Broadband dielectric response test method for high dynamic leakage current compression

Abstract

The invention relates to a broadband dielectric response test method for high dynamic leakage current compression, and belongs to the technical field of insulation aging diagnosis. According to the method, the adjustable sampling impedance in an RC parallel connection mode is adopted, measurement of micro current signals is converted into measurement of voltages at the two ends of the sampling impedance, the order of magnitude is improved, and the anti-interference capacity is enhanced. And the RC parallel impedance reduces the dynamic range of the voltage, and the capacitance branch plays a role in filtering, so that the measurement accuracy is improved. By reducing the dynamic range of the voltage at the two ends of the sampling impedance, the test process is simplified, the test efficiency and the measurement precision are improved, and a more reliable technical means is provided for insulation aging diagnosis.

Description

Technical Field

[0001] The invention belongs to the technical field of insulation aging diagnosis, and relates to a broadband dielectric response test method for high dynamic leakage current compression. Background Art

[0002] The frequency domain dielectric response method is an insulation aging diagnostic technology based on the response characteristics of the dielectric. Because it is not affected by the accumulation of space charge in the dielectric, it has the advantage of non-destructive testing compared to chemical methods for detecting dielectric insulation. Compared with electrical methods, it has the advantage of carrying rich insulation information and is expected to achieve online monitoring. It is one of the important directions of current research on insulation status assessment.

[0003] However, for the existing frequency domain dielectric spectroscopy technology, the current during low voltage measurement is at the nA level, which is susceptible to on-site electromagnetic interference, resulting in very large measurement errors. The use of series sampling resistors can certainly convert the test quantity from current to voltage, increase the order of magnitude of the test quantity, and reduce errors. However, the frequency variation range of the broadband dielectric response test is large. In order to maintain the voltage across the sampling resistor basically unchanged, the variation range of the sampling resistor value will also be very large, increasing the complexity of the test. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a broadband dielectric response test method with high dynamic leakage current compression. In view of the problem that the adjustment range of the series sampling resistor is large, this patent proposes to change the pure resistor to the RC parallel form, still converting the measured tiny current signal into the measured sampling impedance voltage, improving the order of magnitude and enhancing the anti-interference ability. On this basis, the dynamic range of the sampling impedance voltage is greatly reduced, that is, the adjustment range of the sampling impedance is greatly reduced.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A broadband dielectric response test method for high dynamic leakage current compression comprises the following steps:

[0007] Connect the test sample to the AC power supply and form a loop through the adjustable sampling impedance grounding;

[0008] The voltage signal of the power supply after passing through the voltage divider and the sampling impedance voltage signal are synchronously collected by the signal collection module;

[0009] Calculate input voltage;

[0010] Perform Fourier transform on the collected voltage signal to extract the amplitude and phase of the fundamental frequency component;

[0011] Calculate the dielectric parameters of the specimen based on the extracted amplitude and phase;

[0012] Wherein, the adjustable sampling impedance is an impedance in the form of RC parallel connection, wherein C is a capacitor, R is a resistor, and both the capacitor C and the resistor R are adjustable;

[0013] The values ​​of the resistance R and the capacitance C of the RC parallel impedance are adjusted according to the test frequency;

[0014] The capacitor C of the RC parallel impedance plays a filtering role, thereby improving the accuracy of the dielectric spectrum.

[0015] Furthermore, the signal acquisition module includes a high voltage probe and a signal acquisition circuit.

[0016] Furthermore, the step of calculating the input voltage includes dividing the power supply voltage using a voltage divider, and measuring the divided voltage through a signal acquisition module.

[0017] Furthermore, the step of calculating the dielectric parameters of the sample includes calculating the complex capacitance constant and the dielectric loss tangent.

[0018] Further, the step of calculating the complex capacitance constant and the dielectric loss tangent includes using the following formula:

[0019]

[0020] A broadband dielectric response test device with high dynamic leakage current compression, comprising:

[0021] AC power supply;

[0022] An adjustable sampling impedance, wherein the adjustable sampling impedance is an impedance in the form of RC parallel connection, wherein C is a capacitor, R is a resistor, and both the capacitor C and the resistor R are adjustable;

[0023] A signal acquisition module, used for synchronously acquiring power supply voltage and sampling impedance voltage;

[0024] A calculation module is used to calculate the input voltage, extract the amplitude and phase of the fundamental frequency component, and calculate the dielectric parameters of the test piece according to the collected voltage signal;

[0025] The positive pole of the AC power supply is connected to one end of the test object; the negative pole of the AC power supply is connected to the other end of the test object through an adjustable sampling impedance and is grounded;

[0026] The two ends of the adjustable sampling impedance are respectively connected to the two voltage input channels of the signal acquisition module; the voltage change at the two ends of the adjustable sampling impedance will be synchronously transmitted to the signal acquisition module for acquisition;

[0027] The signal acquisition module transmits the collected power supply voltage and sampled impedance voltage signals to the calculation module; the calculation module performs data processing and calculation according to the received signals, and finally obtains the dielectric parameters of the test sample.

[0028] The beneficial effects of the present invention are:

[0029] The present invention adopts an adjustable sampling impedance in the form of RC parallel connection. Compared with the pure R adjustable sampling resistor, the response current of the measured nA level is still converted into a voltage of several V at both ends of the measured sampling impedance, which increases the order of magnitude, reduces errors, and improves anti-interference ability. The difference is that the RC parallel impedance can play a filtering role while reducing the voltage dynamic range, thereby improving measurement accuracy.

[0030] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0032] Figure 1 This is a schematic diagram of the traditional frequency domain dielectric response test;

[0033] Figure 2 It is the equivalent circuit diagram of the frequency domain dielectric response test;

[0034] Figure 3 This is a schematic diagram of the test sample's response current changing with frequency;

[0035] Figure 4 It is an adjustable sampling impedance model;

[0036] Figure 5 This is a schematic diagram of how the voltage at both ends changes with frequency when two adjustable impedance methods are used. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0038] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0039] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0040] The present invention adopts an adjustable sampling impedance model in the form of RC parallel connection to reduce the voltage dynamic range at both ends of the sampling impedance. The sampling resistor and capacitor in parallel play a certain filtering role and improve the accuracy of the dielectric spectrum.

[0041] like Figure 1 As shown in the figure, in the frequency domain, after applying an external electric field to the medium, the polarization characteristics of the medium under AC voltage are used to measure the voltage and current phase difference flowing through the medium to be measured, so as to obtain the dielectric loss factor, complex capacitance and other values ​​at different frequencies, and express them through curves. The curves are tanδ-f, C*-f, where δ is the dielectric loss angle, C* is the complex capacitance constant, and f is the frequency. They are called frequency domain dielectric spectrum curves. The real part of the complex capacitance represents the part that generates capacitive current, reflecting the polarization characteristics of the medium at the microscopic level; the imaginary part of the complex capacitance represents the part that generates resistive current, representing the loss characteristics at the microscopic level, including the conductivity loss and lossy polarization loss of the medium. Both the real and imaginary parts of the complex capacitance are functions of frequency, so the insulation characteristics of the medium can be studied through the complex capacitance spectrum within a certain frequency range.

[0042] However, for the existing frequency domain dielectric spectroscopy technology, the medium response current is measured, and the current is usually in the pA or nA level, with very low signal-to-noise, and the test error is large due to the interference of the on-site electromagnetic environment.

[0043] Different from the traditional method of measuring response current, there is currently a dielectric response test method that uses a series sampling resistor for voltage division. By switching from measuring the response current to measuring the voltage across the sampling resistor, the magnitude of the measurement signal can be increased and the anti-interference capability can be enhanced.

[0044] The test method is as follows: the AC power supply outputs AC voltage to the test product, which is grounded through an adjustable sampling impedance to form a loop. The signal acquisition module synchronously collects the voltage signal of the power supply after passing through the voltage divider through two voltage information channels. The voltage signal of the sampling impedance The input voltage is obtained by voltage division calculation After that, the computer Perform Fourier transform to extract the amplitude and phase of the fundamental frequency component, and calculate the dielectric parameters of the test sample based on this. The equivalent circuit of the test process is as follows: Figure 2 shown.

[0045] The signal is measured by the high voltage probe of the signal acquisition module through a voltage divider. The oscilloscope uses two voltage signal channels to measure synchronously. and Phase and amplitude information, It can be calculated from the vector relationship:

[0046]

[0047] Where: R1, R2 are the voltage divider resistors; is the voltage across the capacitive device; the dielectric response current The voltage of the sampling resistor can be collected Calculated with the adjustable sampling impedance Z:

[0048]

[0049] The complex capacitance constant and dielectric loss tangent can be obtained based on the dielectric voltage and response current:

[0050]

[0051] Where: C' is the real part of the complex capacitance; C" is the imaginary part of the complex capacitance; the equivalent model of the tested electrical equipment is a capacitive equivalent circuit. As the frequency of the external voltage increases, the amplitude of the leakage current increases continuously, such as Figure 3 If the detection impedance remains unchanged, the voltage dynamic range on the detection impedance will be extremely large, resulting in weak signals, large errors, or signal amplitudes exceeding the measurement range.

[0052] like Figure 4 As shown, as the frequency increases, the medium response current increases. In order to minimize the measurement error, the voltage across the sampling impedance needs to be maintained near a certain set value. Correspondingly, the sampling impedance value also needs to decrease as the frequency increases. The following compares the traditional pure resistance sampling impedance and the RC parallel impedance of this patent.

[0053] Since the wide-band dielectric response test has a large frequency variation range, the corresponding leakage current also has a large variation range. If the adjustable impedance adopts a pure resistance method, the voltage dynamic range at both ends is large. If the voltage at both ends is to be kept basically unchanged, the resistance adjustment range is correspondingly large, which increases the complexity of the test. If the RC parallel impedance method is adopted, then as the frequency continues to increase, due to the presence of the capacitor branch, the voltage dynamic range at both ends is greatly compressed, and the corresponding impedance adjustment range is also greatly reduced. Figure 5 shown.

[0054] In order to make the voltage across the sampling resistor not exceed the measurement range of the signal acquisition module and the measurement error as small as possible, it is required that the voltage across the sampling resistor be maintained near a certain value. Figure 3 It can be seen that the adjustment range of the adjustable resistor also needs to be large, and the parallel capacitor can greatly compress this range and reduce the requirements for resistor adjustment. In addition, the frequency domain dielectric spectrum applies a single swept frequency signal to the medium, and the parallel capacitor can also play a filtering role to improve the accuracy of the dielectric spectrum.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A broadband dielectric response test method for high dynamic leakage current compression, characterized in that: The following steps are involved: Connect the test sample to the AC power supply and form a loop through the adjustable sampling impedance grounding; The voltage signal of the power supply after passing through the voltage divider and the sampling impedance voltage signal are synchronously collected by the signal collection module; Calculate input voltage; Perform Fourier transform on the collected voltage signal to extract the amplitude and phase of the fundamental frequency component; Calculate the dielectric parameters of the specimen based on the extracted amplitude and phase; Wherein, the adjustable sampling impedance is an impedance in the form of RC parallel connection, wherein C is a capacitor, R is a resistor, and both the capacitor C and the resistor R are adjustable; The values ​​of the resistance R and the capacitance C of the RC parallel impedance are adjusted according to the test frequency; The capacitor C of the RC parallel impedance plays a filtering role, thereby improving the accuracy of the dielectric spectrum.

2. The broadband dielectric response test method for high dynamic leakage current compression according to claim 1, characterized in that: The signal acquisition module includes a high voltage probe and a signal acquisition circuit.

3. The broadband dielectric response test method for high dynamic leakage current compression according to claim 1, characterized in that: The step of calculating the input voltage includes dividing the power supply voltage using a voltage divider, and measuring the divided voltage through a signal acquisition module.

4. The broadband dielectric response test method for high dynamic leakage current compression according to claim 1, characterized in that: The step of calculating the dielectric parameters of the sample includes calculating the complex capacitance constant and the dielectric loss tangent.

5. The broadband dielectric response test method for high dynamic leakage current compression according to claim 4, characterized in that: The step of calculating the complex capacitance constant and the dielectric loss tangent includes using the following formula: Where: R1, R2 are the voltage divider resistors; is the voltage across the capacitive device; the dielectric response current The voltage collected by the sampling resistor Calculated with the sample impedance Z, we get: C' is the real part of the complex capacitance; C" is the imaginary part of the complex capacitance; Measured by the high voltage probe of the signal acquisition module through a voltage divider; Measured by the signal acquisition module, the oscilloscope synchronously acquires voltage signals through two channels and Phase and amplitude information.

6. A broadband dielectric response test device with high dynamic leakage current compression, characterized in that: include: AC power supply; An adjustable sampling impedance, wherein the adjustable sampling impedance is an impedance in the form of RC parallel connection, wherein C is a capacitor, R is a resistor, and both the capacitor C and the resistor R are adjustable; A signal acquisition module, used for synchronously acquiring power supply voltage and sampling impedance voltage; A calculation module is used to calculate the input voltage, extract the amplitude and phase of the fundamental frequency component, and calculate the dielectric parameters of the test piece according to the collected voltage signal; The positive pole of the AC power supply is connected to one end of the test object; the negative pole of the AC power supply is connected to the other end of the test object through an adjustable sampling impedance and is grounded; The two ends of the adjustable sampling impedance are respectively connected to the two voltage input channels of the signal acquisition module; the voltage change at the two ends of the adjustable sampling impedance will be synchronously transmitted to the signal acquisition module for acquisition; The signal acquisition module transmits the collected power supply voltage and sampled impedance voltage signals to the calculation module; The calculation module performs data processing and calculation based on the received signals and finally obtains the dielectric parameters of the test piece.

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