Circuit breaker opening and closing time measurement method and system based on DC component of spatial conduction coupling current

Abstract

The present invention discloses a circuit breaker opening and closing time measurement method and system based on the DC component of spatial conduction coupling current, the method comprising: collecting the spatial conduction coupling current signal of the circuit breaker circuit, processing the spatial conduction coupling current signal, obtaining the frequency component and performing frequency decomposition on the frequency component to obtain the spectrum, adjusting the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screening out the AC component in the spatial conduction coupling current signal to the maximum extent, and continuing to screen out the AC component; filtering and denoising the DC component; generating a DC component change curve, the sudden change moment of the DC component of the circuit breaker circuit is the circuit breaker opening and closing moment, and the difference between the circuit breaker opening and closing moment and the opening and closing start moment is the circuit breaker opening and closing time. The present invention does not need to change the original structure of the circuit breaker circuit, and is easy to operate.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment testing, and in particular to a method and system for measuring the opening and closing time of a circuit breaker based on a direct current component of a spatial conduction coupling current. Background Art

[0002] The opening and closing time of the circuit breaker is an important criterion for evaluating the mechanical characteristics of the circuit breaker and the three-phase synchronous performance. Generally speaking, as the service life of the circuit breaker continues to increase, its mechanical characteristics will continue to decline, and the opening and closing time will become longer. The high-voltage circuit breaker shoulders the dual tasks of protecting and controlling other power equipment in the system. The change of its opening and closing time will have a great impact on the safe and stable operation of the system. The short opening and closing time indicates that the operating mechanism of the high-voltage circuit breaker has been subjected to excessive mechanical stress and impact, causing mechanical damage to the structural components, resulting in increased wear and even damage to the mechanical structural components, causing the circuit breaker to open and close failure; and the opening and closing time is too short and long, indicating that there is a jam or conduction failure between the mechanical structural components of the high-voltage circuit breaker, resulting in prolonged arcing time, contact burning, increased system overvoltage, and damage to the equipment. Therefore, it is more important to accurately measure the opening and closing time of the high-voltage circuit breaker.

[0003] The existing testing method is to connect the opening and closing test device in series in the circuit breaker circuit. However, some combination switch circuit breakers do not have lead points on both sides. The busbar needs to be shut down to conduct experiments through adjacent lead intervals, which is complicated to operate. At the same time, in order to avoid the influence of the parallel connection of the earth resistance on the measurement circuit, the grounding wire on one side needs to be removed. When the operator removes the grounding wire, there is a risk of induced electric shock, which poses a safety hazard. On the other hand, the hanging test line often requires the use of an insulating pull rod, and there is a certain risk of the rod falling and touching the adjacent live parts. In addition, if the staff makes a mistake and supplies power to the circuit breaker line during maintenance, the current is directly transmitted to the opening and closing test device because the grounding wire is removed, which not only damages the opening and closing test device, but also puts the operator at risk of electric shock. Summary of the invention

[0004] In view of this, the present invention provides a method and system for measuring the opening and closing time of a circuit breaker based on the DC component of a spatial conduction coupling current. The method is simple to operate and does not require changing the original structure of the circuit breaker circuit, thereby effectively solving the problem of electromagnetic interference when using AC signal analysis.

[0005] The present invention discloses a method for measuring the opening and closing time of a circuit breaker based on a DC component of a spatial conduction coupling current, which comprises:

[0006] Step 1: The switch unit synchronously issues a circuit breaker action command and a current signal acquisition command, and the time starts timing. The time of issuing the command is defined as time zero, and time zero is used as the circuit breaker opening and closing start time;

[0007] Step 2: Collect the spatial conduction coupling current signal of the circuit breaker loop, process the spatial conduction coupling current signal, obtain the frequency component and perform frequency decomposition on it to obtain the spectrum, adjust the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screen out the AC component in the spatial conduction coupling current signal to the greatest extent, retain the DC component, continue to screen out the AC component, and only save the DC component; filter and denoise the DC component to obtain the DC component signal after noise reduction;

[0008] Step 3: Generate a DC component change curve. The moment when the DC component of the circuit breaker circuit changes suddenly is the circuit breaker opening and closing moment. The difference between the circuit breaker opening and closing moment and the opening and closing start moment is the circuit breaker opening and closing time.

[0009] Furthermore, the step 2 comprises:

[0010] Step 21: using a Hall sensor to collect a spatial conduction coupling current signal of the circuit breaker loop, processing the spatial conduction coupling current signal to obtain a frequency component, using Hilbert-Huang transform to perform frequency decomposition on the spatial conduction coupling current, and passing the spectrum obtained by the Hilbert-Huang transform to a low-pass filter;

[0011] Step 22: The low-pass filter adjusts the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screens out the AC component in the spatial conduction coupling current signal to the greatest extent, retains the DC component, and then passes the screened current signal through the inductor. The inductor has the function of isolating the AC signal. After double extraction, the AC component is screened out and only the DC component is preserved; after the DC component is extracted, it is transmitted to the filtering and denoising submodule to filter and denoise the DC component to obtain the DC component signal after noise reduction.

[0012] Furthermore, the step 21 comprises:

[0013] The empirical mode decomposition (EMD) in the Hilbert-Huang transform decomposes a complex signal into several intrinsic mode components (IMFs). The conditions that the intrinsic mode components must meet are: the number of signal maximum and zero points is equal or differs by 1; the local mean of the upper envelope defined by the maximum value and the lower envelope defined by the minimum value of the signal is 0;

[0014] The spatial conduction coupled current signal minus the first modal component is obtained

[0015] r1(t)=x(t)-c1(t) (1)

[0016] Where x(t) is the spatial conduction coupling current signal, r1(t) is the signal residual term, and c1(t) is the first modal component that meets the conditions;

[0017] The remaining term r1(t) is regarded as a new spatial conduction coupling current signal, and formula (1) is repeated until the conditions are met, and the modal decomposition is terminated; x(t) is expressed as the sum of each inherent modal component and the trend function:

[0018]

[0019] In the formula, c i (t) is the i-th IMF component, r n (t) is the trend function;

[0020] Perform an EMD on the spatial conduction coupled current signal to extract the high-frequency component of the signal and obtain a high-frequency IMF and a remainder; perform an EMD on the remainder and repeat the above operation until the last residual signal cannot be decomposed or meets the set termination condition; extract the induced current of the set frequency and perform a Hilbert transform on it to characterize the spectrum;

[0021] HT is defined for a signal x(t) as:

[0022]

[0023] In the formula, Defined as the imaginary part of the original signal c(t), τ represents the time domain representation of the i-th IMF component during convolution transformation, c i (τ) is represented as the convolution of the i-th IMF component;

[0024] Use Fourier transform to construct an analytical signal z(t) from the original modal components:

[0025]

[0026] In the formula, represents the instantaneous amplitude, is the instantaneous phase;

[0027] Instantaneous frequency w i (t) is determined by the instantaneous phase θ i (t) to obtain:

[0028]

[0029] Since r in formula (2) n (t) has no frequency information, so it is ignored. After the Hilbert-Huang transform, the spectrum H(ω,t) of the original signal is obtained:

[0030]

[0031] Furthermore, in step 22, the DC component is extracted and transmitted to the filtering and denoising submodule to filter and denoise the DC component to obtain a DC component signal after denoising, including:

[0032] Step 221: Perform wavelet decomposition on the collected signal, that is, the DC component obtained by filtering out the AC component of the spatial conduction coupling current through a low-pass filter and an inductor:

[0033]

[0034] In formula (7), f(t) represents the DC component, a represents the scale factor of the wavelet function, which controls the contraction of the function, and a>0; τ represents the translation factor, which controls the movement of the wavelet function;

[0035] Step 222: Propose a threshold adaptive filtering denoising technology to process the threshold of wavelet decomposition.

[0036] Further, the step 222 includes:

[0037] Step 2221: Select Morl wavelet as the wavelet basis and transform the input signal y n Perform the first layer of wavelet decomposition to obtain the approximate coefficient β1 and detail coefficient

[0038] Step 2222: Calculate the optimal wavelet selection index γ1 after the first layer of wavelet decomposition, obtain the maximum value in the calculation result, define it as the current optimal wavelet, and record the wavelet result, approximate coefficient β1 and detail coefficient

[0039] Step 2223: Perform whitening test on detail coefficients;

[0040] Step 2224: Decompose to obtain approximate coefficient β i After layer processing, the optimal threshold η of each layer is taken;

[0041] Step 2225: According to the obtained optimal threshold η of each layer, i Perform wavelet denoising;

[0042] Step 2226: Using the optimal wavelet of each layer, the obtained approximate coefficients of the last layer and detail coefficient β i , perform wavelet reconstruction processing to obtain the DC component signal after noise reduction.

[0043] Furthermore, the step 2223 includes: performing a whitening test on the detail coefficients:

[0044]

[0045] Where N is the length of wavelet coefficients; y n To measure the signal;

[0046] If satisfied This indicates that y n is white noise, recording the current approximate coefficient β i , and use it as the target decomposition signal, and return to step 2222. If not satisfied, proceed to step 2224.

[0047] Further, the step 2224 includes:

[0048] The first stage is to import the hierarchical processing results into the optimal threshold η iterative training system, locate the initial optimal threshold η1(k) through multiple training, and first import the initial threshold η1 into the following formula:

[0049] η1(k+1)=η1(k)-2lm1|2m2η1(k)-η1| (9)

[0050] Among them, k is the number of iterations, l is the iteration factor, and m1 and m2 are iteration random numbers;

[0051] A nonlinear convergence factor is applied to the initial optimal threshold η1(k) to obtain the optimal threshold η for each layer.

[0052] Further, the step 2225 includes:

[0053] Substitute the obtained optimal threshold η of each layer into the following formula and perform all β i Wavelet denoising:

[0054]

[0055] In the formula, y n To measure the signal; is the parameter that determines the shape of the threshold function; n ,η) is the threshold function.

[0056] The present invention also discloses a circuit breaker opening and closing time measurement system based on the DC component of spatial conduction coupling current, which realizes any of the above-mentioned circuit breaker opening and closing time measurement methods based on the DC component of spatial conduction coupling current, and comprises a switch unit, a data acquisition unit and a data processing unit; the switch unit, the data acquisition unit and the data processing unit are encapsulated to form a human-computer interaction interface; the data processing unit comprises a DC component extraction submodule, a filtering and denoising submodule and an integrated calculation submodule; the DC component extraction submodule is composed of a time-frequency conversion system and a DC component extraction system; the DC component extraction system is composed of a low-pass filter and an inductor;

[0057] A switch unit, used to issue circuit breaker action instructions and current signal collection instructions;

[0058] The data acquisition unit includes a Hall sensor for real-time acquisition of the circuit breaker circuit space conduction coupling current signal and the opening and closing circuit current signal;

[0059] The time-frequency conversion system is used to process the spatial conduction coupling current signal to obtain the frequency component, use the Hilbert-Huang transform to perform frequency decomposition on the spatial conduction coupling current, and pass the obtained spectrum to the low-pass filter;

[0060] The low-pass filter adjusts the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screens out the AC component in the spatial conduction coupling current signal to the greatest extent and retains the DC component; the inductor is used to continue to screen out the AC component and only retain the DC component; the DC component is filtered and denoised to obtain the DC component signal after noise reduction;

[0061] The filtering and denoising submodule is used to filter and denoise the DC component to obtain a DC component signal after noise reduction;

[0062] The integrated calculation submodule is used to generate a DC component change curve. The moment when the DC component of the circuit breaker circuit changes suddenly is the circuit breaker opening and closing moment. The difference between the circuit breaker opening and closing moment and the opening and closing start moment is the circuit breaker opening and closing time.

[0063] Furthermore, the Hall sensor is equipped with a shielding design, a metal shielding shell is added to the surface of the Hall sensor, and an electromagnetic shielding ring is installed on the data transmission line of the Hall sensor, or an electromagnetic shielding data transmission line is used instead, to achieve double electromagnetic shielding.

[0064] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0065] (1) There is no need to remove the ground wire or use other equipment to change the circuit breaker structure. By measuring the DC component of the spatial conduction coupling current in the circuit breaker circuit, the circuit breaker opening and closing time can be obtained to avoid the risk of electric shock to maintenance personnel and equipment.

[0066] (2) A threshold adaptive filtering denoising technology and a two-order method to determine the optimal filtering threshold are proposed to process the DC component and improve the accuracy of the circuit breaker opening and closing time.

[0067] (3) It has a human-computer interaction function. While obtaining the opening and closing time, the user can also process and analyze the circuit breaker circuit, making it convenient for the user to handle other tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0069] Figure 1 A schematic flow chart of a method for measuring the opening and closing time of a circuit breaker based on the DC component of a spatial conduction coupling current according to an embodiment of the present invention;

[0070] Figure 2 The present invention is a schematic diagram of a circuit breaker opening and closing time measurement system based on the DC component of spatial conduction coupling current according to an embodiment of the present invention. DETAILED DESCRIPTION

[0071] The present invention is further described in conjunction with the accompanying drawings and embodiments, and the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field should fall within the scope of protection of the embodiments of the present invention.

[0072] Considering that the electromagnetic environment in the substation is complex, there is electromagnetic induction between the high-voltage busbars, between the high-voltage busbars and the earth, and between the busbars and various devices, generating induced currents, which can be equivalent to a space capacitor. There is also a space capacitor in the circuit breaker circuit. The circuit breaker opening and closing time can be obtained by analyzing the DC component of the space conduction coupling current generated by the space capacitor. Therefore, see Figure 1 The present invention provides an embodiment of a method for measuring the opening and closing time of a circuit breaker based on the DC component of a spatial conduction coupling current, which comprises the following steps:

[0073] S1: The switch unit sends out the circuit breaker action command and the current signal acquisition command synchronously, and the time starts timing. The time when the command is sent out is defined as time zero, and time zero is used as the circuit breaker opening and closing start time;

[0074] The switch unit synchronously sends out the circuit breaker action command and the current signal collection command, and the time starts counting. The time when the command is issued is defined as time zero. Although there is still a time interval between issuing the command and the circuit breaker receiving the command, and there is also a time interval between the circuit breaker receiving the command, the spring energy starts to convert, and the circuit breaker operating mechanism is driven to act, these time intervals cannot be calculated and are less than 1ms, so they are ignored here. The defined time zero is used as the starting point of the circuit breaker opening and closing time.

[0075] S2: Collect the spatial conduction coupling current signal of the circuit breaker loop, process the spatial conduction coupling current signal, obtain the frequency component and perform frequency decomposition on it to obtain the spectrum, adjust the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, filter out the AC component in the spatial conduction coupling current signal to the greatest extent, retain the DC component, continue to filter out the AC component, and only save the DC component; filter and denoise the DC component to obtain the DC component signal after noise reduction;

[0076] The DC component extraction submodule consists of a time-frequency conversion system and a DC component extraction system, where:

[0077] The time-frequency conversion system processes the spatial conduction coupling current signal to obtain the frequency component, and uses the Hilbert-Huang transform (HHT) to perform frequency decomposition of the conduction coupling current, as follows:

[0078] The empirical mode decomposition (EMD) in HHT can decompose a complex signal into several intrinsic mode components (IMFs). The IMFs must meet the following conditions:

[0079] (1) The maximum value of the signal is equal to the number of zero points or differs by 1;

[0080] (2) The local mean of the upper envelope defined by the maximum value and the lower envelope defined by the minimum value of the signal is 0;

[0081] If the result is not satisfactory, repeat steps (1) and (2) until the condition is satisfied.

[0082] The spatial conduction coupled current signal minus the first modal component is obtained:

[0083] r1(t)=x(t)-c1(t) (1)

[0084] Where x(t) is the spatial conduction coupling current signal, r1(t) is the signal residual term, and c1(t) is the first modal component that meets the conditions.

[0085] The remaining term r1(t) is regarded as a new spatial conduction coupling current signal, and formula (1) is repeatedly used until the decomposition fails to meet the conditions that the intrinsic modal components must meet, and the modal decomposition is terminated. x(t) is expressed as the sum of each IMF component and the trend function.

[0086]

[0087] In the formula, c i (t) is the i-th IMF component, r n (t) is the trend function.

[0088] Performing an EMD on the spatial conduction coupled current signal will extract the high-frequency component of the signal and obtain a high-frequency IMF and a remainder. Then perform EMD on the remainder and repeat the above operation until the last residual signal cannot be decomposed or the termination condition is met. Then extract the induced current of the set frequency and perform Hilbert transform (HT) on it to characterize the spectrum.

[0089] HT is defined for a signal x(t) as

[0090]

[0091] In the formula Defined as the imaginary part of the original signal c(t), τ represents the time domain representation of the i-th IMF component during convolution transformation, c i (τ) is represented as the convolution of the i-th IMF component.

[0092] From equation (3), we can see that HT for signal x(t) is actually the convolution process of calculating signal x(t). According to the convolution property of FT (Fourier transform), HT is actually multiplying the positive frequency part of the frequency domain of signal FT by -j, which is equal to a phase shift of -90°; and multiplying the negative frequency part by j, which is equal to a phase shift of 90°. Based on this property, FT can be used to construct an analytical signal z(t) based on the original modal components.

[0093]

[0094] In the formula, represents the instantaneous amplitude, is the instantaneous phase

[0095] Instantaneous frequency w i (t) can be expressed by the instantaneous phase θ i (t) to obtain:

[0096]

[0097] Since r in formula (2) n (t) has no frequency information, so it is ignored. After HHT, the spectrum H(ω,t) of the spatial conduction coupling current signal is obtained:

[0098]

[0099] The spectrum obtained by HHT transformation is passed to the DC component extraction system, which consists of a low-pass filter and an inductor. First, the low-pass filter adjusts the passband and stopband range settings of the isolated AC signal according to the maximum frequency component in the spectrum, and screens out the AC component in the spatial conduction coupling current signal to the greatest extent, retaining the DC component.

[0100] The filtered current signal is then passed through an inductor, which has the function of isolating the AC signal. After double extraction, the AC component is filtered out and only the DC component is retained.

[0101] After being extracted, the DC component is passed to the filtering and denoising submodule for further processing to improve the accuracy of opening and closing positioning.

[0102] This embodiment proposes a threshold adaptive filtering and denoising technology to filter and denoise the DC component, thereby improving the measurement accuracy. The method is improved based on the basic structure of the wavelet filtering algorithm.

[0103] The details are as follows:

[0104] First, the collected signal, that is, the DC component obtained by filtering the AC component of the spatial conduction coupling current through a low-pass filter and an inductor, is decomposed by wavelet:

[0105]

[0106] Among them, f(t) represents the DC component, a represents the scale factor of the wavelet function, which controls the contraction of the function, a>0; b represents the translation factor, which controls the movement of the wavelet function.

[0107] Then comes the threshold processing of wavelet decomposition. Traditional thresholds are divided into soft thresholds and hard thresholds: Hard threshold: discontinuous in the real number domain, changing from continuous to step at the threshold point, which easily causes signal reconstruction oscillation and produces pseudo-Gibbs phenomenon; although this function overcomes the defect of discontinuity of the hard threshold function at the threshold point, there is a constant deviation from the original wavelet coefficients, which reduces the similarity between the denoised signal and the original signal. In view of the shortcomings of soft and hard thresholds, a threshold adaptive filtering denoising technology is proposed, as follows:

[0108] (1) Select Morl wavelet as the wavelet basis, and n Perform the first layer of wavelet decomposition to obtain the approximate coefficient β1 and detail coefficient

[0109] (2) Calculate the optimal wavelet selection index γ1 after the first layer of wavelet decomposition, obtain the maximum value in the calculation result, define it as the current optimal wavelet, and record the wavelet result, approximate coefficient β1 and detail coefficient

[0110] (3) Due to the detail coefficient β i contains a lot of white noise. In the process of decomposing it, the detail coefficient β i will gradually mix with the noise signal of the substation interference signal, thus resulting in the detail coefficient β i Gradually present non-noise characteristics, perform whitening test on detail coefficients,

[0111]

[0112] In the above formula: N is the length of wavelet coefficient; y n To measure the signal.

[0113] After judging according to formula (3), if the condition is met, it means that y n White noise, record the current approximate coefficient β i , and use it as the target decomposition signal, and return to step 2, if it is not satisfied, proceed to the next step;

[0114] (4) Decomposition to obtain detail coefficient β i After stratification, a second-order method is proposed to select the optimal threshold η;

[0115] 1) The first stage is to import the hierarchical processing results into the optimal threshold η iterative training system, locate the initial optimal threshold η1(k) through multiple training, and first import the initial threshold η1 into the following formula:

[0116] η1(k+1)=η1(k)-2lm1|2m2η1(k)-η1| (9) Among them, k is the number of iterations, l is the iteration factor, and m1 and m2 are iteration random numbers.

[0117] 2) Apply a nonlinear convergence factor to the initial optimal threshold η1(k). Ordinary algorithms introduce linear convergence factors to control the iterative system and find the iterative optimal solution, but they lack global control capabilities, causing the iterative system to fall into a local optimal solution and fail to locate the optimal result. Using a nonlinear convergence factor increases the global exploration capability of the iterative system, accurately locates the optimal result, and obtains the optimal threshold η for each layer.

[0118] (5) Substitute the obtained optimal threshold η of each layer into the following formula and perform all β i The wavelet denoising is:

[0119]

[0120] Where: y n To measure the signal; is the parameter that determines the shape of the threshold function; n ,η) is the threshold function.

[0121] (6) Using the optimal wavelet of each layer, the approximate coefficients of the last layer are obtained and detail coefficient β i , perform wavelet reconstruction processing to obtain the DC component signal after noise reduction.

[0122] S3: Generate a DC component change curve. The moment when the DC component of the circuit breaker circuit suddenly changes is the circuit breaker opening and closing moment. The difference between the circuit breaker opening and closing moment and the opening and closing start moment is the circuit breaker opening and closing time.

[0123] The integrated calculation submodule in the data processing unit processes and analyzes the processed DC component signal and the opening and closing current signal, and at the same time, the horizontal axis is depicted starting from the defined time zero point, and the vertical axis can be freely selected to depict the current amplitude, or it can be normalized for the convenience of analysis. A DC component change curve is generated within the coordinate range, and the moment when the opening and closing circuit current signal suddenly changes is the opening and closing time point, and the moment when the circuit breaker circuit DC component suddenly changes is the circuit breaker opening and closing time.

[0124] When the user processes data in the data processing unit, he can not only obtain the opening and closing time, but also choose not to call the DC component extraction submodule and the filtering and denoising submodule to obtain the circuit breaker loop and the original current signal of opening and closing, which is convenient for the user's other work needs.

[0125] Users can also choose to import data from the outside through the USB serial port, transfer it to the data processing unit, and independently select the DC component extraction submodule, filtering and denoising submodule, and integrated calculation submodule to process and analyze the imported data.

[0126] See also Figure 2 The present invention also provides an embodiment of a circuit breaker opening and closing time measurement system based on the DC component of spatial conduction coupling current, which implements the circuit breaker opening and closing time measurement method based on the DC component of spatial conduction coupling current described in the above embodiment, and includes a switch unit, a data acquisition unit and a data processing unit; the switch unit, the data acquisition unit and the data processing unit are encapsulated to form a human-computer interaction interface; the data processing unit includes a DC component extraction submodule, a filtering and denoising submodule and an integrated calculation submodule; the DC component submodule is composed of a time-frequency conversion system and a DC component extraction system; the DC component extraction system is composed of a low-pass filter and an inductor;

[0127] A switch unit, used to issue circuit breaker action instructions and current signal collection instructions;

[0128] The data acquisition unit includes a Hall sensor for real-time acquisition of the circuit breaker circuit space conduction coupling current signal and the opening and closing circuit current signal;

[0129] The time-frequency conversion system is used to process the spatial conduction coupling current signal to obtain the frequency component, use the Hilbert-Huang transform to perform frequency decomposition on the conduction coupling current, and pass the obtained spectrum to the low-pass filter;

[0130] The low-pass filter adjusts the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screens out the AC component in the spatial conduction coupling current signal to the greatest extent and retains the DC component; the inductor is used to continue to screen out the AC component and only retain the DC component; the DC component is filtered and denoised to obtain the DC component signal after noise reduction;

[0131] The filtering and denoising submodule is used to filter and denoise the DC component to obtain a DC component signal after noise reduction;

[0132] The integrated calculation submodule is used to generate a DC component change curve. The moment when the DC component of the circuit breaker circuit changes suddenly is the circuit breaker opening and closing moment. The difference between the circuit breaker opening and closing moment and the opening and closing start moment is the circuit breaker opening and closing time.

[0133] The switch unit, data acquisition unit and data processing unit are packaged together to form a human-computer interaction interface. The user can choose to call any unit or select the default mode. The user issues a start command, and the system automatically collects signal processing data in the order of the switch unit, data acquisition unit, and data processing unit to generate the opening and closing time. The circuit breaker opening and closing time can be displayed on the human-computer interaction interface, and the DC component signal can be visualized. After the test is completed, the user issues a closing command, and the overall opening and closing measurement time ends.

[0134] The Hall sensor is equipped with a shielding design, adding a metal shielding shell on the surface of the Hall sensor, and installing an electromagnetic shielding ring on the data transmission line of the Hall sensor, or using an electromagnetic shielding data transmission line to achieve double electromagnetic shielding.

[0135] Hall sensors are used to collect space-conducted coupled current signals from circuit breaker loops to avoid further interference from the complex electromagnetic environment of the substation on the collected data. A shielding design is added to the Hall sensor, a metal shielding shell is added to the surface of the Hall sensor, and an electromagnetic shielding ring is added to the data transmission line of the Hall sensor, or an electromagnetic shielding data transmission line is used instead to achieve a double electromagnetic shielding effect.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the opening and closing time of a circuit breaker based on the DC component of a spatial conduction coupling current, characterized in that: include: Step 1: The switch unit synchronously issues a circuit breaker action command and a current signal acquisition command, and the time starts timing. The time of issuing the command is defined as time zero, and time zero is used as the circuit breaker opening and closing start time; Step 2: Collect the spatial conduction coupling current signal of the circuit breaker loop, process the spatial conduction coupling current signal, obtain the frequency component and perform frequency decomposition on it to obtain the spectrum, adjust the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screen out the AC component in the spatial conduction coupling current signal to the greatest extent, retain the DC component, continue to screen out the AC component, and only save the DC component; filter and denoise the DC component to obtain the DC component signal after noise reduction; Step 3: Generate a DC component change curve. The moment when the DC component of the circuit breaker circuit changes suddenly is the circuit breaker opening and closing moment. The difference between the circuit breaker opening and closing moment and the opening and closing start moment is the circuit breaker opening and closing time.

2. The circuit breaker opening and closing time measurement method based on the DC component of the spatial conduction coupling current according to claim 1 is characterized in that: The step 2 comprises: Step 21: using a Hall sensor to collect a spatial conduction coupling current signal of the circuit breaker loop, processing the spatial conduction coupling current signal to obtain a frequency component, using Hilbert-Huang transform to perform frequency decomposition on the spatial conduction coupling current, and passing the spectrum obtained by the Hilbert-Huang transform to a low-pass filter; Step 22: The low-pass filter adjusts the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screens out the AC component in the spatial conduction coupling current signal to the greatest extent, retains the DC component, and then passes the screened current signal through the inductor. The inductor has the function of isolating the AC signal. After double extraction, the AC component is screened out and only the DC component is preserved; after the DC component is extracted, it is transmitted to the filtering and denoising submodule to filter and denoise the DC component to obtain the DC component signal after noise reduction.

3. The circuit breaker opening and closing time measurement method based on the DC component of the spatial conduction coupling current according to claim 2 is characterized in that: The step 21 comprises: The empirical mode decomposition in the Hilbert-Huang transform decomposes a complex signal into several intrinsic mode components. The intrinsic mode components must meet the following conditions: the number of signal maximum and zero points is equal or differs by 1; the local mean of the upper envelope defined by the maximum value and the lower envelope defined by the minimum value of the signal is 0; The spatial conduction coupled current signal minus the first modal component is obtained r1(t)=x(t)-c1(t) (1) In the formula, x(t) is the spatial conduction coupling current signal, r1(t) is the signal residual term, and c1(t) is the first modal component that meets the conditions; The remaining term r1(t) is regarded as a new spatial conduction coupling current signal, and formula (1) is repeatedly used until the decomposition fails to meet the conditions that the intrinsic modal components must meet, and the modal decomposition is terminated; x(t) is expressed as the sum of each intrinsic modal component and the trend function: In the formula, c i (t) is the i-th IMF component, r n (t) is the trend function; Perform an EMD on the spatial conduction coupled current signal to extract the high-frequency component of the signal and obtain a high-frequency IMF and a remainder. Perform an EMD on the remainder and iterate until the last residual signal cannot be decomposed or meets the set termination condition. Extract the induced current of the set frequency and perform a Hilbert transform on it to characterize the spectrum. HT is defined for high-frequency IMF as: In the formula, is defined as the HT change value of the i-th IMF component, τ represents the time domain representation of the i-th IMF component during convolution transformation, and c i (τ) is represented as the convolution of the i-th IMF component; Use Fourier transform to construct an analytical signal z(t) based on the imaginary part of the i-th IMF component and its HT change value: In the formula, represents the instantaneous amplitude, is the instantaneous phase; Instantaneous frequency w i (t) is determined by the instantaneous phase θ i (t) to obtain: Since r in formula (2) n (t) has no frequency information, so it is ignored. After Hilbert-Huang transform, the spectrum H(ω,t) of the spatial conduction coupling current signal is obtained:

4. The circuit breaker opening and closing time measurement method based on the DC component of the spatial conduction coupling current according to claim 2 is characterized in that: In step 22, after the DC component is extracted, it is transmitted to the filtering and denoising submodule to filter and denoise the DC component to obtain a DC component signal after denoising, including: Step 221: Perform wavelet decomposition on the collected signal, that is, the DC component obtained by filtering out the AC component of the spatial conduction coupling current through a low-pass filter and an inductor: Among them, f(t) represents the DC component, a represents the scale factor of the wavelet function, which controls the contraction of the function, a>0; b represents the translation factor, which controls the movement of the wavelet function; Step 222: Propose a threshold adaptive filtering denoising technology to process the threshold of wavelet decomposition.

5. The circuit breaker opening and closing time measurement method based on the DC component of the spatial conduction coupling current according to claim 4 is characterized in that: The step 222 comprises: Step 2221: Select Morl wavelet as the wavelet basis and transform the input signal y n Perform the first layer of wavelet decomposition to obtain the approximate coefficient β1 and detail coefficient Step 2222: Calculate the optimal wavelet selection index γ1 after the first layer of wavelet decomposition, obtain the maximum value in the calculation result, define it as the current optimal wavelet, and record the wavelet result, approximate coefficient β1 and detail coefficient Step 2223: Perform whitening test on detail coefficients; Step 2224: Decompose to obtain approximate coefficient β i After layer processing, the optimal threshold η of each layer is taken; Step 2225: According to the obtained optimal threshold η of each layer, i Perform wavelet denoising; Step 2226: Using the optimal wavelet of each layer, the obtained approximate coefficients of the last layer and detail coefficient β i , perform wavelet reconstruction processing to obtain the DC component signal after noise reduction.

6. The method for measuring the circuit breaker opening and closing time based on the DC component of the spatial conduction coupling current according to claim 5, characterized in that: The step 2223 includes: performing a whitening test on the detail coefficients: Where N is the length of wavelet coefficients; y n To measure the signal; If satisfied This indicates that y n is white noise, recording the current approximate coefficient β i , and use it as the target decomposition signal, and return to step 2222. If not satisfied, proceed to step 2224.

7. The method for measuring the circuit breaker opening and closing time based on the DC component of the spatial conduction coupling current according to claim 5, characterized in that: The step 2224 includes: The first stage is to import the hierarchical processing results into the optimal threshold η iterative training system, locate the initial optimal threshold η1(k) through multiple training, and first import the initial threshold η1 into the following formula: η1(k+1)=η1(k)-2lm1|2m2η1(k)-η1| (9) Among them, k is the number of iterations, l is the iteration factor, and m1 and m2 are iteration random numbers; A nonlinear convergence factor is applied to the initial optimal threshold η1(k) to obtain the optimal threshold η for each layer.

8. The method for measuring the circuit breaker opening and closing time based on the DC component of the spatial conduction coupling current according to claim 5, characterized in that: The step 2225 includes: Substitute the obtained optimal threshold η of each layer into the following formula and perform all β i Wavelet denoising: In the formula, y n To measure the signal; is the parameter that determines the shape of the threshold function; n ,η) is the threshold function.

9. A circuit breaker opening and closing time measurement system based on the DC component of spatial conduction coupling current, realizing the circuit breaker opening and closing time measurement method based on the DC component of spatial conduction coupling current according to any one of claims 1 to 8, characterized in that: It includes a switch unit, a data acquisition unit and a data processing unit; the switch unit, the data acquisition unit and the data processing unit are packaged together to form a human-computer interaction interface; the data processing unit includes a DC component extraction submodule, a filtering and denoising submodule and an integrated calculation submodule; the DC component extraction submodule is composed of a time-frequency conversion system and a DC component extraction system; the DC component extraction system is composed of a low-pass filter and an inductor; A switch unit, used to issue circuit breaker action instructions and current signal collection instructions; The data acquisition unit includes a Hall sensor for real-time acquisition of the circuit breaker circuit space conduction coupling current signal and the opening and closing circuit current signal; The time-frequency conversion system is used to process the spatial conduction coupling current signal to obtain the frequency component, use the Hilbert-Huang transform to perform frequency decomposition on the spatial conduction coupling current, and pass the obtained spectrum to the low-pass filter; The low-pass filter adjusts the passband and stopband range settings of the isolated AC signal according to the maximum frequency component of the spectrum, screens out the AC component in the spatial conduction coupling current signal to the greatest extent and retains the DC component; the inductor is used to continue to screen out the AC component and only retain the DC component; Filtering and denoising the DC component to obtain a DC component signal after noise reduction; The filtering and denoising submodule is used to filter and denoise the DC component to obtain a DC component signal after noise reduction; The integrated calculation submodule is used to generate a DC component change curve. The moment when the DC component of the circuit breaker circuit changes suddenly is the circuit breaker opening and closing moment. The difference between the circuit breaker opening and closing moment and the opening and closing start moment is the circuit breaker opening and closing time.

10. The circuit breaker opening and closing time measurement system based on the DC component of spatial conduction coupling current according to claim 9, characterized in that: The Hall sensor is equipped with a shielding design, adding a metal shielding shell on the surface of the Hall sensor, and installing an electromagnetic shielding ring on the data transmission line of the Hall sensor, or using an electromagnetic shielding data transmission line to achieve double electromagnetic shielding.

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