Continuous monitoring of water content in the solid insulation of a transformer

Abstract

A system, a method, and / or a computer program for measuring the water content in the insulating material of a transformer, including: obtaining measurements of temperature and relative humidity in two points in the oil where the two temperatures are different, obtaining a measurement of temperature in the insulator material, obtaining parameters (a, b, k and d) for the insulator's particular material, and calculating of the water content in the insulating materials from the relative humidity and temperature at two points in the oil, using the parameters of the insulating materials and according to the temperatures measured in the insulating materials.

Description

[0001] CONTINUOUS MONITORING OF WATER CONTENT IN THE SOLID INSULATION OF A TRANSFORMER

[0002] FIELD

[0003] The method and apparatus disclosed herein are related to the field of electric grid, and, more particularly but not exclusively to electric stations, transformers and reactors of power stations and substations, and, more particularly but not exclusively to monitoring and calculating water content in the solid insulation of a transformer.

[0004] BACKGROUND

[0005] A transformer is a critical element of every electric station and grid. The transformer is immersed in dielectric liquid and includes a magnetic core and windings. The winding includes conductor wires that are insulated by cellulose paper, for example Kraft papers. The insulation between the windings, between the windings and the core, between the windings and the tank containing the dielectric liquid is made by pressboard.

[0006] Water in insulating materials adversely affects their properties. In a transformer, approximately 99% of the water is in the cellulose insulation and 1% in the oil. Increasing amount of water in the insulation can lead to the formation of partial discharges and electrical breakdown.

[0007] The lack of direct access to the measurement of the water content of the solid insulation leads to an indirect assessment through the measurement of the water content of the insulating liquid. As the water absorption parameters of insulating liquids are different, and for the same liquid these parameters may change during operation of transformers.

[0008] It would therefore be highly advantageous to have a method and a system for continuously measuring the water content of the oil within the insulation material.

[0009] SUMMARY

[0010] According to one exemplary embodiment there is provided a system, a method, and / or a computer program for measuring the water content in the insulating material of a transformer, including: obtaining measurements of temperature and relative humidity in two points in the oil where the two temperatures are different, obtaining a measurement of temperature in the insulator material, obtaining parameters (a, b, k and d) for the insulator’s particular material, and calculating of the water content in the insulating materials from the relative humidity and temperature at two points in the oil, using the parameters of the insulating materials and according to the temperatures measured in the insulating materials.

[0011] According to another exemplary embodiment a fiber-optic temperature sensor may be used to measure temperature in the insulating material.

[0012] According to yet another exemplary embodiment the obtained parameters are at least one of: for Kraft paper a=6.1, b=0.04, k=0.33 and d=0.0033; and for pressboard B a=3.74, b=0.032, k=0.63 and d= - 0.0017.

[0013] According to still another exemplary embodiment all the measurements, and the calculation of the water content in the insulating materials, are executed repeatedly and / or continuously.

[0014] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the relevant art. The materials, methods, and examples provided herein are illustrative only and not intended to be limiting. Except to the extent necessary or inherent in the processes themselves, no particular order of steps or stages of methods and processes described in this disclosure, including the figures, is intended or implied. In many cases the order of process steps may vary without changing the purpose or effect of the methods described.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Various embodiments are described herein, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the embodiments only, and are presented in order to provide what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the embodiment.

[0017] In this regard, no attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the subject matter, the description taken with the drawings making apparent to those skilled in the art how the several forms and structures may be embodied in practice. In the drawings:

[0018] Fig. l is a simplified illustration of transformer monitoring system including a power transformer, a monitoring computer, and sensors;

[0019] Fig. 2 is a simplified block diagram of a computational device for monitoring the transformer system; and

[0020] Fig. 3 is a simplified flow chart of a process for calculating water content in insulation material of a transformer.

[0021] DETAILED DESCRIPTION

[0022] The present embodiments comprise a system, a method, and / or a computer program for measuring the water content of the insulating material of a transformer of an electric grid.

[0023] The principles and operation of the system, a method, and / or a computer program for accurately measuring the location of origin of an electric signal resulting from an intermittent fault in an electric cable of an electric grid according to the several exemplary embodiments may be better understood with reference to the following drawings and accompanying description.

[0024] Before explaining at least one embodiment in detail, it is to be understood that the embodiments are not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. Other embodiments may be practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

[0025] In this document, an element of a drawing that is not described within the scope of the drawing and is labeled with a numeral that has been described in a previous drawing has the same use and description as in the previous drawings. Similarly, an element that is identified in the text by a numeral that does not appear in the drawing described by the text, has the same use and description as in the previous drawings where it was described.

[0026] The drawings in this document may not be meant to be in any scale. Different Figs, may use different scales and different scales can be used even within the same drawing, for example different scales for different views of the same object or different scales for the two adjacent objects.

[0027] The phrases “at least one” “one or more” and “and / or” are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C, “at least one of A, B, or C, “one or more of A, B, and C. “one or more of A, B, or C and “A, B, and / or C means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together. The terms “a” or “an entity” refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more' and “at least one' can be used interchangeably herein.

[0028] It is also to be noted that the terms ‘comprising’, ‘including’, ‘containing’, ‘characterized by’, and ‘having’ are all inclusive, open-ended, does not exclude additional, unrecited elements or method steps, and can be used interchangeably. Particularly, these terms may imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term “comprising” such as “comprise” and “comprises”.

[0029] Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic that is described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases “in one embodiment,” “in an embodiment, and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0030] The term ‘plurality’, as used herein, is defined as two or more than two. The term ‘another’, as used herein, is defined as at least a second or more. The term ‘coupled’, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.

[0031] In this document, the term ‘computing device’ may refer to any type of computing machine, including but not limited to, a controller, a computer, a portable computer, a laptop computer, a tablet computer, a mobile communication device, a network server, a cloud computer, etc., as well as any combination thereof. Such computing device or computing machine may include any type or combination of devices, including, but not limited to, a processor or a processing device, a memory device, a storage device, a user interface device, and / or a communication device.

[0032] The terms ‘execute’, ‘perform’, compute, calculate, etc. may refer to a processor of a computational device executing a software program code embodied on a non-transitory computer readable medium to achieve a result such as described after any of the terms ‘execute’, ‘perform’, compute, calculate, etc.

[0033] The term ‘client computing device’, or ‘client device’, ‘user device’ may refer to any type of computing device that is directly used, or operated, by a user. Such device may include a user interface that may be used by a user directly, including means for user input and / or user output. Such device may be communicatively coupled to another computing devices such as a network server via a communication network.

[0034] Means for user input may include a keyboard, a pointing devices such as a mouse, a microphone, a camera, a touch-sensitive plate or display, means for user gesture control, means for haptic user control, etc.

[0035] Means for user output may include a display, and / or any other means for providing visual information, a speaker, or an earphone, and / or any other means for providing audible information, means for providing tactile and / or haptic information, etc.

[0036] The term ‘communication network’ or ‘network’ may refer to any type or technology for digital communication including, but not limited to, the Internet, WAN, LAN, MAN, PSDN, etc. Any of the abovementioned technologies may be wired or wireless, for example, Wireless WAN such as WiMAX, WLAN (Wi-Fi), WPAN (Bluetooth), etc. Wireless networking technology may also include PLMN, and / or any type of cellular network. The term ‘communication network’ or ‘network’ may refer to any combination of communication technologies, and to any combination of physical networks. The term ‘communication network’ or ‘network’ may refer to any number of interconnected communication networks that may be operated by one or many network operators.

[0037] The term ‘application’ may refer to a software program running on, or executed by, one or more processors of a computing devices, and particularly by a mobile computing device such as a mobile telephone, a tablet, a smartphone, etc., as well as any other mobile or portable computing facility. The term ‘mobile application’ may refer to an application executed by a mobile computing device. In this document the terms ‘electric transmission network’, ‘electrical transmission network’, ‘electricity transmission network’, ‘electric power transmission’, ‘power line’, ‘power transmission’ and ‘power grid’ can be used interchangeably and relate to either or both underground and overhead transmission. The terms ‘grid’, or ‘electric grid’, or ‘electric network’ may refer to the electric transmission network and / or the electric distribution network, and to any part of such network between the power generating station, or stations, and the load, or the consumer(s).

[0038] The device measuring the electric signal may be an electric sensor operative to measure one or more electric parameters such as electric voltage and / or electric current.

[0039] The term ‘measurement’ or ‘electrical measurement’ may refer to any type of measurement of any electric parameter such as voltage, current, electric field, magnetic field, resistance, capacitance, inductance, electric charge, etc. The term ‘physical measurement’ or ‘mechanical measurement’ may refer to any type of measurement of any physical parameter other than electrical parameters. Such parameters may be temperature, humidity, etc.

[0040] The term ‘electrically coupled’, or ‘electrically connected’, or simply ‘connected’ may refer to direct or indirect electric contact (galvanic contact).

[0041] The terms ‘water content’, ‘moisture content’, ‘moisture’, and ‘humidity’ may be used interchangeably to mean the amount of any water phase that is contained within another fluid or solid.

[0042] The terms ‘insulator’, ‘insulator material’, ‘solid insulation’, ‘paper insulator’, and ‘paper’ may be used interchangeably to refer to the insulator material used in a power transformer, such as oil-impregnated cellulose insulation material.

[0043] The term ‘oil’ may refer to any dielectric fluid that may be used for cooling the core of a power transformer.

[0044] Reference is now made to Fig. 1, which is a simplified illustration of a transformer monitoring system 10 including a transformer 11, a monitoring computer 12, and sensors, according to one exemplary embodiment.

[0045] Fig. 1 shows a simplified illustration of a cut through power transformer 11. The cut reveals a tank 13 that is filled with oil 14, and an active part transformer 15 immersed in oil 14. Active part 15 may include a magnetic core 16 on which a primary winding 17 and a secondary winding 18 are wound. Primary winding 17 and secondary winding 18 are made from conductive wire. Primary winding 17 and a secondary winding 18 are shown in Fig. 1 in a symbolic graphical manner.

[0046] Each of primary winding 17 and a secondary winding 18 is made of insulated wires. Insulation materials, such as insulating barriers 19 may be provided between windings 17 and 18, and between windings 18 and core 16, and between winding 17 and tank 13 by insulating barriers 19. Insulation material 19 may be made of cellulose, such as paper and pressboard, however, any applicable material is contemplated.

[0047] Several sensors of transformer monitoring system 10 are placed in transformer 11 and are electrically coupled to computer 12. A first pair of sensors including one temperature sensor 20 and one humidity sensor 21 is placed in a first location in oil 14, and a second pair of sensors including one temperature sensor 22 and one humidity sensor 23 is placed in a second location in oil 14. The temperature of the oil 14 in the first location should be different than the temperature of the oil 14 in the second location. Therefore, temperature sensor 20 and humidity sensor 21 are located in a higher part of the oil 14 in tank 13, where the temperature is relatively higher, and temperature sensor 22 and humidity sensor 23 are located in a lower part of the oil 14 in tank 13, where the temperature is relatively lower.

[0048] Another group of sensors includes temperature sensor 24 that may be located within the insulation materials 19. It is appreciated that transformer monitoring system 10 may use any number of temperature sensors 24 to calculate the water content in several respective places within insulation materials 19 where temperature sensors 24 are located.

[0049] Equation 1 below calculates the water content Wpx, or humidity, in the insulation 19 where temperature sensor 24 is located, based on the measurements of temperature sensors 20, 22 and 24 and humidity sensors 21 and 23.

[0050] In equation 1, the measurements of temperature sensor 20 is denoted by Ti, the measurements of temperature sensor 22 is denoted as T2, and the measurements of temperature sensor 24 is denoted by Tx, all in Kalvin degrees. RHi denotes the measurement of humidity sensor 21, and REE denotes the measurement of humidity sensor 23, both given as the relative humidity of water in oil.

[0051] Where the term v may be calculated by equation 2

[0052] The parameters a, b, k, and d may depend on the insulation material used. For Example, the parameters a, b, k, and d are given in table A below for two exemplary types of insulation material.

[0053] Table A

[0054] The parameters 8.94 and 2254 in equation 2 are the empirical values for calculating maximum vapor pressure of water in air Pnin torr is function of air temperature, as follows: logPn=8.94-2254 / T.

[0055] Hence, by introducing the measured values T i (of temperature sensor 20), RHi (of moisture sensor 21), T2 (of temperature sensor 22), RH2 (of moisture sensor 23) and Tx(of temperature sensor 24) into equations 1 and 2, and selecting the appropriate parameters a, b, k, and d (for the insulating material is use) it is possible to calculate the moisture content Wpx in percents (%) within the insulation material 19 of a transformer 11.

[0056] It is appreciated that temperature sensor 24 may use optical temperature measurement technology, such as a fiber optic temperature sensors that may be connected to high voltage windings. Other types of sensors simulating winding temperature can be used. It is appreciated that equations 1 and 2, and the parameters (a, b, k, and d) selected for the insulating material is use may provide the water content of the insulating material independently of the type of oil used, the aging of the oil, etc.

[0057] Reference is now made to Fig. 2, which is a simplified block diagram of a computational device 25, typically provided as computer 12 or a similar means of controlling transformer monitoring system 10, according to one exemplary embodiment.

[0058] As an option, the block diagram of Fig. 2 may be viewed in the context of the details of the previous Figures. Of course, however, the block diagram of Fig. 2 may be viewed in the context of any desired environment. Further, the aforementioned definitions may equally apply to the description below.

[0059] As shown in Fig. 2, computational device 25 may include at least one processor unit 26, one or more memory units 27 (e.g., random access memory (RAM), a non-volatile memory such as a Flash memory, etc.), one or more storage units 28 (e.g. including a hard disk drive and / or a removable storage drive, representing a floppy disk drive, a magnetic tape drive, a compact disk drive, a flash memory device, etc.).

[0060] Computational device 25 may also include one or more communication units 29. Such communication unit 29 may use any type of communication technology, particularly RF communication technology, particularly communication technology such as Wi-Fi, Bluetooth, ZigBee, and any remote-control communication technology as may be used by cable device 10 to communicate with any other cable device 10 or with a remote controller, a remote server, or any other computational device.

[0061] Computational device 25 may also include one or more communication buses 30 connecting the above units. Computational device 25 may also include one or more control circuitry 31 for controlling other devices coupled to, or included in, computational device 25. Such devices may be temperature sensors 20, 22 , and / or 24 and / or humidity sensors 21, and / or 23.

[0062] Computational device 25 may also include one or more computer programs 32, or computer control logic algorithms, which may be stored in any of the memory units 27 and / or storage units 28. Such computer programs, when executed, enable computing system 25 to perform various functions as set forth herein. Memory units 27 and / or storage units 28 and / or any other storage are possible examples of tangible computer-readable media. Particularly, computer programs 32 may include a software program and collected data for computing water content in insulation material 19 according to equation 1 and equation 2 as described above.

[0063] Reference is now made to Fig. 3, which is a simplified flow chart of a process 33 for calculating water content in insulation material 19, according to one exemplary embodiment.

[0064] As an option, the block diagram of Fig. 3 may be viewed in the context of the details of the previous Figures. Of course, however, the block diagram of Fig. 3 may be viewed in the context of any desired environment. Further, the aforementioned definitions may equally apply to the description below.

[0065] Fig. 3 may describe process, or method, 33 for using the sensors of Fig. 1 to compute the moisture content in the insulation material 19 of transformer 11. The process, or method, may be executed by a user using computer 12, and may be embodied (in part or in whole) in computer code such as computer code 32 of computational device 25 of Fig. 2.

[0066] Process, or method, 33 may start with action 34 by identifying the type of the insulation material 19 used in the transformer 11. Process 33 may then proceed to action 35 to obtain particular parameters a, b, k, and d for the type of the insulation material 19 used in the transformer 11 and introduce these values to code 32. For example, a user may select particular parameters a, b, k, and d from a database of code 32.

[0067] Process 33, or code 32, may then proceed to action 36 to obtain measurements of temperature and moisture content in two different locations in the oil in transformer 11, where the temperatures are different. For example, the temperature as measured by temperature sensor 20 and the moisture level as measured by co-located humidity sensor 21, both located in a high position in transformer 11, and the temperature as measured by temperature sensor 22 and the moisture level as measured by co-located humidity sensor 23 both located in a low position in transformer 11. If in action 37 these two temperatures are not different then process 33 informs the user and stops (action 38).

[0068] If the two temperatures of temperature sensors 20 and 22 are different, process 33 may proceed to action 39 to obtain temperature measurement within the insulation material in the transformer, such as may be measured by temperature sensors 24. Process 33 may then proceed to action 40 to compute the moisture content in the insulation material according to equations 1 and 2, resulting in the moisture content at the region of the insulation material 19 where temperature sensor 24 is located. Process 33 may then proceed to action 41 to communicate the computation result to a user.

[0069] It is appreciated that process 33 may be executed by computer 12 automatically, repeatedly, and / or continuously. Therefore, all measurements are executed repeatedly and / or continuously and the calculation of the water vapor pressure in the insulator material are all automatically, repeatedly and / or continuously. It is appreciated that the calculation of moisture content, or water vapor pressure, in the insulator material is independent of the characteristics of the oil, and therefore there is no need to sample the oil to measure oil parameters. Therefore, a user may set a threshold value for the water vapor pressure in the insulator and the transformer monitoring system 10 may alarm a user when the calculated water vapor pressure is equal and / or greater than the threshold value.

[0070] Returning to Fig. 3, process 33 may proceed to action 42 to compare the calculated water vapor pressure to the threshold value and, if the calculated water vapor pressure is higher than the threshold value continue to action 43 to alarm a user. Process 33 may repeat actions 36 to 43 continuously. Alternatively, process 33 may repeat actions 36 to 38, and actions 39 to 43 independently of each other.

[0071] It is appreciated that certain features, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

[0072] Although descriptions have been provided above in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation, or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art.

Claims

CLAIMSWhat is claimed is:

1. A method for calculating water content in an insulator material of a voltage transformer, the method comprising: obtaining measurements of temperature and relative humidity in two points in the oil where the two temperatures are different; obtaining a measurement of temperature in the insulator material; obtaining parameters (a, b, k, and d) for the insulator’s particular material; and calculating of the water content in the insulating materials from the relative humidity and temperature at two points in the oil, using the parameters of the insulating materials and according to the temperatures measured in the insulating materials.

2. The method according to claim 1, additionally comprising: using a fiber-optic temperature sensor to measure temperature in the insulating material.

3. The method according to claim 1, wherein the obtained parameters are at least one of: a=6.1, b=0.04, k=0.33, and d=0.0033; and a=3.74, b=0.032, k=0.63, and d= - 0.0017.

4. The method according to claim 1, wherein all measurements and the calculating the water content in the insulating materials are executed at least one of repeatedly and continuously.

5. The method according to claim 1, additionally comprising: obtaining a threshold value; comparing the calculated water content in the insulating material with the threshold value; and alarming a user when the calculated water content in the insulating material is at least one of greater and equal to the threshold value.

6. A system for determining water content in an insulating materials of a transformer, the system comprising: a first pair of first temperature sensor and first humidity sensor located in a first location in oil inside the transformer; a second pair of second temperature sensor and second humidity sensor located in a second location in the oil inside the transformer, wherein the temperature in the second location is different from the temperature in the first location; a third temperature sensors located within the insulator material; a computational device electrically coupled to the first temperature sensor, the first humidity sensor, the second temperature sensor, the second humidity sensor, and the third temperature sensor, and operative to: obtain measurements of temperature and relative humidity in the two locations in the oil; obtain a measurement of temperature in the insulator material; obtain parameters (a, b, k, and d) for the insulating particular material; and compute the water content in the in the insulating materials from the relative humidity and temperature at two points in the oil, using the selected parameters of the insulating materials and according to the temperatures measured in the insulating materials.

7. The system according to claim 6, wherein the temperature sensor in the insulator material is a fiber-optic temperature sensor.

8. The system according to claim 6, wherein the obtained parameters are at least one of: a=6.1, b=0.04, k=0.33, and d=0.0033; and a=3.74, b=0.032, k=0.63, and d=-0.0017.

9. The system according to claim 6, wherein all measurements and the calculating of the water content in the insulating material are executed at least one of repeatedly and continuously.

10. The method according to claim 6, additionally comprising: a user interface module for obtaining a threshold value; a module for comparing the calculated water content with the threshold value; and a user interface module for communicating an alarm to a user when the calculated water content in the insulating material is at least one of greater and equal to the threshold value.

11. A computer program product embodied on a non-transitory computer readable medium, comprising computer code for: obtaining measurements of temperature and relative humidity in two points in the oil where the two temperatures are different; obtaining a measurement of temperature in the insulator material; obtaining parameters (a, b, k, and d) for the insulator’s particular material; and calculating of the water content in the insulating materials from the relative humidity and temperature at two points in the oil, using the parameters of the insulating materials and according to the temperatures measured in the insulating materials.

12. The computer program product according to claim 11, additionally comprising: using a fiber-optic temperature sensor to measure temperature in the insulating material.

13. The computer program product according to claim 11, wherein the obtained parameters are at least one of: a=6.1, b=0.04, k=0.33, and d=0.0033; and a=3.74, b=0.032, k=0.63, and d= - 0.0017.

14. The computer program product according to claim 11, wherein all measurements and the calculating the water content in the insulating materials are executed at least one of repeatedly and continuously.

15. The computer program product according to claim 11, additionally comprising: obtaining a threshold value;comparing the calculated water content in the insulating material with the threshold value; and alarming a user when the calculated water content in the insulating material is at least one of greater and equal to the threshold value.

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