A method for correcting the dielectric loss factor of high-voltage power equipment

Abstract

The present invention relates to the field of insulating medium measurement technology, and discloses a method for correcting the insulating medium loss factor of high-voltage power equipment, comprising the following steps: step 1, measuring the dielectric loss factor of the device to be tested within a certain frequency range to obtain the frequency domain dielectric spectrum measured curve of the device to be tested within the frequency range; step 2, using a curve fitting method to extract from the frequency domain dielectric spectrum measured curve obtained in step 1 through a mathematical model: the frequency-dielectric loss characteristic curve of insulating paper, the frequency-dielectric loss characteristic curve of mineral oil, and the structural characteristics of the insulation system in the device to be tested; step 3, respectively correcting the frequency-dielectric loss characteristic curves of insulating paper and mineral oil. Compared with the traditional empirical coefficient temperature correction method, the accuracy of the results of the present invention has been greatly improved, and the changing trend of the insulation state can be observed more accurately. This method is suitable for most oil-immersed high-voltage power equipment.

Description

Technical Field

[0001] The invention relates to the technical field of insulating medium measurement, and in particular to a method for correcting the insulating medium loss factor of high-voltage power equipment. Background Art

[0002] Insulation degradation is one of the main causes of unexpected failures of high-voltage power equipment. Therefore, discovering the degradation characteristics in the early stage of insulation degradation can take repair actions early, prevent the occurrence of unexpected failures, and improve the operating reliability of the equipment. The 50Hz power frequency dielectric loss factor is a key indicator reflecting the insulation degradation state. Generally speaking, the higher the degree of insulation degradation, the greater the dielectric loss factor value. In theory, the insulation degradation trend can be tracked by observing the change of the value over time. However, the value is related to temperature and insulation material, that is, the value measured at different temperatures for the same equipment will be different. Since the power outage maintenance plan of high-voltage power equipment cannot be accurately controlled, the ambient temperature and equipment temperature at different times are generally different. Before conducting insulation status analysis, the values ​​measured at different temperatures need to be calibrated to the standard temperature (20°C) before comparison.

[0003] The current correction method is completed by multiplying the value measured at the actual temperature by a proportionality coefficient, which is an empirical value and has no strict theoretical basis. Due to the limitations of the proportionality coefficient correction method, the relevant industry standards recommend that measurements should be made at a temperature of 10 to 40°C as much as possible; when the value measured at room temperature is large and the value increases significantly at high temperature, it is considered that the insulation is defective. Due to the uncertainty of the equipment power outage maintenance time and the uncontrollable temperature drop during the cooling process after the equipment power outage, it is difficult to ensure that the test can be performed within the recommended temperature range.

[0004] At present, the temperature correction formula specified in my country's national standard "GB / T 6451-2023 Technical Parameters and Requirements for Three-Phase Oil-Immersed Power Transformers" is: ; and the ratio of the dielectric loss factor actually measured to the dielectric loss factor at standard temperature (20°C) is shown in Table 2. The temperature correction method recommended by the US IEEE C57.12.90-2006 standard is the same as that of my country's national standard method, but there are certain differences in the specific values.

[0005] The insulation system of common high-voltage power equipment such as transformers, bushings, reactors, and mutual inductors is composed of insulating paper and mineral oil, and the composition ratio of paper / board and oil varies greatly in different equipment. In addition, experimental results show that the dielectric loss factor of different materials is affected by temperature to different degrees. Therefore, the method of using proportional coefficient correction is not effective, and the corrected value fluctuates too much, making it impossible for operation and maintenance personnel to discover early signs of insulation degradation through trend analysis. Summary of the invention

[0006] In order to solve the technical problems raised in the background technology, the present invention provides a method for correcting the insulation dielectric loss factor of high-voltage power equipment.

[0007] The present invention is implemented by the following technical solution: A method for correcting the insulation loss factor of high-voltage power equipment comprises the following steps:

[0008] Step 1: measuring the dielectric loss factor of the device under test within a certain frequency range to obtain a frequency domain dielectric spectrum measured curve of the device under test within the frequency range;

[0009] Step 2, using a curve fitting method to extract from the frequency domain dielectric spectrum measured curve obtained in step 1: the frequency-dissipation characteristic curve of the insulating paper, the frequency-dissipation characteristic curve of the mineral oil, and the structural characteristics of the insulation system in the device to be tested;

[0010] Step 3: Correcting the frequency-dissipation characteristic curves of the insulating paper and the mineral oil respectively, which includes:

[0011] Step 3.1: Based on formula (1), calibrate the frequency points of the frequency-dissipation characteristic curve of the insulating paper to obtain the frequency-dissipation characteristic curve after the initial calibration: , and then use the frequency-dissipation characteristic curve after the initial correction Use interpolation method to get the frequency-dissipation characteristic curve of insulating paper at 20℃ .

[0012] (1)

[0013] Step 3.2: Based on formula (2), calibrate the frequency points of the frequency-dissipation characteristic curve of mineral oil; obtain the frequency-dissipation characteristic curve after initial calibration: , and then use the frequency-dissipation characteristic curve after the initial correction Use the interpolation method to obtain the frequency-dissipation characteristic curve of mineral oil at 20°C ;

[0014] (2)

[0015] In formula (1) and formula (2), The actual measurement frequency point of the frequency domain dielectric spectrum test of power equipment. , , ,in is the actual temperature of the device under test during measurement;

[0016] Step 4: The frequency-dissipation characteristic curves of the calibrated insulating paper and mineral oil , The mathematical model and the known structural characteristics of the insulation system in the device under test are used to resynthesize the overall frequency-dissipation characteristic curve of the device under test.

[0017] The mathematical model in step 2 is:

[0018]

[0019] in, is the overall insulation dielectric loss factor of the device, is the dielectric loss factor of the insulating oil, is the insulating dielectric loss factor of the insulating paper; X is the thickness of the partition in the insulation system of the device under test divided by the total width of the oil channel, and Y is the total width of the struts in the insulation system of the device under test divided by the circumference of the oil channel. Both the partition and the struts are insulating paper products, and the structural characteristics of the insulation system in the device under test are the values ​​of X and Y.

[0020] The frequency range in step 1 is: 0.01 Hz - 1000 Hz.

[0021] On the frequency-dissipation characteristic curve synthesized in step 4, the dielectric loss factor corresponding to the values ​​at different frequency points within the measurement frequency range can be extracted as the final result at the standard temperature (20°C). .

[0022] The present invention proposes an electronic device, which includes a memory and a processor. The memory stores program instructions, and when the processor runs the program instructions, the steps in the above correction method are executed.

[0023] The present invention proposes a readable storage medium, in which computer program instructions are stored. When the computer program instructions are executed by a processor, the steps in the above correction method are executed.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The correction method proposed in the present invention comprehensively considers the different temperature characteristics of insulating paper and mineral oil, as well as the structural characteristics of the internal insulation system of the power equipment, and is suitable for oil-immersed high-voltage power equipment; and the correction method proposed in the present invention can accurately correct the dielectric loss factors of different temperatures obtained during multiple inspections to the dielectric loss factor value corresponding to 20°C , thereby discovering the early insulation degradation characteristics caused by Fluctuations, improve equipment operation reliability.

[0026] Compared with the traditional empirical coefficient temperature correction method, the accuracy of the results of this method has been greatly improved, and the changing trend of the insulation state can be observed more accurately. This method is also applicable to most oil-immersed high-voltage power equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flowchart of the correction method proposed by the present invention;

[0028] Figure 2 A schematic diagram of the internal structural features of the insulation system of the oil-immersed power equipment proposed by the present invention;

[0029] Figure 3 This is the overall frequency domain dielectric spectrum curve of the oil-immersed power equipment proposed by the present invention at 30°C;

[0030] Figure 4 To extract the characteristic curves of insulating paper and mineral oil from the overall frequency domain dielectric spectrum of the device under test according to the correction method proposed in the present invention;

[0031] Figure 5 A curve comparison diagram of the temperature characteristics of the insulating paper of the oil-immersed power equipment proposed by the present invention before and after correction;

[0032] Figure 6 A curve comparison diagram of the temperature characteristics of mineral oil of the oil-immersed power equipment proposed by the present invention before and after correction;

[0033] Figure 7 The frequency domain dielectric spectrum curve diagram of the oil-immersed power device proposed by the present invention at 30°C and after being corrected to 20°C;

[0034] Figure 8 The dielectric loss factor-frequency characteristic curve of the insulating paper proposed by the present invention at different moisture contents;

[0035] Fig. 9 The dielectric loss factor-frequency characteristic curve of the mineral oil proposed by the present invention at different electrical conductivities. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0037] Example:

[0038] Reference Figure 1 - Fig. 9 ,This scheme proposes an accurate method for correcting the dielectric loss factor of high voltage power equipment, including the following steps:

[0039] Step 1: Measure the dielectric loss factor of the device under test within a certain frequency range, and obtain the frequency domain dielectric spectrum measured curve of the device under test within the frequency range; this can be achieved by using an FDS tester.

[0040] Step 2, using a curve fitting method to extract from the frequency domain dielectric spectrum measured curve obtained in step 1 through a mathematical model: the frequency-dissipation characteristic curve of the insulating paper, the frequency-dissipation characteristic curve of the mineral oil, and the structural characteristics of the insulation system in the device to be tested, that is, the relative proportion of the insulating paper and the mineral oil in the insulation system;

[0041] Step 3: Correcting the frequency-dissipation characteristic curves of the insulating paper and the mineral oil respectively, which includes:

[0042] Step 3.1: Based on formula (1), calibrate the frequency point of the frequency-dissipation characteristic curve of the insulating paper (expressed as the vertical coordinate on the curve No change, correct the horizontal coordinate The curve is translated as a whole in the coordinate system) to obtain the frequency-dissipation characteristic curve after the initial correction: , and then use the frequency-dissipation characteristic curve after the initial correction ( ) Use the interpolation method to obtain the frequency-dissipation characteristic curve of the final corrected insulation paper at standard temperature (20°C) ;

[0043] (1)

[0044] Step 3.2: Based on formula (2), calibrate the frequency point of the frequency-dissipation characteristic curve of mineral oil (expressed as the vertical coordinate on the curve No change, correct the horizontal coordinate The curve is translated as a whole in the coordinate system); the frequency-dissipation characteristic curve after the initial correction is obtained: , and then use the frequency-dissipation characteristic curve after the initial correction Use the interpolation method to obtain the frequency-dissipation characteristic curve of mineral oil at standard temperature (20°C) ;

[0045] (2)

[0046] in, The actual measurement frequency point of the frequency domain dielectric spectrum test of power equipment. , , ,in is the actual temperature of the device under test during measurement.

[0047] Step 4: The frequency-dissipation characteristic curves of the calibrated insulating paper and mineral oil, namely and The mathematical model is used to resynthesize the frequency-dissipation characteristic curve of the device under test.

[0048] The mathematical model in step 2 is:

[0049]

[0050] in, is the insulation dielectric loss factor of the entire device; X is the thickness of the partition in the insulation system of the device under test divided by the total width of the oil channel, Y = the total width of the support in the insulation system of the device under test divided by the circumference of the oil channel, and the partition and the support are both insulating paper products.

[0051] It should be noted that, refer to Figure 8-9 , which are the dielectric loss curves of insulating paper and mineral oil at different frequencies, and the dielectric loss factor of insulating paper The dielectric loss factor of mineral oil is determined by the water content (M). is determined by the conductivity ( ) decided by.

[0052] Specifically, in step 2, the principle of extracting the frequency-dissipation characteristic curve of the insulating paper, the frequency-dissipation characteristic curve of the mineral oil, and the relative proportion of the insulating paper and the mineral oil from the measured frequency domain dielectric spectrum is as follows:

[0053] There are four unknowns on the right side of the mathematical model formula in step 2 above, namely X, Y, M, Therefore, it is only necessary to measure the dielectric loss factor of the device under test at four different frequencies (specifically obtained through the measured frequency domain dielectric spectrum curve of the device under test within the frequency range), and the four unknowns X, Y, M, , and the water content (M) and conductivity ( ), we can get the corresponding and , so as to obtain the corresponding frequency-dissipation characteristic curve.

[0054] In step 4, the corrected , The result is a frequency-dissipation characteristic curve of the device under test at 20°C.

[0055] As an optional implementation manner of the present invention, the frequency range in step 1 is: 0.01 Hz-1000 Hz.

[0056] In the specific operation, on the frequency-dissipation characteristic curve synthesized in step 4, the dielectric loss factor corresponding to the values ​​of different frequency points within the measurement frequency range can be extracted as the final result. .

[0057] Examples:

[0058] The main transformer (standby transformer) of a nuclear power plant with 300,000 kW units underwent dielectric loss tests in January 2021 and June 2024, respectively. The results are listed in the following table. The transformer was under low load and good working condition during operation, and the oil was filtered at the end of 2022, so the insulation condition in 2024 should be better than that in 2021.

[0059] The two dielectric loss tests were conducted in winter and summer respectively, with a large temperature difference, so the dielectric loss results were also quite different. The difference was even greater after correction using the traditional correction method, while the results obtained using the correction method proposed in the present invention were more consistent with the actual situation.

[0060] Table 1 - Results obtained by the correction method proposed in the present invention and the results obtained by other correction methods

[0061] January 2021 June 2024 Transformer temperature 10℃ 40℃ Measured dielectric loss factor (%) 0.312 0.194 my country's national standard correction value (%) 0.406 0.114 US industry standard correction value (%) 0.390 0.125 Correction value of the present invention (%) 0.277 0.238

[0062] Table 2 - Compensation coefficients recommended by the US IEEE C57.12.90-2006 standard and the Chinese GB / T 6451-2023 standard

[0063] Measurement temperature T, ℃ Chinese Standards American Standard 10 0.77 0.8 15 0.87 0.9 20 1 1.0 25 1.15 1.12 30 1.3 1.25 35 1.5 1.40 40 1.7 1.55 45 1.9 1.75 50 2.2 1.95 55 2.5 2.18 60 3.0 2.42 65 3.5 2.7 70 4.0 3.0

[0064] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for correcting the dielectric loss factor of high-voltage power equipment, characterized in that: The steps include: Step 1: measuring the dielectric loss factor of the device under test within a certain frequency range to obtain a frequency domain dielectric spectrum measured curve of the device under test within the frequency range; Step 2, using a curve fitting method to extract from the frequency domain dielectric spectrum measured curve obtained in step 1: the frequency-dissipation characteristic curve of the insulating paper, the frequency-dissipation characteristic curve of the mineral oil, and the structural characteristics of the insulation system in the device to be tested; Step 3: Correct the frequency-dissipation characteristic curves of the insulating paper and the mineral oil respectively, which includes: Step 3.1: Based on formula (1), calibrate the frequency points of the frequency-dissipation characteristic curve of the insulating paper to obtain the frequency-dissipation characteristic curve after the initial calibration: ,in: is the dielectric loss factor of the insulating paper; then the frequency-dissipation characteristic curve after the initial correction is used Use interpolation method to get the frequency-dissipation characteristic curve of insulating paper at 20℃ ; （1）； Step 3.2: Based on formula (2), calibrate the frequency points of the frequency-dissipation characteristic curve of mineral oil; obtain the frequency-dissipation characteristic curve after initial calibration: ,in: is the dielectric loss factor of mineral oil; then use the frequency-dissipation characteristic curve after the initial correction Use the interpolation method to obtain the frequency-dissipation characteristic curve of mineral oil at 20°C ; （2）； In formula (1) and formula (2), The actual measurement frequency point of the frequency domain dielectric spectrum test of power equipment. , , , is the actual temperature of the device under test during measurement; Step 4: The frequency-dissipation characteristic curves of the calibrated insulating paper and mineral oil , The mathematical model and the known structural characteristics of the insulation system in the device under test are used to resynthesize the overall frequency-dissipation characteristic curve of the device under test.

2. A method for correcting the dielectric loss factor of a high-voltage power device according to claim 1, characterized in that: The mathematical model in step 2 is: ； in, is the overall insulation dielectric loss factor of the device, is the dielectric loss factor of the insulating oil, is the insulation dielectric loss factor of the insulation paper; The thickness of the partition in the insulation system of the equipment under test divided by the total width of the oil channel, is the total width of the braces in the insulation system of the device under test divided by the circumference of the oil channel, and both the partitions and the braces are made of insulating paper. The structural characteristics of the insulation system in the device under test are the and The value of .

3. A method for correcting the dielectric loss factor of a high-voltage power device according to claim 1, characterized in that: The frequency range in step 1 is: 0.01Hz-1000Hz.

4. A method for correcting the dielectric loss factor of high-voltage power equipment according to claim 1, characterized in that: On the frequency-dissipation characteristic curve synthesized in step 4, the final result of the dielectric loss factor at 20°C corresponding to the values ​​of different frequency points within the measurement frequency range can be extracted. .

5. An electronic device, characterized in that: The electronic device comprises a memory and a processor, wherein the memory stores program instructions, and when the processor runs the program instructions, the steps in the method according to any one of claims 1 to 4 are executed.

6. A readable storage medium, characterized in that: The readable storage medium stores computer program instructions, and when the computer program instructions are executed by a processor, the steps in the method according to any one of claims 1 to 4 are executed.

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