A DC demagnetization quantization method, device, and electronic medium based on time-current curves

Abstract

This invention provides a DC demagnetization quantification method based on time-current curves. The method includes the following steps: during DC demagnetization, acquiring the time-current change curve of the transformer through a current monitoring device; marking the intersection points where the current drops from a positive value to zero, and determining the time corresponding to these intersection points to obtain the remanent magnetization points; based on the time information of each remanent magnetization point, calculating the percentage of remanent magnetization relative to the initial remanent magnetization at each stage. This invention, through the curve of current changing with time, can accurately quantify the DC demagnetization process, overcoming the shortcomings of traditional methods that cannot accurately assess the demagnetization effect.

Description

Technical Field

[0001] This invention belongs to the field of transformer demagnetization, specifically relating to a DC demagnetization quantization method, device, and electronic medium based on time-current curves. Background Technology

[0002] During long-term operation, transformers often develop residual magnetism, which can affect their performance, reliability, and operating efficiency. Existing demagnetization methods mainly use direct current, but they lack effective quantitative standards and cannot accurately assess the demagnetization effect, thus failing to guide practical operations.

[0003] Existing methods for evaluating demagnetization effectiveness are mostly based on judging the polarity of residual magnetism, but these methods cannot quantify the demagnetization process and cannot achieve precise control. Quantifying the DC demagnetization process remains a pressing problem to be solved in the field of transformer maintenance. Summary of the Invention

[0004] The purpose of this invention is to provide a DC demagnetization quantification method based on time-current curves. This method quantifies the effect of the demagnetization process by real-time monitoring of the current-time curve during the demagnetization process and combining it with the physical characteristics of the transformer, so as to more accurately evaluate the DC demagnetization effect and optimize the demagnetization process.

[0005] The technical solution of the present invention is as follows:

[0006] A DC demagnetization quantization method based on time-current curves, the method comprising the following steps:

[0007] During DC demagnetization, the time-current change curve of the transformer is obtained through a current monitoring device;

[0008] Mark the intersections where the current drops from a positive value to zero, and determine the time corresponding to these intersections to obtain the remanence points;

[0009] Based on the time information of each remanence point, the percentage of remanence is calculated for each time.

[0010] Furthermore, the remanent magnetization point is the intersection of the current and the horizontal axis when the current decreases from a positive value to zero, defined as B. i Point, where i represents the number of times the reverse voltage is applied.

[0011] Furthermore, the calculation of the percentage of remanence each time is specifically as follows:

[0012] Read the time it takes for the current to reach its forward and reverse peak values;

[0013] Calculate the change in remanence each time based on the time difference between adjacent remanence points;

[0014] By summing up all the changes in remanence, we can obtain the decrease in magnetic induction intensity during the entire demagnetization process, and then calculate the percentage of remanence for each time using this decrease.

[0015] Furthermore, the formula for calculating the change in remanence each time based on the time difference between adjacent remanence points is as follows:

[0016] |Δt j |=(t Nj -t 0j )+(t Nj+1 -t Pj )-(t Pj+1 -t Nj )

[0017] Where, Δt j t represents the time difference corresponding to the change in magnetic flux from the j-th positive remanence point to the (j+1)-th positive remanence point. Nj t is the time when the demagnetizing current reaches its negative peak for the jth time. 0j Let t be the time it takes for the demagnetizing current to decay to 0 from the positive half-region for the j-th time. Pj The time when the demagnetizing current reaches its positive peak value for the jth time.

[0018] Furthermore, the formula for summing up all changes in remanence to obtain the decrease in magnetic induction intensity during the entire demagnetization process is as follows:

[0019]

[0020] Where, |Δt j | Indicates the demagnetizing process, the residual magnetism of the transformer from B. j Change to B j+1 The change in quantity.

[0021] Furthermore, the formula for calculating the percentage of residual magnetism each time through this reduction is as follows:

[0022]

[0023] Among them, t sum Indicates the initial remanence B r The time difference between the value and 0 is Δt, which is the positive voltage time required for the magnetic induction intensity to rise from Br to Bs.

[0024] Furthermore, the t sum The specific formulas for the time required for the reverse and forward voltages to apply through the transformer to reach the positive and negative saturation points, Δt, are as follows:

[0025]

[0026] Δt=t2-t1

[0027] Where t1 is the time required for the transformer flux to reach the forward and reverse saturation points, and t2 is the time required for the transformer flux to reach the forward and reverse saturation points, respectively.

[0028] The present invention also provides an electronic device, including a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to perform the DC demagnetization quantization method described above.

[0029] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the DC demagnetization quantization method as described above.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] This invention can accurately quantify the DC demagnetization process by using the curve of current changing over time, overcoming the shortcomings of traditional methods that cannot accurately evaluate the demagnetization effect. Attached Figure Description

[0032] The accompanying drawings illustrate various embodiments generally by way of example rather than limitation, and are used, together with the specification and claims, to explain embodiments of the invention. Where appropriate, the same reference numerals are used in all drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the apparatus or method.

[0033] Figure 1 A schematic diagram of the demagnetizing voltage and current curves of the present invention is shown;

[0034] Figure 2 A schematic diagram of the simulation structure of the present invention is shown;

[0035] Figure 3 A schematic diagram showing the correspondence between the time-current curve and positive remanence of the present invention is shown;

[0036] Figure 4 A schematic diagram illustrating the determination of remanent magnetic polarity according to the present invention is shown;

[0037] Figure 5 A schematic diagram of the hysteresis loop of the polarity determination process of the present invention is shown. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] This invention provides a DC demagnetization quantization method based on time-current curves, comprising:

[0040] The residual magnetism percentage of a transformer refers to the relationship between the magnitude of residual magnetism generated at different stages of DC demagnetization and the initial magnitude of residual magnetism. Therefore, the residual magnetism percentage can directly reflect the degree of elimination of residual magnetism and the demagnetization process. It can also be used to analyze the increase, decrease, and changes in magnetic flux within the transformer core. In engineering applications, this helps in better analyzing the DC demagnetization process and enhances the understanding and control of magnetic flux and magnetic induction intensity within transformers.

[0041] During DC demagnetization, the hysteresis loop still intersects the vertical axis, representing the various remanence events that occur during demagnetization. It's easy to see that these points correspond to moments when the magnetic field strength is zero, i.e., the transformer current is zero, and the current crosses the coordinate axis from positive to negative. Therefore, the moments when remanence occurs during demagnetization can be correlated with the moments when the current decreases from a positive value to zero in the time-current curve of the demagnetization process.

[0042] A transformer can be represented as a series connection of a resistor and an inductor. Each time a voltage is applied across the transformer, the change in current can be analyzed using a first-order RL series circuit. At the beginning of the demagnetization process, the residual magnetism inside the transformer is at its positive saturation value. Applying a reverse voltage reduces it to the positive saturation residual magnetism B1, and the current continues to decrease until it reaches its reverse peak value. Afterward, the voltage gradually reverses, causing the current amplitude to gradually decrease until the demagnetization requirement is met, and the entire process ends. Throughout this process, the direction of the external voltage is opposite to the direction of the residual magnetism inside the transformer, therefore exhibiting the same changing pattern.

[0043] Analyzing the voltage and current relationship diagram above, by finding the points corresponding to two consecutive positive remanences in the diagram, we can discover that:

[0044] The current between two adjacent positive remanent magnetization points undergoes three changes: applying a reverse voltage to reach the reverse peak; applying a forward voltage to reduce it to zero and reach the forward peak; and applying a reverse voltage to reduce it to 0. According to formula (13), the magnitude of the weakening between two adjacent positive remanent magnetizations is related to the difference in the time between applying the forward and reverse voltages. The entire DC demagnetization process is to gradually apply a voltage with the opposite polarity to the remanent magnetization to the transformer, reducing it to zero. Therefore, it is only necessary to consider the magnitude of complete demagnetization by the transformer as B. r Using the net reverse time required for remanence as a baseline, the percentage of remanence for each positive remanence occurring during the demagnetization process can be determined.

[0045] After obtaining the time-current curve of the DC demagnetization process, the following processing is performed: First, mark the intersection points of the current and the horizontal axis when the current decreases from a positive value to 0. These points are called B. iThe point is where i is the number of times a reverse DC power supply is applied to the transformer (applying a reverse voltage can produce positive residual magnetism), and the corresponding time is read and named t. 0i Then, the time it takes for the current to reach each positive and negative peak value is read and named t. Pi t Ni It can be observed that the net reverse voltage time |Δt| between two adjacent remanent magnetization points j |(1≤j≤i) has the following relation:

[0046] |Δt j |=(t Nj -t 0j )+(t Nj+1 -t Pj )-(t Pj+1 -t Nj )

[0047]

[0048] |Δt j | This can represent the demagnetizing process, where the residual magnetism of the transformer changes from B. j Change to B j+1 The degree of change will be calculated for all |Δt. j The summation of these values ​​yields Σt, which represents the decrease in magnetic flux density during the entire demagnetization process. The demagnetization process begins with the saturation magnetic flux density B. s The process begins with elimination, eventually reducing the magnetic field strength to B0. All the above analyses are based on the premise that the voltage magnitude remains constant. It is easy to see that the net reverse voltage time can represent the difference t between any two magnetic induction intensities. sum Indicates the initial remanence B r The difference between 0 and Σt; Σt represents the positive saturation value B. s The difference between the final residual magnetism B0 and the final residual magnetism B0.

[0049] After obtaining the magnitude of the changes between the various values, the demagnetization process and its results can be quantified (in B). r The calculation formula (based on) is:

[0050]

[0051] like Figure 4 As shown, a reverse voltage is first applied to the transformer until it reaches the reverse saturation point, and then a forward voltage is applied until it reaches the forward saturation point. This process is similar to measuring the hysteresis loop. The current signal throughout the process is monitored and sampled to obtain the time-current curve. The final method for determining the remanent magnetization polarity is as follows:

[0052] The above process can be viewed as two stages: the magnetic flux inside the transformer rises from its initial value to its reverse saturation value; the magnetic flux changes from its reverse saturation value to its forward saturation value, with the change in flux being twice the saturation flux. If the transformer contains positive remanence, the magnitude of the flux change in the first stage should be greater than the saturation flux; conversely, the magnitude of the flux change in the first stage should be less than the saturation flux. The magnitude of the flux change is proportional to the integral of the voltage. Since the voltage remains constant throughout the process, analyzing the time intervals of the two stages allows us to determine the polarity of the remanence.

[0053] t1 and t2 are defined as the time required for the transformer flux to reach the positive and negative saturation points, respectively, and are also the time required for the transformer current to rise from zero to the reverse peak saturation excitation current and to change from the reverse saturation excitation current to the positive saturation excitation current.

[0054] Use the following method to determine the residual magnetism polarity of a transformer: If Then the residual magnetism of the transformer is positive; if Then the residual magnetism of the transformer is in the reverse direction; if If the transformer has no residual magnetism, then there is no residual magnetism inside. Using this method, one can directly and accurately determine whether a transformer has residual magnetism and its polarity without performing complex calculations, and draw a quick conclusion.

[0055] Besides determining the remanent magnetization polarity, the main purpose of this process is to obtain the crucial parameter t for quantifying the DC demagnetization process. sum This refers to the net reverse voltage time required to completely eliminate the residual magnetism inside the transformer. The relationship between magnetic induction intensity and voltage application time during this operation has been discussed above. Based on this conclusion and the hysteresis loop of this process, we can obtain... Figure 5 ,

[0056]

[0057]

[0058] Therefore, the corresponding t sum And Δt (causing the magnitude of the magnetic field strength to change from B) r Rise to B s The formula for calculating the required forward voltage time is as follows:

[0059]

[0060] Δt=t2-t1

[0061] After determining the residual magnetism polarity using the time-current curve data, DC demagnetization can begin. By applying DC power supplies of different polarities, the residual magnetism inside the transformer is now at its positive saturation value. Normally, the initial stage of the DC demagnetization process also magnetizes the transformer, which is then gradually eliminated. Therefore, the impact of the above method on the DC demagnetization process is relatively limited. However, this operation allows for the evaluation of the demagnetization process and its final effect. Furthermore, since the transformer's saturation flux is known, and the flux polarity is guaranteed to be positive after the above treatment, demagnetization of a flux with known polarity and magnitude is relatively easy to achieve.

[0062] like Figure 2 As shown, this invention uses the PSACAD platform to build the simulation model. A single-phase full-bridge inverter circuit is added to both sides of the DC voltage source to achieve voltage direction transformation. The voltage and current signals on both sides of the transformer are sampled and monitored. Based on the signal changes, the switching transistors inside the inverter circuit, as well as the short-circuit circuit, are controlled to turn on and off.

[0063] This simulation employs a bipolar pulse demagnetization method with gradually decreasing pulse width. The control circuit analyzes and processes the current flowing through the transformer during demagnetization, controlling the switching transistors within the inverter circuit to gradually reduce the peak value of the current in each cycle. The voltage magnitude remains constant throughout the demagnetization process; only the duration of the voltage direction is changed to achieve the demagnetizing effect. At the end of demagnetization, a short-circuit circuit is connected to prevent further changes in the transformer's state. The voltage is set to achieve demagnetization after 10 commutations, meaning the current reaches its forward and reverse peak values, and the number of forward residual magnetism cycles is 5.

[0064] In the simulation, the transformer is first set to contain a positive remanence of 1.36. The changes in current, voltage, and magnetic flux density over time during the demagnetization process are recorded. Since magnetic field strength is proportional to current, a hysteresis loop can be formed by plotting current and magnetic flux density on the horizontal and vertical axes, respectively. The magnetic flux density corresponding to the point where the current is zero is the magnitude of the remanence during the demagnetization process.

[0065] Analyzing the time-current curves during the measurement of remanence, we first determine the remanence polarity. Following the method described above, we obtained the following data: t1 = 1.444 s, t2 = 1.632 s. We can see that t1 < 0.5 * t2. Therefore, we can determine that the initial remanence polarity of the transformer is positive, consistent with the experimental preset value. Furthermore, we can obtain t... sum =0.63925S, Δt=0.1945S. At this time, the residual magnetism inside the transformer is in a positive saturation state and the demagnetization process continues.

[0066] To determine the percentage of residual magnetism, first record the time when each positive and negative direction reaches its peak value on the time-current curve, as well as the time when the current decreases from a positive value to 0. Then, find out the duration of the positive and negative voltages acting on the transformer terminals between two adjacent residual magnetism events. The difference between these two times and the absolute value of the difference gives the degree of change between two adjacent residual magnetism events. Then, perform calculations to obtain the predicted and actual values, as shown in the table below.

[0067] Table 1 Comparison of Predicted and Actual Values ​​of Residual Magnetism Percentage

[0068]

[0069]

[0070] The table above analyzes and predicts several positive residual magnetism points during the demagnetization process. As explained in the previous principle description, this method can analyze the entire process of constant-amplitude frequency-increasing DC demagnetization and obtain the percentage of the final magnetic flux density inside the transformer relative to the initial residual magnetism. The table shows that the difference between the predicted and actual values ​​is no more than 2%, with an average error of 1.889%. This method demonstrates high accuracy in predicting the percentage of residual magnetism during DC demagnetization, enabling precise prediction.

[0071] The following shows the relationship between the predicted value of the residual magnetism percentage during the demagnetization process and the actual residual magnetism percentage during the simulation process generated by this method. It can be found that the difference between the two is very small. The residual magnetism percentage gradually decreases as the demagnetization process proceeds, eventually reaching a very small value, which proves that the demagnetization process is completed well.

[0072] By combining the predicted data's position and time within the time-current curve and the hysteresis loop of the demagnetization process, a curve can be obtained with the demagnetization time as the x-axis and the predicted remanence percentage as the y-axis, combining the predicted remanence percentage with the demagnetization process. The actual remanence percentage-time curve is a curve that gradually changes direction and decreases in amplitude over time. Because the above curve only predicts the positive remanence during the demagnetization process and the demagnetization result with a limited sample size, it cannot perfectly match the actual trend. However, by analyzing and predicting more points using the method of this invention, it can increasingly approximate the actual curve. With a sufficient number of data collection points, this curve can be used to better analyze and predict the entire demagnetization process.

[0073] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A DC demagnetization quantization method based on time-current curves, characterized in that, The method includes the following steps: During DC demagnetization, the time-current change curve of the transformer is obtained through a current monitoring device; Mark the intersections where the current drops from a positive value to zero, and determine the time corresponding to these intersections to obtain the remanence points; Based on the time information of each remanence point, calculate the percentage of remanence at each time relative to the initial remanence; The specific calculation of the percentage of residual magnetism for each instance is as follows: Read the time it takes for the current to reach its forward and reverse peak values; Calculate the change in remanence each time based on the time difference between adjacent remanence points; By summing up all the changes in remanence, we can obtain the decrease in magnetic induction intensity during the entire demagnetization process, and then calculate the percentage of remanence for each step using this decrease. The formula for calculating the change in remanence each time based on the time difference between adjacent remanence points is as follows: |Δt j |=(t Nj -t 0j )+(t Nj+1 -t Pj )-(t Pj+1 -t Nj ) Where, Δt j t represents the time difference corresponding to the change in magnetic flux from the j-th positive remanence point to the (j+1)-th positive remanence point. Nj t is the time when the demagnetizing current reaches its negative peak for the jth time. 0j Let t be the time it takes for the demagnetizing current to decay to 0 from the positive half-region for the j-th time. Pj The time when the demagnetizing current reaches its positive peak value for the jth time; The formula for summing all changes in remanence to obtain the decrease in magnetic induction intensity during the entire demagnetization process is as follows: Where, |Δt j | Indicates the demagnetizing process; the residual magnetism of the transformer changes from B. j Change to B j+1 The change in; The formula for calculating the percentage of residual magnetism each time using this reduction is: Among them, t sum Indicates the initial remanence B r The time difference corresponding to the difference between B and 0, Δt is the time difference that makes the magnitude of the magnetic field strength change from B. r Rise to B s Required forward voltage time; The t sum The time required for the reverse and forward voltages to apply through the transformer flux to reach the positive and negative saturation points, Δt, is obtained from the specific formula: Δt=t2-t1 Where t1 is the time required for the transformer flux to reach the positive and negative saturation points, and t2 is the time required for the transformer flux to reach the positive and negative saturation points, respectively, with the reverse voltage applied.

2. The DC demagnetization quantization method based on time-current curves according to claim 1, characterized in that, The remanent magnetization point is the intersection of the current and the horizontal axis when the current decreases from a positive value to zero, and is defined as B. i Point, where i represents the number of times the reverse voltage is applied.

3. An electronic device, characterized in that, The device includes a memory and a processor, the memory being used to store a computer program, and the processor running the computer program to cause the electronic device to perform the DC demagnetization quantization method according to any one of claims 1 to 2.

4. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the DC demagnetization quantization method as described in any one of claims 1 to 2.

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