is amplified by an amplification factor and the amplified current signal is converted into a corresponding voltage signal, so that the arc detection device can distinguish between the arc critical point voltage and the reference voltage range.

12. An arc detection device, characterized in that: include: A sampling and amplification module and a signal processing module connected to the signal output end of the sampling and amplification module; wherein, The sampling and amplification module is used to sample the current signal of the resistive load to obtain a sampling signal. The sampling signal is amplified by an amplification factor of , so that the signal processing module can distinguish the arc critical point voltage and the reference voltage range; wherein, is the magnification, is the allowable deviation of the reference voltage, is the voltage value of the critical point voltage of arcing; the critical point voltage of arcing includes the breakdown point voltage and the disconnection point voltage; the breakdown point voltage is the sampling signal voltage corresponding to the arcing when the applied electric field strength is enhanced to exceed the tolerance range of air, so that the air is ionized to become a conductor and the arc is formed; the disconnection point voltage is the sampling signal voltage corresponding to the arcing when the applied electric field strength is weakened to be insufficient to break through the air, so that the air stops ionizing and the arc is disconnected; The signal processing module is used to determine whether arcing exists according to the comparison of the processed value of the sampled signal after amplification and the preset value; the determination of whether arcing exists according to the comparison of the processed value of the sampled signal after amplification and the preset value includes one of the following methods: Determine whether there is an arc according to the comparison of the amplified sampling signal and the reference voltage range; Determine whether there is arcing according to the comparison slope and the preset slope range, wherein the slope is the slope of the amplified current sampling signal and the slope of the sampling signals several times before the current sampling signal; The existence of arcing is determined based on the comparison difference and the preset difference range, wherein the difference is the difference between the amplified current sampling signal and the sampling signals several times before the current sampling signal.

13. The arc detection device according to claim 12, characterized in that: The arc detection device also includes: A DC bias module, used for performing a DC bias on the sampling signal amplified by the sampling and amplifying module; the signal input end of the DC bias module is connected to the signal output end of the sampling and amplifying module, and the signal output end of the DC bias module is connected to the signal input end of the signal processing module; Correspondingly, the signal processing module is used to determine whether arcing exists according to the sampled signal processing value after DC bias and the preset value including the DC bias amount.

14. The arc detection device according to claim 12, characterized in that: The arc detection device also includes: A full-wave rectifier module, used for inverting the negative half-cycle signal of the amplified sampling signal; the signal input end of the full-wave rectifier module is connected to the signal output end of the sampling and amplification module, and the signal output end of the full-wave rectifier module is connected to the signal input end of the signal processing module; Correspondingly, the signal processing module is used to determine whether arcing exists according to the sampled signal processing value after inversion processing and the preset value.

15. The arc detection device according to claim 13, characterized in that: The sampling and amplification module includes a signal sampling module and an amplification module, wherein the signal output end of the signal sampling module is connected to the signal input end of the amplification module; wherein the signal sampling module is used to sample the current signal of the resistive load to obtain a sampling signal; and the amplification module is used to obtain a sampling signal according to The sampling signal is amplified by an amplification factor of so that the signal processing module can distinguish the arcing critical point voltage and the reference voltage range.

16. The arc detection device according to claim 12, characterized in that: The signal processing module includes an analog-to-digital conversion module and a processor, wherein the signal input end of the analog-to-digital conversion module is connected to the signal output end of the sampling and amplification module, and the signal output end of the analog-to-digital conversion module is connected to the signal input end of the processor; accordingly, the sampling and amplification module is used to The sampling signal is amplified by an amplification factor of so that the analog-to-digital conversion module can distinguish between the arcing critical point voltage and the reference voltage range.

17. The arc detection device according to claim 12, characterized in that: The signal processing module determines whether arcing exists according to comparing the amplified sampling signal and the reference voltage range, including: When the load is in working state, when N continuously collected voltage sampling values ​​are all within the reference voltage range, it is confirmed that an arc is detected; wherein N is a preset first quantity threshold.

18. The arc detection device according to claim 17, characterized in that: The arc detection device also includes: an alarm and / or load disconnection device, which is used to issue an arc alarm and / or disconnect the load from the power supply when the signal processing module detects arcing M times continuously; wherein M is a preset second quantity threshold.

19. The arc detection device according to claim 18, characterized in that: The signal processing module is also used to determine whether the resistive load is in an operating state.

20. The arc detection device according to claim 16, characterized in that: The signal processing module confirms whether the resistive load is in a running state, including: When R voltage sampling values ​​continuously collected by the analog-to-digital conversion module are all greater than a preset voltage threshold, the signal processing module confirms that the resistive load is in an operating state; wherein R is a preset third quantity threshold.

21. The arc detection device according to claim 20, characterized in that: The signal processing module confirms whether the resistive load is in a running state, and further includes: When the S voltage sampling values ​​continuously collected by the analog-to-digital conversion module are all within the reference voltage range, the signal processing module confirms that the load is in a stopped state and clears the counts of M and N therein; where S is a preset fourth quantity threshold.

22. The arc detection device according to any one of claims 12 to 21, characterized in that: The voltage value of the arc critical point voltage is obtained in advance according to the following method: The minimum duration T of the load current being zero during the arcing process to be identified is predetermined; According to the formula Determine the phase of the voltage at the critical point of arcing; According to the formula Determine the voltage value of the arc critical point voltage; in, is the phase angle of the arc critical point voltage, is the AC voltage cycle, is the voltage value of the arc critical point voltage, is the peak value of the AC voltage.

23. The arc detection device according to claim 15, characterized in that: The amplification module and the DC bias module are implemented by an isolation operational amplifier.

24. The arc detection device according to claim 15, characterized in that: The signal sampling module includes a current transformer.

25. The arc detection device according to claim 12, characterized in that: The resistive load includes an electric heating element.

26. An electrical equipment, characterized in that: The electrical equipment includes: Power supply side, a resistive load connected to the power supply terminal, and, An arc detection device as described in any one of claims 12 to 25, arranged between the power supply terminal and the resistive load.

27. The electrical equipment according to claim 26, characterized in that: The electrical equipment includes an electric water heater, and the resistive load includes an electric heating element of the electric water heater.

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