Diagnosis method of low energy discharge of transformer based on copper coordination species content in oil

Abstract

The present application relates to the technical field of transformer fault diagnosis, and discloses a transformer low-energy discharge diagnosis method based on copper coordination species content in oil, which comprises collecting transformer oil samples and dividing them into multiple parts for enrichment to obtain to-be-tested enrichment substances; photoelectron energy spectrum, ICP-MS and gas chromatography are used to detect the to-be-tested enrichment substances, the relative contents of CuC x , Cu 0 and CuO x and the total copper content and the total alcohol concentration are calculated; the equivalent content of each species is calculated in combination with the storage time, and a low-energy discharge copper species index is constructed; the copper species characteristic type is determined according to the above parameters, and a warning report is generated in combination with the DGA result. The present application eliminates the masking interference, the polarity solvent pollution and the influence of natural oxidation on the original state distribution, separates the discharge-induced state and the thermal aging state copper species, and introduces the Dewar triangle and the gas ratio cross-checking, so that the state missing judgment defects caused by the single dependence on the gas index are made up, and a multi-parameter logic warning mechanism is established.

Description

Technical Field

[0001] This invention relates to the field of transformer fault diagnosis technology, specifically to a method for diagnosing low-energy discharge in transformers based on the content of copper coordination species in oil. Background Technology

[0002] Oil-immersed power transformers are subjected to electrical and thermal stresses during long-term operation, leading to deterioration of the internal insulation materials and the release of characteristic gases and dissolved micro-metals into the insulating oil. Currently, the diagnosis of internal discharge faults in transformers primarily relies on dissolved gas analysis (DGA) techniques, assessing the equipment's operating status by detecting the concentrations and proportions of gases such as acetylene and ethylene. During low-energy discharges, the partial discharge energy causes the insulating oil molecules to break down, resulting in chemical reactions on the exposed copper conductors. Because the gas generation rate is limited during low-energy discharges, and the released free copper substances catalyze the consumption or transformation of characteristic gases, the gas ratios obtained from conventional chromatographic detection are distorted. Gas codes derived from conventional guidelines such as the Dewar's triangle deviate from the low-energy discharge determination region, causing delays and misclassifications in diagnostic mechanisms relying on macroscopic gas generation patterns.

[0003] For condition monitoring of solid components inside transformers, conventional oil-based metal detection methods primarily determine the total copper content in the insulating oil, but cannot differentiate between the valence state and coordination structure of copper. The material shed due to thermal aging inside transformers mainly exists as oxidized copper, while the products of stimulated decomposition in low-energy discharge regions are primarily carbon-coordinated copper and zero-valent metallic copper. Relying solely on total copper content data cannot isolate the evolution of specific species caused by low-energy discharge from metal shedding caused by conventional thermal aging. This means that a single total copper concentration indicator cannot be directly applied to qualitative analysis and condition rating of specific discharge types.

[0004] During the extraction and offline transfer of insulating oil samples, carbon-coordinated copper within the oil sample undergoes an oxidative decay reaction upon contact with infiltrated air, transforming into oxidized copper. Polar products such as methanol and ethanol generated from the degradation of transformer insulation paper alter the local polar solvent environment of the oil, interfering with the physical solubility ratios of different copper species. Corrosive sulfides such as dibenzyl disulfide present in the insulating oil form a coating layer on the surface of microscopic copper materials, masking the signal acquisition by surface detection methods such as photoelectron spectroscopy. The combined interference from the aforementioned transfer environment and coexisting substances causes the final detected species response signals and distribution ratios to deviate from the original internal state of the transformer, affecting the engineering practicality of using microscopic species transformation characteristics to verify internal discharge defects in equipment. Summary of the Invention

[0005] The technical problem solved by this invention is that the existing diagnosis of low-energy discharge faults inside transformers mainly relies on dissolved gas analysis (DGA) technology. However, in the early stage of low-energy discharge or when accompanied by the release of free copper particles, partial discharge consumes or catalyzes the conversion of characteristic gases, which can lead to delays or distortions in DGA diagnosis. At the same time, conventional oil dissolved metal detection can only obtain the total copper content and cannot distinguish between oxidized copper produced by thermal aging and carbon-coordinated copper and metallic copper induced by low-energy discharge. Moreover, the detection process is easily affected by environmental factors such as oil sample oxidation, polar solvent contamination, and sulfide masking, and cannot achieve the assessment and early warning of the low-energy discharge state of transformers.

[0006] To address the above problems, the present invention provides the following technical solution: This invention provides a method for diagnosing low-energy discharge in transformers based on the content of copper coordination species in oil, including: Transformer oil samples were collected and divided into parts A, B and C. Part A was enriched to obtain the enriched substance to be tested. X-ray photoelectron spectroscopy was used to detect and calculate CuC in the enriched sample. x relative content, Cu 0 Relative content and CuO x Relative content; The total copper content in sample B was determined by ICP-MS, and the methanol and ethanol concentrations in sample C were determined to calculate the total alcohol concentration. The storage time and DGA results of the transformer oil sample were obtained, and the component benchmark threshold corresponding to the target copper component was determined. According to the CuC x relative content, the Cu 0 relative content, the CuO x Calculate CuC based on relative content, total copper content, total alcohol concentration, and storage time. x Equivalent content after compensation, CuO x Corrected equivalent content and Cu 0 Equivalent content; Based on the CuC x The equivalent content after compensation, the Cu 0 Equivalent content and the CuO x The low-energy discharge copper species index is calculated based on the corrected equivalent content. According to the CuC x relative content, the Cu 0 relative content, the CuO x Relative content, the CuC x The copper species characteristic type is determined by the compensated equivalent content, the low-energy discharge copper species index, and the component benchmark threshold, and an early warning report is generated by combining the DGA results.

[0007] The innovative principle of this invention lies in: Copper species in transformer oil with different valence and coordination states carry information about their internal physicochemical evolution. (CuC) x Associated insulation low-energy discharge, Cu 0 Related metal release, CuO x This approach relates to thermal aging and oxidation processes. It obtains the total copper content and the proportion of each coordination species through multimodal detection, introducing polar solvent contamination correction and in vitro oxidation reverse correction calculations to eliminate physicochemical matrix interference during the detection process and restore the true distribution of copper species. A multidimensional criterion is constructed by combining relative content, equivalent content, and combination index to achieve diagnosis of specific discharge states and cross-validation with conventional dissolved gas analysis results.

[0008] Furthermore, the steps for collecting transformer oil samples and dividing them into portions A, B, and C include: The collected transformer oil sample was sealed and stored by passing it through high-purity N2, and the particle size grade was determined. The new oil replenishment ratio is obtained by calculating the proportion of the new oil replenishment amount to the current oil level in the transformer. When the particle size level is higher than the preset level or the new oil replenishment ratio is higher than the preset ratio, PTFE microporous filter membrane is used for filtration, and the filtrate is used as the analytical reference oil sample. When the particle size level is not higher than the preset level and the new oil replenishment ratio is not higher than the preset ratio, the transformer oil sample is used as the analysis reference oil sample. The analytical reference oil sample was thoroughly mixed under N2 protection and sealing conditions, and then divided into part A, part B and part C.

[0009] Furthermore, the step of enriching the A portion to obtain the target enrichment includes: After homogenizing the A portion at a constant temperature, n-heptane was added for low-polarity dilution. Add thiol-functionalized adsorbent material to the diluted A portion and then concentrate by shaking. Obtain the total copper estimate. When the total copper estimate is not lower than the total copper estimate trigger threshold, a first enrichment temperature and a first enrichment duration are used. When the total copper estimate is lower than the total copper estimate trigger threshold, a second enrichment temperature and a second enrichment duration are used. The second enrichment temperature is higher than the first enrichment temperature, and the second enrichment duration is longer than the first enrichment duration. The solid-liquid mixture system was separated by centrifugation, and the precipitated solid phase was washed with the n-heptane and dried in an N2 environment to obtain the enriched sample to be tested.

[0010] In a preferred embodiment of the present invention, the thiol-functionalized adsorbent material is a polydopamine thiol silane composite modified silica gel.

[0011] Furthermore, X-ray photoelectron spectroscopy was performed on the enriched sample to calculate CuC. x The steps involving relative content include: The concentration of DBDS in the C portion was determined by gas chromatography, and the Cu-S response in the S 2p spectral region was extracted simultaneously. When the DBDS concentration is detected and the Cu-S response is detected in the S 2p spectral region, CuC is extracted. x Initial response area and Cu-S equivalent response area, the CuC x Subtracting the product of the sulfur masking factor and the Cu-S equivalent response area from the initial response area yields the CuC after removing Cu-S interference. x The response area, and based on the CuC after deducting Cu-S interference. x Response area calculation of CuC x Relative content.

[0012] Furthermore, calculate CuC x The process of compensating for equivalent content includes: The total copper content and the CuC x Calculation of CuC by multiplying relative contents x Initial equivalent content, and the total copper content is compared with the CuO content. x Calculation of CuO by multiplying relative content x Initial equivalent content; When the total alcohol concentration exceeds the alcohol contamination trigger threshold, the total alcohol concentration is multiplied by the polar solvent contamination correction coefficient and then incremented by one to obtain the polar solvent contamination correction factor. The CuC... x Dividing the initial equivalent content by the polar solvent contamination correction factor yields the polar solvent contamination-corrected CuC. x Equivalent content; When the total concentration of alcohols is not higher than the alcohol contamination trigger threshold, the polar solvent contamination corrected CuC x The equivalent content is taken from the CuC x Initial equivalent content.

[0013] Furthermore, calculate CuC x Equivalent content after compensation and CuO x The process of revising the equivalent content includes: The CuC after polar solvent contamination correction x The equivalent content is multiplied by a power of the natural constant, where the power is the product of the natural oxidation decay coefficient and the storage time, to obtain the CuC content. x Equivalent content after compensation; Calculate the CuC xThe equivalent content after compensation and the CuC content after polar solvent contamination correction x The difference in equivalent content yields the value of CuC during storage. x CuO formed by conversion x Increment; When the CuO x The increment is no higher than that of CuO x At the initial equivalent content, the CuO x Initial equivalent content minus the CuO x Incremental acquisition of the CuO x Corrected equivalent content; When the CuO x The increment is higher than that of CuO x When the initial equivalent content is reached, the current data is discarded and a resampling instruction is generated.

[0014] Furthermore, the process of calculating the low-energy discharge copper species index includes: The CuC x The equivalent content after compensation is the same as that of Cu. 0 The sum of the equivalent contents, divided by the CuO content. x The low-energy discharge copper species index is calculated by adding the corrected equivalent content to the preset denominator correction term.

[0015] Furthermore, when determining the characteristic types of copper species, the following are included: When the CuO x The relative content is not lower than the thermal aging determination threshold, wherein the Cu 0 The relative content is not lower than the threshold for determining metallic copper, and the CuC x When the relative content is below the threshold of low copper-carbon coordination species, the output exhibits characteristics of copper species with thermal aging and metal release. When the CuO x The relative content is not lower than the thermal aging determination threshold, and the CuO x The corrected equivalent content is higher than that of CuC. x When the equivalent content is compensated, output the thermal aging-related copper species characteristics. When the CuC x The relative content is not lower than the lower limit of the relative content for slight intermittent low-energy discharge and lower than the lower limit of the relative content for sustained strong low-energy discharge, wherein the CuC x The compensated equivalent content is not lower than the component's reference threshold and is less than twice the component's reference threshold; the low-energy discharge copper species index is not lower than the lower limit of the slightly intermittent low-energy discharge index and is less than the lower limit of the sustained strong low-energy discharge index; and the CuO... x When the relative content is below the exclusion threshold for copper-oxygen coordination species, it is judged as having slight intermittent low-energy discharge characteristics; When the CuC x The relative content is not lower than the lower limit of the relative content of sustained strong low-energy discharge, and the CuC x The compensated equivalent content is not less than twice the component's reference threshold, the low-energy discharge copper species index is not less than the lower limit of the sustained strong low-energy discharge index, and the CuO... x When the relative content is lower than the exclusion threshold of the copper-oxygen coordination species, it is determined to be a continuous strong low-energy discharge characteristic.

[0016] Furthermore, the steps for generating an early warning report based on DGA results include: Extract the acetylene and ethylene concentrations from the current detection and the beginning of the detection cycle to calculate the gas ratio offset rate; When the gas ratio offset rate is not lower than the gas ratio offset rate threshold, the CuC x The equivalent content after compensation is not lower than that of CuC corresponding to the gas distortion warning. x When the equivalent content threshold is met and the low-energy discharge copper species index is not lower than the index threshold, a low-energy discharge gas ratio distortion risk warning is output in the warning report. The current code of the Dewar triangle is obtained based on the DGA result. When the current code of the Dewar triangle leaves the low-energy discharge region, and the copper species determination result is a slight intermittent low-energy discharge characteristic or a continuous strong low-energy discharge characteristic, the DGA code deviation prompt is output in the warning report.

[0017] This invention provides a method for diagnosing low-energy discharge in transformers based on the content of copper coordination species in oil. It has the following beneficial effects: 1. This invention extracts DBDS concentration and S 2p spectral region response to subtract the masking interference of sulfur compounds on the copper surface, and constructs a polar solvent correction factor in combination with the measured total alcohol concentration to remove the extraction error caused by the degradation of the insulating paper. At the same time, it uses storage time to compensate for the natural oxidation decay of the test data, eliminates the influence of morphological transformation during the offline storage process of sampling, and restores the original copper species content and distribution ratio in transformer oil.

[0018] 2. This invention separates CuC from the target enrichment by X-ray photoelectron spectroscopy detection. x Cu 0 and CuO x The relative content was used to construct a low-energy discharge copper species index by comparing different forms of copper species. Based on the set threshold conditions, the carbon-coordinated copper and metallic copper induced by discharge were distinguished from the oxide copper produced by simple thermal aging. The specific characteristic types of slight intermittent low-energy discharge or continuous strong low-energy discharge were output, providing a dimension for evaluating the internal state of transformers based on the transformation of microscopic materials.

[0019] 3. This invention interacts with the microscopic copper species characteristic determination results and the macroscopic conventional DGA detection results. It uses the gas ratio offset rate and the spatial distribution of the current encoding of the Dewar triangle for cross-validation. When the characteristic gas index deviates and the species calculation data reaches the set conditions, it outputs a low-energy discharge gas ratio distortion risk warning. This makes up for the judgment omission caused by the energy consumption gas when relying solely on dissolved gas analysis, and establishes a warning mechanism based on multi-parameter logical mutual verification. Attached Figure Description

[0020] Figure 1 This is a system architecture diagram of the present invention; Figure 2 This is a flowchart of the method of the present invention; Figure 3 This is a flowchart of the oil sample collection and pretreatment process of the present invention; Figure 4 This is a flowchart of the oil sample pretreatment and morphology-preserving enrichment process of the present invention; Figure 5 This is a flowchart of the spectral detection and relative content calculation of copper coordination species according to the present invention; Figure 6 This is a flowchart of the calculation of the equivalent content of copper coordination species and the construction of characteristic indices in this invention; Figure 7 This is a flowchart of the low-energy discharge fault auxiliary diagnosis result output and linkage early warning process of the present invention. Detailed Implementation

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

[0022] See attached document Figure 1 This invention provides a transformer low-energy discharge diagnostic system based on the content of copper coordination species in oil, including an oil sample acquisition and preprocessing module, a multi-modal detection module, a data processing and error compensation module, and a diagnostic judgment output module.

[0023] The oil sample collection and pretreatment module is used to complete oil sample collection, N2 sealing, storage condition control, particle size detection, conditional filtration, isothermal homogenization, low polarity dilution, and speciation-preserving enrichment. After particulate matter treatment, the same batch of oil samples is divided into three portions: A, B, and C. Portion A is used for copper coordination species detection, Portion B is used for total copper content determination, and Portion C is used for methanol, ethanol, and DBDS detection. Portions A, B, and C are filtered and mixed under the same conditions.

[0024] The multimodal detection module includes an X-ray photoelectron spectrometer (XPS), an integrated circuit-scanning mass spectrometer (ICP-MS), and a headspace gas chromatograph (HGC). The XPS acquires signals in the Cu 2p, C 1s, O 1s, and S 2p spectral regions; the ICP-MS determines the total copper content of the oil sample; and the HGC determines the concentrations of methanol, ethanol, and DBDS. Different XPS spectrometers use the same batch of reference samples to standardize binding energy, peak shape parameters, FWHM, and satellite peak intensity ratios.

[0025] The data processing and error compensation module is based on CuC x Cu 0 and CuO x The relative content is calculated based on the response area, and the initial equivalent content of each copper coordination species is calculated based on the total copper content. When the alcohol concentration reaches the pollution correction condition, the content of CuC is... x Equivalent content correction was performed. The CuC content was adjusted based on the storage time from sampling to testing. x Oxidation attenuation and CuO x Incremental compensation is applied, and the low-energy discharge copper species index is calculated. .

[0026] Diagnostic judgment output module read , , , , , , and component reference threshold The copper species characteristics are determined in a fixed order. The diagnostic results are then analyzed in conjunction with DGA data, displayed on the detection terminal, and an electronic early warning report is generated and saved to the equipment status archive.

[0027] See attached document Figure 2 This invention provides a method for diagnosing low-energy discharge in transformers based on the content of copper coordination species in oil, comprising the following steps: S100: Collect transformer oil samples and complete N2 sealing, storage condition control, particulate matter detection, conditional filtration, and batch separation.

[0028] S200 is used to homogenize and dilute the oil sample for copper-coordinated species detection at a constant temperature, add morphology-preserving copper-affinity enrichment material for oscillation enrichment, and obtain the enriched product after centrifugation, washing and drying.

[0029] S300, X-ray photoelectron spectroscopy detection of the target enrichment, extraction of CuC x Cu 0 and CuO x The response area was used to complete the binding energy correction, equipment parameter correction, and Cu-S interference subtraction, and the relative content of copper coordination species was calculated.

[0030] S400, the total copper content in the test samples from the same batch was determined using ICP-MS. .

[0031] S500, according to The initial equivalent content of each copper-coordinated species was calculated based on the relative content of copper-coordinated species, and the CuC content was adjusted according to the alcohol concentration. x The initial equivalent content was corrected for contamination.

[0032] S600, calculate CuC based on the storage time from sampling to testing. x Equivalent content after compensation and CuO x Corrected equivalent content.

[0033] S700, according to , and calculate And determine based on the target copper component .

[0034] S800, based on relative content, compensated equivalent content, and Determine the characteristic types of copper species and generate early warning reports based on DGA results.

[0035] See attached document Figure 3 The method S100 provided in this embodiment of the invention includes the following sub-steps: S110, Collect oil samples from the transformer to be tested and perform N2 replacement. After the initial oil sample is discharged through the sampling valve at the bottom of the transformer, collect a predetermined volume of oil sample from the transformer to be tested. The oil sample is placed in a brown glass bottle with a PTFE-lined cap. After collection, high-purity N2 is introduced into the top space of the container. The aeration time is set according to the oil sample volume and the top space of the container. After aeration, tighten the cap.

[0036] N2 displacement reduces the oil sample's contact with air, lowering CuC. x The rate of ligand exchange and oxidative transformation that occurs during storage.

[0037] S120, Control the oil sample storage conditions. The sealed container is placed in refrigeration equipment, and the storage temperature is controlled within a preset temperature range. Record the time the oil sample is removed from the transformer body, and control the storage time from sampling to X-ray photoelectron spectroscopy detection within a preset time limit.

[0038] If any of the following conditions are met: the storage temperature is higher than the preset upper limit or the storage time is longer than the preset time limit, the current oil sample will not enter the testing process, and a new oil sample will be collected.

[0039] S130, Test oil sample particle size and verify maintenance records. Take the oil sample for testing from the sampling container and determine the particle size grade using a laser particle counter. Read the transformer's recent degassing and filtration, new oil replenishment, and oil quantity change records, and calculate the proportion of new oil replenishment to the transformer's current oil quantity.

[0040] The operation of using a laser particle counter to determine the particle size of oil samples by optical obscuration method can be completed by those skilled in the art according to the instrument operating procedures. The particle counting and grade conversion methods are well-known technologies in the field and will not be described in detail here.

[0041] S140, determine the oil sample treatment method based on particle size and the new oil replenishment ratio. If either the particle size grade is higher than the preset grade or the new oil replenishment ratio is higher than the preset ratio, use a PTFE microporous membrane for dead-end filtration.

[0042] During filtration, a set vacuum negative pressure is applied downstream of the filter membrane, causing the oil sample to pass vertically through the membrane. Suspended insulating paper fibers and large-diameter carbon-based debris are retained by the filter membrane, and the filtrate serves as the analytical reference oil sample.

[0043] When the particle size grade is not higher than the preset grade and the new oil replenishment ratio is not higher than the preset ratio, the crude oil sample is used as the analytical reference oil sample.

[0044] Filtration serves as a pretreatment checkpoint for particulate matter and interference from the mixing of new and old oil. Oil samples that have not undergone S130 testing and S140 treatment will not proceed to S200. If any one of the following is missing from the test record: particulate matter data, new oil replenishment data, or filtration information, the current oil sample data will be invalidated, and a resampling instruction will be generated.

[0045] S150, the analytical reference oil sample is divided into batches. The analytical reference oil sample is thoroughly mixed under N2 protection and sealing conditions, and divided into parts A, B and C.

[0046] Part A was used for morphology-preserving enrichment and X-ray photoelectron spectroscopy detection; Part B was used for total copper content determination by ICP-MS; and Part C was used for headspace gas chromatography detection of methanol, ethanol, and DBDS.

[0047] Samples A, B, and C used the same sample number, filtration conditions, and mixing batch. The calculation of the equivalent content of copper coordination species used the relative content obtained from sample A and sample B. .

[0048] See attached document Figure 4 The method S200 provided in this embodiment of the invention includes the following sub-steps: S210, Homogenize oil sample A at a constant temperature. Place oil sample A in a constant temperature device and maintain it at a set temperature for a set time to ensure that the copper coordination species in the oil sample are uniformly distributed.

[0049] S220, add a low-polarity diluent to the homogenized oil sample A. The low-polarity diluent is n-heptane, which is mixed with the oil sample at a set volume ratio.

[0050] n-Heptane is used to reduce the viscosity of transformer oil, improve the mass transfer efficiency between the oil phase and the enriched material, and maintain a low-polarity liquid phase environment. This step does not use methanol, ethanol, acetonitrile, strong acids, strong bases, strong complexing agents, or high-temperature digestion conditions.

[0051] S230 involves adding a thiol-functionalized adsorbent material for oscillation enrichment. Preferably, the thiol-functionalized adsorbent material is a polydopamine-thiol silane composite modified silica gel. The enrichment material is added to the original oil sample at a set mass-to-volume ratio, and the oscillation frequency is set according to the oil sample volume and the amount of enrichment material used.

[0052] The estimated total copper value was obtained based on historical testing records and ICP-MS predictive testing results. The estimated total copper trigger threshold is denoted as... .

[0053] When the total copper estimate Not lower than the estimated total copper trigger threshold At that time, conventional enrichment temperature was used. and the usual enrichment duration .

[0054] When the total copper estimate Below the estimated total copper trigger threshold At that time, the enrichment temperature was enhanced. and enhance enrichment duration Enhance enrichment temperature Higher than conventional enrichment temperature Enhance enrichment duration Longer than the usual enrichment time .

[0055] Each testing batch includes enrichment material blanks and CuC... x Matrix reference sample, metallic copper reference sample and CuO x Reference sample. CuO x The matrix reference sample was prepared using a transformer oil system containing insulating paper and copper sheets, after treatment with set electrical stress, temperature, and duration. The metallic copper reference sample was used to determine the Cu content. 0 Response range, CuO x Reference samples are used to determine the response range of copper-oxygen coordinated species.

[0056] Reference samples are used to standardize the binding energy benchmark, peak shape parameters, FWHM, and satellite peak intensity ratio of different X-ray photoelectron spectrometers.

[0057] S240, centrifuge to separate and wash the enriched solid phase. After enrichment, place the solid-liquid mixture in a centrifuge and centrifuge at the set speed and time to collect the precipitated solid phase.

[0058] The solid phase was washed with n-heptane, with the amount of detergent used per wash and the number of washes determined based on the mass of the enriched material. After each wash, the solid phase was centrifuged and the supernatant was discarded. The washed solid phase was dried in an N2 environment, placed in a sealed sample box, and transferred to the X-ray photoelectron spectroscopy (XPS) sample chamber.

[0059] See attached document Figure 5 The method S300 provided in this embodiment of the invention includes the following sub-steps: S310: Set the X-ray photoelectron spectroscopy detection parameters and correct the binding energy. Send the enriched sample to be tested into the X-ray photoelectron spectrometer and collect the Cu 2p, C 1s, O 1s, and S 2p spectral regions.

[0060] The binding energy is corrected using the C 1s main peak as the reference. Cu 2p 3 / 2 When fitting spectral peaks, the intensity ratios of FWHM and satellite peaks are set according to the reference samples of the same batch.

[0061] Different X-ray photoelectron spectrometers were cross-calibrated using the same batch of reference samples to establish equipment-level transfer parameters and unify the binding energy reference, peak shape parameters, FWHM, and satellite peak intensity ratio.

[0062] S320, fitted spectral peaks and extracted the response area of ​​copper-coordinated species.

[0063] CuC x Identification is based on the copper-carbon interaction response. For quantification, the area components corresponding to the interaction with carbon-based ligands in the copper-related spectral peaks are extracted. The C 1s spectral region is used to confirm the copper-carbon coordination relationship. The same peak decomposition method and area integration rule are used for the same detection batch.

[0064] Cu 0 The copper is identified based on its metallic state, low-valence copper, and metalloid copper responses, and the corresponding copper-related spectral peak area components are extracted.

[0065] CuO x Identification was performed based on the copper-oxygen interaction response, and the peak area components of copper-oxygen bonding, copper hydroxyl, copper carbonyl, copper carboxyl, and the coordination between copper and the oxide products of insulating paper were extracted.

[0066] Record CuC x Initial response area Cu 0 Response area and CuO x Response area .

[0067] Using the rapid spectral screening mode for on-site sampling, Cu 2p was extracted. 3 / 2 Main peak intensity and characteristic satellite peak intensity Calculate the rapid screening ratio using the following formula: ; In the formula, Indicates the rapid screening ratio; Indicates Cu 2p 3 / 2 Main peak intensity; Indicates the intensity of characteristic satellite peaks.

[0068] The rapid screening threshold is denoted as When the rapid screening ratio Higher than the rapid screening threshold At that time, the initial screening results of low-energy discharge tendency are output, and the process proceeds to complete spectrum peak fitting and subsequent calculations.

[0069] Rapid screening results are used for preliminary assessment after on-site sampling and do not replace [other methods of assessment]. , and The combined criteria.

[0070] S330, verifying Cu-S corrosion product interference and reconstructing CuC x Response area. The concentration of DBDS in oil sample C was determined by gas chromatography, and the Cu-S response in the S 2p spectral region was detected by X-ray photoelectron spectroscopy.

[0071] When DBDS is detected by gas chromatography and Cu-S response is detected in the S 2p region, the Cu-S overlap area is subtracted according to the following formula: ; In the formula, This indicates CuC after removing Cu-S interference. x Response area; Indicates CuC x Initial response area; Indicates the sulfur masking factor; This represents the Cu-S equivalent response area calculated based on the S 2p spectral region. The standard reference material Cu2S was used for calibration under the same equipment parameters and fitting conditions.

[0072] When DBDS is not detected by gas chromatography and Cu-S response is not detected in the S 2p region, the CuC after subtracting interference is... x Response area Take CuC x Initial response area .

[0073] S340, calculate the relative abundance of copper coordination species. The spectrum contains only CuC. x Cu 0 and CuO x When, calculate according to the following formula: ; ; ; In the formula, Indicates CuC x Relative content; Indicates Cu 0 Relative content; Indicates CuO x Relative content; Indicates CuC x Response area; Indicates Cu 0 Response area; Indicates CuC x Response area.

[0074] When there are unassigned copper states in the spectrum, the following formula is used for calculation: ; ; ; The sum of the response areas of all copper-related states is calculated using the following formula: ; In the formula, This represents the sum of the response areas for all copper-related states; This represents the response area of ​​the unassigned copper state.

[0075] See attached document Figure 6 The method S400 to S700 provided in this embodiment of the invention includes total copper content determination, initial equivalent content calculation, polar solvent contamination correction, static oxidation attenuation compensation, and... Build.

[0076] S410, determination of total copper content in the reference oil sample. After digestion, sample B was analyzed by ICP-MS to determine the copper content. .

[0077] The same filtration and mixing batches were used as for oil sample A. The total copper content of the filtered oil sample A was not used in the equivalent content calculation.

[0078] For the oil sample digestion, internal standard correction, and copper quantification operations of ICP-MS, those skilled in the art can complete them according to the instrument's testing specifications. The digestion and element quantification methods are well-known techniques in this field and will not be elaborated here.

[0079] S510, calculate the initial equivalent content of copper-coordinated species according to the following formula: ; ; ; In the formula, Indicates CuC x Initial equivalent content; Indicates Cu 0 Equivalent content; Indicates CuO x Initial equivalent content; This indicates the total copper content of the analytical reference oil sample.

[0080] S520, polar solvent contamination correction was performed. The methanol and ethanol concentrations of sample C were determined by headspace gas chromatography, and the total alcohol concentration was calculated using the following formula: ; In the formula, This indicates the total concentration of alcohols in the oil sample; This indicates the methanol concentration in the oil sample; This indicates the concentration of ethanol in the oil sample.

[0081] The alcohol pollution trigger threshold is denoted as The polar solvent contamination correction factor is denoted as .

[0082] When the total concentration of alcohols Above the alcohol pollution trigger threshold When the polar solvent contamination correction factor is calculated, it is as follows: ; Correct CuC according to the following formula x Equivalent content: ; In the formula, Indicates the polar solvent contamination correction factor; Indicates the polar solvent contamination correction factor; This indicates CuC after polar solvent contamination correction. x Equivalent content.

[0083] When the total concentration of alcohols Not exceeding the alcohol contamination trigger threshold At that time, polar solvent contamination correction factor Take 1, CuC after polar solvent contamination correction. x Equivalent content Take CuC x Initial equivalent content .

[0084] S530, perform static oxidation attenuation compensation. Record the storage time from sampling to X-ray photoelectron spectroscopy detection. The natural oxidation attenuation coefficient is denoted as... .

[0085] CuC x The equivalent content after compensation is calculated according to the following formula: ; In the formula, Indicates CuC after static oxidation attenuation compensation x Equivalent content; This indicates CuC after polar solvent contamination correction. x Equivalent content; Indicates the natural oxidation decay coefficient; Indicates the storage time from sampling to testing; Represents the natural constant.

[0086] During storage, CuC x CuO formed by conversion x The increment is calculated according to the following formula: ; CuO formed during storage x Increment Not higher than CuO x Initial equivalent content When calculating CuO, use the following formula. x Corrected equivalent content: ; CuO formed during storage x Increment Higher than CuO x Initial equivalent content If the current oil sample is not included in the diagnostic calculation, the current data is discarded, and a resampling instruction is generated.

[0087] S710, construction And determine the components . Calculate according to the following formula: ; In the formula, This indicates the low-energy discharge copper species index after static oxidation compensation. This represents the denominator correction term.

[0088] The target components were determined based on the transformer structure register and existing partial discharge location records. Corresponding parameters were assigned to different copper components. .

[0089] The lower limit of the relative content of slight intermittent low-energy discharge is denoted as The lower limit of the relative content of sustained low-energy discharge is denoted as The lower limit of the index for slight intermittent low-energy discharge is denoted as The lower limit of the sustained low-energy discharge index is denoted as The exclusion threshold for copper-oxygen coordinated species is denoted as .

[0090] when Not less than And lower than , Not less than And below 2 , Not less than And lower than ,and Below At that time, it was determined to be a slight intermittent low-energy discharge characteristic.

[0091] when Not less than , Not less than 2 , Not less than ,and Below At that time, it was determined to be a continuous strong low-energy discharge characteristic.

[0092] See attached document Figure 7 The method S800 provided in this embodiment of the invention includes data validity verification, copper species status determination, DGA linkage verification, and report output.

[0093] S810, verify the test data and determine the copper species characteristics. Verification includes storage temperature, storage duration, particle size analysis records, new oil replenishment records, filtration records, X-ray photoelectron spectroscopy fitting parameters, and ICP-MS test results. Cu-S subtraction results and static oxidation compensation conditions.

[0094] If any verification condition is not met, the current data will not be entered into the status determination. The detection terminal records the unmet verification item, invalidates the current data, and generates a resampling and testing instruction.

[0095] After verification, status matching is performed in a fixed order. Once a previous condition is met, subsequent condition matching will not be executed.

[0096] The threshold for judging thermal aging is denoted as The threshold for determining metallic copper is denoted as The threshold for low copper carbon coordination species is denoted as .

[0097] when Not less than , Not less than ,and Below At that time, the output thermal aging is accompanied by the release of copper species characteristics.

[0098] when Not less than ,and Higher than At that time, the characteristics of copper species related to thermal aging were output.

[0099] when Not less than , Below ,and Below At that time, the output exhibits high-energy electrical stress-related metal release characteristics.

[0100] The lower limit of the low-energy discharge range with oxidation interference is denoted as The upper limit of the interval is denoted as .

[0101] when Not less than , Not less than ,and Not less than And lower than At that time, the output exhibits low-energy discharge characteristics accompanied by oxidation interference.

[0102] The characteristics of sustained strong low-energy discharge and slight intermittent low-energy discharge are determined according to the classification conditions in S710.

[0103] The lower limit of the relative abundance of weak low-energy discharge is denoted as The lower limit of equivalent content is denoted as The upper limit of equivalent content is denoted as .

[0104] when Not less than And lower than , Not less than And lower than , Higher than ,and Below At that time, it outputs weak low-energy discharge copper species characteristics and continuous sampling prompts.

[0105] when Not less than ,and Below At that time, a low content of copper-carbon species is output as a warning.

[0106] when Below ,and Not less than When this occurs, an abnormal copper-carbon species content warning will be displayed.

[0107] If none of the above criteria are met, the output will not detect the characteristics of low-energy discharge copper species.

[0108] S820, perform DGA ratio offset verification. Extract the acetylene and ethylene concentrations from the oil samples at the beginning of the testing cycle and the current test, and calculate the acetylene to ethylene concentration ratio at the beginning of the testing cycle using the following formula: ; Calculate the current acetylene to ethylene concentration ratio using the following formula: ; The gas ratio offset rate is calculated using the following formula: ; In the formula, This indicates the acetylene concentration in the oil sample at the beginning of the testing cycle; This indicates the ethylene concentration in the oil sample at the beginning of the testing cycle; This indicates the acetylene concentration in the currently tested oil sample; This indicates the ethylene concentration in the currently tested oil sample; This indicates the acetylene to ethylene concentration ratio at the beginning of the detection period. This indicates the current measured concentration ratio of acetylene to ethylene. This indicates the gas ratio offset rate.

[0109] The gas ratio offset rate threshold is denoted as CuC gas distortion warning x The equivalent content threshold is denoted as The exponential threshold is denoted as .

[0110] When the gas ratio offset rate Not lower than the threshold CuC x Equivalent content after compensation Not lower than the threshold ,and Not lower than the threshold At that time, a warning is issued regarding the risk of distortion in the low-energy discharge gas ratio.

[0111] The Dewar triangle uses the normalized volume fractions of CH4, C2H4, and C2H2 to determine the coding region. If the current code deviates from the low-energy discharge region, and the copper species determination result is either a slight intermittent low-energy discharge characteristic or a persistent strong low-energy discharge characteristic, a DGA code deviation warning is output.

[0112] The gas normalization and coding region determination of the Dewar triangle can be completed by those skilled in the art based on the rules for dissolved gas analysis in transformer oil. The coding calculation method is a well-known technology in this field and will not be elaborated here.

[0113] The S830 generates a standardized early warning report. The detection terminal writes the copper species determination result, DGA linkage verification result, and data validity information into an electronic report and saves it to the device status file.

[0114] The report includes a comprehensive diagnostic conclusion recording the copper species characteristics and grading results; and gas deviation information records. , , and changes in the Dewar triangle coding; metal evidence information records. , , , , , , , , and target components.

[0115] When the warning conditions are met and the copper species parameters meet the low-energy discharge criteria, the DGA ratio shift is reported and the copper species detection results are used as an auxiliary basis for judging the low-energy discharge state.

[0116] When the Dewar triangle code leaves the low-energy discharge region and the copper species parameters meet the low-energy discharge criteria, the report does not exclude the low-energy discharge state based on a single DGA code, and provides a recommendation to review the results by combining copper species parameters, DGA change trends, and partial discharge location results.

[0117] When the discharge is determined to be a persistent, high-energy discharge, the report recommends shortening the retesting cycle and conducting ultrasonic and ultra-high frequency partial discharge localization.

[0118] When the discharge is determined to be characterized by slight intermittent low-energy discharge, the report provides recommendations for retesting copper coordination species parameters and DGA data, and analyzing the changing trends.

[0119] When the species is identified as having weak, low-energy discharge characteristics of copper, the report recommends continuous sampling and joint analysis of DGA changes.

[0120] When the classification parameters are inconsistent, the report lists the parameters that have not reached the corresponding level and their values, and does not determine the fault level based on a single parameter.

[0121] Specific application example 1: This embodiment illustrates the process of identifying persistent, high-energy discharge characteristics in oil samples treated with controllable electrical stress.

[0122] Take 50 mL of new transformer oil and add 0.5 g of dried insulating paper. Construct an electrical stress treatment circuit using copper foil electrodes. Control the oil temperature at 350 K, apply 5 kV electrical stress, and treat for 30 hours.

[0123] After processing, take 30 mL of oil sample, put it into a brown glass bottle, and introduce N2 into the top space of the container for 60 seconds, then seal it.

[0124] The oil sample was homogenized at 40℃ for 15 min, and then 60 mL of n-heptane was added. 600 mg of polydopamine mercaptosilane-modified silica gel was added to the diluted oil sample, and the mixture was shaken and enriched at 40℃ for 30 min.

[0125] After enrichment, the enriched material was collected by centrifugation at 5000 rpm for 10 min. The enriched material was washed twice with 6 mL of n-heptane each time. The washed enriched material was dried in an N2 environment and then analyzed by X-ray photoelectron spectroscopy.

[0126] It was detected that =36.4%, =39.8%, =7.6%.

[0127] The total copper content of the oil sample, as determined by ICP-MS, was: =0.082 mg / kg; Based on the formula for calculating the equivalent content of copper-coordinated species, we obtain: =0.082×36.4÷100=0.0298mg / kg; According to Cu 0 The equivalent content is calculated using the following formula: =0.082×39.8÷100=0.0326mg / kg; According to CuO x The equivalent content is calculated using the following formula: =0.082×7.6÷100=0.0062mg / kg; This embodiment did not trigger alcohol contamination correction, and the sampling and storage conditions met the requirements for direct detection. Therefore: =0.0298mg / kg; =0.0062mg / kg Take the denominator correction term: =0.005mg / kg The low-energy discharge copper species index is calculated using the following formula, based on unrounded detection data: =5.56; The reference threshold for the component corresponding to the copper foil winding is: =0.005mg / kg In this embodiment, No less than 30%, No less than 2 times , Not lower than 4.0 Less than 15%.

[0128] The detection terminal outputs a sustained, strong, low-energy discharge characteristic. This embodiment demonstrates that CuC x Relative content, CuC x Equivalent content and They can jointly characterize the features of low-energy discharge copper species formed under continuous electrical stress.

[0129] Specific application example 2: This embodiment illustrates the process by which the present invention distinguishes between oil samples that have undergone simple thermal aging and oil samples that have undergone high-energy electrical stress treatment.

[0130] When preparing a simple thermally aged oil sample, take 50 mL of new transformer oil, add 0.5 g of dry insulating paper, and treat it at 450 K for 30 h without applying electrical stress. Take 30 mL of the treated oil sample and perform copper coordination species detection and total copper content determination according to the pretreatment and detection methods in Example 1 of the specific application.

[0131] It was detected that =0.058mg / kg, =3.8%, =10.6%, =42.5%.

[0132] The equivalent contents of each copper-coordinating species are as follows: =0.0022 mg / kg; =0.0061 mg / kg; =0.0247 mg / kg; The denominator correction term is taken as follows: =0.005mg / kg; The low-energy discharge copper species index was calculated as follows: =0.28; In this oil sample, No less than 30%, Higher than , Less than 5%.

[0133] The detection terminal outputs thermal aging-related copper species characteristics, but does not output low-energy discharge copper species characteristics.

[0134] When preparing the high-energy electrical stress treated oil sample, take 50 mL of new transformer oil, add 0.5 g of dry insulating paper, and treat it under electrical stress conditions higher than those for low-energy discharge treatment. Take 30 mL of the treated oil sample and perform copper coordination species detection and total copper content determination according to the pretreatment and detection methods in Example 1 of the specific application.

[0135] The following was detected: =0.091mg / kg; =48.6%; =4.5%; =6.8%; The equivalent contents of each copper-coordinating species are as follows: =0.0442 mg / kg; =0.0041 mg / kg; =0.0062 mg / kg; The calculation yielded: =4.32; The oil sample It is in a relatively high range, but No less than 30%, Less than 5%.

[0136] The detection terminal outputs high-energy electrical stress-related metal release characteristics, but does not output low-energy discharge copper species characteristics.

[0137] In this embodiment, the oil sample was simply heated and aged using CuC. x The main characteristic is the increased proportion of Cu in the high-energy electrical stress treated oil samples. 0 The main characteristic is an increased proportion. Combined use. , , , and This avoids making state judgments based solely on total copper content and a single index.

[0138] Specific application example 3: This embodiment illustrates the auxiliary verification process of copper coordination species detection results for DGA diagnostic conclusions when the dissolved gas ratio in oil shifts.

[0139] The oil samples were continuously tested using controlled electrical stress treatment, and the acetylene and ethylene concentrations were recorded during the testing period.

[0140] The test results showed that No less than 50%.

[0141] The oil sample corresponding to the current testing cycle was subjected to copper coordination species detection and total copper content determination, and the results were as follows: =0.078mg / kg; =32.8%; =35.6%; =9.1%; CuC x The equivalent content calculation results are as follows: =0.078×32.8÷100=0.0256mg / kg; Cu 0 The equivalent content calculation results are as follows: =0.078×35.6÷100=0.0278mg / kg; CuO x The equivalent content calculation results are as follows: =0.078×9.1÷100=0.0071mg / kg; The denominator correction term is taken as follows: =0.005mg / kg; The low-energy discharge copper species index was calculated as follows: =4.41; In the current oil sample, No less than 50%, Not less than 0.005 mg / kg, Not lower than 2.0 No less than 30%, Less than 15%.

[0142] The detection terminal outputs a warning of the risk of distortion in the low-energy discharge gas ratio, while retaining the characteristics of copper species with persistent strong low-energy discharge.

[0143] When the Dewar triangle code leaves the low-energy discharge region, the electronic report records the DGA code offset state, without relying on a single DGA code to exclude the low-energy discharge state. The report records this synchronously. , , , , and And suggestions are given for conducting ultrasonic and ultra-high frequency partial discharge localization.

[0144] This embodiment shows that when the C2H2 / C2H4 ratio shifts, the content of copper coordination species and the low-energy discharge copper species index can assist in verifying the DGA results and reduce the impact of gas ratio changes on the judgment of low-energy discharge.

Claims

1. A method for diagnosing low-energy discharge in transformers based on the content of copper coordination species in oil, characterized in that, include: Transformer oil samples were collected and divided into parts A, B and C. Part A was enriched to obtain the enriched substance to be tested. X-ray photoelectron spectroscopy was used to detect and calculate CuC in the enriched sample. x relative content, Cu 0 Relative content and CuO x Relative content; The total copper content in sample B was determined by ICP-MS, and the methanol and ethanol concentrations in sample C were determined to calculate the total alcohol concentration. The storage time and DGA results of the transformer oil sample were obtained, and the component benchmark threshold corresponding to the target copper component was determined. According to the CuC x relative content, the Cu 0 relative content, the CuO x Calculate CuC based on relative content, total copper content, total alcohol concentration, and storage time. x Equivalent content after compensation, CuO x Corrected equivalent content and Cu 0 Equivalent content; Based on the CuC x The equivalent content after compensation, the Cu 0 Equivalent content and the CuO x The low-energy discharge copper species index is calculated based on the corrected equivalent content. According to the CuC x relative content, the Cu 0 relative content, the CuO x Relative content, the CuC x The copper species characteristic type is determined by the compensated equivalent content, the low-energy discharge copper species index, and the component benchmark threshold, and an early warning report is generated by combining the DGA results.

2. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 1, characterized in that, The steps for collecting transformer oil samples into portions A, B, and C include: The collected transformer oil sample was sealed and stored by passing it through high-purity N2, and the particle size grade was determined. The new oil replenishment ratio is obtained by calculating the proportion of the new oil replenishment amount to the current oil level in the transformer. When the particle size level is higher than the preset level or the new oil replenishment ratio is higher than the preset ratio, PTFE microporous filter membrane is used for filtration, and the filtrate is used as the analytical reference oil sample. When the particle size level is not higher than the preset level and the new oil replenishment ratio is not higher than the preset ratio, the transformer oil sample is used as the analysis reference oil sample. The analytical reference oil sample was thoroughly mixed under N2 protection and sealing conditions, and then divided into part A, part B and part C.

3. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 1, characterized in that, The steps for enriching sample A to obtain the target concentrate include: After homogenizing the A portion at a constant temperature, n-heptane was added for low-polarity dilution. Add thiol-functionalized adsorbent material to the diluted A portion and then concentrate by shaking. Obtain the total copper estimate. When the total copper estimate is not lower than the total copper estimate trigger threshold, a first enrichment temperature and a first enrichment duration are used. When the total copper estimate is lower than the total copper estimate trigger threshold, a second enrichment temperature and a second enrichment duration are used. The second enrichment temperature is higher than the first enrichment temperature, and the second enrichment duration is longer than the first enrichment duration. The solid-liquid mixture system was separated by centrifugation, and the precipitated solid phase was washed with the n-heptane and dried in an N2 environment to obtain the enriched sample to be tested.

4. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 3, characterized in that, The thiol-functionalized adsorbent material is a polydopamine thiol silane composite modified silica gel.

5. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 1, characterized in that, X-ray photoelectron spectroscopy was used to detect and calculate CuC in the enriched sample. x The steps involving relative content include: The concentration of DBDS in the C portion was determined by gas chromatography, and the Cu-S response in the S 2p spectral region was extracted simultaneously. When the DBDS concentration is detected and the Cu-S response is detected in the S 2p spectral region, CuC is extracted. x Initial response area and Cu-S equivalent response area, the CuC x Subtracting the product of the sulfur masking factor and the Cu-S equivalent response area from the initial response area yields the CuC after removing Cu-S interference. x The response area, and based on the CuC after deducting Cu-S interference. x Response area calculation of CuC x Relative content.

6. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 1, characterized in that, Calculate CuC x The process of compensating for equivalent content includes: The total copper content and the CuC x Calculation of CuC by multiplying relative contents x Initial equivalent content, and the total copper content is compared with the CuO content. x Calculation of CuO by multiplying relative content x Initial equivalent content; When the total alcohol concentration exceeds the alcohol contamination trigger threshold, the total alcohol concentration is multiplied by the polar solvent contamination correction coefficient and then incremented by one to obtain the polar solvent contamination correction factor. The CuC... x The initial equivalent content is divided by the polar solvent contamination correction factor to obtain the polar solvent contamination corrected CuCx equivalent content; When the total concentration of alcohols is not higher than the alcohol contamination trigger threshold, the polar solvent contamination corrected CuC x The equivalent content is taken from the CuC x Initial equivalent content.

7. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 6, characterized in that, Calculate CuC x Equivalent content after compensation and CuO x The process of revising the equivalent content includes: The CuC after polar solvent contamination correction x The equivalent content is multiplied by a power of the natural constant, where the power is the product of the natural oxidation decay coefficient and the storage time, to obtain the CuC content. x Equivalent content after compensation; Calculate the CuC x The equivalent content after compensation and the CuC content after polar solvent contamination correction x The difference in equivalent content yields the value of CuC during storage. x CuO formed by conversion x Increment; When the CuO x The increment is no higher than that of CuO x At the initial equivalent content, the CuO x Initial equivalent content minus the CuO x Incremental acquisition of the CuO x Corrected equivalent content; When the CuO x The increment is higher than that of CuO x When the initial equivalent content is reached, the current data is discarded and a resampling instruction is generated.

8. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 1, characterized in that, The process of calculating the low-energy discharge copper species index includes: The CuC x The equivalent content after compensation is the same as that of Cu. 0 The sum of the equivalent contents, divided by the CuO content. x The low-energy discharge copper species index is calculated by adding the corrected equivalent content to the preset denominator correction term.

9. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 1, characterized in that, When determining the characteristic type of copper species, the following are included: When the CuO x The relative content is not lower than the thermal aging determination threshold, wherein the Cu 0 The relative content is not lower than the threshold for determining metallic copper, and the CuC x When the relative content is below the threshold of low copper-carbon coordination species, the output exhibits characteristics of copper species with thermal aging and metal release. When the CuO x The relative content is not lower than the thermal aging determination threshold, and the CuO x The corrected equivalent content is higher than that of CuC. x When the equivalent content is compensated, output the thermal aging-related copper species characteristics. When the CuC x The relative content is not lower than the lower limit of the relative content for slight intermittent low-energy discharge and lower than the lower limit of the relative content for sustained strong low-energy discharge, wherein the CuC x When the compensated equivalent content is not lower than the component's reference threshold and is less than twice the component's reference threshold, the low-energy discharge copper species index is not lower than the lower limit of the slight intermittent low-energy discharge index and is less than the lower limit of the sustained strong low-energy discharge index, and the relative CuOx content is lower than the copper-oxygen coordination species exclusion threshold, it is determined to be a slight intermittent low-energy discharge characteristic. When the CuC x The relative content is not lower than the lower limit of the relative content of sustained strong low-energy discharge, and the CuC x The compensated equivalent content is not less than twice the component's reference threshold, the low-energy discharge copper species index is not less than the lower limit of the sustained strong low-energy discharge index, and the CuO... x When the relative content is lower than the exclusion threshold of the copper-oxygen coordination species, it is determined to be a continuous strong low-energy discharge characteristic.

10. The transformer low-energy discharge diagnosis method based on the content of copper coordination species in oil according to claim 1, characterized in that, The steps for generating an early warning report based on DGA results include: Extract the acetylene and ethylene concentrations from the current detection and the beginning of the detection cycle to calculate the gas ratio offset rate; When the gas ratio offset rate is not lower than the gas ratio offset rate threshold, the CuC x The equivalent content after compensation is not lower than that of CuC corresponding to the gas distortion warning. x When the equivalent content threshold is met and the low-energy discharge copper species index is not lower than the index threshold, a low-energy discharge gas ratio distortion risk warning is output in the warning report. The current code of the Dewar triangle is obtained based on the DGA result. When the current code of the Dewar triangle leaves the low-energy discharge region, and the copper species determination result is a slight intermittent low-energy discharge characteristic or a continuous strong low-energy discharge characteristic, the DGA code deviation prompt is output in the warning report.

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