Diagnostic method for transformer

Abstract

To identify the source of abnormal indicator components when characteristic abnormal indicator components other than benzenethiol and carbonyl sulfide are generated within an insulating medium.SOLUTION: Whether an abnormal indicator component generated in an insulating medium due to a discharge abnormality or overheating abnormality of a transformer is included in a pre-established list showing the relationship between materials applied to the transformer and abnormal indicator components generated in the insulating medium due to decomposition of those materials shall be investigated. If the abnormal indicator component is included in the list, the material containing the component shall be selected, and the abnormal site to which the material is applied shall be identified.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to transformers, and more particularly to oil-filled transformers and gas-insulated transformers. [Background technology]

[0002] A transformer is a device that has windings and an iron core as the current-carrying medium, and is filled with sulfur hexafluoride gas (hereinafter referred to as SF6 gas) and insulating oil as the insulating medium. As the number of aging transformers exceeding their expected design lifespan of 30 years is increasing, there is a growing need for technology to diagnose internal abnormalities in transformers as a support tool for determining the timing and priority of maintenance and renewal.

[0003] Internal abnormalities in gas-insulated transformers are broadly classified into overheating abnormalities and discharge abnormalities. When an internal abnormality occurs, characteristic abnormality indicator components are generated in the SF6 gas. Therefore, diagnostic technology has been developed to distinguish between discharge abnormalities and overheating abnormalities by detecting the abnormality indicator components in SF6 gas, and maintenance management guidelines have been established. Diagnosis of internal abnormalities by detecting abnormality indicator components in SF6 gas is widely used as a diagnostic method that can detect abnormal symptoms early without the need to shut down the transformer, and can prevent accidents before they occur.

[0004] However, with conventional gas-insulated transformer diagnosis, when abnormal symptoms are detected, it is possible to estimate the nature of the abnormality, but it is not possible to identify the specific part where the abnormality is occurring. Because it is not possible to estimate the abnormal part from the outside, a detailed investigation of the abnormal part requires shutting down the equipment and conducting an internal inspection.

[0005] Patent Document 1 is characterized in that when a winding insulated with polyphenylene sulfide (PPS) film overheats, the insulating PPS film thermally decomposes, producing characteristic abnormality indicator components, benzenethiol and carbonyl sulfide, in the SF6 gas. By detecting these abnormality indicator components, overheating of the winding can be identified. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-290628 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional diagnostic method for gas-insulated transformers described in Patent Document 1, if characteristic abnormality indicator components other than benzenethiol and carbonyl sulfide are produced in the insulating medium, it is not possible to identify abnormal locations other than the windings.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to identify the source of characteristic abnormality indicator components other than benzenethiol and carbonyl sulfide when they are generated in an insulating medium, and to respond quickly when an abnormality is detected. [Means for solving the problem]

[0009] If signs of abnormal discharge or overheating are detected inside a transformer, a check is made to see if the characteristic abnormality indicator component generated in the insulating medium is included in a list showing the relationship between the materials used in the transformer and the abnormality indicator component generated as the material decomposes. If the abnormality indicator component is included in the list, a material containing the abnormality indicator component is selected. The parts where the material is used are investigated to identify the abnormal part. If the abnormality indicator component is not included in the list, a diagnosis is made that the abnormality has occurred in a part not on the list. [Effects of the Invention]

[0010] According to the present disclosure, when an abnormality indicator component is detected inside a transformer in association with the detection of signs of a discharge abnormality or an overheating abnormality, the material containing the abnormality indicator component can be selected and the abnormal portion identified based on a list showing the relationship between the materials used in the transformer and the abnormality indicator component generated in the insulating medium as the material decomposes. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing the appearance of a gas-insulated transformer according to a first embodiment. [Figure 2] 4 is a diagnostic flow chart for identifying an abnormal portion of the gas-insulated transformer according to the first embodiment. [Figure 3] 10 is a diagnostic flow chart for identifying an abnormal portion of an oil-filled transformer according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 FIG. 1 is a perspective view showing the appearance of a gas-insulated transformer 100 according to a first embodiment. The X-axis, Y-axis, and Z-axis in the figure are three mutually perpendicular axes, with the X-axis and Y-axis being horizontal axes. The Z-axis is a vertical axis. The gas-insulated transformer 100 includes a tank 10, an iron core 11, a high-voltage winding 12, and a low-voltage winding 13. The windings are concentrically arranged around the iron core 11, with the high-voltage winding 12 wound on the outside and the low-voltage winding 13 wound on the inside in the Z-axis direction. Although not shown in the figure, the gas-insulated transformer 100 also includes lead wires connecting the winding ends to a bushing, an electrostatic plate that suppresses potential oscillations and alleviates the electric field at the winding ends when voltage is applied, and a shielded iron core that prevents magnetic interference. While FIG. 1 illustrates an example of a single-phase transformer, a three-phase transformer may also be used.

[0013] The components of the gas-insulated transformer 100, such as the tank 10, iron core 11, high-voltage winding 12, and low-voltage winding 13, are required to have high insulation performance and rust prevention, and to meet these requirements, insulating coatings and paints are applied to each component.

[0014] [Table 1]

[0015] Table 1 is a list showing the relationship between the materials, such as insulating coatings and paints, used for the components of the gas-insulated transformer 100 according to the first embodiment and the abnormality indicator components that each material generates in the SF6 gas due to a discharge abnormality or an overheating abnormality. The list includes the name of the material, the application location of the material, the function of the material, and the abnormality indicator components that accompany the decomposition of the material.

[0016] Assuming that an abnormal discharge or overheating occurred in the lead wires, electrostatic plate, between the winding and the core, on the core surface, inside the tank, and on the shield core of a gas-insulated transformer 100, an experimental investigation was conducted to determine the abnormality indicators generated in the SF6 gas from the materials used in each component. The windings were insulated with polyphenylene sulfide (PPS), the lead wires and electrostatic plate were insulated with polyethylene terephthalate (PET), aromatic polyamide fiber was insulated between the winding and the core, silicone paint and varnish were applied to the core surface as rust prevention, and urethane resin paint was applied to the inside of the tank and the shield core. Each material was subjected to thermal decomposition individually, and the abnormality indicators resulting from thermal decomposition were analyzed. Experimental investigations revealed two distinctive abnormality indicators in each material.

[0017] 2 shows a diagnostic flow for identifying an abnormal portion of the gas-insulated transformer 100 according to the first embodiment. Step 1 is a step for evaluating whether the gas-insulated transformer 100 is in an "abnormal," "caution required," or "normal" state by analyzing SF6 gas, and step 2 is a step for identifying an abnormality in the gas-insulated transformer 100 based on step 1. Both steps are reported in Electrical Cooperative Research, Vol. 54, No. 5 (Part 2). In this disclosure, step 3 is added to a diagnostic flow for identifying an abnormal portion by investigating an abnormality indicator component in the SF6 gas based on the relationship between the materials used in the gas-insulated transformer 100 and the abnormality indicator component associated with the decomposition of each material, as created in Table 1.

[0018] In Figure 2, in step 1, hydrogen fluoride (HF) and fluorine ions (F -) and carbon monoxide (CO), and depending on whether the concentration of each abnormality indicator component exceeds or is below the threshold, the gas-insulated transformer 100 is diagnosed as being in an "abnormal," "caution required," or "normal" state. Step 1 shows the evaluation method described in Electrical Cooperative Research, Vol. 54, No. 5 (Part 2), but other methods may also be used as long as they can identify deviations from the normal state.

[0019] HF and F in SF6 gas - If the analysis of CO and SF6 gas indicates an "abnormal" or "caution required," the process moves to step 2, where the abnormality is identified. In step 2, thionyl fluoride (SOF2), sulfonyl fluoride (SO2F2), and sulfur dioxide (SO2) in the SF6 gas are analyzed, and the concentrations of each abnormality indicator component are compared to diagnose whether the abnormality is an "arc discharge," "partial discharge," or "overheating." Step 2 uses the evaluation method described in Electrical Engineering Research, Vol. 54, No. 5 (Part 2), but other methods can also be used as long as they can identify the abnormality.

[0020] After identifying any abnormalities through the analysis of SOF2, SO2F2, and SO2 in the SF6 gas, the process moves to step 3, where the abnormal location is identified. In step 3, an investigation is conducted to determine whether any of the abnormality indicator components shown in Table 1 have been detected in the SF6 gas at concentrations above the lower detection limit. If any abnormality indicator components are detected, the material containing the abnormality indicator component is identified, and the abnormal location is identified from the location where the material is used. If no abnormality indicator components shown in Table 1 are detected in the SF6 gas, it is diagnosed that a discharge abnormality or overheating abnormality has occurred in a location where a material other than those listed in Table 1 is used. In Table 1, there are two types of characteristic abnormality indicator components generated by each material, and the abnormal location is identified by detecting at least one abnormality indicator component.

[0021] In Table 1, if vinyl benzoate or crotonaldehyde is detected as an abnormality indicator, the abnormal part can be narrowed down to the winding, lead wire, or electrostatic plate. An internal inspection is required to identify the abnormal part. Similarly, if butyl acetate or phthalic acid is detected as an abnormality indicator, the abnormal part can be narrowed down to the inner surface of the tank or the shield iron core. An internal inspection is required to identify the abnormal part.

[0022] The abnormality indicator components described in steps 1 and 2 are analyzed by a gas chromatograph, and the abnormality indicator components described in step 3 are analyzed by a gas chromatograph or a gas chromatograph mass spectrometer.

[0023] In the first embodiment, the abnormal portion can be identified by detecting a characteristic abnormality indicator component in the SF6 gas sampled from the gas-insulated transformer 100, and when an abnormality is detected, a quick response can be taken.

[0024] Embodiment 2 3 shows a diagnostic flow for identifying an abnormal portion of an oil-filled transformer according to the second embodiment. In the first embodiment, the diagnostic flow for identifying an abnormal portion of the gas-insulated transformer 100 has been described, but the same can also be applied to oil-filled transformers that use the materials listed in Table 1. An oil-filled transformer is a transformer that includes windings and an iron core as current-carrying media, and is filled with insulating oil as an insulating medium, and examples of the insulating oil include mineral oil and vegetable oil (referred to as biodegradable electrical insulating oil in JIS C 2390).

[0025] In Figure 3, step 1 is a step for evaluating whether the state corresponds to "normal" or "attention level 1 or higher," and is reported in Electrical Cooperative Research, Vol. 65, No. 1. In embodiment 2, step 2 is added as a diagnostic flow for identifying the abnormal part from an investigation of the abnormality indicator components based on Table 1. Note that "attention level 1" refers to a state that deviates from the normal state and is determined to have some kind of internal change. Step 1 shows the evaluation method described in Electrical Cooperative Research, Vol. 65, No. 1, but other methods may be used as long as they can determine deviations from the normal state.

[0026] In Figure 3, in step 1, hydrogen (H2), methane (CH4), ethane (C2H6), ethylene (C2H4), acetylene (C2H2), and carbon monoxide (CO) in the insulating oil are analyzed, and the result is classified as "normal" or "at least level 1 caution required" depending on whether the concentration of each gas or the total concentration of each gas (TCG) exceeds or is below the threshold.

[0027] If step 1 determines that the level is "Caution Level 1 or higher," the process moves to step 2, in which the abnormal part is identified. In step 2, an investigation is conducted to determine whether any of the abnormality indicator components in Table 1 have been detected in the insulating oil at a concentration above the lower detection limit. As in embodiment 1, if at least one abnormality indicator component is detected, the material containing that abnormality indicator component is identified, and the abnormal part is identified from the location where the material is used. If no abnormality indicator component is detected, it is diagnosed that a discharge abnormality or overheat abnormality has occurred in a location where a material other than the material listed in Table 1 is used.

[0028] As in the first embodiment, if butyl acetate or phthalic acid is detected as an abnormality indicator component, the abnormal part can be narrowed down to the inner surface of the tank or the shield iron core. An internal inspection is required to identify the abnormal part.

[0029] The abnormality indicator components described in steps 1 and 2 are analyzed by a gas chromatograph, and the abnormality indicator components described in step 3 are analyzed by a gas chromatograph or a gas chromatograph mass spectrometer.

[0030] In the second embodiment, in an oil-filled transformer using the materials listed in Table 1, the abnormal part can be identified by detecting characteristic abnormality indicator components in the insulating oil, and if an abnormality is detected, a quick response can be taken. [Explanation of symbols]

[0031] 10 Tank, 11 Iron core, 12 High voltage winding, 13 Low voltage winding, 100 Gas insulated transformer.

Claims

1. A method for diagnosing a transformer, comprising: a first step of determining whether the state of the transformer is normal or not by analyzing an insulating medium collected from the transformer; a second step of investigating, if the transformer is determined to be abnormal in the first step, whether an abnormality indicator component generated in the insulating medium is included in a list created in advance that shows the relationship between materials used in the transformer and the abnormality indicator component generated in the insulating medium due to decomposition of the materials; a third step of identifying the material containing the abnormality indicator component if the abnormality indicator component is included in the list in the second step; and a fourth step of identifying an abnormal portion to which the material identified in the third step is applied.

2. 2. The transformer diagnosis method according to claim 1, wherein when the abnormality indicator component is methyl methacrylate or butyl methacrylate, an abnormal discharge or an abnormal overheat occurs in an iron core coated with a silicone paint.

3. 2. The transformer diagnostic method according to claim 1, wherein when the abnormality indicator component is butylaldehyde or butanoic acid, a discharge abnormality or an overheat abnormality occurs in an iron core coated with varnish.

4. 2. The transformer diagnostic method according to claim 1, wherein when the abnormality indicator component is butyl acetate or phthalic acid, a discharge abnormality or an overheat abnormality occurs on the tank surface or shield core of the transformer coated with urethane resin paint.

5. 2. The transformer diagnosis method according to claim 1, wherein when the abnormality indicator component is diphenyl sulfide, a discharge abnormality or an overheat abnormality occurs in a winding wound with polyphenylene sulfide.

6. 2. The transformer diagnostic method according to claim 1, wherein when the abnormality indicator component is vinyl benzoate, a discharge abnormality or an overheat abnormality occurs in a winding, a lead, or an electrostatic plate wound with polyethylene terephthalate.

7. 2. The transformer diagnostic method according to claim 1, wherein when the abnormality indicator component is benzonitrile, a discharge abnormality or an overheat abnormality occurs in aromatic polyamide fibers disposed between the winding and the iron core.

8. 8. The transformer diagnosis method according to claim 1, wherein the transformer is a gas-insulated transformer, and an insulating medium of the gas-insulated transformer is sulfur hexafluoride gas.

9. 8. The transformer diagnosis method according to claim 1, wherein the transformer is an oil-filled transformer, and an insulating medium of the oil-filled transformer is insulating oil.

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