Light-emitting connection detection method for low-voltage alternating-current electrical circuit
Through discrete wavelet analysis and fast Fourier transform method, combined with threshold comparison, the problem of luminescence connection detection in low-voltage AC systems is solved, accurate detection of luminescence connections is achieved, and equipment safety is improved.
Patent Information
- Application Number
- CN202411114877.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-14
- Publication Date
- 2024-12-13
AI Technical Summary
The light luminous connections in low-voltage AC systems are highly concealed, and high temperatures can lead to ablation of contact elements and fires, and the prior art is difficult to effectively detect and prevent failures.
Discrete wavelet analysis and fast Fourier transform method are used to extract the d5 band mode maximum and spectrum integration of the current signal, combined with the comparison of two thresholds, to achieve accurate detection of the luminous connection of low-voltage AC electrical lines.
Highly accurate luminous connection detection is achieved under various load and current levels, which can promptly determine the occurrence of faults and avoid fire and explosion risks.
Smart Images
Figure CN119125970A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of luminous connection detection of low-voltage AC electrical circuits, and in particular to a luminous connection detection method of low-voltage AC electrical circuits. Background Art
[0002] In low-voltage AC systems, luminous connections may occur at electrical connections due to poor contact. Luminous connections are highly concealed and the temperature can be as high as 1000 to 1500°C. The high temperature of luminous connections will burn the contact elements and eventually cause connection failure. It will also ignite surrounding non-flame retardant materials, causing a chain reaction that can lead to large-scale fires or even explosions, posing a serious threat to the safe operation of equipment.
[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention
[0004] The present invention provides a light-emitting connection detection method for a low-voltage AC electrical circuit, which has high accuracy under various loads and current levels.
[0005] A light-emitting connection detection method for a low-voltage AC electrical line comprises: Step 1, extracting a current signal of a low voltage AC electrical line; Step 2, performing discrete wavelet analysis on the current signal, extracting the modulus maximum of the d5 frequency band signal after 5-layer wavelet decomposition for determination, dividing the modulus maximum by the current effective value for load normalization, and when the normalized value is greater than the first threshold, executing step 3, and when the normalized value is less than or equal to the first threshold, it is considered that no light-emitting connection is generated, and returning to step 1; Step 3, simultaneously select a time window to perform a fast Fourier transform on the current signal, obtain a current spectrum amplitude distribution diagram, integrate the current spectrum amplitude value and divide it by the integral value of the current effective value to normalize, compare the normalized value with the second threshold, and if the normalized value is less than or equal to the second threshold, it is considered that no light-emitting connection is generated, and return to step 1. If the normalized value is greater than the second threshold, a light-emitting connection is generated to determine that a fault has occurred.
[0006] In the method for detecting luminous connection of a low-voltage AC electrical circuit, in step 2, the first threshold is 0.0492.
[0007] In the method for detecting luminous connection of a low-voltage AC electrical circuit, in step 3, a fast Fourier transform is performed on the current signal using a 400 ms sliding time window to obtain the current spectrum amplitude distribution.
[0008] In the method for detecting luminous connection of a low-voltage AC electrical circuit, in step 3, the spectrum integral of the 100-1000 Hz characteristic frequency band signal is selected to perform fault judgment on the current signal.
[0009] In the luminous connection detection method for a low-voltage AC electrical circuit, the second threshold is 0.0099.
[0010] In the luminous connection detection method for a low-voltage AC electrical circuit, step 1 is to extract the current signal of the low-voltage AC electrical circuit using a current sensor at a sampling rate of 625kHz.
[0011] In the method for detecting luminous connection of a low-voltage AC electrical circuit, in step 2, the ratio of the normalized value to the first threshold is at least 1.3 times.
[0012] In the luminous connection detection method for a low-voltage AC electrical circuit, the low-voltage AC electrical circuit is an AC electrical circuit with a voltage less than 1 kV.
[0013] Compared with the prior art, the present invention has the following advantages: the present invention extracts the line current signal of the luminous connection, performs discrete wavelet transform and sliding time window spectrum integration on the current value, and can realize the judgment of electrical line fault by comparing two thresholds. The present invention relies on the high-frequency component of the frequency domain of the luminous connection current signal, extracts the amplitude of the wavelet transform coefficient and the spectrum integration as the characteristic value of the threshold detection method, and can effectively detect the luminous connection fault under different loads in the low-voltage AC electrical circuit, solves the problem of luminous connection electrical signal detection, is applicable to various load types under low-voltage AC conditions, and has high judgment accuracy. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.
[0015] In the attached picture: Figure 1 is a schematic diagram of the process of this method; Figure 2 It is the amplitude distribution diagram before and after the fault of this method; Figure 3 This is the distribution diagram of the modulus maximum value of the d5 frequency band before and after the fault of this method.
[0016] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION
[0017] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.
[0018] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.
[0019] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.
[0020] like Figures 1 to 3 As shown, the luminous connection detection method of the low-voltage AC electrical line includes the following steps: Step 1, extracting a current signal of a low voltage AC electrical line; Step 2, performing discrete wavelet analysis on the current signal, extracting the modulus maximum of the d5 frequency band signal after 5-layer wavelet decomposition for determination, dividing the modulus maximum by the current effective value for load normalization, and when the normalized value is greater than the first threshold, executing step 3, when the normalized value is less than or equal to the first threshold, it is considered that no light-emitting connection is generated, and returning to step 1; Step 3, simultaneously select a time window to perform a fast Fourier transform on the current signal, obtain a current spectrum amplitude distribution diagram, integrate the current spectrum amplitude value and divide it by the integral value of the current effective value for normalization, compare the normalized value with the second threshold, if the normalized value is less than or equal to the second threshold, it is considered that no luminous connection is generated, and return to step 1, if the normalized value is greater than the second threshold, a luminous connection is generated to determine that a fault has occurred. In a preferred embodiment of the luminous connection detection method for a low-voltage AC electrical line, in step 2, the first threshold is 0.0492.
[0021] In a preferred implementation of the luminous connection detection method for a low-voltage AC electrical circuit, in step 3, a fast Fourier transform is performed on the current signal using a 400 ms sliding time window to obtain the current spectrum amplitude distribution.
[0022] In a preferred implementation of the luminous connection detection method for a low-voltage AC electrical circuit, in step 3, the spectrum integration of the 100-1000 Hz characteristic frequency band signal is selected to perform fault judgment on the current signal.
[0023] In a preferred implementation of the method for detecting luminous connection of a low-voltage AC electrical circuit, the second threshold is 0.0099.
[0024] In a preferred implementation of the luminous connection detection method for a low-voltage AC electrical circuit, step 1 is to extract a current signal of the low-voltage AC electrical circuit using a current sensor at a sampling rate of 625kHz.
[0025] In a preferred implementation of the method for detecting luminous connection of a low-voltage AC electrical line, in step 2, the normalized value is at least 1.3 times the first threshold value.
[0026] In a preferred implementation of the luminous connection detection method for a low-voltage AC electrical circuit, the low-voltage AC electrical circuit is an AC electrical circuit with a voltage less than 1 kV.
[0027] In one embodiment, reference Figure 1 , a luminous connection detection method for a low voltage AC electrical line comprises the following steps: The current waveform of the luminous connection branch is detected in real time, and a 5-layer discrete wavelet transform is performed on the luminous connection current signal. The modulus maximum of the d5 band signal is selected for judgment, and the modulus maximum is divided by the effective value of the current for load normalization. When the normalized value is greater than the threshold value of 0.049, it can be used as a criterion for judging the occurrence of a luminous connection.
[0028] The current signal is fast Fourier transformed using a 400ms sliding time window to obtain the spectrum amplitude distribution. The spectrum integral of the 100-1000Hz characteristic frequency band signal is selected to determine the signal fault. The integral value is normalized by dividing the current effective value. If the integral value is greater than the set second threshold value of 0.903, it can be used as a criterion. When the above two criteria are met at the same time, it is determined that the light connection occurs. Example 1
[0029] The current sensor is used to measure the luminous connection current at a sampling rate of 625kHz. When a luminous connection occurs in the line, a 0.4s time window is used to perform FFT transformation on the current. The distribution of the current spectrum 0-2000Hz for luminous connection failure and normal situation is shown in the following figure: Figure 2 It is found that the luminous connection current is significantly greater than that without abnormality in 100-1000Hz. The amplitudes of the two frequency bands are integrated, and the results are shown in Table 1. The spectrum integral value is normalized for load processing. It can be seen that there is a significant difference before and after the fault, and it can be clearly distinguished according to the first threshold, which can be used as a criterion for luminous connection fault.
[0030] Table 1 Spectrum integration before and after the fault Before the failure After the failure 3.2850A*Hz 6.6440 A*Hz 0.0066 (normalized) 0.0134 (normalized) The 5-layer wavelet transform is performed on the light-emitting connection current signal. The maximum value distribution of the modulus of the d5 frequency band signal before and after the fault is as follows: Figure 3 As shown, the modulus maximum value of the d5 frequency band signal is taken to determine the signal fault. The maximum value of the fault is 1.3 times that before the fault. It can be clearly distinguished according to the second threshold value and can be used as a criterion for the light connection fault.
[0031] Table 2 Wavelet modulus maximum in d5 band before and after fault Before the failure After a failure 0.1902A 0.2421A 0.0432 (normalized) 0.0550 (normalized) When wavelet transform and spectrum integration are used together to judge the fault, the method outputs the final result that a luminous connection fault occurs.
[0032] It should be noted that the method for obtaining the first threshold and the second threshold is as follows: After normalizing the current effective value of the 5 groups of light-emitting connection conditions and the maximum value of the signal modulus under normal conditions, the corresponding normalized values of the following 5 normal conditions are obtained respectively: a 11 =0.0061,a 12 =0.0067,a 13 =0.0064, a 14 =0.0066, a 15 =0.0065, add them up and calculate the average value a 1i =0.0065; at the same time, the normalized values of the five luminous connection conditions are obtained: b 11 =0.0138,b 12 =0.0130,b 13 =0.0132, b 14 =0.0135, b 15 =0.0134, add them up and calculate the average value b 1i=0.0134. Therefore, we can take (0.0065+0.0134) / 2=0.0099 as the specific value of a certain threshold and use this average value as the value of the first threshold; After normalizing the signals of the five groups of light-emitting connection conditions and the normal conditions, the corresponding normalized values of the following five normal conditions are obtained respectively: a 21 =0.0430,a 22 =0.0429,a 23 =0.0433, a 24 =0.0435, a 25 =0.0432, add them up and calculate the average value a 2i =0.0432; meanwhile, the normalized values of 5 luminous connection conditions are obtained: b 21 =0.0555, b22 =0.0551,b 23 =0.0553, b 24 =0.0549, b 25 =0.0548, add them up and calculate the average value b 2i =0.0551. Therefore, we can take (0.0065+0.0134) / 2=0.0492 as the specific value of a certain threshold and use this average value as the value of the second threshold; Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.
Claims
1. A light-emitting connection detection method for a low-voltage AC electrical circuit, characterized in that: The steps include: Step 1, extracting a current signal of a low voltage AC electrical line; Step 2, performing discrete wavelet analysis on the current signal, extracting the modulus maximum of the d5 frequency band signal after 5-layer wavelet decomposition for determination, dividing the modulus maximum by the current effective value for load normalization, and when the normalized value is greater than the first threshold, executing step 3, and when the normalized value is less than or equal to the first threshold, it is considered that no light-emitting connection is generated, and returning to step 1; Step 3, simultaneously select a time window to perform a fast Fourier transform on the current signal, obtain a current spectrum amplitude distribution diagram, integrate the current spectrum amplitude value and divide it by the integral value of the current effective value to normalize, compare the normalized value with the second threshold, and if the normalized value is less than or equal to the second threshold, it is considered that no light-emitting connection is generated, and return to step 1. If the normalized value is greater than the second threshold, a light-emitting connection is generated to determine that a fault has occurred.
2. A light-emitting connection detection method for a low-voltage AC electrical circuit according to claim 1, characterized in that: Preferably, in step 2, the first threshold is 0.0492.
3. A light-emitting connection detection method for a low-voltage AC electrical circuit according to claim 1, characterized in that: In step 3, a fast Fourier transform is performed on the current signal using a 400 ms sliding time window to obtain the current spectrum amplitude distribution.
4. A light-emitting connection detection method for a low-voltage AC electrical circuit according to claim 1, characterized in that: In the step 3, the frequency spectrum integration of the 100-1000 Hz characteristic frequency band signal is selected to perform fault determination on the current signal.
5. The method for detecting light connection of a low voltage AC electrical circuit according to claim 1, characterized in that: The second threshold is 0.0099.
6. A light-emitting connection detection method for a low-voltage AC electrical circuit according to claim 1, characterized in that: Step 1: Use a current sensor to extract a current signal of a low-voltage AC electrical line at a sampling rate of 625 kHz.
7. A light-emitting connection detection method for a low-voltage AC electrical circuit according to claim 1, characterized in that: In step 2, the normalized value is at least 1.3 times the first threshold value.
8. A light-emitting connection detection method for a low-voltage AC electrical circuit according to claim 1, characterized in that: The low-voltage AC electrical circuit is an AC electrical circuit with a voltage less than 1 kV.