Parameter acquisition method of an oscillating waveform detection system

Abstract

This application discloses a parameter acquisition method for an oscillation waveform detection system, relating to the field of power system control technology. By accurately acquiring parameters such as the equivalent inductance, capacitance, resistance, and minimum test voltage of the transformer winding under test, as well as the maximum and minimum oscillation frequencies of the oscillation waveform detection system, the lower limit of the input impedance of the waveform acquisition module, the upper limit of the range, the upper limit of the output voltage amplitude of the DC power supply, and the maximum allowable output current, the method obtains the equivalent total capacitance of the oscillation waveform detection system, the series capacitance of the upper and lower arms of the voltage divider, the first capacitance of the waveform adjustment capacitor, the second and third capacitances of the upper and lower arms of the voltage divider, and the resistance of the current-limiting resistor. This avoids uncertainties arising from empirical design, ensures the stable and controllable quality of the generated oscillation waveform, and guarantees consistent and reliable detection results on transformers of different capacities and voltage levels.

Description

Technical Field

[0001] This invention relates to the field of power system control technology, and in particular to a method for obtaining parameters of an oscillation waveform detection system. Background Technology

[0002] As a key core component of the power system, the reliability of transformers is the cornerstone of power grid security. During equipment transportation, installation, and commissioning, or when a short-circuit fault occurs in the power grid and the windings are subjected to a large short-circuit current impact, transformer windings often face the risk of mechanical deformation, including typical fault modes such as displacement, torsion, and bulging. These faults gradually lead to a decline in the electrical performance of the equipment and the failure of the insulation system, ultimately inducing serious power safety accidents. In the field of transformer fault detection, existing technologies such as the short-circuit impedance method and frequency response analysis method, although used for many years, have revealed common problems in practice: insufficient ability to identify early latent faults, insufficient detection sensitivity to meet the needs of accurate diagnosis, poor resistance to external interference, and susceptibility to misjudgment due to the influence of the field environment. Oscillating wave detection is an emerging fault diagnosis technology. Its principle is to inject DC energy into the windings and excite them to generate free damped oscillations. By analyzing the frequency, amplitude, and attenuation characteristics of the oscillation waves, the mechanical deformation and insulation status of the windings are evaluated. This method has potential advantages such as strong anti-interference ability and high detection sensitivity. However, the design methods for existing oscillation wave detection systems are still immature. The design of these systems often relies on engineering experience or simple estimations, lacking systematic theoretical guidance. This empirical design leads to unstable and uncontrollable quality of the generated oscillation waveforms, making it difficult to obtain consistent and reliable detection results on transformers of different capacities and voltage levels. This, in turn, affects the accuracy and universality of the technology in practical applications. Summary of the Invention

[0003] In view of this, the present invention provides a method for obtaining parameters of an oscillation waveform detection system.

[0004] The specific technical solution of the first embodiment of the present invention is as follows: a parameter acquisition method for an oscillation waveform detection system, applied to an oscillation waveform detection system for transformer windings. The system includes a DC power supply, a current-limiting resistor, a changeover switch, a waveform adjustment capacitor, an upper arm capacitor of a voltage divider, a lower arm capacitor of a voltage divider, and a waveform acquisition module. The upper arm capacitor and the lower arm capacitor of the voltage divider constitute a voltage divider. The current-limiting resistor is used to limit the charging current of the system and to limit the abnormal current generated when the changeover switch is closed under abnormal conditions. The changeover switch is used to switch the state of the system, including a charging state and a discharging state. The waveform adjustment capacitor is used to adjust the oscillation frequency of the system. The voltage divider is used to provide a measurement port for the waveform acquisition module. The waveform acquisition module is used to acquire the oscillation waveform of the transformer winding under test oscillating at the oscillation frequency through the measurement port. The method includes: acquiring the minimum equivalent inductance, maximum equivalent inductance, equivalent capacitance range, maximum equivalent resistance, and minimum test voltage of the transformer winding under test; acquiring the maximum and minimum oscillation frequencies of the oscillation waveform detection system; and acquiring the lower limit of the input impedance of the waveform acquisition module. The upper limit of the output voltage amplitude and the maximum allowable output current value of the DC power supply are obtained from the upper limit of the equivalent voltage amplitude and the upper limit of the range. The equivalent total capacitance value of the oscillation waveform detection system is obtained based on the minimum equivalent inductance, the maximum equivalent inductance, the maximum oscillation frequency, and the minimum oscillation frequency. The series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider is obtained based on the preset proportional coefficient, the equivalent total capacitance value, the lower limit of the input impedance, and the minimum oscillation frequency. The preset proportional coefficient is used to determine the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider relative to the upper limit of the range. The proportional relationship of the equivalent total capacitance value; the first capacitance value of the waveform adjustment capacitor is obtained based on the series capacitance value, the equivalent total capacitance value, and the equivalent capacitance range value; the second capacitance value of the upper arm capacitor of the voltage divider and the third capacitance value of the lower arm capacitor of the voltage divider are obtained based on the series capacitance value, the upper limit of the range, and the upper limit of the output voltage amplitude; the resistance value of the current limiting resistor is obtained based on the maximum equivalent resistance value, the minimum equivalent inductance value, the minimum test voltage, the maximum allowable output current value, the equivalent total capacitance value, and the preset damping ratio of the circuit in the charging state of the system.

[0005] Preferably, obtaining the equivalent total capacitance value of the oscillation waveform detection system based on the minimum equivalent inductance, the maximum equivalent inductance, the maximum oscillation frequency, and the minimum oscillation frequency includes: obtaining the minimum equivalent total capacitance value based on the maximum oscillation frequency and the minimum equivalent inductance; obtaining the maximum equivalent total capacitance value based on the minimum oscillation frequency and the maximum equivalent inductance; and calculating the average value of the numerical range formed by the minimum equivalent total capacitance value and the maximum equivalent total capacitance value to obtain the equivalent total capacitance value.

[0006] Preferably, the equivalent total capacitance value is obtained using the following formula:

[0007] in, This is the equivalent total capacitance value. This is the minimum value of the oscillation frequency. The maximum value of the oscillation frequency. This is the minimum value of the equivalent inductance. This is the maximum value of the equivalent inductance.

[0008] Preferably, obtaining the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider based on a preset proportional coefficient, the equivalent total capacitance value, the lower limit of the input impedance, and the minimum oscillation frequency includes: obtaining a first upper limit value of the series capacitance of the upper arm capacitor and the lower arm capacitor of the voltage divider based on the preset proportional coefficient and the equivalent total capacitance value; obtaining a second upper limit value of the series capacitance of the upper arm capacitor and the lower arm capacitor of the voltage divider based on the lower limit of the input impedance and the minimum oscillation frequency; and selecting the minimum value between the first upper limit value of the series capacitance and the second upper limit value of the series capacitance as the series capacitance value.

[0009] Preferably, the upper limit values ​​of the first series capacitor and the second series capacitor are obtained using the following formula:

[0010]

[0011] in, This is the upper limit value of the first series capacitor. This is the upper limit value of the second series capacitor. This is the equivalent total capacitance value. The preset proportional coefficient, This refers to the lower limit of the input impedance. This is the minimum value of the oscillation frequency.

[0012] Preferably, the first capacitance value of the waveform adjustment capacitor is obtained using the following formula:

[0013] in, The first capacitance value, This is the equivalent total capacitance value. The value of the series capacitance. This is the maximum value within the range of equivalent capacitance values. It is the minimum value among the range of equivalent capacitance values.

[0014] Preferably, the second capacitance value of the upper arm capacitor of the voltage divider and the third capacitance value of the lower arm capacitor of the voltage divider are obtained using the following formula:

[0015] in, This is the second capacitance value of the upper arm capacitor of the voltage divider. This is the third capacitance value of the lower arm capacitor of the voltage divider. The value of the series capacitance. The upper limit of the output voltage amplitude. This is the upper limit value of the range.

[0016] Preferably, obtaining the resistance value of the current-limiting resistor based on the maximum equivalent resistance, the minimum equivalent inductance, the minimum test voltage, the maximum allowable output current, the total equivalent capacitance, and the preset damping ratio of the system loop in the charging state includes: obtaining a first minimum resistance value of the current-limiting resistor based on the preset damping ratio, the minimum equivalent inductance, the total equivalent capacitance, and the maximum equivalent resistance; obtaining a second minimum resistance value of the current-limiting resistor based on the minimum test voltage and the maximum allowable output current; and selecting the maximum value between the first minimum resistance value and the second minimum resistance value as the resistance value of the current-limiting resistor.

[0017] Preferably, the minimum values ​​of the first and second resistances are obtained using the following formulas:

[0018]

[0019] in, The minimum value of the first resistance. The preset damping ratio, This is the minimum value of the equivalent inductance. This is the equivalent total capacitance value. This is the maximum value of the equivalent resistance. This is the minimum value of the second resistance. The minimum test voltage, This refers to the maximum allowable output current value.

[0020] Preferably, the method further includes: obtaining the highest oscillation frequency based on the length of the transformer winding to be tested and the dielectric constant around the winding; and setting the maximum value of the oscillation frequency below the highest oscillation frequency.

[0021] Implementing the embodiments of the present invention will have the following beneficial effects: This invention accurately acquires parameters such as the equivalent inductance, capacitance, resistance, and minimum test voltage of the transformer winding under test, as well as indicators such as the maximum and minimum oscillation frequency of the oscillation waveform detection system, the lower limit of the input impedance of the waveform acquisition module, the upper limit of the range, the upper limit of the output voltage amplitude of the DC power supply, and the maximum allowable output current. Based on these indicators, it obtains the equivalent total capacitance of the oscillation waveform detection system, the series capacitance of the upper and lower arms of the voltage divider, the first capacitance of the waveform adjustment capacitor, the second and third capacitances of the upper and lower arms of the voltage divider, and the resistance of the current-limiting resistor. This avoids the uncertainties caused by empirical design, ensures the stable and controllable quality of the generated oscillation waveform, and ensures consistent and reliable test results on transformers of different capacities and voltage levels, thereby improving the accuracy and universality of the oscillation wave detection method in practical applications. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A flowchart illustrating the steps of a parameter acquisition method for an oscillation waveform detection system; Figure 2 This is a schematic diagram of the wiring diagram for the first embodiment of the transformer winding fault detection device; Figure 3 This is a schematic diagram of the equivalent circuit of the first embodiment of a fault detection system for lumped parameters of the transformer winding under test and the transformer oscillation wave winding. Figure 4 A schematic diagram of a circuit model for a first embodiment of a fault detection system for the complex frequency domain operation of a transformer winding under test and a transformer oscillation wave winding. Figure 5 This is a schematic diagram of the wiring diagram for a second embodiment of the transformer winding fault detection device; Figure 6This is a schematic diagram of the equivalent circuit of the second embodiment of the lumped parameter system for detecting faults in the transformer windings under test and the transformer oscillation wave windings. Figure 7 This is a schematic diagram of a circuit model for a second embodiment of a fault detection system for the transformer winding under test and the transformer oscillation wave winding. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] The terms "first," "second," etc., used in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include steps or modules not listed, or may optionally include other steps or modules inherent to such processes, methods, products, or apparatus.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] Please see Figure 1 This is a flowchart illustrating the steps of a parameter acquisition method for an oscillation waveform detection system according to the first embodiment of this application. The method is executed in the transformer control system, which detects transformer winding faults based on the oscillation waveform, thereby improving the accuracy and universality of the oscillation waveform detection method in practical applications. This method is applied to an oscillation waveform detection system for transformer windings. Please refer to the schematic diagram of the oscillation waveform detection system. Figure 2As shown, the system includes a DC power supply, a current-limiting resistor, a changeover switch, a waveform adjustment capacitor, an upper arm capacitor of a voltage divider, a lower arm capacitor of a voltage divider, and a waveform acquisition module. The upper arm capacitor and the lower arm capacitor of the voltage divider constitute a voltage divider. The current-limiting resistor is used to limit the charging current of the system and to limit the abnormal current generated when the changeover switch is closed under abnormal conditions. The changeover switch is used to switch the system state, including charging state and discharging state. The waveform adjustment capacitor is used to adjust the oscillation frequency of the system. The voltage divider provides a measurement port for the waveform acquisition module. The waveform acquisition module is used to acquire the oscillation waveform of the transformer winding under test at the oscillation frequency through the measurement port. The method includes: Step 101: Obtain the minimum equivalent inductance, maximum equivalent inductance, equivalent capacitance range, maximum equivalent resistance, and minimum test voltage of the transformer winding under test; obtain the maximum and minimum oscillation frequency of the oscillation waveform detection system; obtain the lower limit of the input impedance and the upper limit of the range of the waveform acquisition module; and obtain the upper limit of the output voltage amplitude and the maximum allowable output current of the DC power supply. Step 102: Obtain the equivalent total capacitance of the oscillation waveform detection system based on the minimum equivalent inductance, maximum equivalent inductance, maximum oscillation frequency, and minimum oscillation frequency. Step 103: Obtain the series capacitance values ​​of the upper arm capacitor and the lower arm capacitor of the voltage divider based on the preset proportional coefficient, the equivalent total capacitance value, the lower limit of the input impedance, and the minimum oscillation frequency. The preset proportional coefficient is used to determine the proportional relationship between the series capacitance values ​​of the upper arm capacitor and the lower arm capacitor of the voltage divider and the equivalent total capacitance value. Step 104: Obtain the first capacitance value of the waveform adjustment capacitor based on the series capacitance value, the equivalent total capacitance value, and the equivalent capacitance range value. Step 105: Obtain the second capacitance value of the upper arm capacitor and the third capacitance value of the lower arm capacitor of the voltage divider based on the series capacitance value, the upper limit of the range, and the upper limit of the output voltage amplitude. Step 106: Obtain the resistance value of the current limiting resistor based on the maximum equivalent resistance, minimum equivalent inductance, minimum test voltage, maximum allowable output current, equivalent total capacitance, and the preset damping ratio of the circuit in the charging state.

[0028] The circuit connections of this system are as follows: A current-limiting resistor is connected in series with the positive terminal of the DC power supply, which then splits into two paths. One path connects to one end of a changeover switch; the other end of the changeover switch is grounded to control the charging and discharging states of the circuit. Initially, the changeover switch is in the open state, and the circuit is in the charging state. Once the voltage measured by the waveform acquisition module reaches the preset voltage, the changeover switch is closed, allowing the circuit to enter the discharging state. The other path connects to one end of a waveform adjustment capacitor, the other end of which is connected to one end of the upper arm capacitor of the voltage divider. The other end of the upper arm capacitor is connected in series with the lower arm capacitor of the voltage divider and then grounded. This series connection point, together with ground, forms the measurement port. The waveform acquisition module is connected in parallel across this measurement port to monitor the voltage.

[0029] During testing, the two ends of the transformer winding under test are connected in parallel to the two ends of the waveform adjustment capacitor, thus forming a complete damped oscillation circuit together with the detection system. This connection method ensures that the oscillation wave signal is accurately attenuated by the voltage divider and then captured with high fidelity by the waveform acquisition module.

[0030] Specifically, a lumped parameter equivalent circuit is constructed, incorporating the fault detection system for the transformer winding under test and the transformer oscillation wave winding. Based on this lumped parameter equivalent circuit, a complex frequency domain operational circuit model is established, incorporating the fault detection system for the transformer winding under test and the transformer oscillation wave winding. Complex frequency domain equations are written based on this model to obtain the relationships between the loop damping ratio and the equivalent resistance, equivalent inductance, and equivalent total capacitance of the transformer winding under test in the discharge state after the switching switch is closed; and the relationships between the oscillation frequency and the equivalent total capacitance and equivalent inductance of the transformer winding under test. After determining these relationships, the minimum and maximum equivalent inductance values ​​of the transformer winding under test are obtained. The system obtains parameters such as the maximum value, equivalent capacitance range value, maximum equivalent resistance value, and minimum test voltage; the maximum and minimum oscillation frequency values ​​of the oscillation waveform detection system; the lower limit of the input impedance and upper limit of the range of the waveform acquisition module; the upper limit of the output voltage amplitude and the maximum allowable output current value of the DC power supply; and based on these parameters, it obtains the equivalent total capacitance value, the series capacitance value of the upper and lower arm capacitors of the voltage divider, the first capacitance value of the waveform adjustment capacitor, the second capacitance value of the upper arm capacitor of the voltage divider, the third capacitance value of the lower arm capacitor of the voltage divider, and the resistance value of the current limiting resistor, in order to construct an accurate oscillation waveform detection system for transformer windings.

[0031] Specifically, the lumped parameter equivalent circuit of the fault detection system for the transformer winding under test and the transformer oscillation wave winding includes a DC power supply V0, a ​​current-limiting resistor R, a waveform conditioning capacitor C, a changeover switch S, and the transformer equivalent capacitance C. T Transformer equivalent resistance R T Transformer equivalent reactance L TCapacitor C1 on the upper arm of the voltage divider, capacitor C2 on the lower arm of the voltage divider.

[0032] Specifically, the relationships between the circuit damping ratio in the discharge state after the changeover switch is closed and the equivalent resistance of the transformer winding under test, the equivalent inductance of the transformer winding under test, and the equivalent total capacitance of the circuit include:

[0033] in, The loop damping ratio under discharge conditions; The equivalent resistance value of the transformer winding under test; This is the equivalent inductance value of the transformer; The equivalent total capacitance of the circuit is [value missing]. C1 is the capacitance value of the upper arm of the voltage divider, and C2 is the capacitance value of the lower arm of the voltage divider. C is the equivalent capacitance of the transformer; C is the waveform conditioning capacitance.

[0034] Specifically, the relationships between the oscillation frequency and the system's equivalent total capacitance and the equivalent inductance of the transformer winding under test include:

[0035] in, The oscillation frequency; This is the equivalent inductance of the transformer, and its value is... : This is the equivalent capacitance value in the charging circuit.

[0036] The method in this embodiment accurately acquires parameters such as the equivalent inductance, capacitance, resistance, and minimum test voltage of the transformer winding under test, as well as indicators such as the maximum and minimum oscillation frequency of the oscillation waveform detection system, the lower limit of the input impedance of the waveform acquisition module, the upper limit of the range, the upper limit of the output voltage amplitude of the DC power supply, and the maximum allowable output current. Based on these indicators, it acquires the equivalent total capacitance of the oscillation waveform detection system, the series capacitance of the upper and lower arms of the voltage divider, the first capacitance of the waveform adjustment capacitor, the second and third capacitances of the upper and lower arms of the voltage divider, and the resistance of the current-limiting resistor. This avoids the uncertainties caused by empirical design, ensures that the generated oscillation waveform is stable and controllable, and ensures consistent and reliable test results on transformers of different capacities and voltage levels, thereby improving the accuracy and universality of the oscillation wave detection method in practical applications.

[0037] In a specific embodiment, the equivalent total capacitance value of the oscillation waveform detection system is obtained based on the minimum equivalent inductance, the maximum equivalent inductance, the maximum oscillation frequency, and the minimum oscillation frequency, including: The minimum value of the equivalent total capacitance is obtained by using the maximum value of the oscillation frequency and the minimum value of the equivalent inductance. The maximum value of the equivalent total capacitance is obtained by using the minimum oscillation frequency and the maximum value of the equivalent inductance. The equivalent total capacitance value is obtained by averaging the range of values ​​formed by the minimum and maximum equivalent total capacitance values.

[0038] Specifically, the numerical range formed by the maximum and minimum values ​​of the equivalent total capacitance is obtained using the following formula: ; in, The preset target oscillation frequency is the maximum value; To preset the minimum target oscillation frequency, satisfying ; The maximum value of the equivalent inductance of the transformer winding under test is [value]. ; The minimum equivalent inductance of the transformer winding under test is given by the value of . ,in As a conservative factor; the range of the equivalent inductance of the transformer winding under test and the range of the preset target oscillation frequency should meet the following requirements. .

[0039] In a specific embodiment, the equivalent total capacitance value is obtained using the following formula:

[0040] in, This is the equivalent total capacitance value. This is the minimum oscillation frequency. The maximum value of the oscillation frequency. This is the minimum equivalent inductance. This is the maximum value of the equivalent inductance.

[0041] In a specific embodiment, the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider is obtained according to a preset proportional coefficient, the equivalent total capacitance value, the lower limit of the input impedance value, and the minimum oscillation frequency value. This includes: obtaining a first upper limit value of the series capacitance of the upper arm capacitor and the lower arm capacitor of the voltage divider according to the preset proportional coefficient and the equivalent total capacitance value; obtaining a second upper limit value of the series capacitance of the upper arm capacitor and the lower arm capacitor of the voltage divider according to the lower limit of the input impedance value and the minimum oscillation frequency value; and selecting the minimum value between the first upper limit value and the second upper limit value of the series capacitance as the series capacitance value.

[0042] In a specific embodiment, the upper limit values ​​of the first series capacitor and the second series capacitor are obtained using the following formula:

[0043]

[0044] in, This is the upper limit value of the first series capacitor. This is the upper limit value of the second series capacitor. This is the equivalent total capacitance value. This is a preset proportional coefficient. This is the lower limit of the input impedance. This is the minimum oscillation frequency.

[0045] Specifically, The series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider. 100 to 1500 times, that is, n is and The ratio of , takes a value ranging from 100 to 1500.

[0046] In a specific embodiment, the first capacitance value of the waveform adjustment capacitor is obtained using the following formula:

[0047] in, This is the first capacitance value. This is the equivalent total capacitance value. This is the value of the series capacitor. This is the maximum value within the range of equivalent capacitance values. This is the minimum value within the range of equivalent capacitance values. and All values ​​were selected based on a table of typical empirical values.

[0048] In a specific embodiment, the second capacitance value of the upper arm capacitor and the third capacitance value of the lower arm capacitor of the voltage divider are obtained using the following formula:

[0049] in, This is the second capacitance value of the capacitor on the upper arm of the voltage divider. This is the third capacitance value of the lower arm capacitor of the voltage divider. This is the value of the series capacitor. This is the upper limit of the output voltage amplitude. This is the upper limit of the measurement range.

[0050] In a specific embodiment, the resistance value of the current-limiting resistor is obtained based on the maximum equivalent resistance, minimum equivalent inductance, minimum test voltage, maximum allowable output current, equivalent total capacitance, and a preset damping ratio of the system's circuit in the charging state. This includes: obtaining a first minimum resistance value of the current-limiting resistor based on the preset damping ratio, minimum equivalent inductance, equivalent total capacitance, and maximum equivalent resistance; obtaining a second minimum resistance value of the current-limiting resistor based on the minimum test voltage and maximum allowable output current; and selecting the maximum value between the first and second minimum resistance values ​​as the resistance value of the current-limiting resistor. Specifically, the equivalent resistance value of the transformer winding under test is selected based on statistical data of transformers of the same model.

[0051] In a specific embodiment, the minimum values ​​of the first and second resistances are obtained using the following formula:

[0052]

[0053] in, This is the minimum value of the first resistance. To preset the damping ratio, This is the minimum equivalent inductance. This is the equivalent total capacitance value. This is the maximum equivalent resistance. This is the minimum value of the second resistance. This is the lowest test voltage. This is the maximum allowable output current value.

[0054] In a specific embodiment, the method further includes: obtaining the highest oscillation frequency based on the length of the transformer winding to be tested and the dielectric constant around the winding; and setting a maximum oscillation frequency below the highest oscillation frequency.

[0055] Specifically, the formula for obtaining the highest oscillation frequency that satisfies the lumped parameter model conditions is:

[0056] in, To satisfy the highest oscillation frequency of the lumped parameter model conditions, For the speed of light, take a value of , The physical length of the transformer winding to be tested; It is the relative permittivity of the insulating medium surrounding the winding.

[0057] Implementation Example Overview: Objective: To design a system capable of detecting oscillation waves in the windings of an oil-immersed transformer within a target oscillation frequency range, generating damped oscillations with appropriate amplitude, clear frequency, and controllable attenuation.

[0058] The DC power supply is generated by a DC high-voltage generator, with a voltage range of 1KV-100KV. In this embodiment, we take... Waveform acquisition module range upper limit Lower limit of input impedance for waveform acquisition module ; Maximum allowable output current of DC power supply ; Preset target damping ratio Underdamped oscillation decay characteristics.

[0059] The example calculation selects the equivalent parameters of the transformer under test from the empirical typical value table for calculation. In practical applications, more accurate parameter values ​​can be obtained by calculation based on the equivalent parameter formula and on-site testing.

[0060] ; The maximum value of the equivalent inductance of the transformer winding under test is [value]. ; The minimum equivalent inductance of the transformer winding under test is given by the value of . ,in As a conservative factor, the commonly used default value is: =0.25, =2.5; if the data is extremely uncertain, it can be taken as 2.5. =0.1, =3.00 Equivalent inductance range: , ; Equivalent capacitance range: , ; Equivalent resistance: ; based on Figure 2 The wiring diagram of the transformer winding fault detection system shown includes the following methods: S1: Construct a lumped-parameter equivalent circuit that includes the fault detection system for the transformer winding under test and the transformer oscillation wave winding, referring to... Figure 3 ; The highest oscillation frequency satisfying the lumped parameter model is determined based on the winding length and dielectric constant. The physical length of the transformer winding under test is l = 2.0 m, and the relative dielectric constant of the medium surrounding the winding is... ; Conditions for applying lumped parameter models in transformer oscillation wave detection: ; in The length of the transformer winding to be tested. The oscillation wavelength is the electromagnetic wavelength that propagates along the winding and the surrounding medium.

[0061] The maximum permissible frequency that satisfies the lumped parameter model conditions: ,in , , , It is the relative permittivity of the medium surrounding the winding; approximately 2-3 for insulating oil and approximately 1 for air.

[0062] Target oscillation frequency range: , ,satisfy The lumped parameter model has been verified to be applicable within the target frequency band (1kHz-10kHz). Therefore, design can continue based on the lumped parameter equivalent circuit. This model is used to accurately simulate the transient response characteristics of the winding under oscillating wave voltage excitation, thus providing a theoretical basis for fault diagnosis.

[0063] like Figure 3 The diagram shows a lumped-parameter equivalent circuit model of the transformer winding under test and its fault detection system, constructed according to an embodiment of the present invention. The lumped-parameter equivalent circuit including the transformer winding under test and the transformer oscillation wave winding fault detection system includes: a DC power supply V0, a ​​current-limiting resistor R, a waveform adjustment capacitor C, a changeover switch S, and a transformer equivalent capacitance C. T Transformer equivalent resistance R T Transformer equivalent reactance L T Capacitor C1 on the upper arm of the voltage divider, capacitor C2 on the lower arm of the voltage divider.

[0064] S2: Based on the lumped parameter equivalent circuit, establish a complex frequency domain operation circuit model that includes the fault detection system for the transformer winding under test and the transformer oscillation wave winding, referring to... Figure 4 ; S3: Based on the complex frequency domain operation circuit model, write the complex frequency domain equations to obtain the relationship between the damping ratio and the equivalent total capacitance and equivalent resistance of the circuit, and the relationship between the oscillation frequency and the equivalent total capacitance of the system and the equivalent reactance of the transformer winding under test; the complex frequency domain equations are: Switch off: , ; Switch closed: , , ; in, Equivalent inductance of transformer L T The value of the current on the circuit instant before the switch is activated ("0") "Indicates the moment immediately preceding the switch"); This represents the total voltage value of the circuit instant before the switch is activated. This is the equivalent total capacitance of the circuit; After the changeover switch is closed, the relationship between the damping ratio in the discharge state and the equivalent resistance of the transformer winding under test, the equivalent inductance of the transformer winding under test, and the equivalent total capacitance of the circuit is as follows: ; The relationship between the oscillation frequency and the system's equivalent total capacitance and the transformer's measured winding equivalent reactance is as follows: .

[0065] S4: Determine the design range of the system's equivalent total capacitance value based on the range of the equivalent short-circuit reactance of the transformer winding under test and the preset target oscillation frequency range. .

[0066] ; ; The equivalent short-circuit reactance range and the preset target oscillation frequency range of the transformer winding under test are:

[0067] satisfy .

[0068] S5: Take the geometric mean of the system's equivalent total capacitance value within the design range as the system's equivalent total capacitance value. .

[0069] S6: Determine the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider, and the equivalent total capacitance value of the system. The proportional relationship is determined, and one of the upper limits of the series capacitance value between the upper and lower arm capacitors of the voltage divider is further determined. Based on the lower limit of the input impedance of the waveform acquisition module and the lower limit of the preset target oscillation frequency, another upper limit of the series capacitance value between the upper and lower arm capacitors of the voltage divider is determined. The smaller value between one of the upper and lower limit values ​​of the series capacitance value between the upper and lower arm capacitors of the voltage divider is taken as the series capacitance value between the upper and lower arm capacitors of the voltage divider.

[0070] The system's equivalent total capacitance is among With voltage divider and capacitor in series The ratio n can be taken from 100 to 10000. In this example, n=1000. The lower limit of the input impedance of the waveform acquisition module is set to the minimum input impedance of 10Ω given in the datasheet.

[0071] ; ; .

[0072] S7. Determine the value of the waveform adjustment capacitor based on the series capacitance values ​​of the upper arm capacitor and the lower arm capacitor of the voltage divider, the equivalent total capacitance of the system, and the upper limit of the equivalent capacitance of the transformer winding under test.

[0073] The standard value for the project is 1.5nF.

[0074] S8: Determine the upper arm capacitor and lower arm capacitor of the voltage divider based on the upper limit of the waveform acquisition module's range and the upper limit of the DC power supply's output voltage.

[0075] Standard values ​​are used in engineering. Select a 1.5 pF capacitor. Select a 3.3nF capacitor.

[0076] Alternatively, it can be obtained using the following formula: .

[0077] S9: Preset target damping ratio. Determine the first lower limit of the current limiting resistor based on the maximum equivalent resistance of the transformer winding, the minimum equivalent reactance, the equivalent total capacitance of the system, and the target damping ratio. Determine the second lower limit of the system current limiting resistor based on the minimum test voltage of the target transformer and the maximum allowable output current of the DC power supply. Take 130% of the larger of the first and second lower limits of the current limiting resistor as the current limiting resistor value. Preset target damping ratio It satisfies the underdamped oscillation decay characteristics.

[0078] The first lower limit value of the system current-limiting resistor is:

[0079] in, This is the first lower limit value of the system current-limiting resistor; It is the damping ratio, which is usually preset to 1; This is the minimum equivalent inductance. This represents the maximum equivalent resistance of the transformer winding under test. The second lower limit value of the system current-limiting resistor is:

[0080] in, This is the second lower limit value of the system current-limiting resistor; This is the output voltage value of the DC power supply. This is the maximum allowable output current value of the DC power supply; Alternatively, the current-limiting resistor value can be determined by selecting the maximum value between the minimum values ​​of the first and second resistors. Another method is to use the following formula to determine the current-limiting resistor value. Where 1.5 is the design coefficient. .

[0081] The design method of this invention is scientific and rigorous, overcoming reliance on experience: This invention pioneers a complete design method from theoretical model to parameter calculation. By establishing a lumped parameter equivalent circuit and a complex frequency domain model, the engineering requirement of "generating high-quality oscillating waves" is transformed into precise mathematical constraints and calculation formulas for the parameters of components such as capacitors and resistors. This completely changes the traditional extensive design mode that relies on trial and error based on experience, making system design systematic and the results predictable.

[0082] The high quality of the detected waveform significantly improves diagnostic reliability: The system manufactured based on this design method can generate ideal oscillation waveforms with appropriate amplitude, accurate target frequency, and controllable decay rate. This high-quality, consistent waveform provides a stable and reliable data foundation for subsequent analysis, greatly reducing the risk of misjudgment due to waveform distortion or non-reproducibility, and significantly improving the accuracy and reliability of winding condition assessment.

[0083] Greater versatility and adaptability: This design method fully considers the equivalent parameters of the transformer windings and the detection target, enabling the device parameters to be accurately adapted to the specific specifications of the transformer under test. This means that the same design method can be applied to transformers of different capacities and voltage levels, solving the problem of poor universality of existing devices, achieving "one method for multiple uses," and improving the breadth of technology application.

[0084] In a specific embodiment, the second embodiment of this application provides a parameter acquisition system for an oscillation waveform detection system. The system includes a data acquisition module, an equivalent total capacitance output module, a series capacitance output module, a waveform adjustment capacitor output module, a voltage divider capacitor output module, and a current limiting resistor output module. The data acquisition module is used to acquire the minimum equivalent inductance, maximum equivalent inductance, equivalent capacitance range, maximum equivalent resistance, and minimum test voltage of the transformer winding under test; to acquire the maximum and minimum oscillation frequencies of the oscillation waveform detection system; to acquire the lower limit of the input impedance and the upper limit of the range of the waveform acquisition module; and to acquire the upper limit of the output voltage amplitude and the maximum allowable output current of the DC power supply. The equivalent total capacitance output module is used to obtain the equivalent total capacitance value of the oscillation waveform detection system based on the minimum equivalent inductance, maximum equivalent inductance, maximum oscillation frequency, and minimum oscillation frequency. The capacitance output module is used to obtain the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider based on the preset proportional coefficient, the equivalent total capacitance value, the lower limit of the input impedance, and the minimum oscillation frequency. The preset proportional coefficient is used to determine the proportional relationship between the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider and the equivalent total capacitance value. The waveform adjustment capacitor output module is used to obtain the first capacitance value of the waveform adjustment capacitor based on the series capacitance value, the equivalent total capacitance value, and the equivalent capacitance range value. The voltage divider capacitor output module is used to obtain the second capacitance value of the upper arm capacitor and the third capacitance value of the lower arm capacitor of the voltage divider based on the series capacitance value, the upper limit of the range, and the upper limit of the output voltage amplitude. The current limiting resistor output module is used to obtain the resistance value of the current limiting resistor based on the maximum equivalent resistance value, the minimum equivalent inductance value, the minimum test voltage, the maximum allowable output current value, the equivalent total capacitance value, and the preset damping ratio of the circuit in the charging state of the system.

[0085] In a specific embodiment, the third embodiment of this application provides a parameter acquisition device for an oscillation waveform detection system, including a memory and a processor. The memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method as described in any one of the first embodiments of this application.

[0086] In a specific embodiment, the fourth embodiment of this application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method as described in any one of the first embodiments of this application.

[0087] In a specific embodiment, when the oscillation waveform detection system does not include a waveform adjustment capacitor (see [link to relevant documentation]). Figure 5 At this point, the lumped parameter equivalent circuit reference is... Figure 6 The complex frequency domain operational circuit model of the experimental loop was established by applying the Laplace transform. Figure 7 The formula for calculating the equivalent parameters of the transformer winding under test is as follows:

[0088] in, This is the rated voltage of the transformer. This refers to the rated capacity of the transformer. This refers to the transformer's rated frequency. This represents the short-circuit loss of the winding. This represents the percentage of the transformer winding short-circuit voltage. It is the vacuum permittivity; The relative permittivity of the insulating material; The average diameter of the winding; The height of the winding; This is the oil gap distance.

[0089] The equivalent total capacitance of the circuit at the oscillation frequency is:

[0090] in, The equivalent total capacitance of the discharge detection circuit at the oscillation frequency; To set the target oscillation frequency, This is the equivalent inductance value of the transformer winding under test.

[0091] The capacitance values ​​of the upper arm capacitor and the lower arm capacitor of the voltage divider are:

[0092] in, For the upper arm capacitor of the voltage divider. This is the lower arm capacitor of the voltage divider. Let be the equivalent total capacitance of the discharge detection circuit at the target oscillation frequency. This is the output voltage value of the DC power supply. This refers to the upper limit of the measuring range of the measuring device. This represents the equivalent capacitance value of the transformer winding under test.

[0093] The above embodiments merely illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A parameter acquisition method of an oscillation waveform detection system, applied to an oscillation waveform detection system of a transformer winding, characterized in that, The system comprises a direct current power supply, a current-limiting resistor, a switching switch, a waveform adjustment capacitor, an upper arm capacitor of a voltage divider, a lower arm capacitor of the voltage divider, and a waveform acquisition module, the upper arm capacitor and the lower arm capacitor constitute the voltage divider, the current-limiting resistor is used to limit the charging current of the system and the abnormal current generated when the switching switch is closed in an abnormal condition, the switching switch is used to switch the state of the system, the state includes a charging state and a discharging state, the waveform adjustment capacitor is used to adjust the oscillation frequency of the system, the voltage divider is used to provide a measurement port for the waveform acquisition module, the waveform acquisition module is used to acquire the oscillation waveform of the winding of the transformer under test when the winding is oscillated at the oscillation frequency through the measurement port, and the method comprises: obtaining the minimum equivalent inductance value, the maximum equivalent inductance value, the equivalent capacitance range value, the maximum equivalent resistance value and the minimum test voltage of the winding of the transformer under test, obtaining the maximum oscillation frequency value and the minimum oscillation frequency value of the oscillation waveform detection system, obtaining the lower limit value of the input impedance and the upper limit value of the range of the waveform acquisition module, and obtaining the upper limit value of the output voltage amplitude and the maximum allowed output current value of the direct current power supply; obtaining the equivalent total capacitance value of the oscillation waveform detection system according to the minimum equivalent inductance value, the maximum equivalent inductance value, the maximum oscillation frequency value and the minimum oscillation frequency value; obtaining the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider according to a preset proportion coefficient, the equivalent total capacitance value, the lower limit value of the input impedance and the minimum oscillation frequency value; the preset proportion coefficient is used to determine the proportional relationship between the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider and the equivalent total capacitance value; obtaining the first capacitance value of the waveform adjustment capacitor according to the series capacitance value, the equivalent total capacitance value and the equivalent capacitance range value; obtaining the second capacitance value of the upper arm capacitor and the third capacitance value of the lower arm capacitor of the voltage divider according to the series capacitance value, the upper limit value of the range and the upper limit value of the output voltage amplitude; obtaining the resistance value of the current-limiting resistor according to the maximum equivalent resistance value, the minimum equivalent inductance value, the minimum test voltage, the maximum allowed output current value, the equivalent total capacitance value and the preset damping ratio of the loop of the system in the charging state.

2. The parameter acquisition method of an oscillating waveform detection system according to claim 1, wherein The method comprises: obtaining the equivalent total capacitance minimum value according to the maximum oscillation frequency value and the minimum equivalent inductance value; obtaining the equivalent total capacitance maximum value according to the minimum oscillation frequency value and the maximum equivalent inductance value; averaging the numerical range formed by the equivalent total capacitance minimum value and the equivalent total capacitance maximum value to obtain the equivalent total capacitance value.

3. The parameter acquisition method of an oscillating waveform detection system according to claim 2, wherein The equivalent total capacitance value is obtained by the following formula: wherein, is the equivalent total capacitance value, is the oscillation frequency minimum value, is the oscillation frequency maximum value, is the equivalent inductance minimum value, is the equivalent inductance maximum value.

4. The parameter acquisition method of an oscillating waveform detection system according to claim 1, wherein The step of obtaining the series capacitance value of the upper arm capacitor and the lower arm capacitor of the voltage divider based on the preset proportional coefficient, the equivalent total capacitance value, the lower limit of the input impedance value, and the minimum value of the oscillation frequency includes: The upper limit value of the first series capacitance of the upper arm capacitor and the lower arm capacitor of the voltage divider is obtained according to the preset proportional coefficient and the equivalent total capacitance value. The upper limit of the second series capacitance of the upper arm capacitor and the lower arm capacitor of the voltage divider is obtained based on the lower limit of the input impedance and the minimum value of the oscillation frequency. The minimum value between the first upper limit value of the series capacitor and the second upper limit value of the series capacitor is selected as the series capacitor value.

5. The parameter acquisition method of an oscillatory waveform detection system according to claim 4, wherein The upper limits of the first series capacitor and the second series capacitor are obtained using the following formulas: wherein, is the first series capacitance upper limit value, is the second series capacitance upper limit value, is the equivalent total capacitance value, is the preset proportion coefficient, is the input impedance lower limit value, is the oscillation frequency minimum value.

6. The parameter acquisition method of an oscillatory waveform detection system according to claim 1, wherein, The first capacitance value of the waveform adjustment capacitor is obtained using the following formula: wherein, is the first capacitance value, is the equivalent total capacitance value, is the series capacitance value, is the maximum value in the equivalent capacitance range value, is the minimum value in the equivalent capacitance range value.

7. The parameter acquisition method of an oscillatory waveform detection system according to claim 1, wherein, The second capacitance value of the upper arm capacitor and the third capacitance value of the lower arm capacitor of the voltage divider are obtained using the following formula: wherein, is a second capacitance value of the voltage divider upper arm capacitance, is a third capacitance value of the voltage divider lower arm capacitance, is the series capacitance value, is the output voltage magnitude upper limit value, is the range upper limit value.

8. The parameter acquisition method of an oscillatory waveform detection system according to claim 1, wherein, The step of obtaining the resistance value of the current-limiting resistor based on the maximum equivalent resistance, the minimum equivalent inductance, the minimum test voltage, the maximum allowable output current, the equivalent total capacitance, and the preset damping ratio of the system loop in the charging state includes: The first minimum resistance value of the current-limiting resistor is obtained based on the preset damping ratio, the minimum equivalent inductance, the total equivalent capacitance, and the maximum equivalent resistance. The second minimum resistance value of the current-limiting resistor is obtained based on the minimum test voltage and the maximum allowable output current value. The maximum value between the first minimum resistance value and the second minimum resistance value is selected as the resistance value of the current-limiting resistor.

9. The parameter acquisition method of an oscillatory waveform detection system according to claim 8, wherein, The minimum values ​​of the first and second resistors are obtained using the following formulas: wherein, is the first resistance minimum value, is the preset damping ratio, is the equivalent inductance minimum value, is the equivalent total capacitance value, is the equivalent resistance maximum value, is the second resistance minimum value, is the lowest test voltage, is the maximum allowed output current value.

10. The parameter acquisition method of an oscillatory waveform detection system according to claim 1, wherein, The method further includes: The highest oscillation frequency is obtained based on the length of the transformer winding and the dielectric constant around the winding. The maximum value of the oscillation frequency is set below the highest oscillation frequency.

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