Method for evaluating insulation life of power equipment under high-frequency harmonic voltage

Abstract

The invention discloses a method for evaluating the insulation life of power equipment under high-frequency harmonic voltage. According to the method, a sheet-shaped sample of an electrical equipment insulating material under different high-frequency harmonic voltage conditions is obtained through an accelerated electric heating aging test, and the breakdown field strength and the activation energy of the sheet-shaped sample are tested. And further establishing a relationship among the breakdown field strength, the aging time and the high-frequency harmonic frequency, and obtaining an expected insulation failure life of the power equipment under an actual working condition by utilizing data fitting. In addition, according to the method, a thermal life equation is established through activation energy, a temperature acceleration factor is calculated, and the insulation expected life of the power equipment under high-frequency harmonic voltage is finally obtained in combination with high-frequency harmonic and temperature of an actual working condition. The method has important significance for improving the insulation reliability of the power equipment, and provides an effective evaluation means for safe operation of the power equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power systems, and particularly relates to a method for evaluating the insulation life of power equipment under high-frequency harmonic voltage. BACKGROUND

[0002] In a power system, the operation reliability of power equipment is crucial to power supply safety, and the insulation performance of power equipment is an important guarantee for its stable and safe operation. Epoxy resin and other solid insulation materials are the main insulation medium of most power equipment, and their life prediction and evaluation are important means to ensure the safe operation of power equipment. With the development of flexible power transmission and distribution technology, the harmonic pollution of power systems presents a high-frequency (2-150 kHz) characteristic. Studies have shown that the dielectric loss generated by high-frequency harmonic voltage increases by 3-7 times compared to power frequency conditions, which reduces the partial discharge inception voltage of epoxy resin and other solid insulation materials by about 40%, accelerating the process of dielectric thermal aging. These high-frequency harmonics cause more serious degradation of solid insulation materials, thereby shortening the insulation life of power equipment. Therefore, targeted life evaluation can not only improve the insulation reliability of equipment, but also optimize economic benefits. SUMMARY

[0003] In order to solve the problems existing in the prior art, the purpose of the present application is to provide a method for evaluating the insulation life of power equipment under high-frequency harmonic voltage. The present application establishes an evaluation method for the aging time, aging frequency, temperature and expected life of the insulation material of power equipment through accelerated aging test, studies the expected life of the insulation of power equipment under high-frequency harmonics, and provides evaluation for the insulation reliability of power equipment.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: A method for evaluating the insulation life of power equipment under high-frequency harmonic voltage, comprising the following steps: S1. In an accelerated electrothermal aging test of power equipment, obtain sheet-shaped samples of the insulation part of the power equipment under different high-frequency harmonic voltages; the parameters of the accelerated electrothermal aging test of the power equipment include: aging temperature 、 accelerated aging time and high-frequency harmonic frequency; S2. Test the breakdown field strength and activation energy of the sheet-shaped samples; S3. Use the data obtained in S2 to establish a fitting curve of the relationship between the breakdown field strength and the aging time, and a fitting curve of the relationship between the high-frequency harmonic frequency and the frequency expected life; S4. Establish a thermal life equation through the fitting curve of the breakdown field strength and the aging time; S5. Calculate the temperature acceleration factor through the thermal life equation; S6. Calculate the expected insulation life of the power equipment insulation under high-frequency harmonic voltage in actual operating conditions using the fitting curve of the high-frequency harmonic frequency and the expected frequency lifetime and the temperature acceleration factor.

[0005] Preferably, in the accelerated electrothermal aging test of power equipment, the accelerated thermal aging temperature is lower than the glass transition temperature of the power equipment, but higher than the actual application temperature.

[0006] Preferably, in the accelerated electrothermal aging test of power equipment, the accelerated electrothermal aging time of the power equipment is t≥1000h, and the number of sample aging time values ​​m≥5 is set in the experiment.

[0007] Preferably, in the accelerated electrothermal aging test of power equipment, the accelerated electrothermal harmonic frequency is... f The harmonic frequency is greater than that in practical applications, and the number of voltage harmonic frequency values ​​is set in the experiment. n ≥3.

[0008] Preferably, when testing the breakdown field strength of the sheet-like sample, the breakdown field strength is obtained using the Weibull distribution at different aging times and harmonic frequencies. E [m，n] Breakthrough field strength E [m，n] The corresponding aging time is t m Harmonic frequencies are f n ; The activation energy of the sheet-like sample was obtained using TGA (Thermogravimetric Analysis). E a[m，n] ,activation energy E a[m，n] The corresponding aging time is t m Harmonic frequencies are f n .

[0009] Preferably, the fitted curve expression for the relationship between breakdown field strength and aging time is as follows:

[0010] in, To break through the field strength, t For aging time, A , B These are the aging parameters obtained from the accelerated aging test through fitting.

[0011] Preferably, the fitted curve expression for the relationship between high-frequency harmonic frequency and expected frequency lifetime is as follows:

[0012] in, For frequency expected lifetime, It is a high-frequency harmonic frequency. a , b , c These are the frequency-related influence factor parameters obtained from the fitting.

[0013] Preferably, the expression for the thermal lifetime equation is as follows:

[0014] in: The estimated lifetime under a specific transformation, in minutes; The activation energy is expressed in J / mol. The gas constant is 8.314 J / (mol·K); The failure temperature under a specific transformation, expressed in K; This is the heating rate, expressed in °C / min; is the integration constant.

[0015] Preferably, the temperature acceleration factor is calculated using the thermal lifetime equation, including the following process: The accelerated aging test temperature will be included in the thermal life equation. T e and actual operating temperature T u Substituting into the thermal lifetime equation, we obtain the corresponding expected lifetime. t e and t u ,use t e and t u The temperature acceleration factor AF was calculated. T The specific expression is:

[0016] Preferably, the expected insulation life of power equipment insulation under actual operating conditions and high-frequency harmonic voltage is as follows:

[0017] in, AF represents the expected insulation life of power equipment insulation under actual operating conditions and high-frequency harmonic voltage. T As a temperature acceleration factor, L ( f () represents the expected frequency lifetime under high-frequency harmonics in actual operating conditions.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: This invention, through a series of experimental steps, first obtains sheet-like insulating samples under different high-frequency harmonic voltages in accelerated electrothermal aging tests of power equipment, and then tests the breakdown field strength and activation energy, providing fundamental data for life assessment. Using this data, the invention establishes fitting curves relating breakdown field strength to aging time, and high-frequency harmonic frequency to expected lifespan, clarifying the impact of high-frequency harmonic frequency on insulation lifespan. This method not only enriches the theoretical basis for power equipment insulation lifespan assessment but also provides a more accurate tool for judging insulation performance under actual operating conditions. In terms of technical effects, this invention has several significant advantages: First, it improves the accuracy of power equipment insulation performance assessment, enabling a comprehensive and in-depth analysis of the aging process of insulating materials under high-frequency harmonic environments. Second, the calculated temperature acceleration factor and expected insulation lifespan under actual operating conditions provide a scientific basis for the safe operation of equipment, effectively preventing equipment failure accidents caused by insulation degradation. Furthermore, this method is relatively simple and efficient, applicable to different types of power equipment, and has significant practical value and promising prospects for application in the safe operation of power systems. Overall, this invention effectively fills the gap in the prior art and provides a scientific and reasonable method for assessing the insulation life of power equipment, which has important practical significance and application value for improving the overall safety and stability of power systems. Attached Figure Description

[0019] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a schematic diagram of the process for evaluating the insulation life of power equipment under high-frequency harmonic voltage in an embodiment of the present invention. Figure 2 The breakdown field strength established in the embodiments of the present invention E With aging time t The relationship is established and the curve is fitted. Figure 3 To establish the expected frequency lifetime in the embodiments of the present invention L With high frequency harmonic frequency f The relationship is established and the curve is fitted. Figure 4 The thermal lifetime equation and temperature acceleration factor AF in the embodiments of the present invention T . Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] A single aging factor model cannot characterize the multi-physics coupling effect of high-frequency harmonics and temperature field. This invention proposes a new method for evaluating the insulation life of power equipment under high-frequency harmonic voltage at different temperatures and high-frequency harmonic frequencies under actual operating conditions. By accelerating electrothermal aging experiments and then testing the breakdown field strength and activation energy, the expected insulation life of the power equipment insulation under the corresponding actual operating temperature and high-frequency harmonic voltage can be obtained through fitting.

[0024] Reference Figure 1 The present invention provides a method for assessing the insulation life of power equipment under high-frequency harmonic voltage, comprising the following steps: S1. Conduct accelerated electrothermal aging tests on power equipment, subjecting the power equipment to accelerated thermal aging under different high-frequency harmonic voltages. The insulation of the power equipment is sliced ​​to obtain sheet-like samples of the insulation under different high-frequency harmonic voltages. The parameters of the accelerated electrothermal aging test include aging temperature. T、 Aging time [ t 1, t 2, t 3··· t m Harmonic frequencies f 1, f 2, f 3··· f nSpecifically, the accelerated electrothermal aging test temperature. T It is lower than the glass transition temperature of electrical equipment, but higher than the actual application temperature. This accelerates the electrothermal aging time. t ≥1000h, and the number of sample aging time values ​​set in the experiment. m ≥5. Accelerating electrothermal harmonic frequency of electrical equipment f The voltage harmonic frequency should be greater than the harmonic frequency in practical applications, and the number of voltage harmonic frequency values ​​should be set in the experiment. n ≥3.

[0025] S2. Test the breakdown field strength and activation energy of the sheet-like insulating sample of the power equipment (i.e., the sheet-like sample); specifically including: obtaining the breakdown field strength of the sheet-like insulating sample of the power equipment using the Weibull distribution at different aging times and harmonic frequencies. E [m，n] Breakthrough field strength E [m，n] The corresponding aging time is t m Harmonic frequency is f n .

[0026] S3. Establish the relationship between breakdown field strength and aging time to obtain the breakdown field strength. E [m，n] With aging time t The relationship fitting curve is given below, and its expression is as follows:

[0027] in, To break through the field strength (abbreviated as) E ), t For aging time, A , B These are the aging parameters obtained from the accelerated aging test through fitting.

[0028] According to the breakdown field strength E [m，n] With aging time t The relationship fitting curve can be used to obtain the accelerated aging time corresponding to the failure breakdown field strength of different power equipment; specifically, the failure breakdown field strength of the power equipment is set. E 1[m，n] , E 2[m，n] , E 3[m，n]··· E i[m，n] ( i ≥3), the accelerated aging times corresponding to failure under different high-frequency harmonics are respectively t [1，n] , t[2，n] , t [3，n]··· t [i，n] .

[0029] S4. Establish expected frequency lifetime L With high frequency harmonic frequency f By relating the frequency to the fitted curve, the expected lifespan of insulation failure under high-frequency harmonics in actual operating conditions of power equipment is obtained; specifically, this is determined by the high-frequency harmonic frequency. f 1, f 2, f 3··· f n With accelerated aging time t [1，n] , t [2，n] , t [3，n]··· t [i，n] Established frequency expected lifetime (abbreviated as) L ) and high-frequency harmonic frequencies f The expression for the fitted curve is:

[0030] in, a , b , c These are the frequency-related influence factor parameters obtained from the fitting.

[0031] S5. Establish the thermal lifetime equation through activation energy; specifically, the activation energy of the electrical equipment insulation sheet sample is obtained by TGA testing. E a[m，n] The specific expression for the thermal lifetime equation established using activation energy is as follows:

[0032] in: The estimated lifetime under a specific transformation, in minutes; The activation energy is expressed in J / mol. The gas constant is 8.314 J / (mol·K); The failure temperature under a specific transformation, expressed in K; This is the heating rate, expressed in °C / min; Let be the integration constant. The value is obtained from Table 1 of the international standard ASTM E1641-07.

[0033] S6. The temperature acceleration factor is obtained using the thermal lifetime equation. Specifically, the accelerated aging test temperature is included in the thermal lifetime equation. T e and actual operating temperature T u Substituting into the thermal lifetime equation, we obtain the corresponding expected lifetime. t e and t u ,use t e and t u The temperature acceleration factor AF was calculated. T The specific expression is:

[0034] S6. Using the fitting curve of the high-frequency harmonic frequency and the expected frequency lifetime, and the temperature acceleration factor, calculate the expected insulation lifetime of the power equipment insulation under high-frequency harmonic voltage in actual operating conditions. Its specific expression is as follows:

[0035] Based on the above scheme, the present invention provides the following embodiments.

[0036] Example 1 This embodiment of the method for assessing the insulation life of power equipment under high-frequency harmonic voltage includes the following steps: S1. In the accelerated electrothermal aging test of power equipment, sheet-like samples of the power equipment insulation under different high-frequency harmonic voltages were obtained; wherein, the parameters of the accelerated electrothermal aging test of power equipment are: aging temperature T= 115℃ 、 Aging time [200h, 400h, 600h, 800h, 1000h] and harmonic frequency [60kHz, 80kHz, 100kHz].

[0037] S2. Test the breakdown field strength and activation energy of sheet-like insulating samples of power equipment; the insulating part of the power equipment is sliced, and the breakdown field strength is obtained using the Weibull distribution. E .

[0038] S3. Establish the relationship between breakdown field strength and aging time and fit the curve, and establish the relationship between high frequency harmonic frequency and expected life and fit the curve to obtain the expected life of insulation failure under high frequency harmonics in actual power equipment operation. Among them, the established breakdown field strength E With aging time t The relationship and the fitted curve are as follows Figure 2 As shown, the fitting expression is: .

[0039] The fitting parameters are: The harmonic frequency is 60kHz. A =72.97766, B =-3.02200×10 -4 The harmonic frequency is 80kHz. A =72.29383, B =-3.30789×10 -4 The harmonic frequency is 80kHz. A =83.38066, B =-5.67142×10 -4 The breakdown field strengths of the power equipment failure were set to 25kV / mm, 20kV / mm, and 15kV / mm, respectively. The accelerated aging times corresponding to failures under different high-frequency harmonics are shown in Table 1.

[0040] Table 1

[0041] Frequency expected lifetime is established based on high-frequency harmonic frequencies and accelerated aging time. L With high frequency harmonic frequency f The relationship and fitting curve are as follows Figure 3 As shown, the expression for the fitted curve is:

[0042] in, a , b , c These are the frequency-related influence factor parameters obtained from the fitting.

[0043] The fitting parameters are: The breakdown field strength of the power equipment failure is set at 25kV: a =2839.38132, b =-111484.91865, c =0.938 The breakdown field strength of the power equipment failure is set at 20kV: a =2353.27398, b =-77880.54879, c =0.94023 The breakdown field strength of the power equipment failure is set at 15kV: a =1974.66932, b =-53608.68403, c=0.94286. Setting the high-frequency harmonic frequency in the actual operating conditions of the power equipment to 30kHz, the expected frequency lifetime under different failure field strengths of the power equipment under actual operating conditions at high-frequency harmonic frequencies is as follows: Expected frequency lifetime when the breakdown field strength of power equipment failure is 25kV L 25 =11149.6h≈1.27 years; Expected frequency lifetime when the breakdown field strength of power equipment failure is 20kV L 20 =14613.5h≈1.67 years; Expected frequency lifetime when the breakdown field strength of power equipment failure is 15kV L 15 =19182.8h≈2.21 years.

[0044] The activation energy of the insulating sheet sample from the power equipment was obtained using TGA testing. E a =208.49 kJ•mol -1 , =630.44 K, Ea / RT≈42, from the table we get =21.5066 The thermal lifetime equation is established using activation energy, and the specific expression is as follows:

[0045] The accelerated aging test temperature will be included in the thermal life equation. T e =115℃ and actual operating temperature T u Substituting 80℃ into the thermal life equation, we get... t e =3.44 years, t u =0.18 years.

[0046] S4, Utilization t e and t u Solve for the temperature acceleration factor AF T The specific expression is:

[0047] S5. Calculate the expected insulation life of the power equipment insulation under high-frequency harmonic voltage. as follows:

[0048] Expected insulation life when the breakdown field strength of power equipment failure is 15kV ; Expected insulation life when the breakdown field strength of power equipment failure is 20kV ; Expected insulation life when the breakdown field strength of power equipment failure is 25kV . Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for assessing the insulation life of power equipment under high-frequency harmonic voltage, characterized in that, Includes the following steps: S1, In the accelerated electrothermal aging test of power equipment, sheet-like samples of the insulation part of the power equipment under different high-frequency harmonic voltages were obtained; The parameters for the accelerated electrothermal aging test of the power equipment include: aging temperature. 、 Accelerated aging time and high-frequency harmonics; S2, test the breakdown field strength and activation energy of the sheet-like sample; S3. Using the data obtained in S2, establish a fitting curve for the relationship between breakdown field strength and aging time, and a fitting curve for the relationship between high-frequency harmonic frequency and expected frequency lifetime. S4, establish the thermal lifetime equation by fitting the breakdown field strength and aging time; S5, the temperature acceleration factor is calculated using the thermal lifetime equation; S6. Calculate the expected insulation life of the power equipment insulation under high-frequency harmonic voltage in actual operating conditions using the fitting curve of the high-frequency harmonic frequency and the expected frequency lifetime and the temperature acceleration factor.

2. The method for assessing the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that, In the accelerated electrothermal aging test of power equipment, the accelerated thermal aging temperature is lower than the glass transition temperature of the power equipment, but higher than the actual application temperature.

3. The method for assessing the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that, In the accelerated electrothermal aging test of power equipment, the accelerated electrothermal aging time of the power equipment is t≥1000h, and the number of sample aging time values ​​m≥5 is set in the experiment.

4. The method for assessing the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that, In accelerated electrothermal aging tests of power equipment, the accelerated electrothermal harmonic frequency is... f The harmonic frequency is greater than that in practical applications, and the number of voltage harmonic frequency values ​​is set in the experiment. n ≥3.

5. The method for evaluating the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that: When testing the breakdown field strength of the sheet-like sample, the breakdown field strength was obtained using the Weibull distribution at different aging times and harmonic frequencies. E [m，n] Breakthrough field strength E [m，n] The corresponding aging time is t m Harmonic frequencies are f n ; The activation energy of the sheet-like sample was obtained using TGA (Thermogravimetric Analysis). E a[m，n] ,activation energy E a[m，n] The corresponding aging time is t m Harmonic frequencies are f n .

6. The method for assessing the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that, The fitted curve expression for the relationship between breakdown field strength and aging time is as follows: in, To break through the field strength, t For aging time, A , B These are the aging parameters obtained from the accelerated aging test through fitting.

7. The method for evaluating the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that, The fitted curve expression for the relationship between high-frequency harmonic frequency and expected lifetime is as follows: in, For frequency expected lifetime, It is a high-frequency harmonic frequency. a , b , c These are the frequency-related influence factor parameters obtained from the fitting.

8. The method for assessing the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that, The expression for the thermal lifetime equation is as follows: in: The estimated lifetime under a specific transformation, in minutes; The activation energy is expressed in J / mol. The gas constant is 8.314 J / (mol·K); The failure temperature under a specific transformation, expressed in K; This is the heating rate, expressed in °C / min; is the integration constant.

9. A method for assessing the insulation life of power equipment under high-frequency harmonic voltage according to claim 8, characterized in that, The temperature acceleration factor is calculated using the aforementioned thermal lifetime equation, including the following process: The accelerated aging test temperature will be included in the thermal life equation. T e and actual operating temperature T u Substituting into the thermal lifetime equation, we obtain the corresponding expected lifetime. t e and t u ,use t e and t u The temperature acceleration factor AF was calculated. T The specific expression is: 。 10. The method for assessing the insulation life of power equipment under high-frequency harmonic voltage according to claim 1, characterized in that, In actual operating conditions, the expected insulation life of power equipment insulation under high-frequency harmonic voltage is as follows: in, AF represents the expected insulation life of power equipment insulation under actual operating conditions and high-frequency harmonic voltage. T As a temperature acceleration factor, L ( f () represents the expected frequency lifetime under high-frequency harmonics in actual operating conditions.

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