Transformer opening angle detection method and device

Abstract

The embodiment of the invention provides a transformer opening angle detection method and device. The method comprises the following steps: in response to the opening operation of the transformer, sampling the no-load current of the transformer to obtain a current signal; converting the current signal into a voltage signal; amplifying the voltage signal to obtain a voltage amplification signal; according to the voltage amplification signal, a sudden change moment and a reference moment are determined, the sudden change moment is the moment when the voltage change value of the voltage amplification signal is larger than a set threshold value, and the voltage value of the voltage amplification signal is smaller than zero at the previous moment of the reference moment; the voltage value of the voltage amplification signal at the next moment of the reference moment is greater than zero; and determining the opening angle of the transformer based on the sudden change moment and the reference moment. The method is used for improving the calculation accuracy of the opening angle of the transformer.

Description

Technical Field

[0001] The present application relates to the field of electrical technology, and in particular to a method and device for detecting a trip angle of a transformer. Background Art

[0002] When closing a power transformer, a magnetizing inrush current may be generated due to the saturation characteristics of the ferromagnetic material in the transformer core. The maximum magnitude of this inrush current can reach 6 to 8 times the rated current. This inrush current can cause malfunction of the differential protection, leading to transformer closing failure. Therefore, it is necessary to detect the transformer's trip angle and control closing based on the actual trip angle to effectively suppress the inrush current.

[0003] At present, the same-phase closing method is mainly used to detect the transformer opening angle. A current transformer is installed in a certain phase of the transformer, and current sampling is performed through the current transformer. Then, the transformer opening moment is detected based on the sampled current value.

[0004] However, in this conventional method, since the transformer is generally in a no-load state before tripping, the no-load current is generally very small, which can easily lead to calculation errors and inaccurate judgment of the tripping moment. Summary of the Invention

[0005] The embodiments of the present application provide a transformer trip angle detection method and device for solving the problem that when the transformer is unloaded, the current value is small, resulting in inaccurate trip angle calculation.

[0006] In a first aspect, an embodiment of the present application provides a method for detecting a transformer trip angle, comprising:

[0007] In response to a transformer tripping operation, sampling the no-load current of the transformer to obtain a current signal;

[0008] converting the current signal into a voltage signal;

[0009] amplifying the voltage signal to obtain an amplified voltage signal;

[0010] determining a mutation moment and a reference moment based on the voltage amplified signal, wherein the mutation moment is a moment when a voltage change value of the voltage amplified signal is greater than a set threshold, the voltage value of the voltage amplified signal at a moment before the reference moment is less than zero, and the voltage value of the voltage amplified signal at a moment after the reference moment is greater than zero;

[0011] Based on the sudden change moment and the reference moment, a trip angle of the transformer is determined.

[0012] In a possible implementation, converting the current signal into a voltage signal includes: acquiring a first amplification factor; and converting the current signal into the voltage signal according to the first amplification factor.

[0013] In a possible implementation, amplifying the voltage signal to obtain an amplified voltage signal includes:

[0014] Obtaining a set voltage threshold value of an inrush current suppression device, wherein the inrush current suppression device is used to adjust a closing moment of the transformer according to the opening angle;

[0015] determining a value range of a second amplification factor of the voltage signal according to the voltage value of the voltage signal and the voltage threshold value;

[0016] Based on the value range of the second amplification factor, the voltage signal is amplified to obtain a voltage amplified signal.

[0017] In a possible implementation, determining the mutation moment according to the voltage amplified signal includes:

[0018] Performing a low-order DoBechie wavelet transform on the voltage amplified signal to obtain a transformed waveform;

[0019] The transformer tripping moment is obtained according to the transformed waveform and determined as the sudden change moment.

[0020] In a possible implementation, determining a reference time according to the amplified voltage signal includes:

[0021] Obtaining a target moment when the voltage amplified signal changes from a negative value to a positive value;

[0022] Acquire a previous moment and a next moment adjacent to the target moment, as well as a first voltage value of the voltage-amplified signal at the previous moment and a second voltage value of the voltage-amplified signal at the next moment;

[0023] The reference time is determined based on the previous time, the next time, the first voltage value, and the second voltage value.

[0024] In a possible implementation, determining the trip angle of the transformer based on the mutation moment and the reference moment includes:

[0025]

[0026] In the above formula, Indicates the trip angle, Indicates the moment of mutation, Indicates the base time.

[0027] In one possible implementation, the method further includes:

[0028] Before closing the transformer, adjusting the closing moment according to the opening angle until the current phase of the transformer when closing based on the closing moment is the same as the current phase before opening, where the current phase before opening is determined according to the opening angle;

[0029] Based on the closing time, the transformer is controlled to close.

[0030] In a second aspect, an embodiment of the present application provides a transformer trip angle detection device, comprising: a current-voltage converter, an active voltage amplifier module, and a trip angle calculation module;

[0031] The current-to-voltage converter is used to access the transformer no-load current sampled by the current transformer and convert the transformer no-load current into a voltage signal;

[0032] The active voltage amplifier module is connected to the current-voltage converter and is used to amplify the voltage signal to obtain a voltage amplified signal;

[0033] The trip angle calculation module is connected to the active voltage amplifier module and is used to determine the trip angle of the transformer according to the voltage amplification signal.

[0034] In a possible implementation, the active voltage amplifier module includes: at least one voltage amplifier and an adjustable resistor, wherein the adjustable resistor is connected to the voltage amplifier;

[0035] The voltage amplifier is used to amplify the voltage signal;

[0036] The adjustable resistor is used to receive a control signal and adjust the resistance value until the amplification factor of the voltage amplifier is the same as the target amplification factor.

[0037] In a possible implementation manner, the current-to-voltage converter is specifically configured to convert the milliampere-level current sampling signal into a millivolt-level voltage signal according to the first amplification factor.

[0038] The transformer trip angle detection method and device provided in the embodiments of the present application samples the microcurrent when the transformer is tripped, then converts the sampled current signal into a voltage signal, and further amplifies it, and then uses the amplified voltage signal waveform to determine the mutation moment and the reference moment, thereby determining the actual tripping moment of the transformer, and calculating the tripping angle of the transformer based on this, which can improve the accuracy of the judgment of the tripping moment, so that the residual magnetism can be estimated based on the tripping moment, and the excitation inrush current can be suppressed by the phase-controlled closing method, thereby improving the reliability of the excitation inrush current suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0040] Figure 1 A schematic structural diagram of a surge suppression device provided in an embodiment of the present application;

[0041] Figure 2 A method for detecting a transformer trip angle provided in an embodiment of the present application;

[0042] Figure 3 A waveform diagram provided for an embodiment of the present application;

[0043] Figure 4 A schematic diagram of a reference time determination process provided in an embodiment of the present application;

[0044] Figure 5 A schematic diagram of the structure of a transformer trip angle detection device provided in an embodiment of the present application;

[0045] Figure 6 This is a high-precision micro-current amplification and voltage amplification circuit diagram provided in the embodiments of the present application.

[0046] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0047] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0048] When a power transformer is closed, due to the saturation characteristics of the ferromagnetic material of the transformer core, an excitation inrush current may be generated in the transformer, and the maximum amplitude of the excitation inrush current may reach 6 to 8 times the rated current. The excitation inrush current may cause the differential protection to malfunction, resulting in the failure of the transformer to close. In addition, excessive current will also cause an impact on the transformer itself, shorten the life of the transformer, and may even affect the safe operation of the power system. For this reason, it is necessary to provide a reliable excitation inrush current suppression strategy. In related technologies, the same-phase closing method can effectively suppress inrush current by detecting the opening angle of the transformer when it is opened and controlling the closing according to the actual opening angle. However, since the transformer is mainly installed with a current transformer in actual engineering, a voltage transformer may not be installed, and the transformer is generally in a no-load state before opening, the no-load current is generally less than 5% of the rated current. For large transformers, it may even be less than 1%. The minimum secondary value of an actual current transformer is 1 amp, and a certain margin is left when selecting the current transformer. That is, the rated current of the transformer may be only 0.5 amps after conversion to the secondary value, and the effective value of the transformer's no-load current is about 5 mA. This is a very small current, which can easily make it difficult for the current transformer to accurately detect it, resulting in errors in judging the opening moment. Once the opening moment is judged incorrectly, an excitation inrush current may occur during subsequent closing.

[0049] In response to the above problems, the present application provides a method for detecting the tripping angle of a transformer when it is running at no-load. The method first connects the micro-current when the transformer is tripped through a current transformer, then converts it into a voltage signal through a small converter, and then amplifies the micro-current to a size that can be sampled through an active voltage amplifier module. The amplified current waveform is then used for wavelet transform, and the actual tripping moment is judged by its waveform change characteristics. The tripping angle of the transformer is thereby calculated, and the residual magnetism is estimated. The excitation inrush current is suppressed by the phase-controlled closing method, which can avoid errors in the judgment of the tripping moment and improve the reliability of the excitation inrush current suppression.

[0050] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0051] For example, Figure 1 This is a schematic diagram of the structure of the surge suppression device provided in the embodiment of the present application, as shown in FIG. Figure 1As shown, the circuit breaker is connected to the transformer. When the circuit breaker is opened, the micro-current generated when the transformer is opened is connected through the current transformer. At the same time, the micro-current signal is converted into a voltage signal through the current-voltage converter. The voltage is then amplified through the resistor voltage divider module and the active voltage amplifier module. The amplified voltage signal is input to the opening angle calculation module for opening angle calculation. The circuit breaker is closed according to the calculated opening angle to achieve inrush current suppression.

[0052] Figure 2 The transformer trip angle detection method provided in the embodiment of the present application can be applied to an excitation inrush current suppression device, such as Figure 2 As shown, the method may specifically include the following steps:

[0053] Step S210: In response to the transformer opening operation, sampling the transformer no-load current to obtain a current signal;

[0054] Step S220, converting the current signal into a voltage signal;

[0055] Step S230: amplify the voltage signal to obtain a voltage amplified signal;

[0056] Step S240: Determine the mutation time and the reference time according to the voltage amplification signal.

[0057] The sudden change moment is the moment when the voltage change value of the voltage amplified signal is greater than the set threshold value, the voltage value of the voltage amplified signal at the moment before the reference moment is less than zero, and the voltage value of the voltage amplified signal at the moment after the reference moment is greater than zero;

[0058] Step S250: Determine the trip angle of the transformer based on the mutation time and the reference time.

[0059] In an embodiment of the present application, the microcurrent when the transformer is tripped is sampled, and the sampled current signal is converted into a voltage signal and further amplified. The amplified voltage signal waveform is then used to determine the mutation moment and the reference moment, thereby determining the actual tripping moment of the transformer. The tripping angle of the transformer is calculated based on this, which can improve the accuracy of the judgment of the tripping moment, so that the residual magnetism can be estimated based on the tripping moment, and the excitation inrush current can be suppressed by the phase-controlled closing method, thereby improving the reliability of the excitation inrush current suppression.

[0060] In step S210, the transformer is typically in a no-load state before tripping, and the no-load current is generally less than 5% of the rated current. For large transformers, it may even be less than 1%. Furthermore, in actual engineering applications, the circuit breaker side of the transformer is typically equipped with a current transformer, and not necessarily a voltage transformer. This results in the current signal being sampled only through the current transformer during tripping.

[0061] The minimum secondary value (i.e., the sampled output value) of an actual current transformer is 1 A, and a certain margin is often left when selecting the current transformer. This means that the transformer's rated current may be converted to a secondary value of only 0.5 A, resulting in an effective no-load current of approximately 5 mA. This is a very small current, and it is usually difficult to determine the specific opening moment of the circuit breaker based on this current. Inaccurate judgment of the opening moment will affect closing and cause magnetizing inrush current.

[0062] For step S220, the current signal may be converted into a voltage signal by a current-to-voltage converter. For example, in some embodiments, the current signal may be converted into a voltage signal according to the first amplification factor. Specifically, a high-precision small current converter (1 mA: k1 mV) may be used to convert the small current signal i obtained by sampling the transformer no-load current into a voltage signal. 0Π Converted to voltage signal, the conversion formula is as follows:

[0063]

[0064] In the above formula, u T represents the voltage signal, and k1 represents the first amplification factor.

[0065] In this embodiment, in the process of converting the current signal into a voltage signal, a first amplification factor is set and the small current signal i is converted into a voltage signal. 0Π Converting it into a voltage signal makes it easier to detect the voltage signal, thereby further improving the accuracy of subsequent trip angle determination and ensuring the accuracy of the judgment of the trip moment.

[0066] In step S230, the voltage signal can be amplified by an amplifier. Specifically, in some embodiments, the amplifier can be an active voltage amplifier. After determining a range of values ​​for a second amplification factor of the voltage signal based on the set voltage threshold value of the inrush current suppression device and the voltage value of the voltage signal at each sampling moment, the voltage signal can be amplified based on the range of values ​​of the second amplification factor to obtain an amplified voltage signal.

[0067] Specifically, the amplification factor k of the active voltage amplifier can be calculated as the second amplification factor based on the following formula and the voltage threshold values ​​of the analog-to-digital conversion circuit of the inrush current suppression device and other related test instruments:

[0068]

[0069] In the above formula, u th is the voltage threshold value of the analog-to-digital conversion circuit of the inrush current suppression device, which can be 0.6 volts. T and u div is the voltage value of the voltage signal before amplification, uout is the voltage value of the amplified voltage signal, i 0Π is the current value of the small current signal.

[0070] Through the above formula, the value range of the second magnification k is obtained as follows:

[0071]

[0072] In this embodiment, the value range of the second amplification factor is determined by using the set voltage threshold value of the inrush current suppression device, so that the final amplified voltage signal can meet the minimum requirement of the inrush current suppression device for calculating the trip angle, thereby ensuring that the trip angle can be accurately calculated.

[0073] In step S240, the voltage signal can be directly output through an oscilloscope or other device to generate a corresponding signal waveform. By analyzing the waveform, the sudden change moment and the reference moment can be quickly determined. Furthermore, in some embodiments, the amplified voltage signal can be subjected to a low-order DoBechie wavelet transform to obtain a transformed waveform. Based on the transformed waveform, the transformer tripping moment can be determined as the sudden change moment.

[0074] Among them, the Low-Order Daubechies Wavelet Transform (LODWT) is based on the Daubechies Wavelet (DW) and uses a wavelet function with low vanishing moments (VM) to perform multi-level decomposition and reconstruction of the signal. For signal detection with low smoothness requirements, the use of low-order wavelets is sufficient to capture local features. For example, Figure 3 The waveform diagram provided in the embodiment of the present application is as follows: Figure 3 As shown in the figure, with the current value as the ordinate of the waveform graph and the time as the abscissa of the waveform graph, the waveform change of the sampled original current signal waveform is not obvious enough, while the waveform change of the amplified current signal obtained after amplification is more obvious. Furthermore, through the low-order Dobesi wavelet transform, it can be clearly found that when the ordinate value is 300, the corresponding voltage signal value fluctuates violently, so the reference time and the mutation time can be determined based on the waveform.

[0075] In this embodiment, since the low-order DoBechie wavelet transform has the advantages of simple expression, small computational complexity, sensitivity to sudden change signals and high time resolution, by using the low-order DoBechie wavelet transform, the reference moment and the sudden change moment can be found more accurately, thereby improving the accuracy of subsequent trip angle detection.

[0076] In step S250, the difference between the sudden change time and the reference time can be calculated, and the trip angle can be determined based on the difference. Alternatively, the trip angle can be determined by an indirect method (such as residual flux estimation or voltage phase inference).

[0077] The trip angle refers to the current phase angle at the moment the transformer is tripped (i.e., the circuit breaker opens). Specifically, when the circuit breaker opens, the current in the transformer winding is abruptly interrupted. At this moment, the instantaneous phase of the current (i.e., the trip angle) determines the magnitude and direction of the residual magnetic flux in the core. For example, if the current is exactly crossing zero (a phase angle of 0 or 180 degrees) at the time of trip, the residual magnetism in the core is low. However, if the current is at its peak (a phase angle of 90 or 270 degrees) at the time of trip, the residual magnetism may be high.

[0078] The trip angle directly affects the flux change during the next closing. If the voltage phase at closing does not match the current phase before opening, the core flux will suddenly change, triggering an excitation inrush current (a sudden increase in current). For this reason, a same-phase closing method can be used during closing. This involves detecting the trip angle and adjusting the closing moment so that the current after closing is consistent with the current phase before opening, thereby smoothing the flux change and suppressing the inrush current. Specifically, before closing the transformer, the closing moment can be adjusted based on the trip angle until the current phase at closing, based on the closing moment, is the same as the current phase before opening. The transformer closing is then controlled based on the closing moment. The current phase before opening is determined based on the trip angle.

[0079] The following describes in detail how to calculate the trip angle through some embodiments.

[0080] Before calculating the trip angle, we first need to determine the mutation moment and the reference moment. As mentioned above, we can use Figure 3 The transformation waveform shown in the figure is used to determine the transformer opening time t brk As a mutation moment. Further, in some embodiments, Figure 4 The following is a flow chart of the reference time determination process provided in the embodiment of the present application: Figure 4 As shown, the reference time t0 can be determined by the following steps:

[0081] Step S410, obtaining the target time when the voltage amplified signal changes from a negative value to a positive value;

[0082] Step S420: Acquire a previous moment and a next moment adjacent to the target moment, as well as a first voltage value of the voltage-amplified signal at the previous moment and a second voltage value of the voltage-amplified signal at the next moment;

[0083] Step S430: Determine a reference time based on the previous time, the next time, the first voltage value, and the second voltage value.

[0084] In this embodiment, please refer to the above Figure 3 , monitor the change value of the voltage signal in the wavelet analysis signal waveform, when its voltage sampling value changes from a negative sampling value u less than zero - (ie, the first voltage value) changes to a positive sampling value u greater than zero + (i.e. the second voltage value) is taken as the target time, and then the previous time t - , and the next moment t of the target moment + , the reference time t0 is calculated by the following formula:

[0085]

[0086]

[0087] Furthermore, based on the above embodiment, in some embodiments, after the mutation time and the reference time are determined, the trip angle of the transformer can be calculated using the following formula:

[0088]

[0089] In the above formula, Indicates the trip angle, Indicates the moment of mutation, Indicates the base time.

[0090] By determining the mutation moment and the reference moment according to the voltage zero-crossing moment in the above embodiment, and calculating the trip angle based on the transformer trip angle calculation formula, the method is simple, easy to implement, efficient and has high measurement accuracy.

[0091] The following describes the entire opening angle detection method process in detail through a complete embodiment, which specifically includes the following steps:

[0092] S11, select any phase voltage of the transformer as a reference, which will be used to calculate the trip angle;

[0093] S12. To ensure measurement accuracy, use a current transformer with higher precision (such as a measurement and control current transformer (Measurement and Control CT)) to sample the no-load current of the transformer phase and connect it to the excitation inrush current device. The current transformer secondary side current signal is i 0Π ;

[0094] S13, through the high-precision small current converter (1 mA: k1 mV) to convert the micro-current signal i 0Π Converted to voltage signal, the specific formula is as follows:

[0095]

[0096] In the above formula, k1 is the amplification factor of the high-precision small current converter.

[0097] S21. Calculate the amplification factor k of the active voltage amplifier based on the voltage threshold values ​​of the analog-to-digital conversion circuit of the inrush current suppression device and other related test instruments. The specific formula is as follows:

[0098]

[0099] In the above formula, u th is the voltage threshold value of the analog-to-digital conversion circuit of the inrush current suppression device, which can be 0.6 volts. T and u div is the voltage value of the voltage signal before amplification, u out is the voltage value of the amplified voltage signal, i 0Π is the current value of the small current signal.

[0100] Through the above formula, the value range of the second magnification k is obtained as follows:

[0101]

[0102] In the above formula, the value of k1 can be 4.

[0103] S22, calculating the amplification factor according to the no-load current, changing the resistance in the voltage amplifier circuit to adjust the amplification factor k of the active voltage amplifier module, and sampling and amplifying the voltage signal;

[0104] S31. Since the low-order DoBechie wavelet transform has the advantages of simple expression, small computational complexity, sensitivity to sudden change signals, and high time resolution, the amplified voltage signal is subjected to a low-order DoBechie wavelet transform to obtain a transformed waveform;

[0105] S32. According to the waveform characteristics of the low-order Dobesi wavelet transform, the moment when the sampled and amplified voltage signal suddenly changes is obtained, which is the tripping moment t brk ;

[0106] S33. According to the selected phase voltage sampling value, the negative sampling value u - To the positive sample value u + Taking the moment t0 as the reference, calculate the opening angle :

[0107]

[0108]

[0109]

[0110] The above-mentioned trip angle detection method can be applied to the trip angle detection method for no-load closing excitation inrush current suppression. By sampling the signal through a measuring current transformer and using a high-precision current-voltage converter and an amplifier circuit, the transformer no-load micro current is amplified, which can detect tiny electric quantities with high measurement accuracy. At the same time, a low-order Dobesi wavelet transform is used to accurately determine the tripping moment and calculate the trip angle based on the voltage zero-crossing moment. The method is simple, easy to implement, efficient and has high measurement accuracy.

[0111] Figure 5 A schematic diagram of the structure of the transformer trip angle detection device provided in the embodiment of the present application is shown as follows: Figure 5 As shown, it includes: a current-voltage converter 51 , an active voltage amplifier module 52 and a trip angle calculation module 53 .

[0112] The current-to-voltage converter 51 is used to access the transformer no-load current sampled by the current transformer and convert the transformer no-load current into a voltage signal.

[0113] An active voltage amplifier module 52 is connected to the current-voltage converter and is used to amplify the voltage signal to obtain a voltage amplified signal;

[0114] The trip angle calculation module 53 is connected to the active voltage amplifier module and is used to determine the trip angle of the transformer according to the voltage amplification signal.

[0115] Optionally, an active voltage amplifier module includes: at least one voltage amplifier and an adjustable resistor, the adjustable resistor being connected to the voltage amplifier; the voltage amplifier being used to amplify the voltage signal; and the adjustable resistor being used to receive a control signal and adjust the resistance value until the amplification factor of the voltage amplifier is the same as the target amplification factor.

[0116] The target magnification may refer to the second magnification k mentioned above.

[0117] Optionally, the current-to-voltage converter is specifically configured to convert the milliampere-level current sampling signal into a millivolt-level voltage signal according to the first amplification factor.

[0118] The following describes in detail the transformer trip angle detection device through some embodiments.

[0119] Refer to the above attached Figure 1 To install the inrush current suppression device, the microcurrent signal generated during the tripping operation must be connected to the inrush current suppression device from the transformer-side measurement and control CT. The microcurrent signal then undergoes high-precision microcurrent amplification via a current-to-voltage converter, and then amplifies it through an active voltage amplifier module to produce an amplified voltage signal. Finally, the signal is filtered and processed using a low-order Dobesi wavelet transform in the tripping angle calculation module. Based on the waveform characteristics, the tripping moment and the tripping angle are calculated.

[0120] Among them, when amplifying the voltage signal, Figure 6 The high-precision micro-current amplification and voltage amplification circuit diagram provided in the embodiment of the present application is as follows: Figure 6 As shown, the active voltage amplifier module includes two amplifiers. After obtaining the current signal sampled by the current transformer during the current and voltage variation period, the active voltage amplifier module calculates the second amplification factor k of the active voltage amplifier module based on the no-load current, the amplification factor of the current-voltage converter, and the analog-to-digital loop threshold value of the inrush current suppression device. The second amplification factor k of the adjustable active voltage amplifier module is adjusted through an adjustable resistor, specifically including:

[0121] (1) Monitor the transformer no-load current i connected by the measurement and control CT 0Π size;

[0122] (2) Based on the threshold voltage value of the analog-to-digital conversion circuit of the selected inrush current suppression device, the final amplification factor k of the active voltage amplifier is determined by the following formula:

[0123]

[0124] In the above formula, k1 is the first magnification mentioned above, u th is the voltage threshold value of the analog-to-digital conversion circuit of the inrush current suppression device, i 0Π is the current value of the small current signal.

[0125] (3) After adjusting and testing the amplification factor of the adjustable active voltage amplifier module, the debugging of the high-precision microcurrent amplifier module is completed.

[0126] After debugging, the inrush current suppression device can be put into transformer operation and maintenance, continuously detecting the current sampling value when the transformer is tripped, continuously performing low-order Multi-Bechy wavelet transform on the amplified signal, judging whether to trip based on the current signal and the wavelet transform signal characteristics, recording the tripping moment and the most recent voltage zero-crossing moment, and calculating the tripping angle based on this. This is used to evaluate the residual magnetism of the transformer to determine the closing moment and achieve inrush current suppression.

[0127] The above-mentioned transformer trip angle detection device has a simple circuit structure, simple calculation, good trip angle detection effect, is conducive to realizing the residual magnetism estimation of the power transformer, and has high engineering feasibility and practicality.

[0128] Those skilled in the art will appreciate that all or part of the steps in the above-described method embodiments can be implemented using hardware associated with program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0129] Finally, it should be noted that those skilled in the art will readily identify other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. The present invention is not limited to the precise structure described above and illustrated in the accompanying drawings, and various modifications and variations may be made without departing from the scope thereof. The scope of the present invention is limited solely by the appended claims.

Claims

1. A method for detecting a transformer trip angle, characterized in that: include: In response to a transformer tripping operation, sampling the no-load current of the transformer to obtain a current signal; converting the current signal into a voltage signal; amplifying the voltage signal to obtain an amplified voltage signal; determining a mutation moment and a reference moment based on the voltage amplified signal, wherein the mutation moment is a moment when a voltage change value of the voltage amplified signal is greater than a set threshold, the voltage value of the voltage amplified signal at a moment before the reference moment is less than zero, and the voltage value of the voltage amplified signal at a moment after the reference moment is greater than zero; Based on the sudden change moment and the reference moment, a trip angle of the transformer is determined.

2. The method according to claim 1, characterized in that Converting the current signal into a voltage signal comprises: obtaining a first magnification; The current signal is converted into the voltage signal according to the first amplification factor.

3. The method according to claim 1, characterized in that The amplifying the voltage signal to obtain an amplified voltage signal includes: Obtaining a set voltage threshold value of an inrush current suppression device, wherein the inrush current suppression device is used to adjust a closing moment of the transformer according to the opening angle; determining a value range of a second amplification factor of the voltage signal according to the voltage value of the voltage signal and the voltage threshold value; Based on the value range of the second amplification factor, the voltage signal is amplified to obtain the voltage amplification signal.

4. The method according to claim 1, wherein Determining the mutation moment according to the voltage amplified signal includes: Performing a low-order DoBechie wavelet transform on the voltage amplified signal to obtain a transformed waveform; The transformer tripping moment is obtained according to the transformed waveform and determined as the sudden change moment.

5. The method according to claim 1, wherein Determining a reference time according to the voltage amplified signal includes: Obtaining a target moment when the voltage amplified signal changes from a negative value to a positive value; Acquire a previous moment and a next moment adjacent to the target moment, as well as a first voltage value of the voltage-amplified signal at the previous moment and a second voltage value of the voltage-amplified signal at the next moment; The reference time is determined based on the previous time, the next time, the first voltage value, and the second voltage value.

6. The method according to claim 1, characterized in that The step of determining the trip angle of the transformer based on the mutation moment and the reference moment includes: In the above formula, Indicates the trip angle, Indicates the moment of mutation, Indicates the base time.

7. The method according to any one of claims 1 to 6, characterized in that The method further comprises: Before the transformer performs a closing operation, adjusting the closing moment according to the opening angle until the current phase of the transformer when closing based on the closing moment is the same as the current phase before opening, where the current phase before opening is determined according to the opening angle; Based on the closing time, the transformer is controlled to close.

8. A transformer trip angle detection device, characterized in that: include: Current-to-voltage converter, active voltage amplifier module and trip angle calculation module; The current-to-voltage converter is used to access the transformer no-load current sampled by the current transformer and convert the transformer no-load current into a voltage signal; The active voltage amplifier module is connected to the current-voltage converter and is used to amplify the voltage signal to obtain a voltage amplified signal; The trip angle calculation module is connected to the active voltage amplifier module and is used to determine the trip angle of the transformer according to the voltage amplification signal.

9. The device according to claim 8, characterized in that The active voltage amplifier module includes: at least one voltage amplifier and an adjustable resistor, wherein the adjustable resistor is connected to the voltage amplifier; The voltage amplifier is used to amplify the voltage signal; The adjustable resistor is used to adjust the resistance value according to the magnification adjustment signal until the amplification factor of the voltage amplifier is the same as the target amplification factor. When the resistance value is adjusted and changed, the amplification factor of the voltage amplifier changes accordingly.

10. The device according to claim 8, characterized in that The current-to-voltage converter is specifically configured to convert a current sampling signal at the milliampere level into a voltage signal at the millivolt level according to a first amplification factor.

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