JP2008241451A - Method for diagnosing anomaly of oil-filled electric apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of detecting anomalies of oil-filled electric apparatuses, on the basis of the state of generation of BTEX in insulating oils of the electric apparatuses and estimating the form of the anomalies (for example, by electric discharge or overheating). <P>SOLUTION: An insulating oil is collected from an oil-filled electric apparatus as a sample. The contents of BTEX (benzene, toluene, ethylbenzene and xylene) in the sample are each measured to subsequently determine their distributions. The acquired contents and their distributions are each compared with and analyzed against the contents of BTEX and their distributions of a sample of which the form of anomalies is known to predict the presence or the absence of anomalies of the oil-filled electric apparatus and the form of the anomalies. It is preferable that each of the amounts of BTEX generated in the insulating oil be measured by solid phase micro extraction and gas chromatograph/mass spectrometry. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for detecting and diagnosing abnormalities in discharge and overheating of oil-filled power devices such as transformers, capacitors, and OF (oil-immersion) cables, and relates to benzene, toluene, ethylbenzene, and xylene generated in insulating oil. Abnormalities are diagnosed based on the generation amount and the distribution of the generation amount.

Early detection of discharge and overheating is important for maintenance of oil-filled power equipment such as transformers, capacitors, and OF cables.
So far, a method has been used in which the concentration of gas generated by discharge or overheating is measured and the gas concentration ratio is determined (Denki Kenkyu vol. 54, No. 5 (1999), IEC 60599-1999). .

In particular, the concentration of acetylene produced in insulating oil has been used as an indicator of abnormal overheating and discharge. However, since acetylene is generated by either discharge or overheating, diagnosis is carried out in proportion to other decomposition products such as hydrogen, ethylene, and ethane.
Moreover, since acetylene reacts with copper and the concentration in oil falls, it has been pointed out that the state is not necessarily grasped accurately. Furthermore, there is a case where detection is difficult at a normal acetylene analysis level in oil, such as flow electrification of a transformer, and a deterioration index that is easier to detect is desired.

  Furthermore, it has been pointed out that in the case of a transformer having a B-type conservator, it is difficult to detect the discharge of the main body because acetylene generated by the tap changer permeates the main body oil.

Incidentally, it has been reported by Kraemer et al. That benzene, toluene, ethylbenzene, and xylene (hereinafter abbreviated as BTEX) are produced in insulating oil by arc discharge (CIGRE 12-108, 1996).
They found that BTEX was generated with arc discharge in terms of contact wear due to arc generation in on-road tap changer (LTC) contact switching.
It has been reported that the amount of BTEX, particularly benzene and toluene, increases in proportion to the exchange current and the number of switching.

However, the Kraemer et al. Report does not relate the state of BTEX generated in the insulating oil and the abnormal form of the oil-filled electrical device.
DENKOKEN Vol.54 No.5 (1999), IEC 60599-1999 Kraemer et al, CIGRE 12-108, 1996

  Therefore, the problem in the present invention is to detect an abnormality of the electric device from the state of generation of BTEX in the insulating oil of the oil-filled electric device, and to estimate the form of the abnormality (for example, due to discharge or overheating). It is to provide a technique that can be used.

To solve this problem,
The invention according to claim 1 is a method for diagnosing an abnormality in an oil-filled electrical device from the production amounts of benzene, toluene, ethylbenzene, and xylene dissolved in insulating oil and the distribution of the production amounts.

  According to a second aspect of the present invention, there is provided the oil-filled electrical device according to the first aspect, wherein the production amounts of benzene, toluene, ethylbenzene, and xylene in the insulating oil are measured by solid phase microextraction-gas chromatography-mass spectrometry. This is a method for diagnosing abnormalities.

  The invention according to claim 3 is the method of diagnosing an abnormality of the oil-filled electrical device according to claim 2, wherein the solid-phase microextraction is performed in a temperature range of 20 to 60 ° C.

  According to a fourth aspect of the present invention, there is provided the oil filler according to any one of the first to third aspects, wherein discharge and overheating in the oil-filled electrical device are discriminated based on respective production amounts and distributions of toluene, ethylbenzene, and xylene. This is a method for diagnosing abnormalities in electrical equipment.

  The invention according to claim 5 is an oil according to any one of claims 1 to 4, wherein the magnitude and frequency of discharge in an oil-filled electrical device are determined based on the respective production amounts and distribution of toluene, ethylbenzene, and xylene. This is a method for diagnosing abnormalities in input electrical equipment.

  According to a sixth aspect of the present invention, in the method according to the fourth or fifth aspect, the oil-filled electrical device is diagnosed by benzene, toluene, ethylbenzene, xylene in oil concentration and C1-C3 hydrocarbon gas in oil. This is a method of diagnosing an abnormality of an oil-filled electrical device that is performed in combination with the analysis results of

ADVANTAGE OF THE INVENTION According to this invention, the form of abnormality other than the presence or absence of abnormality can be known based on each production amount of BTEX in insulating oil of oil-filled electrical equipment and each production amount distribution situation.
If solid phase microextraction-gas chromatography-mass spectrometry is used for measurement of the amount of BTEX produced in insulating oil, the measurement can be carried out easily and in a short time.

The present invention will be described in detail below.
The present applicant examines the influence of the discharge type and heating temperature on the production of BTEX, and the distribution and generation amount in the insulating oil differ depending on the discharge and heating form and conditions, and the possibility of being applicable to diagnosis. I found it.
The form of discharge varies depending on the equipment, such as transformers, capacitors, and cables, even in oil-filled electrical equipment. Capacitors and cables are exposed to a high electric field by insulating oil placed in a narrow electrode gap. Corona discharge (partial discharge) occurs when it further develops. In addition, discharge due to poor insulation due to impurities or the like has been reported.

On the other hand, in the case of transformers, static electricity generated and accumulated by minute discharge due to voids due to oil not impregnated with insulating paper, medium energy discharge or arc discharge due to poor conductor contact, poor insulation between windings, etc. Various electric discharges such as direct current insulation breakdown due to can occur.
A part of insulating oil (main component is hydrocarbon with about 20-30 carbon atoms) is decomposed by the energy at the time of discharge, and hydrogen, ethylene, methane, etc. are generated, but acetylene is produced when the energy is high to some extent. To do. The diagnosis by the gas analysis in oil described above is performed using this.

  Further, overheating includes overheating of the conductor due to overload, circulating current, overheating of the iron core due to foreign matters, and the like, and it is said that overheating occurs at 700 ° C. or higher. Thermal decomposition of the insulating oil occurs due to overheating, but the product varies depending on the temperature, and up to acetylene is formed at high temperatures. Accordingly, acetylene is generated during both discharge and overheating, and it may be unclear whether it is generated.

A laboratory study was conducted on how BTEX is generated by such discharge and overheating.
Fig. 1 shows the amount of BTEX produced in insulating oil by repeating the dielectric breakdown in the AC dielectric breakdown test of mineral oil-based insulating oil specified in JIS C2101 (Type 1 oil specified in JIS C2320). Distribution is shown.
In this discharge accompanied by dielectric breakdown, only toluene was produced and no other components were produced. By repeating the dielectric breakdown, only the amount of toluene produced increased.

In some cases, only toluene is used in the case of several different types of insulating oils (JIS C 2320 Type 1 No. 2 oil, two types of mineral insulating oils refined from paraffinic and naphthenic crude oils, linear and branched alkylbenzenes). Generated. In this way, toluene was produced exclusively in the AC breakdown.
Moreover, it was confirmed that the production | generation of BTEX by such discharge does not depend on the kind of insulating oil.

In FIG. 2, various discharge experiments were conducted for mineral oil-based insulating oil (Type 1 No. 2 oil defined in JIS C2320), and the generation distribution of BTEX after discharge was compared. A glow discharge in argon was performed on the oil surface of the insulating oil, and the arc was extinguished by being immersed in the oil. When this was repeated, mainly benzene and toluene were produced, and a small amount of ethylbenzene and each xylene was produced.
In the partial discharge (microdischarge), only benzene or toluene was generated depending on the form. When this was contrasted with the generation of acetylene, it was thought that benzene was generated in a partial discharge that was thought to have a high amount of acetylene, that is, high energy.

FIG. 2 also shows the result of the overheating experiment of the insulating oil. The formation of BTEX was not observed at 300 ° C. and 450 ° C., but when overheating at 750 ° C. was repeated, o-xylene, p-xylene, toluene, ethylbenzene and m-xylene were produced.
As described above, the distribution of BTEX generated differs depending on the form of discharge and the overheating temperature, and the generation amount is considered to depend on the progress (time or cumulative frequency) of each discharge or overheating, depending on the generation distribution and generation amount of BTEX in oil. The possibility of diagnosis was suggested.

Next, FIG. 3 summarizes the results of BTEX analysis in insulating oil collected from actual oil-filled electrical equipment in operation.
In the case of an on-load tap changer (LTC), benzene and toluene were the main products, and showed a pattern similar to the glow discharge shown in FIG. In the case of the transformer, components other than benzene were detected, and there were many toluene and p-xylene, but the distribution was different depending on the equipment.
In the case of a transformer, it is possible that not only one type of discharge / overheating but also multiple events have occurred, and by detecting changes in product distribution over time, new abnormalities are detected. Could be possible.

  This trend management is easy, unlike acetylene that reacts with copper, because BTEX is chemically stable, so it exists stably in insulating oil, and the concentration of BTEX that is generated increases constantly. It is to do. In the case of the condenser, xylenes and ethylbenzene were produced, including those in which a large amount of acetylene was produced, and p-xylene was the most. The distribution was different from the partial discharge in the laboratory, and it was considered that different discharges or overheating occurred.

  Analyzing BTEX generation distribution and generation amount in insulating oil after model experiment of discharge or overheating assumed in this way, and comparing with BTEX generation distribution and generation amount in insulating oil collected from operating oil-filled electrical equipment By doing so, useful means for detecting the presence / absence of an abnormality occurring in the device and the form of the abnormality can be obtained. If it is estimated from the product distribution that multiple events are occurring, it can be said that recent events can be analyzed by tracking them over time.

The tendency of acetylene formation by gas analysis in oil, which is currently widely used, does not necessarily match BTEX, indicating that the generation mechanism may be different.
This may be able to detect abnormalities that could not be detected or identified in the past by analyzing BTEX in the insulating oil in the electrical equipment in operation.
Moreover, it is shown that there is a possibility that abnormality diagnosis can be made more accurately than conventional gas analysis alone diagnosis by combining with the gas analysis result in oil if necessary.

The BTEX content in the insulating oil can be measured by various analytical methods, but solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS method) is easy to operate and requires a long time. It is suitable because it takes a short time.
In SPME, a fiber-like solid phase bonded to the tip of a thin needle is used as a fixed layer for adsorption or distribution.

  Insert the needle into the sealed container containing the sample, take out the fiber stored in the needle, and place the fiber on the surface of the sample liquid without contacting the sample liquid (headspace), and at a predetermined temperature. By holding for this time, the components in the head space are adsorbed to the fixed layer (referred to as head space extraction).

  If a fiber is immersed in and extracted from insulating oil, a large amount of insulating oil is adsorbed by the fiber, making it difficult to measure the target component. Moreover, it is preferable to perform head space extraction in the temperature range of 20 ° C to 60 ° C. If the temperature exceeds 60 ° C., a part of the insulating oil is extracted, which disturbs the measurement. If it is less than 20 ° C., it is difficult to concentrate the target component. A temperature range of 20 ° C to 60 ° C is required to suppress the extraction of interfering components and to keep the extraction time within one hour.

  As the SPME fiber used in the present invention, most commercially available fibers can be used. However, considering the desorption temperature and the number of times it can be used repeatedly, PDMS / DVB (polydimethylsiloxane is supported on the styrenedivinylbenzene adsorbent. The use of the above is particularly preferred.

  If the amount of insulating oil is large with respect to the volume of the head space, it takes a long time for equilibration, and the amount extracted to the fiber becomes larger than necessary, and the GC-MS separation performance is lowered. If the headspace capacity is too large for the amount of insulating oil, a long time is required for equilibration and adsorption. A preferable insulating oil amount and head space volume are in the range of 0.2-0.5 mL / 5-30 mL.

Thereafter, the measurement is performed by inserting the needle into the GC-MS inlet held at a predetermined temperature and desorbing the adsorbed component.
As GC-MS conditions, the injection part temperature required for desorption of the target component is 150 to 270 ° C., preferably 230 to 250 ° C. The column can be a general polar or nonpolar column, but a small amount of contaminated oil is purged. Therefore, a column having a heat resistance of 250 ° C. or higher is preferable.

  In the present invention, a Carbowax column capable of separating xylene isomers is particularly preferably used. Of course, the separation column can be a packed column or a capillary column. The GC-MS analysis can be performed in total ion mode (TIM) or in selected ion mode (SIM).

  The former is preferably used for identification of components in oil, and the latter is particularly suitable for sensitive analysis of target components. In the present invention, the SIM mode is preferably used from the viewpoint of sensitivity. By confining the monitor ions to the molecular ions of BTEX, the interference of interference components can be minimized. The column temperature is preferably set to a temperature at which BTEX is separated and eluted at an appropriate time according to the column, and it is desirable to raise the temperature after elution of these to elute a small amount of oil components.

Other methods can be used for the measurement of BTEX in the present invention. For example, a method of combining the purge and trap extraction method and GC-MS disclosed in JP-A-8-72892, a method by HPLC, and the like can be mentioned.
However, in the former case, a large amount of insulating oil may be injected into the GC-MS. In this case, the subsequent measurement is hindered. The latter is also difficult to separate from oil and is insufficient in sensitivity. A headspace extraction method that does not use a solid phase is simple, but is not sensitive because it is not a concentration means.

  Thus, the SPME-GC-MS method is the simplest and quickest extraction / measurement method. Conventionally, this method has been used for extraction of organic components in water. However, the present inventors have found that this method can be applied to extraction of components in insulating oil by optimizing the extraction conditions.

Specific examples are shown below.
[A] The insulating oil collected from the oil-filled electrical equipment in operation was analyzed.
The analysis conditions are as follows.
SPME fiber: PDMS / DVB (manufactured by Spelco)
Extraction temperature: 30 ° C. (equilibrated by standing for 10 minutes in advance), 10 minutes
Insulating oil amount: 0.2 mL
Headspace: 25 mL
GC-MS: Shimadzu GC-MS QP5050
Column: DB-Wax ID 0.25 mm, film thickness 0.25 μm, length 25 m (manufactured by J & W)
Inlet temperature: 240 ° C
Column temperature: 50 ° C
MS: SIM mode

(1) From the insulating oil collected from the tap changer A, B, C when loaded,
Toluene is A: 22.9 ppm, B: 29.7 ppm, C: 14.5 ppm,
Benzene is A: 5.0 ppm, B: 5.1 ppm, C: 20.1 ppm
In addition to detection, a small amount (about 1 ppm) of ethylbenzene and three types of xylene were also detected.

(2) From the insulating oil collected from the transformers D, E, and F, in which acetylene in the oil was detected in a small amount of 0.02-0.1%,
Toluene D: 8.6 ppm, E: 7.1 ppm, F: 12.7 ppm,
p-xylene is D: 15.7 ppm, E: 6.3 ppm, F: 15.2 ppm,
o-xylene D: 6.6 ppm, E: 4.0 ppm, F: 6.4 ppm,
m-xylene is D: 4.7 ppm, E: 2.7 ppm, F: 4.2 ppm,
Ethylbenzene has D: 5.2 ppm, E: 2.5 ppm, F: 3.8 ppm,
was detected. Benzene was 1 ppm or less.

(3) Since 1 ppm or more of acetylene in the oil was detected, from the insulating oil of the transformers G and H suspected of internal discharge,
G: Toluene 48.2 ppm, p-xylene 2.4 ppm, o-xylene 2.2 ppm, m-xylene 0.7 ppm, ethylbenzene 1.6 ppm,
H: Toluene 10.3 ppm, p-xylene 14.5 ppm, o-xylene 5.8 ppm, m-xylene 4.5 ppm, and ethylbenzene 5.0 ppm were detected. Benzene was 1 ppm or less.

(4) From the insulating oil collected from oil immersion capacitors I, J, K suspected of discharging from the generation of acetylene and hydrogen,
Toluene I: 2.2 ppm, J: 1.8 ppm, K: 2.1 ppm,
p-xylene I: 11.4 ppm, J: 10.2 ppm, K: 12.2 ppm,
o-xylene I: 5.4 ppm, J: 4.6 ppm, K: 5.7 ppm,
m-xylene I: 3.2 ppm, J: 2.8 ppm, K: 3.5 ppm,
Ethylbenzene was detected at I: 2.4 ppm, J: 2.2 ppm, and K: 2.6 ppm. Benzene was not detected.

      (5) BTEX was not detected from the insulating oil collected from the transformers L and M suspected of being overheated from the generation pattern of acetylene and ethylene.

  [B] Insulating oil (JIS C2320 Type 1 No. 2 insulating oil) subjected to various discharges and heating in the laboratory was analyzed. The analysis conditions are the same as above.

(6) A stainless steel 2 wire having an outer diameter of 2 mm was used as an electrode, held on the surface of the insulating oil at intervals of 5 mm, and immersed in oil while glow discharge at 9 kV AC in an argon gas atmosphere to extinguish the arc. 5.9 ppm of benzene, 4.1 ppm of toluene, 0.5 ppm of p-xylene, 0.3 ppm of o-xylene, 0.3 ppm of m-xylene, and 1.2 ppm of ethylbenzene were detected from the insulating oil after repeating this 300 times. . Moreover, it was 18.7 ppm in acetylene as a result of the gas analysis in oil.

      (7) 11.6 ppm of toluene was detected from the insulating oil after repeating the AC dielectric breakdown test using a spherical electrode defined in JIS C2101 200 times, and other components were hardly detected. As a result of gas analysis in oil, 110.6 ppm of acetylene was detected.

      (8) 0.3 ppm of benzene and 607.4 ppm of acetylene were detected from insulating oil after partial discharge was continued for 120 minutes at 5 kV AC using a flat plate electrode specified in ASTM D887. Not detected.

      (9) A gas absorption test using concentric electrodes as defined in ASTM D2330 is performed in a nitrogen atmosphere, and hydrogen is generated from 40000 ppm and 80000 ppm, and from the insulating oil, toluene is 0.4 ppm, 0.5 ppm, respectively. Acetylene 0.8 ml, 6.2 ppm was detected, and other components were hardly detected.

      (10) A heating test was conducted using a cartridge heater immersed in insulating oil under a nitrogen atmosphere. Generation of BTEX was not observed at 300 ° C. or less after heating for 8 hours.

      (11) High temperature heating of the insulating oil was performed in a nitrogen atmosphere using a Curie point induction heater. The temperature was raised to a predetermined temperature (450, 760 ° C.) using a specific pyrofoil, and heating was terminated after 15 seconds. In the insulating oil after repeating this 40 times, no BTEX was observed at 450 ° C, and at 760 ° C, 2.4 ppm of o-xylene, 0.9 ppm of p-xylene, and 0.8 ppm of toluene were detected. It was done. Other components were also detected in small amounts (about 0.3 ppm).

  As described above, the amount of BTEX produced and the product distribution differ depending on various discharge modes. In addition, BTEX was not generated at 300 ° C. or lower even with overheating, but generation of xylene or the like was observed at about 700 ° C. The tendency of acetylene formation does not necessarily match that of BTEX, indicating that the generation mechanism may be different.

By analyzing the BTEX of the oil-filled electrical device in operation, there is a possibility that an abnormality that could not be detected or identified in the past can be detected.
Moreover, it is shown that there is a possibility that abnormality diagnosis can be made more accurately than conventional gas analysis alone diagnosis by combining with the gas analysis result in oil if necessary. The SPME-GC-MS method is a simple BTEX analysis method for that purpose.

It is a graph which shows the production | generation amount and distribution of BTEX produced | generated when the dielectric breakdown was repeated by the alternating current dielectric breakdown test of the mineral oil type | system | group insulation oil prescribed | regulated to JIC C2101 (Type 1 No. 2 oil prescribed | regulated to JIC C2320). It is a graph which shows the production | generation distribution of BTEX after implementing various discharge and overheating experiment about mineral oil type | system | group insulation oil (1 type 2 oil prescribed | regulated to JIS C2320). It is a graph which shows the production | generation amount of BTEX in the insulation oil extract | collected from the oil-filled electrical equipment in operation, and its distribution.

Claims (6)

  A method of diagnosing abnormalities in oil-filled electrical equipment from the amount of benzene, toluene, ethylbenzene, and xylene dissolved in insulating oil and the distribution of these amounts.   The method for diagnosing an abnormality of an oil-filled electrical device according to claim 1, wherein the production amounts of benzene, toluene, ethylbenzene, and xylene in the insulating oil are measured by solid phase microextraction-gas chromatography-mass spectrometry.   The method for diagnosing an abnormality of an oil-filled electrical device according to claim 2, wherein the solid-phase microextraction is performed in a temperature range of 20 to 60 ° C.   The method for diagnosing abnormality in an oil-filled electrical device according to any one of claims 1 to 3, wherein discharge and overheating in the oil-filled electrical device are discriminated based on respective production amounts and distributions of toluene, ethylbenzene, and xylene. .   The abnormality of the oil-filled electrical device according to any one of claims 1 to 4, wherein the magnitude and frequency of discharge in the oil-filled electrical device are determined based on the respective production amounts and distributions of toluene, ethylbenzene, and xylene. Method.   6. The method according to claim 4 or 5, wherein the diagnosis of the oil-filled electrical device is performed by combining the concentration in oil of benzene, toluene, ethylbenzene and xylene and the analysis result of the gas in oil of hydrocarbon having 1 to 3 carbon atoms. A method for diagnosing abnormalities in oil-filled electrical equipment.

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