阅读说明：本技术 一种电弧故障检测方法及保护装置 (Arc fault detection method and protection device ) 是由 林晖 林世锋 于 2019-09-17 设计创作，主要内容包括：本发明提供一种电弧故障检测方法及保护装置,其特征在于,包括主控芯片获取负载运行的每个周期的电流特征值；根据电流值进行分区,获取多个不同的电流分区；测试设定模式下根据每个周期的电流特征值更新每个电流区间的参考保护阈值；正常模式下根据电流有效值所处区间,与该电流区间的参考保护阈值进行对比,判断是否出现电弧故障周期。本发明可以轻易获取不同负载的参考保护阈值,针对性强,可以简化算法,减少内存占用量及计算量,且提高了正常模式下电弧故障判断的灵敏度和准确性。(the invention provides an arc fault detection method and a protection device, which are characterized by comprising the steps that a main control chip obtains a current characteristic value of each cycle of load operation; partitioning according to the current value to obtain a plurality of different current partitions; updating the reference protection threshold value of each current interval according to the current characteristic value of each period in a test setting mode; and in the normal mode, comparing the current effective value with a reference protection threshold value of the current interval according to the interval in which the current effective value is positioned, and judging whether an arc fault period occurs. The method can easily acquire the reference protection threshold values of different loads, has strong pertinence, can simplify the algorithm, reduce the memory occupation amount and the calculated amount, and improve the sensitivity and the accuracy of the arc fault judgment in the normal mode.)

1. An arc fault detection method, comprising

the method comprises the steps that a main control chip obtains a current characteristic value of each period of load operation;

Partitioning according to the current value to obtain a plurality of different current partitions;

Updating the reference protection threshold value of each current interval according to the current characteristic value of each period in a test setting mode;

and in the normal mode, comparing the current effective value with a reference protection threshold value of the current interval according to the interval in which the current effective value is positioned, and judging whether an arc fault period occurs.

2. The arc fault detection method of claim 1, wherein the obtaining of the current characteristic value for each cycle of load operation by the main control chip comprises:

The current transformer acquires a load operation current signal;

the current signal enters a main control chip after passing through an amplifying and filtering circuit;

the master control chip samples the current signal at the frequency of fsHZ, and takes 10ms as 1 period, so that each period can be sampled to obtain 0.01 x fs current values I (m), m =1, 2, … …, 0.01 x fs;

And the main control chip analyzes the current value I (m) in each period to obtain a current characteristic value of each current value I (m).

3. An arc fault detection method according to claim 2, wherein the current characteristic values include an effective current value Irms, a fundamental component Ba, a 3 rd harmonic component Sy3, a 4 th harmonic component Sy4, a 5 th harmonic component Sy5, a 6 th harmonic component Sy6, a 7 th harmonic component Sy7, an 8 th harmonic component Sy8, a 9 th harmonic component Sy9, a 10 th harmonic component Sy10, a high frequency signal amplitude maximum value HFmax, a maximum di/dt value Vdimax, a zero-crossing flat shoulder duration Tfla.

4. The arc fault detection method of claim 3, wherein said partitioning according to current values to obtain a plurality of different current partitions comprises:

the maximum operation current allowed by the arc protection device is Cu, a current interval is divided by nA, and the current interval has W current intervals, wherein: w = Cu/n;

Each current interval has 13 current characteristic reference protection values, which are respectively as follows: a maximum value of a fundamental component Bamaxref (j) in a j-th current interval, a minimum value of a fundamental component Baminref (j) in a j-th current interval, a maximum value Sy3maxref (j) of a harmonic component Sy3 in a j-th current interval, a maximum value Sy4 of a harmonic component Sy4maxref (j) in a j-th current interval, a maximum value Sy5 of a harmonic component Sy5maxref (j) in a j-th current interval, a maximum value Sy6 of a harmonic component Sy 356 maxref (j) in a j-th current interval, a maximum value Sy7 of a harmonic component Sy7maxref (j) in a j-th current interval, a maximum value Sy8 of a harmonic component Sy8maxref (j) in a j-th current interval, a maximum value Sy9 of a harmonic component Sy9maxref (j) in a j-th current interval, a maximum value Sy10 of a harmonic component Sy10maxref (j) in a vdj-th current interval, a maximum value hfaj/aj (j) in a j-th current interval, The zero-crossing shoulder duration maximum for the jth current interval Tflaref (j), where j =1, 2, … …, W.

5. The arc fault detection method of claim 4, wherein updating the reference protection threshold for each current interval according to the current signature for each cycle in the test setup mode comprises:

judging which current interval the Irms (i) of the ith period is in;

comparing the current characteristic parameter of the ith period in the current interval with the current characteristic reference protection value in the current interval;

And updating the current characteristic reference protection value of the current interval according to the comparison result.

6. the arc fault detection method of claim 4, wherein the determining whether the arc fault occurs according to the comparison between the current effective value and the reference protection threshold of the current interval in the normal mode comprises:

Judging that the effective value Irms (k) of the current is in a current interval p;

Comparing the current characteristic parameter of the kth period with the current characteristic reference protection value of the current interval p;

and judging whether the kth period is a fault arc period or not according to the comparison result.

7. An arc fault detection method according to claim 7, characterized in that if the reference protection value of Irms (k) of the kth period has no current characteristic parameter of the fault arc in the interval p, the characteristic value of the kth period is compared with the reference protection value of the interval (p-1) to make a judgment.

8. an arc fault detection method according to claim 1, wherein within 0.5s 6 arc fault cycles an alarm signal is issued and/or the load power supply is disconnected.

9. An arc fault protection device, characterized in that it comprises an arc fault detection method according to any one of claims 1 to 8.

10. the arc fault protection device of claim 9, wherein the arc fault protection device comprises a push button or a dial switch, and the arc fault protection device is set to a normal mode or a test set mode by changing a state of the push button or the dial switch.

Technical Field

the invention relates to the field of electronic circuit protection, in particular to an arc fault detection method and a protection device.

Background

Wire insulation degradation or breakage or poor contact may cause a fault arc. The fault arc spark is at a high temperature, which can cause surrounding combustibles to catch fire, resulting in an electrical fire.

The fault arc detection protection technology has many researches, and related researches and patents exist in China. However, these patents are often used in a variety of loads, but the waveforms of normal operation of different loads are different, and the characteristics of the arc fault are not necessarily the same, for example, when an inductive load has an arc fault, the high frequency signal is larger, and when a resistive load has an arc fault, the high frequency signal is smaller, so the calculation is complicated, the calculation amount is large, and even the protection is not sensitive.

the normal operation current waveforms of different loads may be different, as shown in fig. 1, fig. 2 and fig. 3, it can be seen that the current waveforms of the 300W dimming lamp, the desktop personal computer and the fixed frequency air conditioner during normal operation are greatly different, for example, the 300W dimming lamp has a flat shoulder during normal operation, the desktop personal computer has a large di/dt, and the upper and lower half-waves of the household fixed frequency air conditioner current are not symmetrical. The amplitude, effective value, high-frequency noise and the like of the normal operation are different. If the fixed characteristic value is used for judging whether the arc fault occurs, misjudgment or judgment insensitivity can be caused.

chinese patent application publication No. CN101154800A discloses a method and a protection device for detecting a fault arc, which selects a current waveform data set of one cycle as a reference data set at a normal time at intervals of several cycles or at fixed intervals, and updates reference parameters. This method may select a period as the arc fault period, resulting in the reference parameter being not a current parameter for normal operation. Whether the arc fault occurs is judged by judging whether a flat shoulder exists or not, whether positive and negative half-cycles are asymmetrical or not and whether di/dt exists or not. Different loads have different di/dt and flat shoulders, which leads to misjudgment.

Chinese patent publication No. CN102621377A discloses a method for detecting a fault arc, which determines whether an arc fault occurs by analyzing whether zero-break, asymmetry of positive and negative half-cycles, unobvious periodicity, and rich high-frequency harmonics are present, and comparing these four characteristic values with corresponding threshold values. The patent does not describe how the corresponding threshold is determined.

Chinese patent publication No. CN103278734B discloses an arc fault detection apparatus and a detection method thereof, which identify an arc through a load arc feature library, a load arc type analysis module, and a load arc determination module. Load arc signature library: the type of load arc and its corresponding load arc characteristic curve and threshold are stored. Load arc type analysis module: and performing characteristic analysis on the output signal of the signal acquisition and processing unit to obtain a load arc characteristic parameter, and comparing the load arc characteristic parameter with a load arc characteristic curve in the load arc characteristic library to obtain the type of the load arc. A load arc judgment module: and comparing the current output value of the signal acquisition processing unit with the threshold value according to the type of the load arc, and outputting an action signal to the control output unit when the current output value exceeds the threshold value. The method needs to store the arc characteristic curves and the threshold values of various loads in the characteristic library in advance, occupies large storage space, and the stored loads are not necessarily complete.

chinese patent publication No. CN101673934B discloses a series arc fault circuit interrupter and a series arc fault protection method thereof, which utilize short-time fourier transform to obtain fundamental component, even harmonic component and odd harmonic component of each cycle. Setting a first threshold as a fundamental component threshold, a second threshold as an even harmonic component threshold, a third threshold as an odd harmonic component threshold, a fourth threshold as an even harmonic increment threshold, and a fifth threshold as an odd harmonic increment threshold. The patent does not describe how the respective thresholds are determined.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides the arc fault detection method and the protection device.

The purpose of the invention is realized by the following technical scheme in two aspects:

in a first aspect, the present invention provides an arc fault detection method, comprising

the method comprises the steps that a main control chip obtains a current characteristic value of each period of load operation;

Partitioning according to the current value to obtain a plurality of different current partitions;

Updating the reference protection threshold value of each current interval according to the current characteristic value of each period in a test setting mode;

And in the normal mode, comparing the current effective value with a reference protection threshold value of the current interval according to the interval in which the current effective value is positioned, and judging whether an arc fault period occurs.

Further, the acquiring, by the main control chip, the current characteristic value of each cycle of the load operation includes:

the current transformer acquires a load operation current signal;

the current signal enters a main control chip after passing through an amplifying and filtering circuit;

sampling the current signal by the master control chip at the frequency of fsHZ, and obtaining a current value I (m) every 100 cycles;

the master chip samples the current signal at the frequency fsHZ, and takes 10ms as 1 cycle, so that each cycle can sample 0.01 × fs current values I (m), m =1, 2, … …, and 0.01 × fs.

further, the current characteristic value includes a current effective value Irms, a fundamental component Ba, a harmonic component Sy3 of the 3 rd harmonic, a harmonic component Sy4 of the 4 th harmonic, a harmonic component Sy5 of the 5 th harmonic, a harmonic component Sy6 of the 6 th harmonic, a harmonic component Sy7 of the 7 th harmonic, a harmonic component Sy8 of the 8 th harmonic, a harmonic component Sy9 of the 9 th harmonic, a harmonic component Sy10 of the 10 th harmonic, a high frequency signal amplitude maximum value HFmax, a maximum di/dt value Vdimax, a zero cross flat shoulder duration Tfla.

furthermore, the maximum operation current allowed by the arc protection device is Cu, a current interval is divided by nA, and the current interval has W current intervals, wherein: w = Cu/n;

Each current interval has 13 current characteristic reference protection values, which are respectively as follows: a maximum value of a fundamental component Bamaxref (j) in a j-th current interval, a minimum value of a fundamental component Baminref (j) in a j-th current interval, a maximum value Sy3maxref (j) of a harmonic component Sy3 in a j-th current interval, a maximum value Sy4 of a harmonic component Sy4maxref (j) in a j-th current interval, a maximum value Sy5 of a harmonic component Sy5maxref (j) in a j-th current interval, a maximum value Sy6 of a harmonic component Sy 356 maxref (j) in a j-th current interval, a maximum value Sy7 of a harmonic component Sy7maxref (j) in a j-th current interval, a maximum value Sy8 of a harmonic component Sy8maxref (j) in a j-th current interval, a maximum value Sy9 of a harmonic component Sy9maxref (j) in a j-th current interval, a maximum value Sy10 of a harmonic component Sy10maxref (j) in a vdj-th current interval, a maximum value hfaj/aj (j) in a j-th current interval, The zero-crossing shoulder duration maximum for the jth current interval Tflaref (j), where j =1, 2, … …, W.

Further, updating the reference protection threshold of each current interval according to the current characteristic value of each cycle in the test setting mode includes:

judging which current interval the Irms (i) of the ith period is in;

Comparing the current characteristic parameter of the ith period in the current interval with the current characteristic reference protection value in the current interval;

and updating the current characteristic reference protection value of the current interval according to the comparison result.

Further, in the normal mode, comparing the current effective value with a reference protection threshold of the current interval according to the interval in which the current effective value is located, and determining whether an arc fault occurs includes:

Judging that the effective value Irms (k) of the current is in a current interval p;

comparing the current characteristic parameter of the kth period with the current characteristic reference protection value of the current interval p;

And judging whether the kth period is a fault arc period or not according to the comparison result.

further, if the reference protection value of Irms (k) in the k-th period has no current characteristic parameter of the fault arc in the interval p, the characteristic value of the k-th period is compared with the reference protection value in the interval (p-1) for judgment.

further, within 6 arc fault cycles of 0.5s, an alarm signal is issued and/or the load power is disconnected.

In a second aspect, the present invention provides an arc fault protection device for implementing the arc fault detection method of the first aspect.

further, the arc fault protection device comprises a key or a dial switch, and the arc fault protection device is set to be in a normal mode or a test setting mode by changing the state of the key or the dial switch.

The invention has the beneficial effects that: the invention provides an arc fault detection method and a protection device.A test setting mode is opened on an installation or use site, a load runs for a period of time in the test setting mode, and a normal running current is detected and analyzed, so that a reference protection threshold value for judging an arc fault is obtained; the method can easily obtain the reference protection threshold values of different loads, has strong pertinence, can simplify the algorithm, reduce the memory occupation amount and the calculated amount, and improve the sensitivity and the accuracy of the arc fault judgment in the normal mode.

Drawings

the invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be derived on the basis of the following drawings without inventive effort.

Fig. 1 is a waveform diagram of the normal operation current of a 300W dimming lamp according to the background art of the present invention.

fig. 2 is a waveform diagram of a normal operation current of a desktop personal computer according to the background art of the present invention.

Fig. 3 is a waveform diagram of a normal operation current of a domestic fixed-frequency air conditioner according to the background art of the present invention.

Fig. 4 is a schematic diagram illustrating the protection device entering the test setting mode according to an embodiment of the present invention.

FIG. 5 is a flow chart of selecting a mode based on a key or dip switch according to one embodiment of the invention.

fig. 6 is a flow chart of the main control chip saving data, analyzing data, and saving current characteristic values according to an embodiment of the present invention.

FIG. 7 is a flowchart of the test setup mode operation of one embodiment of the present invention.

FIG. 8 is a normal mode operational flow diagram of one embodiment of the present invention.

Detailed Description

in order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 4 to 8, an arc fault detection method of the present embodiment is used for an arc fault protection device, where the arc fault protection device is an arc fault detection protector or a protection socket, and a test setting mode and a normal mode can be selected through a key or a dial switch.

The arc fault detection method comprises the following steps:

Acquiring a load operation current signal through a current transformer;

the current signal enters a main control chip after passing through an amplifying and filtering circuit;

the current signal after passing through the amplifying and filtering circuit is more stable, and is more beneficial to the receiving of the main control chip.

the master chip samples the current signal at a frequency fsHZ, and takes 10ms as 1 cycle, so that each cycle can sample 0.01 × fs current values I (m), m =1, 2, … …, 0.01 × fs, for example, 2K current values I (m) are obtained when the sampling frequency is 200 KHz.

The main control chip analyzes the current values I (m) in each period to obtain current characteristic values of each current value I (m), wherein the current characteristic values comprise effective current values Irms, fundamental wave components Ba, harmonic components Sy3 of the 3 rd harmonic, harmonic components Sy4 of the 4 th harmonic, harmonic components Sy5 of the 5 th harmonic, harmonic components Sy6 of the 6 th harmonic, harmonic components Sy7 of the 7 th harmonic, harmonic components Sy8 of the 8 th harmonic, harmonic components Sy9 of the 9 th harmonic, harmonic components Sy10 of the 10 th harmonic, maximum amplitude values HFmax of high-frequency signals, maximum di/dt values Vdimax and zero-crossing flat shoulder duration Tfla.

For example, the current characteristic value of the ith cycle is:

current effective value Irms (i), fundamental component Ba (i), kth harmonic component Syk (i), HFmax (i), Vdimax (i), Tfla (i);

wherein i =1, 2, … …, N;

wherein k =3, … …, 10;

the HFmax (i) is the maximum value of the amplitude of the signal in the frequency range from fs/4 Hz ~ fs/2 Hz, for example, when the sampling frequency is 200KHz, the HFmax (i) is the maximum value of the amplitude of the signal in the frequency range from 50KHz ~ 100 KHz.

Vdeimax (i) is the maximum value of the absolute value of the difference value of two adjacent sampling current values in the ith period, namely

Vdimax(i)=max（|Ii(m+1)- Ii(m)| ），m=1，2，……，0.01*fs

tflo (i) is the number of sampling current values with absolute value less than or equal to 0.5A in the ith period.

each cycle can result in 13 eigenvalues.

partitioning according to the current value to obtain a plurality of different current partitions;

if the maximum operation current allowed by the arc protector or the protection socket is Cu, dividing a current interval according to nA, and totally dividing W intervals, wherein: w = Cu/n, for example, when n =0.5, the interval division is as follows:

the interval one: 0.1A-0.5A;

The interval two: 0.5A-1A;

Interval three: 1A-1.5A;

……

interval W = Cu/0.5: (Cu-0.5) A- (Cu) A;

for example, if Cu is 32A and W =64, there are 64 sections.

Each interval has 13 characteristic reference guard values: respectively as follows: a maximum value of a fundamental component Bamaxref (j) in a j-th current interval, a minimum value of a fundamental component Baminref (j) in a j-th current interval, a maximum value Sy3maxref (j) of a harmonic component Sy3 in a j-th current interval, a maximum value Sy4 of a harmonic component Sy4maxref (j) in a j-th current interval, a maximum value Sy5 of a harmonic component Sy5maxref (j) in a j-th current interval, a maximum value Sy6 of a harmonic component Sy 356 maxref (j) in a j-th current interval, a maximum value Sy7 of a harmonic component Sy7maxref (j) in a j-th current interval, a maximum value Sy8 of a harmonic component Sy8maxref (j) in a j-th current interval, a maximum value Sy9 of a harmonic component Sy9maxref (j) in a j-th current interval, a maximum value Sy10 of a harmonic component Sy10maxref (j) in a vdj-th current interval, a maximum value hfaj/aj (j) in a j-th current interval, The zero-crossing shoulder duration maximum for the jth current interval Tflaref (j), where j =1, 2, … …, W.

updating the reference protection threshold value of each current interval according to the current characteristic value of each period in a test setting mode;

Judging which current interval the Irms (i) of the ith period is in;

comparing the current characteristic parameter of the ith period in the current interval with the current characteristic reference protection value in the current interval;

and updating the current characteristic reference protection value of the current interval according to the comparison result.

For example: and recording and analyzing 13 characteristic values of the 1 st period, comparing the current interval in which the Irms (1) is positioned, and setting a characteristic reference protection value of the current interval according to the 12 characteristic values of the 1 st period. For example

0.1A is not less than Irms (1) is not less than 0.5A, and within the interval one, 12 characteristic reference protection values of the interval one are as follows:

Bamaxref(1)= Ba(1)；

Baminref(1)= Ba(1)；

Sy3maxref (1)=Sy3 (1)；

Sy4maxref (1)=Sy4 (1)；

……

Sy10maxref (1)=Sy10 (1)；

HFmaxref (1)=HFmax(1)；

Vdimaxref (1)= Vdimax (1)；

Tflaref (1)= Tfla (1)；

And recording and analyzing 13 characteristic values of the 2 nd period, comparing the current interval in which Irms (2) is positioned, and if the current interval is still positioned in the interval I:

If Ba (2) > Bamaxref (1), updating Bamaxref (1) to Ba (2): bamaxref (1) = Ba (2). Otherwise, Bamaxref (1) is not changed;

if Ba (2) < Baminref (1), updating Baminref (1) to Ba (2): baminref (1) = Ba (2). Otherwise, the Baminref (1) is not changed;

if Sy3(2) > Sy3maxref (1), Sy3maxref (1) is updated to Sy3 (2): sy3maxref (1) = Sy3 (2). Otherwise Sy3maxref (1) is unchanged;

If Sy4(2) > Sy4maxref (1), Sy4maxref (1) is updated to Sy4 (2): sy4maxref (1) = Sy4 (2). Otherwise Sy4maxref (1) is unchanged;

……

if Sy10(2) > Sy10maxref (1), Sy10maxref (1) is updated to Sy10 (2): sy10maxref (1) = Sy10 (2). Otherwise Sy10maxref (1) is unchanged;

if HFmax (2) > HFmaxref (1), HFmaxref (1) is updated to HFmax (2): HFmaxref (1) = HFmax (2). Otherwise Sy10maxref (1) is unchanged;

if Vdimax (2) > Vdiaxref (1), updating Vdiaxref (1) to Vdimax (2): vdimaxref (1) = Vdimax (2). Otherwise Vlimixref (1) is unchanged;

If Tvla (2) > Tlaref (1), then Tlaref (1) is updated to Tvla (2): tfaref (1) = Tfla (2). Otherwise Tflaref (1) is not changed;

the 13 eigenvalues of the ith cycle are obtained through the above steps, and then the current interval in which Irms (i) is located is compared. If the current is in the jth current interval, comparing the characteristic value of the ith period with the reference protection value of the jth current interval, and updating the reference protection value of the jth current interval. The following table of reference protection values was obtained:

Interval of current

Bamaxref

Baminref

Sy3maxref

Sy4maxref

……

Sy10maxref

HFmaxref

Vdimaxref

Tflaref

0.1~0.5

Bamaxref(1)

Baminref(1)

Sy3maxref(1)

Sy4maxref(1)

……

Sy10maxref(1)

HFmaxref(1)

Vdimaxref(1)

Tflaref(1)

0.5~1

Bamaxref(2)

Baminref(1)

Sy3maxref(2)

Sy4maxref(2)

……

Sy10maxref(2)

HFmaxref(2)

Vdimaxref(2)

Tflaref(2)

1~1.5

Bamaxref(3)

Baminref(3)

Sy3maxref(3)

Sy4maxref(3)

……

Sy10maxref(3)

HFmaxref(3)

Vdimaxref(3)

Tflaref(3)

……

……

……

……

……

……

……

……

……

……

Interval W

Bamaxref(W)

Baminref(W)

Sy3maxref(W)

Sy4maxref(W)

Sy10maxref(W)

HFmaxref(W)

Vdimaxref(W)

Tflaref(W)

Closing the test setting mode, and in normal operation, comparing the current effective value interval with the reference protection threshold value of the current interval in the normal mode to judge whether an arc fault period occurs;

Judging that the effective value Irms (k) of the current is in a current interval p;

Comparing the current characteristic parameter of the kth period with the current characteristic reference protection value of the current interval p;

and judging whether the kth period is a fault arc period or not according to the comparison result.

For example, if the k-th cycle, whose Irms (k) is in the interval p, then

if Ba (k) is not less than delta 1 Bamaxref (p), the k-th cycle is a fault arc cycle;

if Ba (k) is less than or equal to delta 2 Baminref (p), the k cycle is a fault arc cycle;

if Sy3(k) ≧ δ 3 Sy3maxref (p), the kth cycle is the fault arc cycle;

If Sy4(k) ≧ δ 4 Sy4maxref (p), the kth cycle is the fault arc cycle;

……

if Sy10 (k) ≧ δ 10 Sy10maxref (p), the kth cycle is the fault arc cycle;

If HFmax (k) is ≧ δ 11 HFmaxref (p), the kth cycle is a fault arc cycle;

If Vdimax (k) is not less than δ 12 Vdimaxref (p), the kth cycle is a fault arc cycle;

if Tflo (k) is larger than or equal to delta 13 Tflag (p), the k-th cycle is a fault arc cycle;

Where δ 1 × Bamaxref (p) represents the maximum reference protection value of the updated fundamental component in the p current interval, and δ 2 × Baminref (p), δ 3 × Sy3maxref (p), and the like are similar.

if the reference protection value of the Irms (k) of the kth period has no current characteristic parameter of the fault arc in the interval p, the characteristic value of the kth period is compared with the reference protection value of the interval (p-1) for judgment.

if there are 6 arc fault cycles within 0.5s, an alarm signal is issued and/or the load power is disconnected.

The invention provides an arc fault detection method and a protection device.A test setting mode is opened on an installation or use site, a load runs for a period of time in the test setting mode, and a normal running current is detected and analyzed, so that a reference protection threshold value for judging an arc fault is obtained; the method can easily obtain the reference protection threshold values of different loads, has strong pertinence, can simplify the algorithm, reduce the memory occupation amount and the calculated amount, and improve the sensitivity and the accuracy of the arc fault judgment in the normal mode.

finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.