Frequency domain dielectric response test platform sampling resistor self-adaptive adjusting method

Abstract

The invention relates to a frequency domain dielectric response test platform sampling resistor adaptive adjustment method, and belongs to the technical field of power system detection. According to the invention, the adjustable sampling resistor is connected in series for voltage division, and the voltage comparator and the counter are combined, so that the sampling resistor can be continuously and automatically adjusted along with the test frequency, the voltage at the two ends of the sampling resistor is maintained in a set range, the measurement error is effectively reduced, and the accuracy of the high-voltage frequency domain dielectric spectrum is improved. The method is suitable for insulation state diagnosis of high-voltage electrical equipment, and a new technical scheme is provided for application of the dielectric response method in the field of power system detection.

Description

Technical Field

[0001] The invention belongs to the technical field of power system detection, and relates to a method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform. Background Art

[0002] By studying the correlation mechanism and influence law between the dielectric insulation state and macroscopic dielectric properties, the analytical method of inverting the dielectric insulation state with macroscopic dielectric characteristics is called the dielectric response method. Compared with the time domain method, the advantages of the frequency domain method are: 1) The measurement bandwidth is wide, usually 0.1mHz~~1MHz, which can explore the electrical state of the insulating medium in a wider frequency band, especially the high-frequency dielectric properties of the medium under working conditions such as harmonics and transient voltages; 2) The dielectric spectrum is measured point by point, and the field application can avoid power frequency interference and has strong anti-interference ability. Therefore, the insulation state diagnosis based on the frequency domain dielectric response method has been widely used in the field.

[0003] However, for the existing frequency domain dielectric spectroscopy technology, the measured medium response current is usually at the nA level, with weak anti-interference ability and large error. Although the current method of measuring voltage rather than current by series sampling resistor voltage division has been adopted to increase the test quantity and enhance anti-interference ability, there is still a problem: if the detection impedance remains unchanged, then as the frequency changes, the leakage current of the medium changes greatly, and the voltage dynamic range on the detection impedance is extremely large, resulting in weak signals, large errors, or signal amplitudes exceeding the measurement range. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform. A method for adaptively adjusting sampling resistance based on a frequency domain dielectric response test platform is proposed to meet the broadband measurement of high-voltage dielectric spectra and reduce measurement errors; continuous automatic adjustment of sampling resistance is achieved to ensure the uninterrupted collection and measurement.

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

[0006] A method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform, the method comprising the following steps:

[0007] The AC test power supply outputs AC voltage to the test product;

[0008] The adjustable sampling resistor is connected in series with the test sample;

[0009] The signal acquisition module synchronously acquires the input voltage signal and the sampling impedance voltage signal through two voltage information channels;

[0010] The computer simultaneously performs Fourier transform on the collected voltage signal to extract the amplitude and phase of the fundamental frequency component, and calculates the dielectric parameters of the test piece based on this;

[0011] The voltage across the sampling resistor passes through a voltage comparator, the output of the voltage comparator is connected to the clock signal port of the counter, and the output of the counter controls the output resistance value of the adjustable resistor;

[0012] The adjustable resistor is connected in parallel, and the resistance value is changed by controlling the on and off of the parallel switch.

[0013] Furthermore, the output resistance value of the adjustable resistor decreases as the frequency increases.

[0014] Furthermore, in the parallel connection mode, the resistance value of the parallel resistor is selected according to the frequency interval division so as to make the dynamic range of both ends of the impedance as small as possible.

[0015] Furthermore, the voltage across the sampling resistor is compared with a set value Up by a voltage comparator. When the voltage is greater than Up, the voltage comparator outputs a pulse signal to trigger a counter to count. The output end of the counter controls the adjustable resistor parallel switch to reduce it.

[0016] Furthermore, the output terminals Q3Q2Q1Q0 of the counter control the on / off state of the adjustable resistor parallel switch, where "0" indicates that the switch is open and "1" indicates that the switch is closed.

[0017] The beneficial effect of the present invention is that the sampling resistor adaptive adjustment method based on the frequency domain dielectric response test platform proposed by the present invention makes the voltage across the sampling resistor always maintained within a very small dynamic range when the voltage frequency changes. This range can reduce the measurement and analysis calculation errors while meeting the range requirements of the acquisition module, and improve the accuracy of the high-voltage frequency domain dielectric spectrum. At the same time, the continuous automatic adjustment of the sampling resistor with the test frequency ensures the uninterrupted acquisition measurement.

[0018] 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

[0019] 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:

[0020] Figure 1 It is the equivalent circuit diagram of the frequency domain dielectric response test;

[0021] Figure 2 Schematic diagram of variable resistance changing with frequency

[0022] Figure 3 This is the internal schematic diagram of the variable resistor;

[0023] Figure 4 Schematic diagram of the variable resistor voltage changing with frequency. DETAILED DESCRIPTION

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The sampling resistor adaptive adjustment method is based on a frequency domain dielectric response test platform with a series adjustable resistor voltage divider. The equivalent circuit of the platform test process is as follows: Figure 1 As shown. The AC test power supply outputs AC voltage to the test piece, which is grounded through an adjustable sampling resistor to form a loop. The signal acquisition module synchronously collects the input voltage signal and the sampling impedance voltage signal through two voltage information channels. The computer simultaneously performs Fourier transform on the collected voltage signal to extract the amplitude and phase of the fundamental frequency component, and calculates the dielectric parameters of the test piece based on this.

[0028] 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:

[0029]

[0030] Where: R1, R2 are the voltage divider resistors; is the voltage across the capacitive device. Dielectric response current The voltage of the sampling resistor can be collected Calculated with the adjustable sampling impedance:

[0031]

[0032] According to the dielectric voltage and the response current The complex capacitance constant C* and dielectric loss tangent tanδ can be obtained:

[0033]

[0034] Where: C' is the real part of the complex capacitance; C" is the imaginary part of the complex capacitance; j is the imaginary unit. The equivalent model of the tested electrical equipment is a capacitive equivalent circuit. As the frequency of the applied voltage increases, the leakage current amplitude increases continuously. If the detection impedance remains unchanged, the voltage dynamic range on the detection impedance is extremely large, resulting in weak signals, large errors, or signal amplitudes exceeding the measurement range. In order to prevent the measured voltage from exceeding the range and reduce the measurement error, the voltage across the detection resistor should be maintained at a certain set value U p Nearby, according to formula (3), the resistance of the variable resistor needs to decrease accordingly as the frequency increases. The adjustable resistance and leakage current change with frequency as follows Figure 2 shown.

[0035] like Figure 1 As shown, the adaptive adjustment of the adjustable resistor is achieved by the following method: sampling the voltage across the resistor After the voltage comparator, the output of the voltage comparator is connected to the clock signal port of the counter. The output terminal Q3Q2Q1Q0 of the counter is collected by the industrial computer for calculation and analysis through the I / O quantity acquisition device, and controls the output resistance value of the adjustable resistor. The adjustable resistor adopts parallel connection. Its internal schematic diagram is as follows Figure 3 shown.

[0036] At the beginning of the test, the reset terminal of the counter is controlled to reset the counter. As the test frequency increases, the medium response current increases, and the voltage across the sampling resistor increases. When the voltage is greater than the set value U p When the voltage comparator outputs a pulse signal, the pulse signal is used as the clock signal of the 4-bit synchronous binary counter. The counter counts automatically in sequence. The output terminal "Q3Q2Q1Q0" of the counter controls the adjustable resistor parallel switch to reduce the value. On the other hand, it is used by the I / O quantity acquisition device to obtain the resistance value at this time for analysis and calculation. "0" represents the switch Q i (i=0,1,2,3) is disconnected, "1" means closed, then the connected state of the resistor "Q3Q2Q1Q0" corresponds to the output of the counter "Q3Q2Q1Q0", as the frequency increases, the counter counts sequentially, and the resistance gradually decreases, thereby achieving the control of the resistance value of the connected resistor. Table 1 shows the parallel combination of variable resistors.

[0037] Table 1

[0038]

[0039] According to the division of frequency intervals, the resistance value of each parallel resistor should be selected to minimize the dynamic range of the impedance. Although the resistance value is fixed within a certain frequency range, the voltage across the resistor still increases with the increase of the response current. However, according to the division density of the frequency interval and the selection of the resistance value, the dynamic range of the voltage across the impedance can be kept small, the measurement error can be reduced, and the dielectric parameters can be accurately measured. Figure 4 shown.

[0040] 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 method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform, characterized in that: The method comprises the following steps: The AC test power supply outputs AC voltage to the test product; The adjustable sampling resistor is connected in series with the test sample; The signal acquisition module synchronously acquires the input voltage signal and the sampling impedance voltage signal through two voltage information channels; The computer simultaneously performs Fourier transform on the collected voltage signal to extract the amplitude and phase of the fundamental frequency component, and calculates the dielectric parameters of the test piece based on this; The voltage across the sampling resistor passes through a voltage comparator, the output of the voltage comparator is connected to the clock signal port of the counter, and the output of the counter controls the output resistance value of the adjustable resistor; The adjustable resistor is connected in parallel, and the resistance value is changed by controlling the on and off of the parallel switch.

2. The method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform according to claim 1, characterized in that: The output resistance value of the adjustable resistor decreases as the frequency increases.

3. The method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform according to claim 1, characterized in that: In the parallel connection mode, the resistance value of the parallel resistor is selected according to the frequency interval division to make the dynamic range of both ends of the impedance as small as possible.

4. The method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform according to any one of claims 1 to 3, characterized in that: The voltage across the sampling resistor is compared with the set value Up by a voltage comparator. When the voltage is greater than Up, the voltage comparator outputs a pulse signal to trigger a counter to count. The output end of the counter controls the adjustable resistor parallel switch to reduce it.

5. The method for adaptively adjusting sampling resistance of a frequency domain dielectric response test platform according to any one of claim 4, characterized in that: The output terminal Q3Q2Q1Q0 of the counter controls the on-off state of the adjustable resistor parallel switch, where "0" indicates that the switch is open and "1" indicates that the switch is closed.

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