A method, device and sensor system for evaluating the aging degree of transformer oil

Abstract

The embodiment of the present invention provides a method, device and sensor system for evaluating the aging degree of transformer oil, the method comprising: recording the polarization curve and non-polarization curve of transformer oil under DC voltage; collecting at least one voltage effective value and at least one current effective value of transformer oil under AC excitation signal; calculating the first conductivity of transformer oil in combination with the capacitance of conductivity electrodes at both ends of transformer oil; calculating at least one second conductivity according to the voltage effective value and the current effective value; obtaining the infrared light absorption rate of each aging product, combining the first conductivity and at least one second conductivity, calculating the aging index of transformer oil, and obtaining the aging degree evaluation result of transformer oil. Compared with the prior art, the test can be performed online, and by obtaining at least one conductivity of transformer oil under DC voltage and AC voltage, the influence of impurities on the conductivity of transformer oil is taken into account, thereby improving the accuracy and real-time performance of the test.

Description

Technical Field

[0001] The invention relates to the field of transformer oil, and in particular to a method, a device and a sensing system for evaluating the aging degree of transformer oil. Background Art

[0002] Transformer oil is a mineral insulating oil based on petroleum products after refining. Its main components include alkanes, cycloalkanes and aromatic hydrocarbons. Transformer oil is the main liquid insulating medium used for insulation, cooling and arc extinguishing in power equipment. As the equipment runs for a long time, transformer oil will experience oxidation and aging, generating aging products such as free radicals, alcohols, aldehydes and ketones, which seriously affect the insulation performance of transformer oil.

[0003] At present, the main method for evaluating the aging degree of transformer oil is to take out the transformer oil, place it in a constant temperature drying oven, heat it to a temperature 10 degrees Celsius lower than the flash point of the transformer oil, and determine the components and their contents through chromatography and infrared spectroscopy. This method cannot perform real-time testing when the equipment is online, so it often cannot reflect the aging degree of the transformer oil in a timely manner. The information obtained by the existing online tester is single, and it can only be tested under the condition of a single frequency conductivity, so it is difficult to accurately judge the aging degree of the transformer oil. Summary of the invention

[0004] The present invention provides a method, a device and a sensing system for evaluating the aging degree of transformer oil, and obtains a more accurate aging degree evaluation result by acquiring the conductivity of the transformer oil under different voltage conditions.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a method for evaluating the aging degree of transformer oil, comprising:

[0006] The polarization current and non-polarization current of the transformer oil under the DC voltage are respectively collected in real time, and the polarization curve and non-polarization curve of the transformer oil under the DC voltage are recorded according to the collected polarization current and non-polarization current; wherein the polarization curve is a curve of the polarization current of the transformer oil changing with time; and the non-polarization curve is a curve of the non-polarization current of the transformer oil changing with time;

[0007] respectively collecting in real time at least one voltage effective value and at least one current effective value of the transformer oil under each AC excitation signal; wherein each AC excitation signal corresponds to a type of aging product;

[0008] According to the polarization curve, the non-polarization curve and the DC voltage, in combination with the capacitance of the conductivity electrodes at both ends of the transformer oil, a first conductivity of the transformer oil is calculated; according to the at least one voltage effective value and the at least one current effective value, at least one second conductivity of the transformer oil is calculated respectively;

[0009] The infrared light absorption rate of each of the aging products is obtained, and the aging index of the transformer oil is calculated in combination with the first conductivity and the at least one second conductivity to obtain an aging degree evaluation result of the transformer oil; wherein each of the infrared light absorption rates corresponds to a characteristic frequency of each of the aging products. Compared with the prior art, an online evaluation method is provided, which takes into account the influence of impurities on the conductivity of the transformer oil by obtaining at least one conductivity of the transformer oil under DC voltage and AC voltage, thereby improving the accuracy and real-time performance of online detection.

[0010] As a preferred solution, the infrared light absorption rate of each aging product is obtained, and the aging index of the transformer oil is calculated by combining the first conductivity and the at least one second conductivity, specifically:

[0011] Obtain the infrared absorption rate x of the aging product i1 、x i2 , …, x im , combined with the first conductivity σ i1 , the at least one second conductivity σ i2 , σ i3 , σ i4 and σ i5 , perform multiple linear regression analysis according to the following formula to obtain the aging index y of the transformer oil in the i-th test i :

[0012] y i =b 0 +b 1 σ i1 +b 2 σ i2 +…+b 5 σ i5 +c 1 x i1 +c 2 x i2 +c 3 x i3 +…+c m x im +D i ;

[0013] Among them, b 0 is the intercept, D i is the residual, the number of samples in the calibration set is n, the number of spectra is m, and n>m + 5. The embodiment of the present application is implemented, the conductivity of transformer oil under DC voltage and AC voltage is combined with the analysis of the absorption spectra of different aging products, the aging degree of transformer oil is effectively evaluated, and the aging index is obtained.

[0014] As a preferred solution, the first conductivity of the transformer oil is calculated respectively according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil, specifically:

[0015] Get the polarization curve i p (t), the non-polarization curve i d (t) and the DC voltage U 0 , the first conductivity σ of the transformer oil is calculated according to the following formula:

[0016]

[0017] Among them, C 0 is the capacitance of the conductive electrodes at both ends of the transformer oil, ε 0 is the dielectric constant of transformer oil.

[0018] Correspondingly, an embodiment of the present invention further provides a transformer oil aging degree evaluation device, comprising a first acquisition module, a second acquisition module, a conductivity acquisition module and an aging evaluation module; wherein,

[0019] The first acquisition module is used to respectively acquire the polarization current and non-polarization current of the transformer oil under a DC voltage in real time, and record the polarization curve and non-polarization curve of the transformer oil under a DC voltage according to the acquired polarization current and non-polarization current; wherein the polarization curve is a curve of the polarization current of the transformer oil changing with time; and the non-polarization curve is a curve of the non-polarization current of the transformer oil changing with time;

[0020] The second acquisition module is used to respectively and in real time acquire at least one voltage effective value and at least one current effective value of the transformer oil under each AC excitation signal; wherein each AC excitation signal corresponds to a type of aging product;

[0021] The conductivity acquisition module is used to calculate the first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil; and calculate at least one second conductivity of the transformer oil according to the at least one voltage effective value and the at least one current effective value;

[0022] The aging assessment module is used to obtain the infrared light absorption rate of each of the aging products, and calculate the aging index of the transformer oil in combination with the first conductivity and the at least one second conductivity to obtain an aging degree assessment result of the transformer oil; wherein each of the infrared light absorption rates corresponds one-to-one to a characteristic frequency of each of the aging products.

[0023] As a preferred solution, the aging assessment module obtains the infrared light absorption rate of each of the aging products, and calculates the aging index of the transformer oil by combining the first conductivity and the at least one second conductivity, specifically:

[0024] The aging assessment module obtains the infrared absorption rate x of the aging product i1 、x i2 , …, x im , combined with the first conductivity σ i1 , the at least one second conductivity σ i2 , σ i3 , σ i4 and σ i5 , perform multiple linear regression analysis according to the following formula to obtain the aging index y of the transformer oil in the i-th test i :

[0025] y i =b 0 +b 1 σ i1 +b 2 σ i2 +…+b 5 σ i5 +c 1 x i1 +c 2 x i2 +c 3 x i3 +…+c m x im +D i ;

[0026] Among them, b 0 is the intercept, D i is the residual, the number of samples in the calibration set is n, the number of spectra is m, and n>m+5.

[0027] As a preferred solution, the conductivity acquisition module calculates the first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil, specifically:

[0028] The conductivity acquisition module acquires the polarization curve i p (t), the non-polarization curve i d (t) and the DC voltage U 0 , the first conductivity σ of the transformer oil is calculated according to the following formula:

[0029]

[0030] Among them, C 0is the capacitance of the conductive electrodes at both ends of the transformer oil, ε 0 is the dielectric constant of transformer oil.

[0031] Correspondingly, an embodiment of the present invention further provides a transformer oil aging degree sensing system, the sensing system comprising a computer and an infrared composite sensor;

[0032] The infrared composite sensor comprises a conductivity cell and an infrared absorption cell; the first end of the conductivity cell is connected to an output end of the transformer to be tested; the second end of the conductivity cell is connected to the first end of the infrared absorption cell, and the second end of the infrared absorption cell is connected to an input end of the transformer to be tested;

[0033] Two opposite planes of the conductivity cell are provided with conductivity electrodes for measuring the conductivity of transformer oil;

[0034] The infrared absorption cell is used to measure the infrared light absorption rate of each aging product of the transformer oil under the irradiation of infrared incident light; wherein the infrared light absorption rate corresponds to the characteristic frequency of each aging product one by one;

[0035] The computer is used to execute the transformer oil aging degree evaluation method. When the embodiment of the present application is implemented, the transformer oil flows into the first end of the conductivity cell and flows out of the second end of the infrared absorption cell, thereby realizing online and real-time detection of the transformer oil during the operation of the transformer, without taking the transformer oil out of the transformer, thereby improving the convenience of detection.

[0036] As a preferred solution, the conductivity electrode adopts a bright platinum electrode. In the implementation of the present application, by adopting a bright platinum electrode, the electrode is prevented from adsorbing trace amounts of water, the influence of capacitance change on conductivity is avoided, and the error of conductivity testing is reduced.

[0037] As a preferred solution, an electromagnetic shielding box is further provided outside the conductivity cell. By implementing the embodiment of the present application, the electromagnetic shielding box eliminates the influence of the external electromagnetic field on the test results, thereby improving the accuracy of the test results.

[0038] As a preferred solution, sapphire windows are provided at both the entrance and exit of the infrared incident light of the infrared absorption cell; and several layers of silicone gaskets are provided between the sapphire windows. In the implementation of the embodiment of the present application, sapphire windows are used to avoid the erosion of water in the transformer oil sample and extend the service life of the infrared absorption cell; the size of the infrared absorption cell can be changed by adjusting the silicone gaskets between the sapphire windows, thereby changing the optical path length of the infrared incident light in the infrared absorption cell to adapt to the concentration range of the aging product and improve the accuracy of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1: A schematic flow chart of an embodiment of a method for evaluating the degree of transformer oil aging provided by the present invention.

[0040] Figure 2 : A schematic structural diagram of an embodiment of a device for evaluating the aging degree of transformer oil provided by the present invention.

[0041] Figure 3 : A schematic structural diagram of an embodiment of an infrared composite sensor provided by the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that the existing technology cannot accurately determine the degree of transformer oil aging online. -14 S / m, while the conductivity of ordinary mineral oil containing impurities is 10 -9 S / m. The existing technology generally uses a megohmmeter or an online conductivity meter, but because the conductivity instrument uses a fixed, single frequency for testing, the basis for judging the conductivity or aging degree obtained is relatively simple, and it is difficult to give a reliable result.

[0044] Embodiment one:

[0045] Please refer to Figure 1 , Figure 1 A method for evaluating the aging degree of transformer oil provided by an embodiment of the present invention comprises steps S1 to S4; wherein:

[0046] Step S1, respectively collecting the polarization current and non-polarization current of the transformer oil under a DC voltage in real time, and recording the polarization curve and non-polarization curve of the transformer oil under a DC voltage according to the collected polarization current and non-polarization current; wherein the polarization curve is a curve of the polarization current of the transformer oil changing with time; and the non-polarization curve is a curve of the non-polarization current of the transformer oil changing with time.

[0047] In this embodiment, a DC voltage U is applied to the conductivity electrodes at both ends. 0 , real-time collection of the polarization current and non-polarization current of the transformer oil at this time. As time goes by, the transformer oil under the DC voltage U can be obtained based on the polarization current and non-polarization current. 0 The polarization curve ip (t) and non-polarization curve i d (t).

[0048] Step S2, collecting in real time at least one voltage effective value and at least one current effective value of the transformer oil under each AC excitation signal; wherein each AC excitation signal corresponds to a type of aging product.

[0049] In this embodiment, according to the types of aging products, including but not limited to alcohol, aldehyde, ketone and carboxylic acid, the frequency and amplitude of the AC excitation signal are changed in turn, and at least one voltage effective value and at least one current effective value of the transformer oil are collected in real time.

[0050] Step S3, calculating a first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil; and calculating and obtaining at least one second conductivity of the transformer oil according to the at least one voltage effective value and the at least one current effective value.

[0051] In this embodiment, the polarization curve i is obtained. p (t), the non-polarization curve i d (t) and the DC voltage U 0 , the first conductivity σ of the transformer oil is calculated according to the following formula:

[0052]

[0053] Among them, C 0 is the capacitance of the conductive electrodes at both ends of the transformer oil, ε 0 is the dielectric constant of transformer oil.

[0054] The second conductivity is the ratio of the current effective value I to the voltage effective value, which is used as the test signal. In this embodiment, four second conductivity values ​​σ are obtained. i2 , σ i3 , σ i4 and σ i5 .

[0055] Step S4, obtaining the infrared light absorption rate of each of the aging products, combining the first conductivity and the at least one second conductivity, calculating the aging index of the transformer oil to obtain an aging degree evaluation result of the transformer oil; wherein each of the infrared light absorption rates corresponds one-to-one to the characteristic frequency of each of the aging products.

[0056] In this embodiment, the number of samples in the calibration set in the infrared spectrum analysis is n, and the characteristic frequency λ of the aging product is selected and obtained. 1 , 2 , …, λm , and the corresponding infrared absorption rate x i1 、x i2 , …, x im Combined with the first conductivity σ i1 , the at least one second conductivity σ i2 , σ i3 , σ i4 and σ i5 , perform multiple linear regression analysis according to the following formula to obtain the aging index y of the transformer oil in the i-th test i :

[0057] y i =b 0 +b 1 σ i1 +b 2 σ i2 +…+b 5 σ i5 +c 1 x i1 +c 2 x i2 +c 3 x i3 +…+c m X im +D i ;

[0058] Among them, b 0 is the intercept, D i is the residual, the number of samples in the calibration set is n, the number of spectra is m, and n>m+5. The aging index yi can accurately evaluate the aging degree of transformer oil. The method combines the conductivity of transformer oil under DC voltage and AC excitation signal, and can effectively evaluate the aging degree of transformer oil by analyzing the absorption spectra of different aging products.

[0059] Accordingly, refer to Figure 2 The embodiment of the present invention further provides a transformer oil aging degree evaluation device, comprising a first acquisition module 101, a second acquisition module 102, a conductivity acquisition module 103 and an aging evaluation module 104; wherein,

[0060] The first acquisition module 101 is used to respectively acquire the polarization current and non-polarization current of the transformer oil under a DC voltage in real time, and record the polarization curve and non-polarization curve of the transformer oil under a DC voltage according to the acquired polarization current and non-polarization current; wherein the polarization curve is a curve of the polarization current of the transformer oil changing with time; and the non-polarization curve is a curve of the non-polarization current of the transformer oil changing with time;

[0061] The second acquisition module 102 is used to respectively and in real time acquire at least one voltage effective value and at least one current effective value of the transformer oil under each AC excitation signal; wherein each AC excitation signal corresponds to a type of aging product;

[0062] The conductivity acquisition module 103 is used to calculate the first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil; and calculate at least one second conductivity of the transformer oil according to the at least one voltage effective value and the at least one current effective value;

[0063] The aging assessment module 104 is used to obtain the infrared light absorption rate of each of the aging products, and calculate the aging index of the transformer oil in combination with the first conductivity and the at least one second conductivity to obtain an aging degree assessment result of the transformer oil; wherein each of the infrared light absorption rates corresponds to a characteristic frequency of each of the aging products one by one.

[0064] In this embodiment, the aging assessment module 104 obtains the infrared light absorption rate of each of the aging products, and calculates the aging index of the transformer oil by combining the first conductivity and the at least one second conductivity, specifically:

[0065] The aging assessment module 104 obtains the infrared absorption rate x of the aging product i1 , X i2 , …, x im , combined with the first conductivity σ i1 , the at least one second conductivity σ i2 , σ i3 , σ i4 and σ i5 , perform multiple linear regression analysis according to the following formula to obtain the aging index y of the transformer oil in the i-th test i :

[0066] y i =b 0 +b 1 σ i1 +b 2 σ i2 +…+b 5 σ i5 +c 1 x i1 +c 2 x i2 +c 3 x i3 +…+c m X im +D i ;

[0067] Among them, b 0 is the intercept, D i is the residual, the number of samples in the calibration set is n, the number of spectra is m, and n>m+5.

[0068] In this embodiment, the conductivity acquisition module 103 calculates the first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil, specifically:

[0069] The conductivity acquisition module 103 acquires the polarization curve i p (t), the non-polarization curve i d (t) and the DC voltage U 0 , the first conductivity σ of the transformer oil is calculated according to the following formula:

[0070]

[0071] Among them, C 0 is the capacitance of the conductive electrodes at both ends of the transformer oil, ε 0 is the dielectric constant of transformer oil.

[0072] Accordingly, the embodiment of the present invention also provides a transformer oil aging degree sensing system, the sensing system comprising a computer and an infrared composite sensor (refer to Figure 3 ). The infrared composite sensor is connected to the transformer 1 to be tested, and is used to measure the conductivity and aging degree of the transformer oil of the transformer 1 to be tested.

[0073] The computer is used as an execution subject to execute the transformer oil aging degree evaluation method. The infrared composite sensor includes a conductivity electrode 2, a conductivity cell 3, an electromagnetic shielding box 4, a constant temperature box 5, an infrared absorption cell 6 and a sapphire window 7.

[0074] The first end of the conductivity cell 3 is connected to an output end of the transformer 1 to be tested; the second end of the conductivity cell 3 is connected to the first end of the infrared absorption cell 6, and the second end of the infrared absorption cell 6 is connected to an input end of the transformer 1 to be tested. During the operation of the transformer 1 to be tested, the transformer oil flows out from an output end of the transformer 1 to be tested, enters the conductivity cell 3, flows into an input end of the transformer 1 to be tested after passing through the infrared absorption cell 6, and flows back into the transformer 1 to be tested.

[0075] An electromagnetic shielding box 4 is provided outside the conductivity cell 3, and the electromagnetic shielding box 4 is used to shield the influence of the electromagnetic field of the external environment on the test process (since it is an online, real-time test, the provision of the electromagnetic shielding box is very necessary). A constant temperature box 5 is also provided outside the electromagnetic shielding box 4 to eliminate the influence of temperature on conductivity.

[0076] The conductivity cell 3 is provided with conductivity electrodes 2 on two opposite planes for measuring the conductivity of transformer oil. The conductivity electrode 2 is a bright platinum electrode to prevent the adsorption of trace moisture by the platinum black electrode, which may affect the test result due to capacitance changes. At the same time, the surface area of ​​the conductivity electrode 2 is appropriately increased relative to the conductivity electrode of the prior art, and the distance between the conductivity electrodes 2 is appropriately reduced, thereby increasing the capacitance C of the conductivity electrode 2. 0 Since the conductivity of any sample is certain, when the capacitance C 0 When it becomes larger, the corresponding current value will change more, that is, i p (t)-i d The larger (t), the higher the sensitivity and the more accurate the conductivity obtained. 1 .

[0077] The infrared absorption cell 6 is used to measure the infrared light absorption rate of each aging product of the transformer oil under the irradiation of infrared incident light; wherein the infrared light absorption rate corresponds to the characteristic frequency of each aging product. The infrared absorption cell 6 is provided with sapphire windows 7 at the entrance and exit of the infrared incident light, so as to avoid the erosion of water in the transformer oil sample and extend the service life of the infrared absorption cell 6; at the same time, several layers of silicone gaskets are provided between the sapphire windows 7. By adjusting the number of layers of silicone gaskets, the distance between the sapphire windows 7 can be adjusted, thereby changing the size of the infrared absorption cell 6, and then adjusting the optical path length of the infrared incident light in the infrared absorption cell 6, so that the length of the optical path can adapt to the concentration range of different aging products, thereby improving the accuracy of the measurement.

[0078] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0079] The embodiment of the present invention provides a method, device and sensor system for evaluating the aging degree of transformer oil. The method comprises: respectively collecting the polarization current and non-polarization current of the transformer oil under a direct current voltage in real time, and recording the polarization curve and non-polarization curve of the transformer oil under the direct current voltage according to the collected polarization current and non-polarization current; respectively collecting in real time at least one voltage effective value and at least one current effective value of the transformer oil under each alternating current excitation signal; calculating the first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the direct current voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil; respectively calculating at least one second conductivity of the transformer oil according to the at least one voltage effective value and the at least one current effective value; obtaining the infrared light absorption rate of each of the aging products, and calculating the aging index of the transformer oil in combination with the first conductivity and the at least one second conductivity, so as to obtain the aging degree evaluation result of the transformer oil. Compared with the existing technology, the test can be performed online, by obtaining at least one conductivity of the transformer oil under DC voltage and AC voltage, taking into account the influence of impurities on the conductivity of the transformer oil, thereby improving the accuracy and real-time performance of the test.

[0080] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for evaluating the degree of transformer oil aging, It is characterized in that include: The polarization current and non-polarization current of the transformer oil under the DC voltage are respectively collected in real time, and the polarization curve and non-polarization curve of the transformer oil under the DC voltage are recorded according to the collected polarization current and non-polarization current; wherein the polarization curve is a curve of the polarization current of the transformer oil changing with time; and the non-polarization curve is a curve of the non-polarization current of the transformer oil changing with time; respectively collecting in real time at least one voltage effective value and at least one current effective value of the transformer oil under each AC excitation signal; wherein each AC excitation signal corresponds to a type of aging product; According to the polarization curve, the non-polarization curve and the DC voltage, in combination with the capacitance of the conductivity electrodes at both ends of the transformer oil, a first conductivity of the transformer oil is calculated; according to the at least one voltage effective value and the at least one current effective value, at least one second conductivity of the transformer oil is calculated respectively; The infrared light absorption rate of each of the aging products is obtained, and the aging index of the transformer oil is calculated in combination with the first conductivity and the at least one second conductivity to obtain an aging degree evaluation result of the transformer oil; wherein each of the infrared light absorption rates corresponds to a characteristic frequency of each of the aging products one by one.

2. A method for evaluating the degree of transformer oil aging as claimed in claim 1, It is characterized in that The infrared light absorption rate of each of the aging products is obtained, and the aging index of the transformer oil is calculated by combining the first conductivity and the at least one second conductivity, specifically: Obtain the infrared absorption rate x of the aging product i1 、x i2 , …, x im , combined with the first conductivity σ i1 , the at least one second conductivity σ i2 , σ i3 , σ i4 and σ i5 , perform multiple linear regression analysis according to the following formula to obtain the aging index y of the transformer oil in the i-th test i : y i =b 0 +b 1 s i1 +b 2 s i2 +…+b 5 s i5 +c 1 x i1 +c 2 x i2 +c 3 x i3 +…+c m x im +D i ; Among them, b 0 is the intercept, D i is the residual, the number of samples in the calibration set is n, the number of spectra is m, and n>m+5.

3. A method for evaluating the aging degree of transformer oil as claimed in claim 1, It is characterized in that The first conductivity of the transformer oil is calculated according to the polarization curve, the non-polarization curve and the DC voltage, in combination with the capacitance of the conductivity electrodes at both ends of the transformer oil, specifically: Get the polarization curve i p (t), the non-polarization curve i d (t) and the DC voltage U 0 , the first conductivity σ of the transformer oil is calculated according to the following formula: Among them, C 0 is the capacitance of the conductive electrodes at both ends of the transformer oil, ε 0 is the dielectric constant of transformer oil.

4. A device for evaluating the degree of transformer oil aging, It is characterized in that It includes a first acquisition module, a second acquisition module, a conductivity acquisition module and an aging evaluation module; wherein, The first acquisition module is used to respectively acquire the polarization current and non-polarization current of the transformer oil under a DC voltage in real time, and record the polarization curve and non-polarization curve of the transformer oil under a DC voltage according to the acquired polarization current and non-polarization current; wherein the polarization curve is a curve of the polarization current of the transformer oil changing with time; and the non-polarization curve is a curve of the non-polarization current of the transformer oil changing with time; The second acquisition module is used to respectively and in real time acquire at least one voltage effective value and at least one current effective value of the transformer oil under each AC excitation signal; wherein each AC excitation signal corresponds to a type of aging product; The conductivity acquisition module is used to calculate the first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil; and calculate at least one second conductivity of the transformer oil according to the at least one voltage effective value and the at least one current effective value; The aging assessment module is used to obtain the infrared light absorption rate of each of the aging products, and calculate the aging index of the transformer oil in combination with the first conductivity and the at least one second conductivity to obtain an aging degree assessment result of the transformer oil; wherein each of the infrared light absorption rates corresponds one-to-one to a characteristic frequency of each of the aging products.

5. A transformer oil aging degree assessment device as claimed in claim 4, It is characterized in that The aging assessment module obtains the infrared light absorption rate of each of the aging products, and calculates the aging index of the transformer oil by combining the first conductivity and the at least one second conductivity, specifically: The aging assessment module obtains the infrared absorption rate x of the aging product i1 、x i2 , …, x im , combined with the first conductivity σ i1 , the at least one second conductivity σ i2 , σ i3 , σ i4 and σ i5 , perform multiple linear regression analysis according to the following formula to obtain the aging index y of the transformer oil in the i-th test i : y i =b 0 +b 1 s i1 +b 2 s i2 +…+b 5 s i5 +c 1 x i1 +c 2 x i2 +c 3 x i3 +…+c m x im +D i ; Among them, b 0 is the intercept, D i is the residual, the number of samples in the calibration set is n, the number of spectra is m, and n>m+5.

6. A transformer oil aging degree assessment device as claimed in claim 4, It is characterized in that The conductivity acquisition module calculates the first conductivity of the transformer oil according to the polarization curve, the non-polarization curve and the DC voltage, combined with the capacitance of the conductivity electrodes at both ends of the transformer oil, specifically: The conductivity acquisition module acquires the polarization curve i p (t), the non-polarization curve i d (t) and the DC voltage U 0 , the first conductivity σ of the transformer oil is calculated according to the following formula: Among them, C 0 is the capacitance of the conductive electrodes at both ends of the transformer oil, ε 0 is the dielectric constant of transformer oil.

7. A transformer oil aging degree sensing system, It is characterized in that The sensing system includes a computer and an infrared composite sensor; The infrared composite sensor comprises a conductivity cell and an infrared absorption cell; the first end of the conductivity cell is connected to an output end of the transformer to be tested; the second end of the conductivity cell is connected to the first end of the infrared absorption cell, and the second end of the infrared absorption cell is connected to an input end of the transformer to be tested; Two opposite planes of the conductivity cell are provided with conductivity electrodes for measuring the conductivity of transformer oil; The infrared absorption cell is used to measure the infrared light absorption rate of each aging product of the transformer oil under the irradiation of infrared incident light; wherein the infrared light absorption rate corresponds to the characteristic frequency of each aging product one by one; The computer is used to execute the method for evaluating the aging degree of transformer oil as claimed in any one of claims 1 to 3.

8. A transformer oil aging degree sensing system as claimed in claim 7, It is characterized in that The conductivity electrode adopts a bright platinum electrode.

9. A transformer oil aging degree sensing system as claimed in claim 7, It is characterized in that An electromagnetic shielding box is also arranged outside the conductivity cell.

10. A transformer oil aging degree sensing system as claimed in claim 7, It is characterized in that Sapphire windows are arranged at both the incident and the exit points of the infrared incident light of the infrared absorption cell; and several layers of silicone gaskets are arranged between the sapphire windows.

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