A method for improving the compatibility between synthetic ester insulating oil and insulating paper

Abstract

The present invention discloses a method for improving the compatibility between synthetic ester insulating oil and insulating paper, which relates to the field of insulating materials. The method includes the following steps: drying the synthetic ester insulating oil until the water content is lower than 50 ppm; using a function generator to generate low-voltage electrical pulses, and then converting them into high-voltage electrical pulse signals through a power amplifier, setting the pulse duty cycle to 10-20%, and performing the first-stage electrical pulse treatment on the synthetic ester insulating oil; then increasing the pulse duty cycle to 20-30% and performing the second-stage electrical pulse treatment on the synthetic ester insulating oil. The present invention selects the synthetic ester insulating oil as the object of electrical pulse treatment, and uses the electrical pulse treatment to further improve the relative permittivity of the synthetic ester insulating oil to be close to that of the insulating paper, thereby improving the compatibility between the synthetic ester insulating oil and the insulating paper in the subsequent application stage.

Description

Technical Field

[0001] The present invention relates to the field of insulating materials, and particularly to a method for improving the compatibility between synthetic ester insulating oil and insulating paper. Background Art

[0002] The oil-paper insulation system composed of insulating oil and insulating paper is the most important insulation structure in transformers. Its insulation performance is directly related to the normal operation of transformers. Therefore, improving the compatibility of oil-paper insulation can enhance the safety and stability of transformer operation. Existing research shows that the closer the relative dielectric constants of insulating oil and insulating paper are, the more uniform the electric field distribution in the oil-paper insulation system under an alternating current electric field, and the higher the insulation compatibility between the two. Compared with traditional mineral insulating oil, the relative dielectric constants of ester-based insulating oil and insulating paper are closer, and the advantages of ester-based insulating oil being degradable and renewable meet the requirements of green and clean performance. It is an excellent choice to replace non-renewable and non-degradable mineral insulating oil. Therefore, filling transformers with ester-based insulating oil can not only improve the compatibility of oil-paper insulation but also meet the sustainable development requirements of low-carbon environmental protection.

[0003] Ester-based insulating oils are divided into natural ester insulating oils and synthetic ester insulating oils. Since the molecular structure of natural ester insulating oils contains unstable groups such as C=C and β-H, its stability is insufficient compared with synthetic ester insulating oils that can eliminate the influence of unstable groups. Therefore, it is more appropriate to choose synthetic ester insulating oils. However, there is still a certain gap between the relative dielectric constant of synthetic ester insulating oil and insulating paper, and the insulating paper modification technologies involved in current research may cause an increase in the relative dielectric constant of insulating paper, further widening the gap. Summary of the Invention

[0004] The present invention provides a method for improving the compatibility between synthetic ester insulating oil and insulating paper, which uses the electro-pulse method to increase the relative dielectric constant of synthetic ester insulating paper to be close to that of insulating paper, thereby improving the compatibility of oil-paper insulation in the subsequent application stage.

[0005] To solve the above technical problems, one of the objectives of the present invention is to provide a method for improving the compatibility between synthetic ester insulating oil and insulating paper, including the following steps:

[0006] (1) Dry the synthetic ester insulating oil to a water content of less than 50 ppm;

[0007] (2) Use a function generator to generate a low-voltage electrical pulse, and then convert it into a high-voltage electrical pulse signal through a power amplifier. Set the pulse duty cycle to 10-20%, and perform the first-stage electro-pulse treatment on the synthetic ester insulating oil;

[0008] (3) Then increase the pulse duty cycle to 20-30% and perform the second-stage electro-pulse treatment on the synthetic ester insulating oil.

[0009] The present invention uses the electric pulse method to treat synthetic ester insulating oil, enhancing the rotational polarization and displacement polarization of synthetic ester insulating oil molecules, improving the polarization characteristics of synthetic ester insulating oil, manifested as an increase in the relative dielectric constant, so as to make the relative dielectric constant of synthetic ester insulating oil closer to that of insulating paper; at the same time, the higher relative dielectric constant can make the synthetic ester insulating oil have better water resistance, absorb the moisture in the insulating paper, and effectively improve the electric field distribution under the action of an alternating electric field in the insulating system, improving the matching degree of oil-paper insulation.

[0010] As a preferred solution, in step (2), the frequency of the first-stage electric pulse treatment is 20 - 50 Hz; in step (3), the frequency of the second-stage electric pulse treatment is 50 - 70 Hz.

[0011] As a preferred solution, in step (2), the voltage of the first-stage electric pulse treatment is 3 - 7 kV; in step (3), the voltage of the second-stage electric pulse treatment is 7 - 12 kV.

[0012] As a preferred solution, in step (2), the temperature of the first-stage electric pulse treatment is 20 - 30 °C; in step (3), the temperature of the second-stage electric pulse treatment is 30 - 40 °C.

[0013] As a preferred solution, in step (2), the time of the first-stage electric pulse treatment is 48 - 72 h; in step (3), the time of the second-stage electric pulse treatment is 12 - 20 h.

[0014] As a preferred solution, the synthetic ester insulating oil is TMP triester insulating oil or PETP tetraester insulating oil.

[0015] As a preferred solution, in step (1), the drying temperature is 65 - 95 °C and the drying time is 36 - 48 h.

[0016] As a preferred solution, in step (3), the synthetic ester insulating oil obtained by the second dielectric pulse treatment is dried and then subjected to performance testing. The drying temperature is 70 - 95 °C and the drying time is 36 - 48 h.

[0017] To solve the above technical problems, the second object of the present invention provides a synthetic ester insulating oil prepared by the method for improving the matching degree of synthetic ester insulating oil and insulating paper as described above.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] Since the relative dielectric constant of synthetic ester insulating oil is significantly higher than that of mineral insulating oil and vegetable insulating oil, the present invention selects synthetic ester insulating oil as the object of electric pulse treatment, and uses electric pulse treatment to further improve the relative dielectric constant of synthetic ester insulating oil, so as to be close to the relative dielectric constant of insulating paper, and can improve the compatibility between synthetic ester insulating oil and insulating paper. Detailed implementation manners

[0020] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0021] The TMP triester insulating oil used in this application is obtained by the esterification synthesis reaction of trimethylolpropane and medium-chain saturated fatty acids, and the TMP triester insulating oil is prepared according to the synthesis method of medium-chain fatty acid triester insulating oil recorded in the public literature "Wang Kaizheng. Research on breakdown and streamer discharge of anti-aging medium-chain fatty acid triester insulating oil [D]. Chongqing University, 2020. DOI: 10.27670 / d.cnki.gcqdu.2020.000166". The PETP tetraester insulating oil is obtained by the esterification synthesis reaction of pentaerythritol and medium-chain saturated fatty acids, and the PETP tetraester insulating oil is prepared according to the synthesis method of pentaerythritol ester insulating oil recorded in the public literature "[1] Yao Jiachen. Molecular regulation and preparation method research of low pour point pentaerythritol ester insulating oil [D]. Chongqing University, 2022. DOI: 10.27670 / d.cnki.gcqdu.2022.003586".

[0022] Example 1

[0023] A method for improving the compatibility between synthetic ester insulating oil and insulating paper includes the following steps:

[0024] (1) Take the TMP triester insulating oil and place it in a vacuum drying oven. Dry it at a high temperature of 70 °C for 48 h to remove the moisture in the insulating oil. After drying, use the coulomb method for trace water determination to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electric pulse treatment can be carried out;

[0025] (2) Use a function generator to generate a low-voltage electric pulse, and then convert it into a high-voltage electric pulse signal through a power amplifier. The pulse duty cycle is set to 10%, the voltage is 3 kV, the frequency is 50 Hz, and the temperature is 20 °C. Carry out electric pulse treatment on the synthetic ester insulating oil for 48 h;

[0026] (3) Then increase the duty cycle to 20%, the voltage to 7 kV, the frequency to 70 Hz, and the temperature to 30 °C, and perform electrical pulse treatment on the synthetic ester insulating oil for 15 h. After the electrical pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 70 °C for 36 h, and then measure its relative permittivity.

[0027] Example 2

[0028] A method for improving the compatibility between synthetic ester insulating oil and insulating paper, comprising the following steps:

[0029] (1) Take TMP triester insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 85 °C for 48 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electrical pulse treatment can be carried out;

[0030] (2) Use a function generator to generate low-voltage electrical pulses, and then convert them into high-voltage electrical pulse signals through a power amplifier. Set the pulse duty cycle to 15%, the voltage to 5 kV, the frequency to 35 Hz, and the temperature to 25 °C, and perform electrical pulse treatment on the synthetic ester insulating oil for 60 h;

[0031] (3) Then increase the duty cycle to 25%, the voltage to 10 kV, the frequency to 60 Hz, and the temperature to 35 °C, and perform electrical pulse treatment on the synthetic ester insulating oil for 18 h. After the electrical pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 75 °C for 48 h, and then measure its relative permittivity.

[0032] Example 3

[0033] A method for improving the compatibility between synthetic ester insulating oil and insulating paper, comprising the following steps:

[0034] (1) Take TMP triester insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 90 °C for 36 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electrical pulse treatment can be carried out;

[0035] (2) Use a function generator to generate low-voltage electrical pulses, and then convert them into high-voltage electrical pulse signals through a power amplifier. Set the pulse duty cycle to 20%, the voltage to 7 kV, the frequency to 25 Hz, and the temperature to 30 °C, and perform electrical pulse treatment on the synthetic ester insulating oil for 72 h;

[0036] (3) Then increase the duty cycle to 30%, the voltage to 12 kV, the frequency to 50 Hz, and the temperature to 40 °C, and perform an electrical pulse treatment on the synthetic ester insulating oil for 20 h. After the electrical pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 90 °C for 36 h, and then test its relative dielectric constant.

[0037] Example 4

[0038] A method for improving the compatibility between synthetic ester insulating oil and insulating paper includes the following steps:

[0039] (1) Take PETP tetraester insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 75 °C for 40 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electrical pulse treatment can be carried out;

[0040] (2) Use a function generator to generate a low-voltage electrical pulse, and then convert it into a high-voltage electrical pulse signal through a power amplifier. Set the pulse duty cycle to 10%, the voltage to 6 kV, the frequency to 35 Hz, and the temperature to 20 °C, and perform an electrical pulse treatment on the synthetic ester insulating oil for 48 h;

[0041] (3) Then increase the duty cycle to 20%, the voltage to 7 kV, the frequency to 70 Hz, and the temperature to 30 °C, and perform an electrical pulse treatment on the synthetic ester insulating oil for 15 h. After the electrical pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 75 °C for 40 h, and then test its relative dielectric constant.

[0042] Example 5

[0043] A method for improving the compatibility between synthetic ester insulating oil and insulating paper includes the following steps:

[0044] (1) Take PETP tetraester insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 80 °C for 40 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electrical pulse treatment can be carried out;

[0045] (2) Use a function generator to generate a low-voltage electrical pulse, and then convert it into a high-voltage electrical pulse signal through a power amplifier. Set the pulse duty cycle to 15%, the voltage to 3 kV, the frequency to 50 Hz, and the temperature to 25 °C, and perform an electrical pulse treatment on the synthetic ester insulating oil for 48 h;

[0046] (3) Then increase the duty cycle to 20%, the voltage to 12 kV, the frequency to 50 Hz, and the temperature to 35 °C, and perform electrical pulse treatment on the synthetic ester insulating oil for 12 h. After the electrical pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 80 °C for 40 h, and then measure its relative dielectric constant.

[0047] Example Six

[0048] A method for improving the compatibility between synthetic ester insulating oil and insulating paper, comprising the following steps:

[0049] (1) Take PETP tetraester insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 95 °C for 36 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electrical pulse treatment can be carried out;

[0050] (2) Use a function generator to generate low-voltage electrical pulses, and then convert them into high-voltage electrical pulse signals through a power amplifier. Set the pulse duty cycle to 20%, the voltage to 6 kV, the frequency to 40 Hz, and the temperature to 30 °C, and perform electrical pulse treatment on the synthetic ester insulating oil for 70 h;

[0051] (3) Then increase the duty cycle to 25%, the voltage to 9 kV, the frequency to 70 Hz, and the temperature to 40 °C, and perform electrical pulse treatment on the synthetic ester insulating oil for 20 h. After the electrical pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 95 °C for 36 h, and then measure its relative dielectric constant.

[0052] Comparative Example One

[0053] A method for improving the compatibility between mineral insulating oil and insulating paper, comprising the following steps:

[0054] (1) Take Karamay #25 mineral insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 70 °C for 48 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the mineral insulating oil is less than 50 ppm, and subsequent electrical pulse treatment can be carried out;

[0055] (2) Use a function generator to generate low-voltage electrical pulses, and then convert them into high-voltage electrical pulse signals through a power amplifier. Set the pulse duty cycle to 10%, the voltage to 3 kV, the frequency to 50 Hz, and the temperature to 20 °C, and perform electrical pulse treatment on the mineral insulating oil for 48 h;

[0056] (3) Then increase the duty cycle to 20%, the voltage to 7 kV, the frequency to 70 Hz, and the temperature to 30 °C, and perform an electric pulse treatment on the mineral insulating oil for 15 h. After the electric pulse ends, place the mineral insulating oil in a vacuum drying oven again and dry it at a high temperature of 70 °C for 36 h, and then measure its relative permittivity.

[0057] Comparative Example 2

[0058] A method for improving the compatibility between vegetable insulating oil and insulating paper, comprising the following steps:

[0059] (1) Take FR3 vegetable insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 70 °C for 48 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the trace water content of the vegetable insulating oil is less than 50 ppm, and subsequent electric pulse treatment can be carried out;

[0060] (2) Use a function generator to generate low-voltage electric pulses, and then convert them into high-voltage electric pulse signals through a power amplifier. Set the pulse duty cycle to 10%, the voltage to 3 kV, the frequency to 50 Hz, and the temperature to 20 °C, and perform an electric pulse treatment on the vegetable insulating oil for 48 h;

[0061] (3) Then increase the duty cycle to 20%, the voltage to 7 kV, the frequency to 70 Hz, and the temperature to 30 °C, and perform an electric pulse treatment on the vegetable insulating oil for 15 h. After the electric pulse ends, place the vegetable insulating oil in a vacuum drying oven again and dry it at a high temperature of 70 °C for 36 h, and then measure its relative permittivity.

[0062] Comparative Example 3

[0063] A method for improving the compatibility between synthetic ester insulating oil and insulating paper, comprising the following steps:

[0064] (1) Take TMP triester insulating oil and place it in a vacuum drying oven, and dry it at a high temperature of 70 °C for 48 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the trace water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electric pulse treatment can be carried out;

[0065] (2) Use a function generator to generate low-voltage electric pulses, and then convert them into high-voltage electric pulse signals through a power amplifier. Set the pulse duty cycle to 10%, the voltage to 3 kV, the frequency to 50 Hz, and the temperature to 20 °C, and perform an electric pulse treatment on the synthetic ester insulating oil for 63 h. After the electric pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 70 °C for 36 h, and then measure its relative permittivity.

[0066] Comparative Example 4

[0067] A method for improving the compatibility between synthetic ester insulating oil and insulating paper, comprising the following steps:

[0068] (1) Place the TMP triester insulating oil in a vacuum drying oven and dry it at a high temperature of 70 °C for 48 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent electrical pulse treatment can be carried out;

[0069] (2) Use a function generator to generate a low-voltage electrical pulse, and then convert it into a high-voltage electrical pulse signal through a power amplifier. The pulse duty cycle is set to 20%, the voltage is 7 kV, the frequency is 70 Hz, and the temperature is 30 °C. Carry out electrical pulse treatment on the synthetic ester insulating oil for 63 h. After the electrical pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 70 °C for 36 h, and then test its relative dielectric constant.

[0070] Comparative Example 5

[0071] A method for improving the compatibility between synthetic ester insulating oil and insulating paper, comprising the following steps:

[0072] (1) Place the TMP triester insulating oil in a vacuum drying oven and dry it at a high temperature of 70 °C for 48 h to remove the moisture in the insulating oil. After drying, use the coulometric trace water determination method to measure that the micro water content of the synthetic ester insulating oil is less than 50 ppm, and subsequent high-temperature pulse treatment can be carried out;

[0073] (2) Seal the synthetic ester insulating oil and place it in a temperature-controlled pulse box. Set the frequency, temperature, voltage, and pressure to 50 Hz, 90 °C, 8 kV, and 40 Pa respectively, and carry out high-temperature pulse treatment on the synthetic ester insulating oil for 100 h. After the high-temperature pulse ends, place the synthetic ester insulating oil in a vacuum drying oven again and dry it at a high temperature of 70 °C for 36 h, and then test its relative dielectric constant.

[0074] Performance detection test

[0075] After the insulating oil obtained by the method of the embodiment and comparative example of the present application is tested for relative dielectric constant according to the international standard IEC 60247 and compared with domestic aramid insulating paper, the results are shown in Table 1 below.

[0076] Table 1 - Relative dielectric constant results of the embodiment and comparative example of the present application

[0077] Test Items Relative Dielectric Constant Insulating Paper 3.642 Untreated TMP Triester Insulating Oil 3.141 Example 1 3.575 Example 2 3.581 Example 3 3.596 Untreated PETP Tetraester Insulating Oil 3.016 Example 4 3.422 Example 5 3.457 Example 6 3.479 Untreated Karamay #25 Mineral Insulating Oil 2.213 Comparative Example 1 2.216 Untreated FR3 Vegetable Insulating Oil 2.803 Comparative Example 2 2.811 Comparative Example 3 3.324 Comparative Example 4 3.371 Comparative Example 5 3.208

[0078] From the comparison of the performance test results of Example 1 and Comparative Examples 1-2 in Table 1, it can be seen that compared with vegetable insulating oil and mineral insulating oil, the relative permittivity of synthetic ester insulating oil is less different from that of insulating paper. After two-stage electric pulse treatment, it can be increased to be close to the relative permittivity of insulating paper, thereby improving the compatibility between synthetic ester insulating oil and insulating paper.

[0079] From the comparison of the performance test results of Example 1 and Comparative Examples 3-4 in Table 2, it can be seen that the single-stage electric pulse has a poor efficiency in increasing the relative permittivity of synthetic ester insulating oil. If the electric pulse treatment is carried out only with the parameter settings of the first stage, its low voltage and frequency cannot maximize the increase of the relative permittivity of the oil sample; while if the electric pulse treatment is carried out only with the parameter settings of the second stage, it will cause electrolysis of the oil sample due to the long-term action of electric stress with high voltage and frequency, damaging the molecular structure of some insulating oil, thus affecting the increase of its relative permittivity; therefore, the test condition parameters for generating two-stage pulses in this application are set, and the treatment temperature is increased in the second stage to shorten the electric pulse treatment time under high voltage and frequency.

[0080] From the comparison of the performance test results of Example 1 and Comparative Example 5 in Table 2, it can be seen that the high-temperature pulse treatment has a small effect on increasing the relative permittivity of synthetic ester insulating oil, so the electric pulse treatment method is adopted.

[0081] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. In particular, it is pointed out that for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the compatibility between synthetic ester insulating oil and insulating paper, characterized in that, It includes the following steps: (1) Dry the synthetic ester insulating oil until the water content is lower than 50 ppm; (2) Use a function generator to generate low-voltage electrical pulses, and then convert them into high-voltage electrical pulse signals through a power amplifier. Set the pulse duty cycle to 10-20% and perform the first-stage electrical pulse treatment on the synthetic ester insulating oil; (3) Then increase the pulse duty cycle to 20-30% and perform the second-stage electrical pulse treatment on the synthetic ester insulating oil; In step (2), the frequency of the first-stage electrical pulse treatment is 20-50 Hz; in step (3), the frequency of the second-stage electrical pulse treatment is 50-70 Hz; In step (2), the voltage of the first-stage electrical pulse treatment is 3-7 kV; in step (3), the voltage of the second-stage electrical pulse treatment is 7-12 kV; In step (2), the temperature of the first-stage electrical pulse treatment is 20-30 °C; in step (3), the temperature of the second-stage electrical pulse treatment is 30-40 °C.

2. The method for improving the compatibility between synthetic ester insulating oil and insulating paper according to claim 1, wherein In step (2), the time of the first-stage electrical pulse treatment is 48-72 h; in step (3), the time of the second-stage electrical pulse treatment is 12-20 h.

3. The method for improving the compatibility between synthetic ester insulating oil and insulating paper according to claim 1, wherein The synthetic ester insulating oil is TMP triester insulating oil or PETP tetraester insulating oil.

4. A method for improving the compatibility between synthetic ester insulating oil and insulating paper according to claim 1, characterized in that, In step (1), the drying temperature is 65-95 °C and the drying time is 36-48 h.

5. A method for improving the compatibility between synthetic ester insulating oil and insulating paper as claimed in claim 1, characterized in that, In step (3), after drying the synthetic ester insulating oil obtained by the second dielectric pulse treatment, perform a performance test. The drying temperature is 70-95 °C and the drying time is 36-48 h.

6. A synthetic ester insulating oil prepared by the method for improving the compatibility between synthetic ester insulating oil and insulating paper according to any one of claims 1-5.