JP2012204635A - Oil feeding device and insulating oil evaluation method for evaluating insulating oil in oil feeding pipe of oil feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil feeding device which can detect an insulating oil that was fed at the last time and remains in an oil feeding path, and can surely prevent the previous oil from being mixed in the oil feeding path.SOLUTION: Insulating oil evaluation means 2 of an oil feeding device comprises: feature point determination means 23 for comparing the infrared absorption spectrum of the previous oil and the current oil acquired from an insulating oil database 21 by spectrum acquisition means 22, and determining a feature point which becomes the feature among the differences therebetween; and residue detection means 24 for referring to the feature point for the infrared absorption spectrum of the insulating oil in a storage tank 14 measured by an infrared spectrometer 25, and detecting the residue of the previous oil.

Description

  The present invention is directed to injecting insulating oil into the container via an oil feeding pipe or supplying insulating oil from the container to an electric device in which the insulating oil is injected into the container in which the component is accommodated. The present invention relates to an oil feeding device to be dispensed and an insulating oil evaluation method for evaluating insulating oil in an oil feeding pipe of the oil feeding device.

  2. Description of the Related Art Conventionally, as an electric device in which vegetable oil as insulating oil is injected, as shown in Patent Document 1 below, a transformer in which vegetable oil with an antioxidant added is injected into the transformer is known. In such a transformer, even if the water in which oxygen in the air is dissolved is absorbed by the vegetable oil, the oxidation of the vegetable oil is suppressed by the antioxidant, so that the deterioration of the vegetable oil due to the oxidation is suppressed, thereby extending the replacement life of the vegetable oil. Can do. Thus, the insulating oil used for electrical equipment is an important component in securing and maintaining the performance of the equipment.

Special Table 2000-502493

  Here, the oil feeding device that injects the insulating oil into the transformer or dispenses the insulating oil from the transformer is used for vegetable oil to prevent the insulating oil used last time from being mixed into the insulating oil used this time. However, when the frequency of use is not high enough to make a dedicated machine, the same oil feeder is also used when injecting or pouring mineral oil in addition to vegetable oil.

  Further, even if a specific oil feeding device is used as a dedicated machine for vegetable oil, it may be mistakenly used for injection or extraction of mineral oil.

  In such a case, it is necessary to remove the previously used insulating oil remaining in the oil feeding path by thoroughly washing the oil feeding path in the oil feeding device including the oil feeding pipe with the insulating oil used this time. .

  However, since the insulating oil remaining in the oil feeding path is indistinguishable from the oil used this time, the oil feeding path is washed out more than necessary, or conversely, the washing is insufficient and the previous use There was a problem that the next use was started even though the insulating oil remained.

  In view of the above circumstances, the present invention detects an oil that has been supplied last time and remains in the oil supply path, and can reliably prevent the previous oil from being mixed in the oil supply path. An object of the present invention is to provide an insulating oil evaluation method for evaluating an insulating oil in an oil feeding pipe of a device and an oil feeding device.

According to a first aspect of the present invention, there is provided an oil feeding device that injects insulating oil into an electric device through which an insulating oil is injected into a container in which a component is accommodated, or the container through an oil feeding pipe. An oil feeding device for pouring insulating oil from the inside,
First spectrum acquisition means for acquiring an infrared absorption spectrum of the previous oil that is the insulating oil sent last time;
Second spectrum acquisition means for acquiring an infrared absorption spectrum of the current oil which is an insulating oil different from the previous oil and is supplied this time;
Spectrum measuring means for measuring the infrared absorption spectrum of the oil in the pipe extracted from the oil feeding pipe;
By comparing the infrared absorption spectrum of the previous oil acquired by the first spectrum acquisition means with the infrared absorption spectrum of the current oil acquired by the second spectrum acquisition means, among the differences between them A feature point determining means for determining a feature point as a feature;
With respect to the infrared absorption spectrum of the pipe oil measured by the spectrum measuring means, the residual detection means for detecting the previous oil remaining in the pipe oil by referring to the feature point determined by the feature point determining means. It is characterized by that.

  The present inventor has found that a plurality of insulating oils that are difficult to distinguish in appearance have characteristic differences on the infrared absorption spectrum. Based on this knowledge, the oil feeding device according to the first aspect of the invention determines a characteristic point from the difference in the infrared absorption spectrum between the previous oil and the current oil, which is different from the previous oil. The previous oil remaining in the pipe is detected. According to this, the previous oil and the current oil, which are difficult to distinguish in appearance, are focused on the feature points on the infrared absorption spectrum, so that the previous oil and the current oil are easily distinguished and the remaining previous oil is detected. be able to. Thereby, it is possible to reliably prevent the previous oil from being mixed in the oil feeding path.

The oil feeding device of the second invention is the first invention,
The feature point determination means calculates and calculates the difference between the infrared absorption spectrum of the previous oil acquired by the first spectrum acquisition means and the infrared absorption spectrum of the current oil acquired by the second spectrum acquisition means. The feature point is determined based on the difference.

  According to the oil feeding device of the second invention, the difference between these can be extracted by calculating the difference between the infrared absorption spectrum of the previous oil and the infrared absorption spectrum of the current oil. As a result, by determining the characteristic points from the differences extracted in this way, it is possible to distinguish the previous oil and the current oil that are difficult to distinguish in appearance, and to detect the previous oil remaining and to detect the oil supply route. It is possible to reliably prevent the previous oil from being mixed in.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the feature point determining means includes the peak value of the infrared absorption spectrum of the previous oil acquired by the first spectrum acquiring means, and the second spectrum acquisition. The feature point is determined based on a difference from the peak value of the infrared absorption spectrum of the current oil obtained by the means.

  According to the oil feeding device of the third invention, it is possible to extract the difference between the peak values by paying attention to the peak value between the infrared absorption spectrum of the previous oil and the infrared absorption spectrum of the current oil. As a result, by determining the characteristic points from the differences extracted in this way, it is possible to distinguish the previous oil and the current oil that are difficult to distinguish in appearance, and to detect the previous oil remaining and to detect the oil supply route. It is possible to reliably prevent the previous oil from being mixed in.

The oil feeding device of the fourth invention is any one of the first to third inventions,
The residual oil detection means detects the residual concentration of the previous oil from the appearance degree of the feature point determined by the feature point determination means.

  The present inventor has obtained knowledge that the degree of appearance has a correlation with the concentration of the remaining previous oil by paying attention to the degree of appearance of the feature points on the infrared absorption spectrum. Based on this knowledge, the oil feeding device of the fourth invention detects the concentration of the remaining previous oil from the relationship between the appearance degree of the feature points on the infrared absorption spectrum and the concentration of the remaining previous oil. This makes it possible not only to detect the previous oil that is difficult to distinguish from the previous appearance and the previous oil remaining from the current oil, but also to detect the concentration of the previous oil and reliably prevent the previous oil from being mixed in the oil supply path. it can.

In the insulating oil evaluation method of the fifth invention, the insulating oil is injected into the container for the electric equipment into which the insulating oil is injected into the container in which the component is accommodated, or the insulating oil is injected from the container. An insulating oil evaluation method for evaluating insulating oil in an oil feeding pipe of an oil feeding device to be dispensed,
A first spectrum acquisition step of acquiring an infrared absorption spectrum of the previous oil that is the insulating oil that was previously supplied by the oil supply device;
A second spectrum acquisition step of acquiring an infrared absorption spectrum of the present oil that is different from the previous oil, which is an insulating oil that is supplied this time by the oil feeding device;
A spectrum measuring step for measuring an infrared absorption spectrum of the oil in the pipe extracted from the oil feeding pipe of the oil feeding device;
By comparing the infrared absorption spectrum of the previous oil acquired by the first spectrum acquisition means with the infrared absorption spectrum of the current oil acquired by the second spectrum acquisition means, among the differences between them A feature point determination step for determining a feature point as a feature;
A residual detection step of detecting the previous oil remaining in the pipe oil by referring to the feature point determined by the feature point determination means for the infrared absorption spectrum of the pipe oil measured by the spectrum measurement means; It is characterized by that.

  According to the insulating oil evaluation method of the fifth invention, a characteristic point is determined from the difference in the infrared absorption spectrum between the previous oil and the current oil that is different from the previous oil, and the residual oil remains in the oil feed pipe from the characteristic point. The previous oil is detected. According to this, the previous oil and the current oil, which are difficult to distinguish in appearance, are focused on the feature points on the infrared absorption spectrum, so that the previous oil and the current oil are easily distinguished and the remaining previous oil is detected. be able to. As a result, it is possible to reliably prevent the previous oil from being mixed in the oil feeding path.

The block diagram which shows the whole structure of an oil-feeding apparatus. Explanatory drawing which shows the processing content of the feature point determination means of FIG. Explanatory drawing which shows the processing content of the residual detection means of FIG. Explanatory drawing which shows the processing content of the residual detection means of FIG.

  With reference to FIG. 1, the oil feeding apparatus of this embodiment is demonstrated. The oil feeding device is a device for injecting insulating oil into, for example, the tank 101 of the transformer 100 (corresponding to the container of the present invention), and the oil feeding means 1 for feeding the insulating oil and the oil feeding by the oil feeding means. And insulating oil evaluation means 2 for managing and evaluating the insulating oil. As the insulating oil, a plurality of kinds of mineral oils and vegetable oils (for example, rapeseed oil) are used.

  First, the configuration of the oil feeding means 1 will be described. The oil feeding means 1 includes a new oil tank 11, a deaeration tank 12, an oil feeding pump 13, a storage tank 14, and a vacuum pump 15.

  The fresh oil tank 11 and the deaeration tank 12 are connected by a pipe 16a, and the deaeration tank 12 and the storage tank 14 are connected by a pipe 16b and a pipe 16c so as to sandwich the oil feed pump 13.

  A pipe 16 d communicating with the interior of the deaeration tank 12 is connected to the suction part of the vacuum pump 15. Furthermore, the pipe 16a is provided with a valve 17a, the pipe 16b is provided with a valve 17b, and the pipe 16d is provided with valves 17c and 17d. It can be changed to connected or disconnected.

  The new oil tank 11 is a container for storing insulating oil (current oil) to be injected into the tank 101 of the transformer 100, and one end side of the pipe 16a is disposed at the bottom thereof.

  The deaeration tank 12 is a sealed container that temporarily stores the insulating oil sucked up from the new oil tank 11, and the valve 17 a and the valve 17 b are shut off, and the inside of the deaeration tank 12 is evacuated by the vacuum pump 15. By doing so, the air dissolved in the insulating oil is removed.

  The oil feed pump 13 is a pump that delivers liquid, and is constituted by a canned motor pump, for example.

  The storage tank 14 is a tank in which the insulating oil that has passed through the oil supply path from the new oil tank 11 through the deaeration tank 12 to the discharge port of the pipe 16c is stored. Further, the infrared absorption spectrum of the insulating oil in the storage tank 14 is measured by an infrared spectroscopic device 25 described later.

  Next, the configuration of the insulating oil evaluation means 2 will be described. The insulating oil evaluation unit 2 includes an insulating oil database 21, a spectrum acquisition unit 22 (corresponding to the first spectrum acquisition unit and the second spectrum acquisition unit of the present invention), a feature point determination unit 23, and a residual detection unit 24. And an infrared spectrometer 25 (corresponding to the spectrum measuring means of the present invention). In addition, the insulation evaluation unit 2 includes an operation unit 26 such as a keyboard or a mouse (not shown) that is allowed to be operated by the user, and a display unit 27 on which a detection result by the residual detection unit 24 is displayed.

  The processing by the spectrum acquisition unit 22 corresponds to the first spectrum acquisition step and the second spectrum acquisition step of the present invention, the processing by the feature point determination unit 23 corresponds to the feature point determination step of the present invention, and the residual detection unit 24. The processing according to the above corresponds to the residual detection step, and the processing by the infrared spectroscopic device 25 corresponds to the spectrum measurement step.

  The insulating oil database 21 stores measured values of infrared absorption spectra of a plurality of types of insulating oils used for insulating transformers and other electrical devices. Here, the measured value of the infrared spectrum stored in the insulating oil database 21 includes not only the transmittance measurement data but also the absorbance converted from the transmittance.

  The spectrum acquisition means 22 reads out and acquires the measured value of the infrared spectrum of the insulating oil (previous oil) sent by the previous oil feeding means 1 from the insulating oil database 21, and is stored in the new oil tank 11. The measured value of the infrared spectrum of the insulating oil (current oil) sent to the container 101 of the container 100 is read from the insulating oil database 21 and acquired.

  In addition, when the order of the plurality of insulating oils to be fed using the oil feeding device is determined, the spectrum acquisition unit 22 insulates the measured values of the infrared absorption spectra of the previous oil and the current oil according to the order. When the previous oil and the current oil are designated by the operation of the operation unit 26 by the user, the measured values of the infrared absorption spectra of the previous oil and the current oil are determined according to the designation. You may read from.

  The feature point determination unit 23 determines a feature point that is a characteristic among the differences between the two infrared absorption spectra acquired by the spectrum acquisition unit 22. Details of the feature point determination method will be described later.

  The residual detection means 24 is based on whether the infrared absorption spectrum of the insulating oil in the storage tank 14 measured by the infrared spectroscopic device 25 described later has a feature point determined by the feature point determination means 23. It detects the previous oil residue in the oil supply path from the oil tank 11 through the deaeration tank 12 to the discharge port of the pipe 16c. Details of the method for detecting the remaining oil in the previous time will be described later.

  The infrared spectroscopic device 25 is configured by, for example, a Fourier transform infrared spectrophotometer (FT-IR), and in addition to the infrared absorption spectrum of the insulating oil in the storage tank 14, an outlet of the transformer 100 as necessary. The infrared absorption spectrum of the insulating oil collected from the side is measured.

  The infrared spectroscopic device 25 may be another measuring device having the same or similar function as the Fourier transform type infrared spectrophotometer, such as a dispersive infrared spectrophotometer. It is preferable to use a Fourier transform infrared spectrophotometer because it can be analyzed in units of seconds, and the wave number accuracy and wave number reproducibility are good.

  The transformer 100 contains a transformer body (not shown) in which primary and secondary coils are wound around an iron core in a tank 101, and the upper partition wall is filled with rapeseed oil or mineral oil as an insulating oil. It has a sealed structure.

  Further, the transformer 100 includes an injection pipe 102a to which the pipe 16c of the oil feeding device is connected, and a discharge pipe 102b for discharging the insulating oil in the tank 101. The pipe 16c is connected to the injection pipe 102a. A connecting valve 103a is provided, and a valve 103b is provided in the discharge pipe 102b.

  In this embodiment, the insulating oil evaluation means 2 is constituted by a microcomputer or the like, and the insulating oil database 21 and the respective processing means 22 to 24 are constituted by hardware such as CPU, ROM, RAM, etc. The components 21 to 24 may be configured by common hardware, and some or all of these components 21 to 24 may be configured by different hardware. For example, the insulating oil database 21 may be an external server accessible via a network.

  Next, with reference to FIG. 2, the feature point determination means 23, which will be described later, determines the feature points that are characteristic among the differences between the two infrared absorption spectra acquired by the spectrum acquisition means 22. Processing will be described.

  First, the spectrum acquisition means 22 uses the infrared absorption spectrum (transmittance) of the mineral oil shown in FIG. 2A as the current oil and the infrared absorption spectrum of the rapeseed oil, which is the vegetable oil shown in FIG. When the transmission factor is acquired, the feature point determination unit 23 specifies (1) the peak value and the intensity of the infrared absorption spectrum of the current oil, and the transmittance of the infrared absorption spectrum of the previous oil. Identify the peak value and its intensity.

  Specifically, the current oil in FIG. 2A has three peak values (x> y> z) with wave numbers of x [1 / cm], y [1 / cm], and z [1 / cm]. Identified. In the previous oil in FIG. 2 (b), the wave numbers are generally 5 of a [1 / cm], b [1 / cm], c [1 / cm], d [1 / cm], and e [1 / cm]. Two peak values (a> b> c> d> e) are identified.

  Next, the feature point determination means 23 takes (2) the difference in intensity at the wave number of the peak value specified for the current oil and the previous oil, and sets the feature value (wave number) that has the maximum absolute value of the difference as the feature point (wave number). decide.

  Specifically, in FIGS. 2 (a) and 2 (b), for wave numbers x, y, z and a, b, c, d, e, the difference in transmittance intensity of the peak value is calculated, and the difference The wave number with the maximum absolute value is taken as the feature point. In FIGS. 2A and 2B, the wave numbers x and a are substantially equal, and the wave numbers y and c are approximately equal. When the difference between the respective peak values is calculated, the absolute value of the difference at the wave number y (c) is maximized. In this case, the wave number y (c) is used as a feature point.

  In addition, supplementally, the wave number y (c) [1 / cm], which is a feature point, is a peak value that is characteristic when oil is present in the previous time. This is a characteristic point that indicates that the previous oil remained.

  Next, with reference to FIGS. 3 and 4, a method for detecting the residual oil in the previous time by the residual oil detection means 24, which will be described later, will be described.

  First, as a premise, the relationship between the peak value intensity (height) of the wave number serving as a feature point and the content (concentration) of the rapeseed oil that is the previous oil will be described.

  FIG. 3A shows a spectrum obtained by converting the transmittance of the infrared absorption spectrum shown in FIG. 2A into absorbance based on the following equation.

Absorbance = −log (transmittance / 100)
The reason why the transmittance of the infrared absorption spectrum is converted to the absorbance is to make the appearance of the peak value intensity of the feature point stand out, and the infrared absorption spectrum of the mineral oil in FIG. Then, no peak value appears at the wave number y (c) [1 / cm] as the feature point.

  On the other hand, when 0.119 [g / 100 ml] of the previous oil (rapeseed oil) shown in FIG. 2 (b) is contained in the mineral oil of FIG. 3 (a), it is shown in FIG. 3 (b). Thus, a peak value appears at the wave number y (c) [1 / cm] as a feature point. And if the content rate of last time oil (rapeseed oil) is raised to 0.511 [g / 100 ml], as shown in Drawing 3 (c), the peak value will appear large. Further, when the content of the previous oil (rapeseed oil) is increased to 1.029 [g / 100 ml], the peak value appears larger as shown in FIG.

  FIG. 4 shows the relationship between the peak value intensity (height) of wave number y (c) [1 / cm], which is a feature point, and the content (concentration) of rapeseed oil, which is the previous oil.

  Thus, since there is a direct proportional relationship between the peak value intensity (height) of the wave number serving as a feature point and the content (concentration) of rapeseed oil as the previous oil, the residual detection means 24 is characterized by The residual concentration of the previous oil is detected from the peak value intensity (height) of the wave number y (c) [1 / cm] as a point.

  More specifically, after the previous oil supply by the oil supply means 1, a predetermined amount of insulating oil is circulated from the new oil tank 11, and the deaeration tank 12, the pipes 16b and 16c are circulated from the pipe 16a. For the infrared absorption spectrum obtained by collecting the insulating oil from the storage tank 14 and measuring the collected insulating oil by the infrared spectroscopic device 25, the residual detection means 24 has a characteristic peak value at the wave number that is the characteristic point of the previous oil. It is determined whether or not there is residual oil from the previous time, and if there is a peak value, the residual concentration of the previous oil contained in the current oil is calculated from the appearance intensity (peak value height). . Then, the processing result by the residual detection means 24 is appropriately displayed on the display unit 27.

  As described above, according to the oil feeding device of the present embodiment, the previous oil and the current oil are easily distinguished from each other by focusing on the feature points on the infrared absorption spectrum of the previous oil and the current oil that are difficult to distinguish in appearance. It is possible to detect the previous oil that remains distinctly.

  Then, after confirming that there is no oil remaining last time, the pipe 16c is connected to the injection pipe 102a via the connection valve 103a, and this time oil is sent from the new oil tank 11 to the tank 101 of the transformer 100. By doing this, it is possible to reliably prevent the previous oil from being mixed in the oil feeding path.

  In this embodiment, the insulating oil is evaluated when the insulating oil is fed to the tank 101 of the transformer 100 by the oil feeding device. However, the invention is not limited to this, and the discharge pipe of the transformer 100 is not limited thereto. You may evaluate the insulating oil extract | collected from 102b. In this case, the quality of the insulating oil in the transformer 100 can be ensured by collecting the insulating oil in the tank 101 of the actually injected transformer 100 as a sample and evaluating it with the insulating oil evaluation means 2. .

  In the present embodiment, the feature point determination means 23 specifies (1) the peak value and the intensity of the infrared absorption spectrum of the current oil and the peak value of the transmittance of the infrared absorption spectrum of the previous oil. The strength was specified, and (2) the difference in strength at the wave number of the peak value specified for the current oil and the previous oil was taken, and the one having the maximum absolute value of the difference was determined as the feature point (wave number). The feature point determination method is not limited to this. For example, by executing one or both of the above (1) and (2), feature point candidates are displayed on the display unit 27, and the user determines one feature point using the operation unit 26. You may do it.

  Further, in the present embodiment, the infrared absorption spectra of the previous oil and the current oil are acquired from the insulating oil database 21, but the insulating oil to be fed by the oil feeding means 1 is measured each time by the infrared spectroscopic device 25 and measured. These values may be stored in a memory or the like for use.

  Moreover, although this embodiment demonstrated the oil-feeding apparatus with which the oil-feeding means 1 and the insulating oil evaluation means 2 were provided, the oil-feeding apparatus was comprised only by the insulating oil evaluation means 2, and this was made into various existing oil feeding. You may make it apply to the means 1. FIG.

  In the present embodiment, the vegetable oil as the insulating oil has been described as rapeseed oil, but is not limited thereto. Veronia oil or the like may be used.

DESCRIPTION OF SYMBOLS 1 ... Oil feeding means, 2 ... Insulating oil evaluation means, 11 ... New oil tank, 12 ... Deaeration tank, 13 ... Oil feeding pump, 14 ... Storage tank, 15 ... Vacuum pump, 16a-16c ... Piping, 17a-17c ... Duct, 21 ... Insulating oil database, 22 ... Spectrum acquisition means (first spectrum acquisition means, second spectrum acquisition means), 23 ... Feature point determination means, 24 ... Residual detection means, 25 ... Infrared spectrometer (spectrum measurement) Means), 100 ... transformer, 101 ... tank.

Claims (5)

For electrical equipment in which insulating oil is injected into the container in which the components are stored, the insulating oil is injected into the container through the oil supply pipe, or the insulating oil is poured out from the container. An oil device,
First spectrum acquisition means for acquiring an infrared absorption spectrum of the previous oil that is the insulating oil sent last time;
Second spectrum acquisition means for acquiring an infrared absorption spectrum of the current oil which is an insulating oil different from the previous oil and is supplied this time;
Spectrum measuring means for measuring the infrared absorption spectrum of the oil in the pipe extracted from the oil feeding pipe;
By comparing the infrared absorption spectrum of the previous oil acquired by the first spectrum acquisition means with the infrared absorption spectrum of the current oil acquired by the second spectrum acquisition means, among the differences between them A feature point determining means for determining a feature point as a feature;
With respect to the infrared absorption spectrum of the pipe oil measured by the spectrum measuring means, the residual detection means for detecting the previous oil remaining in the pipe oil by referring to the feature point determined by the feature point determining means. An oil feeding device characterized by that. The oil feeding device according to claim 1,
The feature point determination means calculates and calculates the difference between the infrared absorption spectrum of the previous oil acquired by the first spectrum acquisition means and the infrared absorption spectrum of the current oil acquired by the second spectrum acquisition means. An oil feeding device characterized in that the feature point is determined based on a difference. The oil feeding device according to claim 1 or 2,
The feature point determination means is a difference between the peak value of the infrared absorption spectrum of the previous oil acquired by the first spectrum acquisition means and the peak value of the infrared absorption spectrum of the current oil acquired by the second spectrum acquisition means. An oil feeding device characterized in that the feature point is determined based on a point. The oil feeding device according to any one of claims 1 to 3,
The residual oil detecting means detects the residual concentration of the previous oil from the appearance degree of the characteristic points determined by the characteristic point determining means. In an oil feeding pipe of an oil feeding device that injects insulating oil into the container for the electrical equipment in which insulating oil is injected into the container in which the component is accommodated, or pours the insulating oil from the container. An insulating oil evaluation method for evaluating the insulating oil of
A first spectrum acquisition step of acquiring an infrared absorption spectrum of the previous oil that is the insulating oil that was previously supplied by the oil supply device;
A second spectrum acquisition step of acquiring an infrared absorption spectrum of the present oil that is different from the previous oil, which is an insulating oil that is supplied this time by the oil feeding device;
A spectrum measuring step for measuring an infrared absorption spectrum of the oil in the pipe extracted from the oil feeding pipe of the oil feeding device;
By comparing the infrared absorption spectrum of the previous oil acquired by the first spectrum acquisition means with the infrared absorption spectrum of the current oil acquired by the second spectrum acquisition means, among the differences between them A feature point determination step for determining a feature point as a feature;
A residual detection step of detecting the previous oil remaining in the pipe oil by referring to the feature point determined by the feature point determination means for the infrared absorption spectrum of the pipe oil measured by the spectrum measurement means; An insulating oil evaluation method characterized by the above.

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