Online monitoring equipment and method for oil paper insulation aging state of oil-filled equipment

Abstract

The invention discloses an online monitoring device and method for the oil paper insulation aging state of oil-filled equipment, and relates to the field of oil paper insulation monitoring. An inlet and an outlet of a circulation channel in the device are communicated with different positions of the oil-filled equipment respectively; the pump is arranged at an inlet of the circulating channel; the oil flow cuvette is arranged on the circulation channel; the opposite surfaces of the oil flow cuvette are respectively provided with a terahertz transmitting probe and a terahertz receiving probe of the transmission-type terahertz time-domain spectrometer; the pump is used for enabling insulating oil in the oil charging equipment to flow into the circulating channel and enter the oil flow cuvette; the terahertz transmitting probe is used for transmitting terahertz waves to penetrate through the oil flow cuvette after insulating oil flows into the oil flow cuvette; the terahertz receiving probe receives the terahertz waves penetrating through the oil flow cuvette and obtains terahertz time-domain signals; and aging state on-line monitoring is carried out. According to the invention, non-sampling, non-contact and rapid in-situ detection of the oil paper insulation aging state of the oil-filled equipment can be realized.

Description

Technical Field

[0001] The present application relates to the field of oil-paper insulation monitoring, and in particular to an online monitoring device and method for the aging state of oil-paper insulation of oil-filled equipment. Background Art

[0002] Under the influence of long-term electrical, thermal, and mechanical stresses and other complex operating conditions, the performance of the insulation material of oil-immersed power equipment gradually deteriorates, and the probability of failure increases year by year, increasing the operating risks of the equipment and the power grid. At present, electrical parameters such as breakdown and dielectric loss, or physical and chemical parameters such as dissolved gas in oil, acid value, and furfural are usually used to judge the deterioration state of oil-paper insulation. However, due to the requirements of test equipment and environment, it is difficult to achieve real-time online monitoring of equipment. Therefore, it is the key to promote the digital transformation of power equipment and realize the full life cycle management of equipment to study new online sensing technologies for oil-filled equipment to achieve real-time sensing of the deterioration state of oil-paper insulation without power outages, so as to make reliable assessments and predictions of the aging state and remaining life of the equipment.

[0003] At present, the dissolved gas analysis method (DGA) in oil can be used for online monitoring on the equipment. However, it mainly monitors the characteristic gases generated by sudden failures in the equipment (such as overheating and discharge), and cannot accurately reflect the aging state of oil-paper insulation. The deterioration of oil-paper insulation will produce a large amount of polar substances (acids, water, aldehydes and alcohols, etc.). Terahertz technology has a strong perception ability for polar substances. Some studies have used it for non-destructive testing of insulating oil quality. By extracting characteristic peaks or integrating spectral lines from the frequency domain spectrum of the insulating oil, the content of aging products in the insulating oil or the overall quality of the insulating oil is characterized. Although these studies can achieve rapid detection without extraction, it is still necessary to sample the insulating oil for measurement. It can be seen that the application of terahertz technology in online monitoring research needs further research.

[0004] In summary, based on the above problems, there is an urgent need to provide a new online monitoring method or device for the aging status of oil-paper insulation of oil-filled equipment, so as to realize non-sampling, non-contact and rapid in-situ detection of the aging status of oil-paper insulation of oil-filled equipment. Summary of the invention

[0005] The purpose of the present application is to provide an online monitoring device and method for the aging state of oil-paper insulation of oil-filled equipment, which can realize non-sampling, non-contact and rapid in-situ detection of the aging state of oil-paper insulation of oil-filled equipment.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides an online monitoring device for the aging state of oil-paper insulation of an oil-filled device, the online monitoring device for the aging state of oil-paper insulation of an oil-filled device comprising: a pump, a circulation channel, an oil circulation cuvette, and a transmission terahertz time-domain spectrometer;

[0008] The inlet and outlet of the circulation channel are respectively connected to different positions of the oil filling device; the pump is arranged at the inlet of the circulation channel; the oil circulation cuvette is arranged on the circulation channel; and the terahertz transmitting probe and the terahertz receiving probe of the transmission terahertz time-domain spectrometer are respectively arranged on opposite sides of the oil circulation cuvette;

[0009] The pump is used to flow the insulating oil in the oil-filled device into the circulation channel and into the oil flow cuvette; the terahertz transmitting probe is used to emit terahertz waves to penetrate the oil flow cuvette after the insulating oil flows into the oil flow cuvette; the terahertz receiving probe receives the terahertz waves passing through the oil flow cuvette and obtains a terahertz time domain signal; the transmission terahertz time domain spectrometer is used to perform online monitoring of the aging status according to the terahertz time domain signal.

[0010] Optionally, the material of the oil flow cuvette is: jgs3 quartz material or polyethylene material.

[0011] Optionally, the oil-filled equipment oil-paper insulation aging state online monitoring device further includes: a temperature sensor and a closed cover;

[0012] The temperature sensor is arranged on the surface of the circulation channel at the inlet of the oil circulation cuvette and is used to monitor the temperature of the insulating oil at the oil circulation cuvette;

[0013] The closed cover is used to cover the oil flow cuvette and the transmission type terahertz time domain spectrometer.

[0014] In a second aspect, the present application provides an online monitoring method for the aging state of oil-paper insulation of an oil-filled device, which is applied to an online monitoring device for the aging state of oil-paper insulation of an oil-filled device, and the online monitoring device method for the aging state of oil-paper insulation of an oil-filled device comprises:

[0015] A terahertz transmitting probe is used to transmit a terahertz wave to penetrate an oil flow cuvette containing dry air; and a terahertz receiving probe is used to receive the terahertz wave passing through the oil flow cuvette, and a terahertz time domain signal of a reference signal is obtained;

[0016] A terahertz transmitting probe is used to transmit a terahertz wave to penetrate an oil flow cuvette containing dry air; and a terahertz receiving probe is used to receive the terahertz wave passing through the oil flow cuvette, and a terahertz time domain signal of a reference signal is obtained;

[0017] The insulating oil in the oil-filled equipment is pumped into the circulation channel and into the oil flow cuvette;

[0018] When insulating oil flows into the oil flow cuvette, the terahertz transmitting probe is used to transmit terahertz waves to penetrate the oil flow cuvette;

[0019] A terahertz receiving probe is used to receive the terahertz wave passing through the oil flow cuvette, and a terahertz time domain signal is obtained;

[0020] The aging status is monitored online based on the terahertz time domain signal.

[0021] Optionally, the online monitoring of the aging status according to the terahertz time domain signal specifically includes:

[0022] Converting terahertz time domain signals into terahertz frequency domain signals;

[0023] The refractive index and extinction coefficient of the insulating oil are determined according to the terahertz frequency domain signal of the insulating oil in the oil flow cuvette, the terahertz frequency domain signal of the reference signal, and the monitored temperature of the temperature sensor;

[0024] Determine the dielectric information of the insulating oil in the terahertz frequency band according to the refractive index and extinction coefficient of the insulating oil;

[0025] Determine the real-time dielectric loss factor tangent angle of the insulating oil in the terahertz frequency band according to the dielectric information of the insulating oil in the terahertz frequency band;

[0026] The daily monitoring curve of the oil-paper insulation is determined according to the tangent angle of the dielectric loss factor; and the aging status of the oil-paper insulation is monitored according to the daily monitoring curve of the oil-paper insulation.

[0027] Optionally, converting the terahertz time domain signal into a terahertz frequency domain signal specifically includes:

[0028] Using the formula Determine terahertz frequency domain signals;

[0029] Among them, E(ω) is the terahertz frequency domain signal, ω is the angular frequency, E(t) is the terahertz time domain signal, A(ω) is the terahertz frequency domain signal amplitude, φ(ω) is the terahertz frequency domain signal phase, e is the natural logarithm, and i is the imaginary unit.

[0030] Optionally, the refractive index and extinction coefficient of the insulating oil are determined according to the terahertz frequency domain signal of the insulating oil in the oil flow cuvette, the terahertz frequency domain signal of the reference signal, and the monitored temperature of the temperature sensor, specifically including:

[0031] Using the formula Determine the refractive index;

[0032] Using the formula n correct =a×(T-T0)+n(ω)corrected refractive index;

[0033] Using the formula Determine the extinction coefficient;

[0034] Where n(ω) is the refractive index at angular frequency ω, n correct is the refractive index after correction, T is the monitoring temperature of the temperature sensor, T0 is the reference temperature, a is the correction constant, κ(ω) is the extinction coefficient at an angular frequency of ω, d is the optical path of the oil flowing through the cuvette, c is the speed of light in vacuum, and A s (ω) and A r (ω) are the amplitudes of the terahertz frequency domain signal of the insulating oil in the oil flow cuvette and the terahertz frequency domain signal of the reference signal, respectively, s (ω) and φ r (ω) are the phases of the terahertz frequency domain signal of the insulating oil in the oil flow cuvette and the terahertz frequency domain signal of the reference signal, respectively.

[0035] Optionally, determining the dielectric information of the insulating oil in the terahertz frequency band according to the refractive index and extinction coefficient of the insulating oil specifically includes:

[0036] Using the formula ε'(ω)=[n correct ] 2 -[κ(ω)] 2 Determine the real part of the dielectric constant in the terahertz frequency band;

[0037] Using the formula ε”(ω)=2n correct κ(ω) determines the imaginary part of the dielectric constant in the terahertz frequency band;

[0038] Among them, ε' is the real part of the dielectric constant in the terahertz band, and ε” is the imaginary part of the dielectric constant in the terahertz band.

[0039] Optionally, determining the real-time dielectric loss factor tangent angle of the insulating oil in the terahertz frequency band according to the dielectric information of the insulating oil in the terahertz frequency band specifically includes:

[0040] The real-time dielectric loss factor tangent angle tanδ is determined using the formula tanδ=ε'(ω) / ε”(ω).

[0041] Optionally, determining a daily monitoring curve of oil-paper insulation according to the tangent angle of the dielectric loss factor; and monitoring the aging state of oil-paper insulation according to the daily monitoring curve of oil-paper insulation specifically includes:

[0042] The average value of the dielectric loss factor tangent angle from 0.3THz to 1.0THz is taken as the characteristic quantity;

[0043] Determine the daily monitoring curve of oil-paper insulation based on the characteristic quantities.

[0044] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0045] The present application provides an online monitoring device and method for the aging state of oil-paper insulation of oil-filled equipment. Through a pump, a circulation channel, an oil circulation cuvette and a transmission terahertz time-domain spectrometer, a non-contact, non-sampling monitoring structure is realized. The oil circulation cuvette is used to realize the non-contact, non-destructive online monitoring of the oil-paper insulation state by terahertz technology; the strong penetration ability of terahertz waves on weak polar substances and the strong perception ability of polar degradation products are used to evaluate the degradation state of insulating oil in real time. Compared with the existing technology, the non-sampling, non-contact and rapid in-situ detection of the aging state of oil-paper insulation of oil-filled equipment is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 It is a front view of the structure of an online monitoring device for the aging state of oil-paper insulation of an oil-filled device in one embodiment of the present application;

[0048] Figure 2 It is a top view of the structure of an online monitoring device for the aging state of oil-paper insulation of an oil-filled device in one embodiment of the present application;

[0049] Figure 3 Schematic diagram of the tangent angle spectrum of the dielectric loss factor of the insulating oil in the terahertz frequency band during the monitoring process;

[0050] Figure 4 This is a schematic diagram of the change of characteristic quantities during daily monitoring of thermal aging of oil-paper insulation;

[0051] Figure 5 Schematic diagram of the change of characteristic quantity with thermal aging time;

[0052] Figure 6 Schematic diagram of the temperature variation experiment results. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0054] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0055] In an exemplary embodiment, Figure 1 and Figure 2 As shown, an online monitoring device for the aging state of oil-paper insulation of oil-filled equipment is provided, the device comprising a pump 2, a circulation channel 3, an oil circulation cuvette 4 and a transmission terahertz time-domain spectrometer;

[0056] The inlet and outlet of the circulation channel 3 are respectively connected to different positions of the oil filling device 1; the pump 2 is arranged at the inlet of the circulation channel 3; the oil circulation cuvette 4 is arranged on the circulation channel 3; and the terahertz transmitting probe 5 and the terahertz receiving probe 6 of the transmission terahertz time-domain spectrometer are respectively arranged on the opposite sides of the oil circulation cuvette 4;

[0057] The pump 2 is used to flow the insulating oil in the oil-filling device 1 into the circulation channel 3 and into the oil circulation cuvette 4; the terahertz transmitting probe 5 is used to emit terahertz waves to penetrate the oil circulation cuvette 4 after the insulating oil flows into the oil circulation cuvette 4; the terahertz receiving probe 6 receives the terahertz waves passing through the oil circulation cuvette 4 and obtains a terahertz time domain signal; the transmission terahertz time domain spectrometer is used to perform online monitoring of the aging status according to the terahertz time domain signal.

[0058] In an exemplary embodiment, the online monitoring device for oil-paper insulation aging status of oil-filled equipment further includes: a temperature sensor 7 and a sealing cover 8;

[0059] The temperature sensor 7 is arranged on the surface of the circulation channel 3 at the inlet of the oil circulation cuvette 4 and is used to monitor the temperature of the insulating oil at the oil circulation cuvette 4;

[0060] The sealing cover 8 is used to cover the oil flow cuvette 4 and the transmission terahertz time-domain spectrometer. The sealing cover 8 is usually made of metal to shield external electromagnetic interference, and the cover is filled with nitrogen or evacuated to prevent the measured optical path from being affected by water vapor.

[0061] In another exemplary embodiment, the material of the oil flow cuvette 4 is: jgs3 quartz material or polyethylene material. Taking the oil flow cuvette 4 made of jgs3 quartz material as an example: the terahertz transmitting probe 5 transmits a terahertz wave, which penetrates the oil flow cuvette 4 made of jgs3 quartz material and is captured by the terahertz receiving probe 6 to obtain a terahertz time domain signal.

[0062] The online monitoring device for the aging state of oil-paper insulation of oil-filled equipment provided in the present application is a non-contact and non-sampling detection structure. In conjunction with the oil circulation cuvette 4, terahertz technology is used to carry out non-contact and non-destructive online monitoring of the oil-paper insulation state, and the deterioration state of the insulating oil is evaluated in real time through terahertz characteristic quantities.

[0063] Based on the same inventive concept, the embodiment of the present application also provides an online monitoring method for the oil-paper insulation aging state of oil-filled equipment for realizing the online monitoring device for the oil-paper insulation aging state of oil-filled equipment involved above. The implementation scheme for solving the problem provided by the method is similar to the implementation scheme recorded in the above-mentioned device, so the specific limitations in one or more embodiments of the online monitoring method for the aging state of oil-paper insulation of oil-filled equipment provided below can refer to the limitations of the online monitoring device for the aging state of oil-paper insulation of oil-filled equipment above, and will not be repeated here.

[0064] In an exemplary embodiment, a method for online monitoring of oil-paper insulation aging status of oil-filled equipment is provided, comprising:

[0065] S101, using the pump 2 to flow the insulating oil in the oil-filled device 1 into the circulation channel 3 and into the oil circulation cuvette 4;

[0066] In an exemplary embodiment, before S101, the step further includes:

[0067] The terahertz transmitting probe 5 is used to transmit the terahertz wave to penetrate the oil circulation cuvette 4 containing dry air; and the terahertz receiving probe 6 is used to receive the terahertz wave passing through the oil circulation cuvette 4, and obtain the terahertz time domain signal of the reference signal.

[0068] S102, when insulating oil flows into the oil flow cuvette 4, the terahertz transmitting probe 5 is used to transmit terahertz waves to penetrate the oil flow cuvette 4;

[0069] S103, using the terahertz receiving probe 6 to receive the terahertz wave passing through the oil flow cuvette 4, and obtaining a terahertz time domain signal;

[0070] S104, performing online monitoring of the aging status according to the terahertz time domain signal.

[0071] After obtaining the terahertz time domain signal of the reference signal, the terahertz receiving probe 6 is used to receive the terahertz wave passing through the oil flow cuvette 4, and the terahertz time domain signal is obtained; then S104 specifically includes:

[0072] S41, converting the terahertz time domain signal into a terahertz frequency domain signal;

[0073] Using the formula Determine terahertz frequency domain signals;

[0074] Among them, E(ω) is the terahertz frequency domain signal, ω is the angular frequency, E(t) is the terahertz time domain signal, A(ω) is the terahertz frequency domain signal amplitude, φ(ω) is the terahertz frequency domain signal phase, e is the natural logarithm, and i is the imaginary unit.

[0075] S42, determining the refractive index and extinction coefficient of the insulating oil according to the terahertz frequency domain signal of the insulating oil in the oil flow cuvette 4, the terahertz frequency domain signal of the reference signal, and the monitored temperature of the temperature sensor 7;

[0076] Using the formula Determine the refractive index;

[0077] Using the formula n correct =a×(T-T0)+n(ω)corrected refractive index;

[0078] Using the formula Determine the extinction coefficient;

[0079] Where n(ω) is the refractive index at angular frequency ω, n correct is the refractive index after correction, T is the monitoring temperature of the temperature sensor 7, T0 is the reference temperature, usually room temperature 20°C, a is the correction constant, and a is related to the type and manufacturer of the insulating oil. It can be obtained by performing variable temperature terahertz testing on the insulating oil to be tested in the laboratory. For #25 Karamay insulating oil, Figure 6 The results of the temperature variation experiment show that a is -7.94×10 -4 κ(ω) is the extinction coefficient at angular frequency ω, d is the optical path of the oil flowing through the cuvette 4, c is the speed of light in vacuum, A s (ω) and A r (ω) are the amplitudes of the terahertz frequency domain signal of the insulating oil in the oil flow cuvette 4 and the terahertz frequency domain signal of the reference signal, respectively, s (ω) and φ r (ω) are the phases of the terahertz frequency domain signal of the insulating oil in the oil flow cuvette 4 and the terahertz frequency domain signal of the reference signal, respectively.

[0080] The temperature of the object will affect the viscosity of the insulating oil, thereby affecting the density of the insulating oil, causing the detected value of n(ω) to change, thereby causing the tanδ subsequently calculated based on the refractive index to change. Therefore, the temperature sensor 7 is used to monitor the temperature of the insulating oil in real time, and the relationship function between the oil temperature and the terahertz refractive index is used to correct the currently obtained terahertz refractive index.

[0081] In the laboratory, the oil temperature was heated and the temperature was varied. It was found that the average refractive index in the terahertz frequency band was approximately linearly related to the temperature. Therefore, when the oil temperature fluctuated widely during the online detection process, the formula n correct=a×(T-T0)+n to correct the refractive index.

[0082] S43, determining dielectric information of the insulating oil in the terahertz frequency band according to the refractive index and extinction coefficient of the insulating oil;

[0083] Using the formula ε'(ω)=[n(ω)] 2 -[κ(ω)] 2 Determine the real part of the dielectric constant in the terahertz frequency band;

[0084] The imaginary part of the dielectric constant in the terahertz frequency band is determined using the formula ε”(ω)=2n(ω)κ(ω);

[0085] Among them, ε' is the real part of the dielectric constant in the terahertz band, and ε” is the imaginary part of the dielectric constant in the terahertz band.

[0086] S44, determining the real-time dielectric loss factor tangent angle of the insulating oil in the terahertz frequency band according to the dielectric information of the insulating oil in the terahertz frequency band, and Figure 3 As shown;

[0087] The real-time dielectric loss factor tangent angle tanδ is determined using the formula tanδ=ε'(ω) / ε”(ω).

[0088] S45, determining a daily monitoring curve of the oil-paper insulation according to the tangent angle of the dielectric loss factor; and monitoring the aging status of the oil-paper insulation according to the daily monitoring curve of the oil-paper insulation.

[0089] The average value of the dielectric loss factor tangent angle between 0.3THz and 1.0THz is taken as the characteristic quantity; the daily monitoring curve of oil-paper insulation is determined based on the characteristic quantity. Figure 4 As shown in Figure 1, the quality of insulating oil is reflected by the characteristic quantity, so as to monitor the real-time degradation state of oil-paper insulation. Figure 5 As shown, the terahertz online monitoring quantity increases with the increase of thermal aging time, and the aging state of the oil-paper insulation of the oil-filled equipment 1 can be judged by the size and fluctuation of the characteristic quantity.

[0090] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0091] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. An online monitoring device for the aging status of oil-paper insulation of oil-filled equipment, characterized in that: The online monitoring device for the aging state of oil-paper insulation of the oil-filling equipment comprises: a pump, a circulation channel, an oil circulation cuvette and a transmission terahertz time-domain spectrometer; The inlet and outlet of the circulation channel are respectively connected to different positions of the oil filling device; the pump is arranged at the inlet of the circulation channel; the oil circulation cuvette is arranged on the circulation channel; and the terahertz transmitting probe and the terahertz receiving probe of the transmission terahertz time-domain spectrometer are respectively arranged on opposite sides of the oil circulation cuvette; The pump is used to flow the insulating oil in the oil-filled device into the circulation channel and into the oil flow cuvette; the terahertz transmitting probe is used to emit terahertz waves to penetrate the oil flow cuvette after the insulating oil flows into the oil flow cuvette; the terahertz receiving probe receives the terahertz waves passing through the oil flow cuvette and obtains a terahertz time domain signal; the transmission terahertz time domain spectrometer is used to perform online monitoring of the aging status according to the terahertz time domain signal.

2. The online monitoring device for oil-paper insulation aging status of oil-filled equipment according to claim 1 is characterized in that: The material of the oil flow cuvette is: jgs3 quartz material or polyethylene material.

3. The online monitoring device for oil-paper insulation aging status of oil-filled equipment according to claim 1 is characterized in that: The oil-filled equipment oil-paper insulation aging state online monitoring device also includes: a temperature sensor and a closed cover; The temperature sensor is arranged on the surface of the circulation channel at the inlet of the oil circulation cuvette and is used to monitor the temperature of the insulating oil at the oil circulation cuvette; The closed cover is used to cover the oil flow cuvette and the transmission type terahertz time domain spectrometer.

4. An online monitoring method for the aging state of oil-paper insulation of oil-filled equipment, applied to an online monitoring device for the aging state of oil-paper insulation of oil-filled equipment as claimed in any one of claims 1 to 3, characterized in that: The online monitoring method for the oil-paper insulation aging state of the oil-filled equipment comprises: A terahertz transmitting probe is used to transmit a terahertz wave to penetrate an oil flow cuvette containing dry air; and a terahertz receiving probe is used to receive the terahertz wave passing through the oil flow cuvette, and a terahertz time domain signal of a reference signal is obtained; The insulating oil in the oil-filled equipment is pumped into the circulation channel and into the oil flow cuvette; When insulating oil flows into the oil flow cuvette, the terahertz transmitting probe is used to transmit terahertz waves to penetrate the oil flow cuvette; A terahertz receiving probe is used to receive the terahertz wave passing through the oil flow cuvette, and a terahertz time domain signal is obtained; The aging status is monitored online based on the terahertz time domain signal.

5. The method for online monitoring of oil-paper insulation aging status of oil-filled equipment according to claim 4 is characterized in that: The online monitoring of the aging status according to the terahertz time domain signal specifically includes: Converting terahertz time domain signals into terahertz frequency domain signals; The refractive index and extinction coefficient of the insulating oil are determined according to the terahertz frequency domain signal of the insulating oil in the oil flow cuvette, the terahertz frequency domain signal of the reference signal, and the monitored temperature of the temperature sensor; Determine the dielectric information of the insulating oil in the terahertz frequency band according to the refractive index and extinction coefficient of the insulating oil; Determine the real-time dielectric loss factor tangent angle of the insulating oil in the terahertz frequency band according to the dielectric information of the insulating oil in the terahertz frequency band; The daily monitoring curve of the oil-paper insulation is determined according to the tangent angle of the dielectric loss factor; and the aging status of the oil-paper insulation is monitored according to the daily monitoring curve of the oil-paper insulation.

6. The method for online monitoring of oil-paper insulation aging status of oil-filled equipment according to claim 5 is characterized in that: The converting of the terahertz time domain signal into the terahertz frequency domain signal specifically includes: Using the formula Determine terahertz frequency domain signals; Among them, E(ω) is the terahertz frequency domain signal, ω is the angular frequency, E(t) is the terahertz time domain signal, A(ω) is the terahertz frequency domain signal amplitude, φ(ω) is the terahertz frequency domain signal phase, e is the natural logarithm, and i is the imaginary unit.

7. The method for online monitoring of oil-paper insulation aging status of oil-filled equipment according to claim 6 is characterized in that: The refractive index and extinction coefficient of the insulating oil are determined according to the terahertz frequency domain signal of the insulating oil in the oil flow cuvette, the terahertz frequency domain signal of the reference signal and the monitored temperature of the temperature sensor, specifically including: Using the formula Determine the refractive index; Using the formula n correct =a×(T-T0)+n(ω)corrected refractive index; Using the formula Determine the extinction coefficient; Where n(ω) is the refractive index at angular frequency ω, n correct is the refractive index after correction, T is the monitoring temperature of the temperature sensor, T0 is the reference temperature, a is the correction constant, κ(ω) is the extinction coefficient at an angular frequency of ω, d is the optical path of the oil flowing through the cuvette, c is the speed of light in vacuum, and A s (ω) and A r (ω) are the amplitudes of the terahertz frequency domain signal of the insulating oil in the oil flow cuvette and the terahertz frequency domain signal of the reference signal, respectively, s (ω) and φ r (ω) are the phases of the terahertz frequency domain signal of the insulating oil in the oil flow cuvette and the terahertz frequency domain signal of the reference signal, respectively.

8. The method for online monitoring of oil-paper insulation aging status of oil-filled equipment according to claim 7 is characterized in that: The method of determining the dielectric information of the insulating oil in the terahertz frequency band according to the refractive index and extinction coefficient of the insulating oil specifically includes: Using the formula ε'(ω)=[n correct ] 2 -[κ(ω)] 2 Determine the real part of the dielectric constant in the terahertz frequency band; Using the formula ε”(ω)=2n correct κ(ω) determines the imaginary part of the dielectric constant in the terahertz frequency band; Among them, ε' is the real part of the dielectric constant in the terahertz band, and ε” is the imaginary part of the dielectric constant in the terahertz band.

9. The method for online monitoring of oil-paper insulation aging status of oil-filled equipment according to claim 8 is characterized in that: Determining the real-time dielectric loss factor tangent angle of the insulating oil in the terahertz frequency band according to the dielectric information of the insulating oil in the terahertz frequency band specifically includes: The real-time dielectric loss factor tangent angle tanδ is determined using the formula tanδ=ε'(ω) / ε”(ω).

10. The method for online monitoring of oil-paper insulation aging status of oil-filled equipment according to claim 9, characterized in that: Determining the daily monitoring curve of the oil-paper insulation according to the tangent angle of the dielectric loss factor; and monitoring the aging state of the oil-paper insulation according to the daily monitoring curve of the oil-paper insulation, specifically includes: The average value of the dielectric loss factor tangent angle from 0.3THz to 1.0THz is taken as the characteristic quantity; Determine the daily monitoring curve of oil-paper insulation based on the characteristic quantities.

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