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WO2008026997A1 - Procédé et dispositif destinés à déterminer la teneur en humidité dans une partie de l'isolation d'un transformateur de puissance pendant le séchage de celui-ci - Google Patents

Procédé et dispositif destinés à déterminer la teneur en humidité dans une partie de l'isolation d'un transformateur de puissance pendant le séchage de celui-ci Download PDF

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Publication number
WO2008026997A1
WO2008026997A1 PCT/SE2007/050583 SE2007050583W WO2008026997A1 WO 2008026997 A1 WO2008026997 A1 WO 2008026997A1 SE 2007050583 W SE2007050583 W SE 2007050583W WO 2008026997 A1 WO2008026997 A1 WO 2008026997A1
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WO
WIPO (PCT)
Prior art keywords
test body
moisture content
insulation
power transformer
determining
Prior art date
Application number
PCT/SE2007/050583
Other languages
English (en)
Inventor
Lars ÖSTMAN
Uno GÄFVERT
Original Assignee
Abb Research Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Abb Research Ltd. filed Critical Abb Research Ltd.
Publication of WO2008026997A1 publication Critical patent/WO2008026997A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity

Definitions

  • the present invention relates to a method of determining the moisture content in a part of the insulation of a power transformer during or after drying thereof.
  • the invention also relates to a test device for determining the moisture content in a part of the insulation of a power transformer, comprising means for the measurement of dielectric frequency response in a piece of material, and means for determining a moisture content in said piece of material upon basis of the measured dielectric frequency response.
  • said measurement of dielectric frequency response is a measurement of frequency dependence of capacitance or permittivity and dielectric losses.
  • the insulation, paper windings as well as insulation made of wood or cellulose will adopt a certain level of humidity depending on the humidity of the surrounding atmosphere. Normally, the insulation material will adopt a humidity of approximately 5-8 percent when being exposed to free air during the production of the power transformer.
  • the manufacturing of power transformers includes a drying step, during which the transformer is subjected to vacuum and heat, and, depending on the specific technique being used, a vapour phase treatment or circulated hot air and vacuum, in order to lower the humidity of the electric insulation.
  • the length of the process is defined by measuring the extraction of water during the vacuum treatment. The process is stopped when a predetermined water extraction value (for example expressed in ml water per ton insulation and hour) is reached.
  • a predetermined water extraction value for example expressed in ml water per ton insulation and hour
  • Another similar situation is to define the need of further drying treatment, preferably vacuum treatment, when, after the drying process, the active part of the transformer is undergoing some final operations before it is placed in a tank in which the humidity of the insulation once again increases due to the surrounding air and needs to be regulated in order not to exceed predetermined maximum levels.
  • further drying treatment preferably vacuum treatment
  • US 6,870,374 of the applicant discloses a method for identifying abnormalities in power transformers, comprising the measurement of dielectric losses in a section of the insulation system, calculating the theoretical dielectric losses for the section based on the material properties, geometry and temperature of the section, and generating a graphical representation of a percent difference between the measured and calculated dielectric losses.
  • the method is only suggested for already produced transformers the condition of which is to be tested by such a method.
  • the disclosed method also teaches that the measurement be conducted on the very transformer itself, preferably on a plurality of parts thereof.
  • An advantage is that the method can be performed without the need of draining the transformer oil and that it may be used to identify which specific abnormality that a transformer insulation might have, possibly but not necessarily an elevated moisture level.
  • the method used is known as Determination of the Frequency Response of a material, DFR. THE OBJECT OF THE INVENTION
  • the object of the invention is achieved by the initially defined method, characterised by the steps of: providing a test body the moisture content characteristics of which corresponds to the moisture content characteristics of said part of the power transformer insulation, ; subjecting said test body to an atmosphere corresponding to the one that said part of the power transformer insulation is subjected to; determining the moisture content of said test body by means of measurement of the dielectric frequency response thereof; and determining the moisture content of said part of the power transformer insulation upon basis of the determined moisture content of said test body.
  • the object of the invention is also achieved by means of the initially defined device, characterised in that it comprises a separate test body the moisture content characteristics of which corresponds to the moisture content characteristics of said part of the power transformer insulation, and that the means for the measurement of dielectric frequency response are arranged so as to perform said measurement on said test body.
  • it comprises the further step of determining which part of the power transformer insulation is the one that dries most slowly, and defining that part as the part the moisture content of which is to be determined.
  • the test body is made of a material corresponding to the material of said part of the power transformer insulation. Thereby a good correspondence between measured moisture content of the test body and the actual moisture content of the transformer insulation may be obtained.
  • test body is preferably provided with a structure corresponding to the structure of said part of the power transformer insulation.
  • the test body has a laminar structure, and the dielectric loss is measured in a direction cross-wise to the extension planes of the laminate layers thereof.
  • a laminar structure is chosen when the transformer insulation the moisture content of which is to be determined has a corresponding laminar structure.
  • a clamping force is applied onto the test body in a direction cross-wise to the extension planes of the laminate layers thereof.
  • the test body is a homogenous body the water diffusion characteristics of which are similar to those of said part of the insulation.
  • the homogenous test body is modelled in order to have water diffusion characteristics as similar to the ones of the transformer insulation as possible.
  • the drying behaviour of the transformer insulation is simulated by means of said test body.
  • the test body could also be determined from experiments (not only modelled to be equivalent).
  • the determination of the moisture content of said part of the power transformer insulation is performed during a drying process in which the moisture content of the transformer insulation is reduced to acceptable transformer operation levels.
  • the transformer insulation is placed in a closed tank, a low pressure and heat is applied inside said tank, and that the test body is placed in the same tank as the transformer insulation.
  • Low pressure is referred to as vacuum or close to vacuum.
  • the measurement of the frequency dependence of capacitance or permittivity and dielectric losses in the test body is an on-line measurement, performed during the drying process.
  • said moisture content characteristics include the drying characteristics of said part of the insulation.
  • said test body corresponds to the part of the insulation that dries most slowly during a drying process.
  • the test body is made of a material corresponding to the material of said part of the power transformer insulation.
  • the test body is provided with a structure corresponding to the structure of said part of the power transformer insulation.
  • the test body presents a laminar structure, and said means for determining the moisture content therein upon basis of the measured dielectric frequency response is arranged to measure the dielectric frequency response in a direction cross-wise to the extension planes of the laminate layers thereof.
  • the device comprises a clamping means arranged to clamp the test body in a direction cross-wise to the extension planes of the laminate layers thereof.
  • the test body comprises a plurality of cellulose sheets joined to a laminate.
  • Such a test body might be preferred in cases when the transformer insulation has a corresponding laminar structure.
  • the test body has a homogenous structure the water diffusion characteristics of which are such that they correspond to those of the transformer insulation the moisture or water content of which is to be determined.
  • the homogenous test body may consist of a sheet or the like, provided with means that prevent or at least suppress the water diffusion in at least one direction, preferably the thickness direction thereof, in order to make the water diffusion therein resemble the one in said part of the transformer insulation.
  • Said means for preventing water diffusion in a predetermined direction may include a clamping means by means of which the test body is subjected to a compressing force, or a separate sheet of a water impermeable material applied to those sides of the test body from which water is not to diffuse to the surrounding environment.
  • a combination of separate sheets of water- impermeable material and clamping means for the accomplishment of predetermined water diffusion characteristics of the test body is also conceivable.
  • Fig. 1 is a schematic side view of a power transformer located in a vacuum tank during a drying step, and a test body and test apparatus assembly according to the invention
  • Fig. 2 is a more detailed view of the test body and test apparatus assembly shown in fig. 1, and
  • Fig. 3 is a view corresponding to the one of fig. 2 of a second embodiment of the inventive test body and apparatus.
  • Fig. 1 shows a tank 1 in which the active part 2 of a power transformer is located in a drying step during the production of a power transformer.
  • the active part 2 of the power transformer comprises paper-insulated copper conductors, pressboard details and a bottom and top insulation part 4, comprised by a laminate structure of compressed cellulose plates.
  • a transformer core or transformer core sheet 12 is also shown as part of the active part 2 of the transformer.
  • vacuum is generated in the tank or container 1, while, simultaneously, the power transformer is subjected to a vapour phase heating, in order to lower the humidity of the electric insulation.
  • the insulation material will have adopted a humidity of approximately 5-8 percent upon previously being exposed to free air during the production of the power transformer.
  • the drying of the active part 2 of the transformer is due to the fact that, under operational conditions, the humidity of the insulation material should be as low as approximately 0,5 percent in order to guarantee the required insulation properties.
  • the test body 5 is made of a piece of material corresponding to that of the electric insulation part 4, namely a structure of compressed cellulose plates, cellulose pressboard, adhered to each other, for example by means of a PE-glue. It has a geometry, for example a thickness, corresponding to the one of that part of the electric insulation part 4 that, upon experimental basis and experience, is known to have the highest moisture content and/or the slowest drying rate upon drying. Moreover, it has drying characteristics, especially a drying rate, that corresponds to said part of the electric insulation.
  • the test apparatus 6, 7 comprises a pair of voltage plates 6, applied on opposite sides of laminated test body 5, by means of which a voltage is applied across the test body 5.
  • the apparatus also comprises a clamping means 7 by means of which a clamping force is applied to the body 5 crosswise to the planes of the plates of the laminate structure.
  • DFR Dielectric Response Measurement
  • a computer 8 is connected to the test apparatus 6 and is provided with software adapted for the execution of the DFR and the presentation of the results thereof.
  • the measured dielectric response signature is compared to referential dielectric response signatures for different moisture contents previously determined for the test body 5 or a corresponding test piece.
  • the measured signature may, alternatively, be compared to calculated theoretical dielectric frequency responses.
  • the comparing may include comparing the shape of one or more graphical representations of a the dielectric frequency response with referential graphical representations.
  • test apparatus 6, 7 should or may comprise all equipment necessary for performing the steps of a conventional Dielectric Response Measurement, DFR, for the purpose of measuring the moisture content in the proposed test body.
  • DFR Dielectric Response Measurement
  • fig. 3 shows an alternative embodiment of the inventive test body 5 and test apparatus 6.
  • the major difference between the embodiment of fig. 3 and that of fig. 2 is the design of the test body 5.
  • the test body 5 is constituted by a homogenous single sheet made of a cellulose, a cellulose pressboard.
  • Two layers or sheets 10, 11 made of a water-impermeable material, such as a resin, are applied to and cover a part, preferably a major part, of the large sides of the test body sheet 5.
  • Said voltage plates 6 are applied at regions of large sides of the test body 5 not covered by said sheets 10, 11 of water- impermeable material.
  • a clamping means 7 by means of which the sheets 10, 11 of water impermeable material are clamped to the test body 5, and by means of which the test body 5 is subjected to a predetermined compressive force in order to make the water diffusion characteristics of the test body 5 resemble those of the transformer insulation 4 as much as possible.
  • the water in the test body will diffuse in a lateral direction, perpendicular to the thickness direction thereof. Thereby, water will diffuse at a rate corresponding to the diffusion rate of the water in the part of transformer insulation 4 the moisture content of which is to be determined.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

La présente invention concerne un procédé destiné à déterminer la teneur en humidité dans une partie de l'isolation (4) d'un transformateur de puissance. Le procédé comprend les étapes suivantes : fourniture d'un dispositif d'essai (5) dont les caractéristiques de la teneur en humidité correspondent aux caractéristiques de la teneur en humidité de ladite partie de l'isolation (4) d'un transformateur de puissance ; exposition dudit dispositif d'essai (5) à une atmosphère correspondant à celle à laquelle ladite partie de l'isolation (4) du transformateur de puissance est soumise ; détermination de la teneur en humidité dudit dispositif d'essai (5) par des moyens de mesure de sa réponse en fréquence diélectrique ; et détermination de la teneur en humidité de ladite partie de l'isolation (4) d'un transformateur de puissance sur la base de la teneur en humidité déterminée dudit dispositif d'essai (5).
PCT/SE2007/050583 2006-08-29 2007-08-28 Procédé et dispositif destinés à déterminer la teneur en humidité dans une partie de l'isolation d'un transformateur de puissance pendant le séchage de celui-ci WO2008026997A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0601766 2006-08-29
SE0601766-9 2006-08-29

Publications (1)

Publication Number Publication Date
WO2008026997A1 true WO2008026997A1 (fr) 2008-03-06

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2138834A1 (fr) * 2008-06-26 2009-12-30 ABB Technology Ltd Corps de test, agencement de test, procédé de fabrication d'un corps de test, et procédé pour déterminer un contenu de moisissure dans l'isolation d'un transformateur d'alimentation au cours de son séchage
RU2495445C2 (ru) * 2008-04-14 2013-10-10 Абб Рисерч Лтд Определение ухудшенной изолирующей способности в изоляции, предусмотренной между двумя объектами индуктивного рабочего элемента
CN107808766A (zh) * 2017-08-24 2018-03-16 西南交通大学 一种大型牵引变压器闭环式干燥的工艺方法
US11193905B2 (en) 2018-10-24 2021-12-07 Hitachi Energy Switzerland Ag Electrical device provided with a moisture sensor
CN115421013A (zh) * 2022-10-09 2022-12-02 哈尔滨理工大学 一种倒立式电流互感器绝缘受潮及老化评估方法
RU2788308C1 (ru) * 2022-06-27 2023-01-17 Общество с ограниченной ответственностью "Инжиниринговый Центр Элхром" (ООО "Инжиниринговый Центр Элхром") Способ и устройство непрерывного контроля влажности бумажно-масляной изоляции высоковольтного маслонаполненного оборудования

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1016899A (en) * 1961-11-07 1966-01-12 Licentia Gmbh Improved method of detecting moisture in insulation material of an electrical winding
US3961246A (en) * 1974-11-07 1976-06-01 Allis-Chalmers Corporation Capacitance method of monitoring insulation dryness of an electrical induction apparatus
DE10013001A1 (de) * 2000-03-06 2001-09-20 Hossein Borsi Verfahren zur Bestimmung der Feuchtigkeit in Flüssigkeits-Papier-isolierten Anlagen wie Transformatoren
US6449580B1 (en) * 1998-05-11 2002-09-10 Entek Ird International Corporation Evaluating properties of oil using dielectric spectroscopy
WO2004008129A2 (fr) * 2002-07-15 2004-01-22 Michel Belanger Procede et dispositif de surveillance du taux d'humidite d'un materiau dielectrique solide immerge

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1016899A (en) * 1961-11-07 1966-01-12 Licentia Gmbh Improved method of detecting moisture in insulation material of an electrical winding
US3961246A (en) * 1974-11-07 1976-06-01 Allis-Chalmers Corporation Capacitance method of monitoring insulation dryness of an electrical induction apparatus
US6449580B1 (en) * 1998-05-11 2002-09-10 Entek Ird International Corporation Evaluating properties of oil using dielectric spectroscopy
DE10013001A1 (de) * 2000-03-06 2001-09-20 Hossein Borsi Verfahren zur Bestimmung der Feuchtigkeit in Flüssigkeits-Papier-isolierten Anlagen wie Transformatoren
WO2004008129A2 (fr) * 2002-07-15 2004-01-22 Michel Belanger Procede et dispositif de surveillance du taux d'humidite d'un materiau dielectrique solide immerge

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2495445C2 (ru) * 2008-04-14 2013-10-10 Абб Рисерч Лтд Определение ухудшенной изолирующей способности в изоляции, предусмотренной между двумя объектами индуктивного рабочего элемента
EP2138834A1 (fr) * 2008-06-26 2009-12-30 ABB Technology Ltd Corps de test, agencement de test, procédé de fabrication d'un corps de test, et procédé pour déterminer un contenu de moisissure dans l'isolation d'un transformateur d'alimentation au cours de son séchage
WO2009156296A1 (fr) * 2008-06-26 2009-12-30 Abb Technology Ltd Corps de test, système de test, procédé de fabrication d’un corps de test, et procédé de détermination d’une teneur en eau de l’isolation d’un transformateur de puissance durant son séchage
US8525535B2 (en) 2008-06-26 2013-09-03 Abb Technology Ltd. Test body, test arrangement, method for manufacturing of a test body, and method for determining a moisture content of the insulation of a power transformer during drying thereof
CN107808766A (zh) * 2017-08-24 2018-03-16 西南交通大学 一种大型牵引变压器闭环式干燥的工艺方法
US11193905B2 (en) 2018-10-24 2021-12-07 Hitachi Energy Switzerland Ag Electrical device provided with a moisture sensor
RU2788308C1 (ru) * 2022-06-27 2023-01-17 Общество с ограниченной ответственностью "Инжиниринговый Центр Элхром" (ООО "Инжиниринговый Центр Элхром") Способ и устройство непрерывного контроля влажности бумажно-масляной изоляции высоковольтного маслонаполненного оборудования
CN115421013A (zh) * 2022-10-09 2022-12-02 哈尔滨理工大学 一种倒立式电流互感器绝缘受潮及老化评估方法

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