Apparatus and method for non-invasively sensing the internal temperature of a fluid contained within a housing - Patents.com

Abstract

An apparatus and method are provided for non-invasively determining the temperature of a fluid within a housing. A first and a second temperature sensor are positioned such that a temperature difference exists between the first and second temperature sensors. The difference between the temperature of the first and second temperature sensors can be used to estimate the temperature of the fluid within the housing and / or a zero heat flow method can be used to determine the temperature of the fluid within the housing.

Description

[Technical field]

[0001] Some embodiments relate to an apparatus for measuring temperature.Some embodiments relate to an apparatus for non-invasively determining and / or estimating a temperature of a fluid contained within a housing.Some embodiments relate to a method for measuring temperature.Some embodiments relate to a method for non-invasively determining and / or estimating a temperature of a fluid contained within a housing. [Background technology]

[0002] Electrical devices are commonplace in modern society. A variety of electrical devices are used in the electrical grid, such as transformers, capacitors, reactors, and voltage regulators. Electrical devices, such as transformers, often contain components enclosed within a housing that is filled with a dielectric fluid, such as mineral oil, natural or synthetic ester fluid, or silicone oil, to maintain a stable operating temperature for the electrical device and to prevent or quickly dissipate any electrical discharges.

[0003] It is important to maintain the operating temperature of an electrical device, as reflected by the temperature of the dielectric fluid contained within the housing of the electrical device, within a desired range. The remaining life of an electrical device, such as a transformer, can decrease as the operating temperature of the electrical device increases. For example, for some electrical devices, such as transformers, the remaining life of the device can decrease by as much as half for approximately every 5°C to 10°C increase in the continuous operating temperature experienced by the device.

[0004] If electrical equipment is regularly or consistently operated at high temperatures, it may fail prematurely (i.e., before the expected life of the electrical equipment has elapsed). If electrical equipment is regularly or consistently operated at higher than desired operating temperatures, it may be prudent to replace such electrical equipment with electrical equipment having a greater load capacity.

[0005] As an example, the longer a transformer operates at an overload temperature, the shorter its expected lifespan will be, since transformer life degradation is a function of both time and temperature. Short term overloads will not have a significant impact on expected lifespan unless the temperature is very extreme. However, frequent overloads will have a significant impact on the expected lifespan of a transformer. Therefore, if the transformer is only slightly overloaded, the utility company will monitor further to determine if this is a regular occurrence or a random event. If found to be a regular occurrence, the transformer can be replaced with a larger one designed to handle the higher load. If the transformer is significantly overloaded, it is an indication that significant life degradation may already have occurred and that the transformer may be overloaded to some degree on a regular basis.

[0006] Some utilities have developed techniques to optimize the lifespan of equipment and the effort required to maintain it. Such techniques may include classifying overloaded equipment based on its operating temperature relative to a reference temperature and taking different actions based on such classification. For example, if a transformer is designed to operate at a reference temperature of 90°C, the transformer may be classified as "overloaded" if it is operating at 110°C and as "severely overloaded" if it is operating at 120°C. Equipment that is "overloaded" may be monitored more closely for a period of time, and equipment that is "severely overloaded" may be replaced immediately.

[0007] There is a need to provide a device that can sense and communicate temperature changes within electrical equipment to assist in determining whether the electrical equipment is operating in an "overloaded" or "extremely overloaded" condition. The sooner such an over-temperature situation can be detected and notified to the relevant power authorities, the sooner the situation can be addressed, thereby preventing premature or catastrophic failure of the electrical equipment.

[0008] There is also a need to provide a device that can non-invasively and accurately sense and communicate temperature changes within electrical equipment. US Patent No. 5,399, 363 to Frounfelker et al. teaches a system and method for estimating the temperature of a fluid contained within an electrical device without direct thermal communication with the fluid. The method includes measuring the temperature of an exterior wall of a housing for the electrical device, measuring an ambient temperature around the housing, and estimating the temperature of the fluid within the housing using the measured wall temperature and the measured ambient temperature. The method also purportedly can adjust the estimated fluid temperature for ambient humidity conditions.

[0009] The foregoing examples of the related art and limitations associated therewith are intended to be illustrative and not exhaustive. Other limitations of the related art will become apparent to those of ordinary skill in the art upon reading this specification and studying the drawings. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 9,395,252 Summary of the Invention [Problem to be solved by the invention]

[0011] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods that are intended to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the problems discussed above are mitigated or eliminated, while other embodiments are directed to other improvements. [Means for solving the problem]

[0012] In one aspect, a device is provided for non-invasively estimating a temperature inside a housing. The device has an environmental shielding portion shaped and configured to shield at least a portion of the housing from prevailing environmental conditions, a first temperature sensing element disposed within the environmental shielding portion and positioned proximate to the housing during use of the device, and a second temperature sensing element spaced from the environmental shielding portion and positioned proximate to the housing during use of the device. In some aspects, the second temperature sensing element is exposed to a majority of prevailing environmental conditions or is exposed to more prevailing environmental conditions than the first temperature sensing element. In some aspects, the device has a cartridge portion shaped and configured for insertion into a cartridge housing extending inside the housing, the cartridge portion housing the second temperature sensing element. In some aspects, the device has a sensor for determining that the cartridge portion is inserted into the cartridge housing.

[0013] In one aspect, a method of using the above-described device is provided, the method comprising the steps of determining whether a cartridge portion is inserted into the cartridge housing, and if it is determined that the cartridge portion is inserted into the cartridge housing, either directly measuring a temperature of a fluid contained in the housing using a third thermal sensing element, or if it is determined that the cartridge portion is not inserted into the cartridge housing, estimating a temperature of a fluid contained in the housing using the first and second thermal sensing elements.

[0014] In one aspect, a method of estimating a temperature of a fluid contained within a housing is provided, the method comprising measuring a first temperature at a first external location on the housing, the first external location being protected from environmental conditions; measuring a second temperature at a second external location on the housing, the second external location being exposed to the environmental conditions or more exposed to the environmental conditions as compared to the first external location; and correlating a difference between the first temperature and the second temperature to estimate a temperature of the fluid contained within the housing.

[0015] In one aspect, an apparatus is provided for estimating a temperature of a fluid contained within a housing, the apparatus having a first thermal sensing element, a second thermal sensing element, a heating element disposed outside both the first and second thermal sensing elements, and insulation differentially disposed relative to the first and second thermal sensing elements.

[0016] In one aspect, a method of estimating a temperature of a fluid contained within a housing is provided, the method comprising the steps of: (i) measuring a first temperature at a first location proximate to the housing; (ii) measuring a second temperature at a second location, where initially a temperature difference exists between the first location and the second location; (iii) if the first temperature differs from the second temperature, activating a heating element disposed outside both the first and second locations; (iv) repeating steps (i)-(iii) until the first and second temperatures are determined to be the same; and (v) determining that the temperature of the fluid contained within the housing is the same as the first and second temperatures.

[0017] In one aspect, an apparatus for estimating a temperature of a fluid contained within a housing is provided, the apparatus having a first thermal sensing element, a second thermal sensing element, and an insulating material arranged to be located between the housing and the second thermal sensing element during use of the apparatus.

[0018] In one aspect, a method of estimating a temperature of a fluid contained within a housing is provided, the method comprising measuring a first temperature at a first location on the housing and a second temperature at a second location, where insulation is disposed between the housing and the second location, and estimating a temperature of the fluid contained within the housing based on a relationship between the first temperature and the second temperature.

[0019] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions. Exemplary embodiments are illustrated in the referenced figures in the drawings. It is intended that the embodiments and figures disclosed herein should be considered illustrative and not restrictive. [Brief description of the drawings]

[0020] [Figure 1] 1 shows an exemplary embodiment of an electrical device, namely a transformer. [Figure 2A] 1 illustrates a second exemplary embodiment of an electrical device, namely a transformer, having an internal recess formed therein. [Figure 2B] 2B is a cross-sectional view of the electrical device of FIG. 2A taken along line 2B-2B. [Figure 3A] 1 illustrates a cross-sectional view of an example embodiment of a temperature sensor that can be used to estimate the temperature of a fluid in a housing using the zero heat flow method. [Figure 3B] 1 shows a cross-sectional view of a second exemplary embodiment of a temperature sensor that can be used to estimate the temperature of a fluid in a housing using the zero heat flow method. [Figure 4] 1 illustrates an exemplary embodiment of a method for estimating the temperature of a fluid in a housing using a zero heat flow method. [Figure 5A] 1 illustrates a cross-sectional view of an example embodiment of a temperature sensor that can be used to estimate the temperature of a fluid in a housing using a temperature difference or delta T method. [Figure 5B]1 illustrates an enlarged cross-sectional view of an example embodiment of a temperature sensor that can be used to estimate the temperature of a fluid in a housing using a temperature difference or delta T method. [Figure 5C] FIG. 1 illustrates a partial perspective view of an example embodiment of a temperature sensor that can be used to estimate the temperature of a fluid in a housing using a temperature difference or delta T method. [Figure 6] 1 illustrates an exemplary embodiment of a method for estimating the temperature of a fluid in a housing using a temperature difference or delta T method. [Figure 7] 1 illustrates an exemplary embodiment for determining whether a temperature sensor is installed to directly measure or estimate the temperature of a fluid contained within a housing. [Figure 8] 1 illustrates an exemplary embodiment of a method for estimating the temperature of a fluid within a housing using a temperature difference or delta T method that incorporates a compensation factor for the ambient environment temperature. [Figure 9] 1 illustrates an exemplary embodiment of a temperature sensor that can be used to estimate the temperature of a fluid contained within a housing using a modified zero heat flow method. [Figure 10] 1 illustrates an exemplary embodiment of a method for estimating the temperature of a fluid in a housing using a hybrid zero heat flow method and a temperature difference or delta T method. [Figure 11] 1 illustrates an exemplary embodiment of a temperature sensor having a wired connection. [Figure 12] 13 shows an exemplary test demonstrating the correlation between estimated internal temperature and measured temperature of the housing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Throughout the following specification, specific details are described to provide a more complete understanding to those skilled in the art. However, well-known elements may not be shown or described in detail to avoid unnecessarily obscuring the present disclosure. Thus, the specification and drawings should be regarded in an illustrative sense rather than a restrictive one.

[0022] As used herein, "environmental conditions" may include any external environmental parameter, or any combination of such parameters, that may affect the internal temperature of the fluid contained within the housing. Examples of environmental conditions include general environmental temperature, humidity, wind conditions, precipitation, solar radiation, etc., including any combination of such conditions. For example, the housing and the fluid contained within the housing may experience a greater cooling effect from a combination of cold and wind compared to the cooling effect of cold alone or wind alone.

[0023] As used herein, "exterior" means the outer surface of the housing and "interior" means the inner surface or portion of the housing. "Outwardly" means facing away from the interior of the housing.

[0024] As used herein, the terms "adjacent" or "proximate" can mean in direct contact, or in close enough contact through any intervening elements or spaces, for example, that a temperature sensor can still measure an approximation of the temperature of the "adjacent" or "proximate" surface.

[0025] 1, one exemplary electrical device is shown that is a transformer 100. The transformer 100 has a tank or housing 102 that encloses a fluid 104 therein. The fluid 104 is fluidly isolated by the housing 102 from an external environment 106 surrounding the housing 102. That is, the fluid 104 is sealed within the housing 102, such that little to no fluid is permitted to escape the housing 102. In some cases, the fluid 104 may be harmful to the environment (e.g., the fluid 104 may be a recognized greenhouse gas or may have adverse or harmful effects on various living organisms), and therefore, it is important to keep the majority of the fluid 104 contained within the housing 102, although some of the fluid 104 may be expelled if the pressure within the transformer 100 rises above a certain level, activating any pressure relief valves associated with the transformer 100. In some embodiments, depending on the design and regulations applicable to the particular transformer 100, the housing 102 may be open to a limited extent to the outside environment to allow for pressure equalization, for example, via a suction tube. In some embodiments, the suction tube may be plugged with mineral wool or other material that allows air to pass but restricts the passage of fluid 104 therethrough.

[0026] Fluid 104 may be any suitable electrically insulating or dielectric fluid suitable for use in electrical equipment, including mineral oil, natural or synthetic ester fluids, silicone oil, or a gas such as SF6.

[0027] The housing 102 may be any suitable tank or housing for a piece of electrical equipment, such as a transformer, like transformer 100. In some embodiments, the housing 102 is formed from carbon steel, stainless steel, or any other suitable material. Different types of housings 102 for different transformers 100 may differ in a number of different designs, such as the thickness of the housing, the material from which the housing is formed, the thermal conductivity of the material from which the housing is formed, the type and thickness of a protective coating (e.g., paint) provided on the housing, the size and dimensions of the housing (e.g., volume, height, length, width, diameter, etc.), the shape of the housing (e.g., circular or rectangular), the fluid circulation pattern of the fluid within the housing, etc.

[0028] In the illustrated embodiment, a first portion of the housing 102, generally indicated as 108, is shielded from the effects of environmental conditions, while a second portion of the housing 102, generally indicated as 110, is exposed to the effects of environmental conditions.

[0029] 2A and 2B, an alternative embodiment of a transformer 200 is shown having a housing 202 with an inlet 250 that houses a cartridge housing 252 therein. The transformer 200 is otherwise similar to the transformer 100, and like elements are illustrated with like reference numbers incremented by 100, including the fluid 204, the external atmosphere 206, the shielded portion 208 and the exposed portion 210 of the housing 202, and will not be described again further. In the illustrated embodiment, the cartridge housing 252 is disposed in sealing engagement with the housing 202 around the inlet 250 to prevent the escape of the fluid 204 from the interior space of the housing 202. A fluid level 212 of the fluid 204 is shown in dashed lines in FIG. 2B, which may be referred to as the top oil level.

[0030] 3A, an exemplary embodiment of a temperature sensor 300 is provided that can be used to determine the temperature of the fluid 104 or 204 in the transformer 100 or 200 using the zero heat flow method described below, which uses two temperature sensing elements to determine the heat flux or flow through the housing 102 or 202 and an actively powered heater to compensate for that heat loss.

[0031] The temperature sensor 300 has a body 302 shaped and configured for attachment to a housing of an electrical device, such as the housing 102. The temperature sensor 300 includes first and second temperature sensing elements 304 and 306 that are spaced apart from one another and separated by a layer of insulation 308. Because the first temperature sensing element 304 is more directly exposed to the housing 102 while the temperature sensing element 306 is thermally shielded from heat exiting the housing 102 by the insulation 308, i.e., because the insulation 308 is differentially positioned relative to the first and second temperature sensing elements during use of the temperature sensor 300, a temperature difference is created between the first and second temperature sensing elements 304, 306 during use of the temperature sensor 300.

[0032] Any suitable temperature sensor, such as a thermocouple, a resistive thermal device (RTD) sensor, a thermistor, a semiconductor-based integrated circuit, or the like, may be used for the first and second temperature sensing elements 304, 306. Any suitable material may be used to provide the insulation 308, such as foam, encapsulated air, a material that forms part of or a component of the temperature sensor 300, or the like. The insulation value provided by the insulation 308 should remain constant throughout use of the temperature sensor 300, so that the calibration of the temperature sensor 300 described below can be used to determine the temperature of the fluid 104 or 204 within the housing 102 or 202 as described herein. For example, components that form part of the insulation 308 should not be removed or modified in a manner that may change the insulation value provided by the insulation 308.

[0033] The heating element 310 is disposed outside the second temperature sensing element 306. The temperature sensor 300 is configured such that the first temperature sensing element 304 can be placed in or near thermal contact with the housing 102. Because the insulation 308 is disposed outside the first temperature sensing element 304, heat moving outward along the heat flow path (indicated by arrows 312) must pass through the insulation 308 to reach the second temperature sensing element 306, which is disposed outside the body 302 from the insulation 308. Eventually, any heat that passes through the second temperature sensing element 306 along the heat flow path 312 will reach the heating element 310. As a result of this configuration, there will be a difference in the temperatures measured by each of the first temperature sensing element 304 and the second temperature sensing element 306, which reflects a portion of the temperature gradient from the fluid 104 to the external environment 106.

[0034] The surface area of ​​the housing 102 covered by the temperature sensor 300 needs to be large enough to ensure that a significant amount of heat is not lost along paths other than the heat flow path 312; i.e., if the surface area of ​​the housing 102 covered by the temperature sensor 300 is too small, heat will not only travel along the heat flow path 312, but also in a direction perpendicular to it, which means that the temperature measured by the second temperature sensing element 306 may be lower than if the heat only flowed along the heat flow path 312. Similarly, the surface area covered by the insulation 308 and the heating element 310 needs to be large enough to ensure that a significant amount of heat is not lost along paths other than the heat flow path 312.

[0035] During use, heat is added to the system using the heating element 310 until there is no longer a temperature gradient between the first thermal sensing element 304 and the second thermal sensing element 306. This situation means that heat stops flowing along the heat flow path 312, such that the first and second temperature sensing elements 304, 306 and the insulation 308 are all at the same temperature as the fluid 104 within the housing 102. At this stage, the readings of the temperature sensors 304, 306 will correspond to the temperature of the fluid 104.

[0036] Alternative configurations may be used to determine the temperature of the fluid 104 or 204 in the transformer 100 or 200 using the zero heat flow method, so long as the temperatures initially measured by the first and second temperature sensing elements 304, 306 are different due to different degrees of insulation between each of the first and second temperature sensing elements 304, 306 and either the housing 102 or the heating element 310 (i.e., a temperature difference is established between the first and second temperature sensing elements 304, 306, which may be because the insulation 308 is differentially positioned relative to the first and second temperature sensing elements 304, 306).

[0037] For example, referring to FIG. 3B, an alternative embodiment of a temperature sensor 300' is shown in which the first and second temperature sensing elements 304', 306' are laterally spaced apart from one another. In the illustrated embodiment, the first temperature sensing element 304' is proximate to the transformer housing 102' within the body 302', but because there is no significant intervening insulating material between the first temperature sensing element 304' and the housing 102', the temperature measured by the first temperature sensing element 304' reflects or more closely approximates the temperature of the housing 102. The second temperature sensing element 306' is spaced from the housing 102' by insulation 308', such that a temperature difference is established between the first temperature sensing element 304' and the second temperature sensing element 306' due to the differential arrangement of the insulation 308' (i.e., the first temperature sensing element 304' will be more affected by changes in temperature of the internal fluid 104 than the second temperature sensing element 306'). With respect to the insulation 308, any suitable material may be used to provide the insulation 308', such as, for example, foam, trapped air, material that forms part of or a component of the temperature sensor 300', etc.

[0038] In the illustrated embodiment, the second temperature sensing element 306' is shown as being disposed farther outward from the housing 102' than the first temperature sensing element 304', however, in alternative embodiments, the first and second temperature sensing elements may be disposed the same distance outward from the housing 102', or the second temperature sensing element 306' may actually be disposed closer to the housing 102' to provide a temperature differential between the first temperature sensing element 304' and the second temperature sensing element 306', so long as the insulating value of the material between the second temperature sensing element 306' and the housing 102' is greater than the insulating value of the material disposed between the first temperature sensing element 304' and the housing 102'.

[0039] Similarly, although in the illustrated embodiment the insulation 308' is shown disposed between the second temperature sensing element 306' and the housing 102' to provide a differential placement of the insulation 308' relative to the first and second temperature sensing elements 304', 306', in alternative embodiments the temperature differential between the first and second temperature sensing elements 304', 306' may instead be created by disposing the insulation 308' between the first temperature sensor 304' and the heating element 310'.

[0040] Additionally, alternative embodiments may be deployed that result in a temperature difference between the sensing element 304' and the sensing element 306' as heat flows by, for example, arranging insulation around the sensors in different orientations to provide a differential arrangement, such as by shielding the first temperature sensing element 304' to a greater extent from lateral heat flow than the second temperature sensing element 306'.

[0041] In the case of the temperature sensor 300', heat flows out of the housing 102' and passes through the first temperature sensing element 304 along a first path 312A of heat flow, while heat flows out of the housing 102' and passes through the insulation 308 and then through the second temperature sensing element 306 along a second path 312B of heat flow. Again, the temperature difference measured by each of the first and second temperature sensing elements 304' and 306' reflects a portion of the temperature gradient from the fluid 104 to the external environment 106, and this temperature difference can be similarly used in conjunction with the application of heat from the heating element 310 until there is no longer a temperature gradient between the first and second thermal sensing elements 304' and 306'. When this condition is reached, which means that heat has stopped flowing along both heat flow paths 312A and 312B, the first and second temperature sensing elements 304', 306' and the insulation 308 are all at the same temperature as the fluid 104 within the housing 102. Again, the readings of the temperature sensors 304', 306' at this point correspond to the temperature of the fluid 104.

[0042] In further alternative embodiments, the shape and configuration of the heating element 310 or 310' may be varied. For example, in some embodiments, the heating element 310 or 310' may be circular or elliptical in shape, and may optionally have an opening through the center of the circle or ellipse (e.g., having a donut shape) to minimize the amount of heat that escapes laterally from the heat flow path 312 (or 312A / 312B). In other embodiments, both the first and second temperature sensing elements may be spaced the same or approximately the same distance from the housing, but insulation is placed only between the second temperature sensing element and the housing (i.e., not between the first temperature sensing element and the housing) or insulation is placed only between the first temperature sensing element and the heating element (i.e., not between the second temperature sensing element and the heating element) to provide a temperature difference between the two temperature sensing elements.

[0043] The temperature sensor 300 or 300' may be used in a method 3000 for estimating the temperature of a fluid in a housing using the zero heat flow method, shown in Figure 4. Initially, at 3002, heat flows outward from the fluid 104 through the housing 102 along the heat flow path 312 (or 312A / 312B) towards the external environment 106. Due to the presence of the insulation 308 or 308', the amount of heat reaching the second temperature sensing element 306 or 306' will be less than the amount of heat reaching the first temperature sensing element 304 or 304', and the temperature T2 measured by the second temperature sensing element 306 or 306' will be lower than the temperature T1 measured by the first temperature sensing element 304 or 304'.

[0044] If, at 3004, it is determined that T1 is greater than T2, then at 3006, the heating element 308 will be activated to provide heat. Steps 3004 and 3006 will be repeated until step 3004 determines that T1 is the same as T2, at which point it will be concluded, at step 3008, that the temperature of the fluid 104 within the housing 102 is the same as both T1 and T2. If, at step 3004, it is determined that T2 is greater than T1, then the heating element 308 may cease applying heat, and step 3004 may be repeated until step 3004 determines that T1 is again greater than T2 (at which point step 3006 may be repeated) or until step 3004 determines that T1 is equal to T2 (at which point it may be concluded, at step 3008, that the temperature of the fluid 104 within the housing 102 is the same as both T1 and T2).

[0045] 5A, 5B, and 5C, an exemplary embodiment of a temperature sensor 400 that can be used to estimate the temperature of the fluid 104 in the housing 102 using a temperature difference or delta T method is shown. The sensor 400 has a body 402 having a first portion or head 404 and a second portion stem 406. In the illustrated embodiment, the head 404 is disposed vertically above the stem 406, although it will be understood that the relative positions of these components may vary depending on the orientation of the sensor 400.

[0046] The sensor 400 has a first or head temperature sensing element 408 disposed within the head 404 such that it may be disposed in thermal contact with the housing 102 when the sensor 400 is in the installed configuration, as shown in FIGURE 5A. The sensor 400 also has a second or stem temperature sensing element 410 disposed within the stem 406 such that it may be disposed in thermal contact with the housing 102 when the sensor 400 is in the installed configuration. Any suitable temperature sensor may be used for the first and second temperature sensing elements 408, 410, such as a thermocouple, a resistance temperature detector (RTD) sensor, a thermistor, a semiconductor-based integrated circuit, or the like.

[0047] 5A is provided within the head 404 to protect the head temperature sensing element 408, and the corresponding shielded portion 414 of the housing 102 to which the head 404 is mounted, from the external environment when the sensor 400 is in the installed configuration. Thus, when the sensor 400 is in the installed configuration, the head temperature sensing element 408, and the corresponding shielded portion 414 of the housing 102 to which the head 404 is mounted, are protected from the external environment.

[0048] In contrast, no such thermal or environmental shielding barrier is provided on the stem 406. Furthermore, because the surface area of ​​the stem 406 that contacts the housing 102 is relatively small, the portion 416 of the housing 102 that the stem temperature sensing element 410 contacts is relatively exposed to the outside environment.

[0049] 5B and 5C, an exemplary embodiment of a physical barrier, thermal and environmental shielding barrier, is shown in more detail. In the illustrated embodiment, the head temperature sensing element 408 is circumferentially surrounded by an inner perimeter gasket 420. The outer perimeter of the portion of the head 404 that contacts the housing 102 is likewise circumferentially surrounded by an outer perimeter gasket 421. The inner perimeter gasket 420 and the outer perimeter gasket 421 may help prevent or minimize the effects of certain environmental conditions by physically preventing and / or reducing the ingress of environmental elements such as wind, rain, and solar radiation to the portion 414 of the housing 102 to which the head temperature sensing element 408 and the head 404 are attached. This minimizes the effect of such environmental elements on the temperature of the portion 414 of the housing 102, which in turn minimizes the effect of such environmental elements on the head temperature sensing element 408.

[0050] The inner gasket 420 and the outer gasket 421 do not need to achieve 100% sealing effect against the exterior surface of the housing 102 to achieve such minimization. The material of the body 402 of the head 404 and the components contained therein (e.g., entrained air 430, circuit board 432, inner gasket 422, etc.) alone make it difficult for wind, rain, and solar radiation to reach the portion 414 of the exterior surface of the housing 102 to which the head 404 is attached. The addition of the inner gasket and / or the outer gasket can enhance the blocking of such environmental elements provided by the head 404, although in some embodiments, either or both of the inner gasket and / or the outer gasket may be removed. The head 404 needs to be designed to cover a sufficient amount of the surface area 414 to shield a sufficiently large surface area of ​​the housing 102 to ensure that the head temperature sensing element 408 is sensing the temperature that is shielded. Therefore, the heat flow laterally from the shielded portion 414 through the wall of the housing 102 must be low enough to allow an adequate determination of the shielded temperature.

[0051] The head temperature sensing element 408 is also thermally shielded from the external environment. In the illustrated embodiment, the material of the body 402 of the head 404 and the components contained therein (e.g., entrained air 430, circuit board 432, inner gasket 422, walls of the body 402, inner gasket 420, and outer gasket 421, etc.) make it difficult for wind, rain, and solar radiation to reach the portion 414 of the exterior surface of the housing 102 to which the head 404 is attached, and collectively act as an insulator to thermally shield the head temperature sensing element 408 from the external environment. This collectively shields the head temperature sensing element 408 and the shielded portion 414 of the housing 102 from the effects of ambient temperature and environmental conditions.

[0052] In contrast to the head temperature sensing element 408, the stem temperature sensing element 410 is not shielded from the external environment, and any shielding provided by the stem 406 is minimized by the stem 406 having a relatively narrow width and small size compared to the head 404, for example.

[0053] 6, a method 4000 for estimating the internal temperature of a fluid 104 using a temperature difference or delta T method is shown. Several embodiments of the method 4000 can be performed using the sensor 400. At 4002, the temperature sensing element 408 measures a temperature T3 of the shielded portion 414 of the housing 102. At 4004, the stem temperature sensing element 410 measures a temperature T4 of the exposed portion 416 of the housing 102.

[0054] Since T3 is measured on the shielded portion 414 and T4 is measured on the exposed portion 416, the temperatures are different from each other. The difference between the temperatures, or delta T, is a function of parameters such as the temperature of the fluid 104 and the effect of the external environment 106 on the cooling of the transformer 100. The head temperature sensing element 408 and the stem temperature sensing element 410 can be calibrated using a reference transformer operating at a known temperature of the fluid 104. Using the known reference measurements, the correlation between T3 and T4 can be used to derive a relationship between these two measurements and the internal temperature of the fluid 104, so that the difference between T3 and T4 can be used in the field in step 4006 to predict the temperature of the fluid 104.

[0055] In some embodiments, the internal oil temperature is estimated using a transfer function, which can take many mathematical forms, such as power, linear, etc. If a power formula is used, it may be as follows:

[0056] T Oil =A(T S -T E ) -B (1) During the ceremony, T Oil is the estimated oil temperature.

[0057] T S is the shielded tank temperature. T E is the exposed tank temperature. · A and B are empirically derived coefficients.

[0058] If a linear function is used, it may take the form of equation (2) below: T Oil =A+BT S +CT E (2) During the ceremony, T Oil is the estimated oil temperature.

[0059] T S is the shielded tank temperature. T E is the exposed tank temperature. · A, B, and C are empirically derived coefficients.

[0060] The above formula for estimating internal oil temperature is merely an example. Those skilled in the art will recognize that the same T S and T E It may be possible to determine alternative transfer equations using forms other than power or linear that would yield similarly valid results given the inputs (corresponding to T3 and T4 above).

[0061] In some embodiments, the stem 406 of the temperature sensor 400 is shaped and configured to be insertable into the cartridge housing 252. In such embodiments, if the transformer 200 includes a cartridge housing 252, the temperature sensor 400 can be inserted therein. In such a configuration, the stem temperature sensing element 410 is disposed inside the interior of the housing 202 during use and can directly or nearly directly measure the temperature of the fluid 204 within the interior space of the housing 202. Thus, a measurement of the actual temperature of the fluid 204 within the housing 202 can be made.

[0062] In one exemplary embodiment, the temperature sensor 400 can be used in a method to determine a calibration factor that can be used to estimate the internal temperature of a fluid within a transformer, such as the transformer 100, that does not include an opening or orifice through which the internal temperature can be determined. For example, calibration of a particular transformer 100 for the difference between T3 and T4 measured by the head temperature sensing element 408 and the stem temperature sensing element 410 when the sensor 400 is mounted on the exterior of the transformer 102 or 202 may depend on various parameters associated with the transformer 100 or housing 102, including the wall thickness of the housing 102, any paint coatings applied, the type of metal the housing 102 is made of, etc. Although the calibration must be done separately for each transformer 100 in which these parameters vary, a calibration performed for one transformer 100 having a particular set of these parameters (i.e., for one particular type of transformer) will be valid across other transformers 100 that share the same set of parameters. The same principles can be applied to derive calibration factors for determining the internal temperature of fluids contained within other electrical equipment or devices.

[0063] Such a calibration can be performed using a sensor 400 by inserting the stem 406 of a first such sensor 400 into the cartridge housing 252 of the transformer 200 and mounting a second such sensor 400 on the outside of the housing 202. The transformer 200 can be exposed to a number of different temperatures and environmental conditions to determine different values ​​of T3 and T4 measured by the head temperature sensor 408 and stem temperature sensor 410 of the second sensor 400 at a number of different temperatures or under different environments, and compare the values ​​of T3 and T4 from the second sensor to a measurement of the temperature of the fluid 204 in the housing 202 measured by the stem temperature sensing element 410 of the first such sensor acting as a third temperature sensor (or by any other method that directly measures the internal temperature of the fluid 204 in the housing 202). The measured data can be used to determine coefficients for the equations used to model the internal temperature of the tank versus T3 and T4.

[0064] In one exemplary embodiment, the temperature sensor 400 further includes an orientation sensor, such as a gyroscope or contact sensor, shown diagrammatically as sensor 440. Examples of sensors that may be used for sensor 440 include a tilt switch to determine if the sensor 400 is mounted vertically (indicating external mounting) or horizontally (indicating mounting inside the cartridge housing 252), a reed switch with a magnet, a logic rule based on the measured temperature, such as if the stem sensor is at a higher temperature than the head sensor then the sensor 400 is likely to be installed inside the cartridge housing 252, but if the opposite temperature condition is true then external mounting is more likely, an acceleration sensor, a physical switch that is toggled when the sensor 400 is installed in a certain configuration, a light gate or other digital switch that is triggered in one mounting position but not the other, etc.

[0065] The direction sensor 440 can be used to determine whether the temperature sensor 400 is mounted on the outside of the housing or whether the temperature sensor 400 is inserted within the cartridge housing 252. If the direction sensor 440 determines that the temperature sensor 400 is inserted within the cartridge housing 252, the stem temperature sensing element 410 can be used to directly measure the internal temperature of the housing and can also be used as a third sensor when performing a calibration of a particular transformer 200. If the direction sensor 440 determines that the temperature sensor 400 is mounted on the outside of the housing, the temperature sensing elements 408 and 410 are used to estimate the internal temperature of the fluid within the housing, for example, by performing the method 4000.

[0066] For example, referring to FIG. 7, a method 700 can be used to determine how a temperature sensor, such as temperature sensor 400, is installed and, accordingly, to determine the temperature of a fluid contained within the housing. At 702, it is determined whether the stem 406 of the temperature sensor 400 is inserted into a cartridge housing in an electrical device. At 704, if it is determined that the stem 406 of the temperature sensor 400 is inserted into the cartridge housing 252, the stem temperature sensing element 410 is used to directly measure the temperature of the fluid contained within the housing. At 706, if it is determined that the stem 406 of the temperature sensor 400 is not inserted into the cartridge housing 252, the thermal sensing elements 410 and 412 separated by insulation 414 are used to estimate the internal temperature of the fluid within the housing, for example, by performing method 4000.

[0067] In some embodiments, a method is provided for estimating the temperature of the fluid 104 using the temperature difference or delta T method that incorporates an additional compensation factor based on the ambient environment temperature. An example of such a method 5000 is shown in FIG. 8. The method 5000 can be performed using any suitable device for measuring the temperature of the housing 102 in the shielded position 108 and the exposed position 110 (e.g., temperature sensor 400), and any suitable device for measuring the ambient environment temperature, such as a thermocouple, a resistive thermal device (RTD) sensor, a thermistor, a semiconductor-based integrated circuit, etc. The ambient temperature can be used as an additional variable in the method 5000 to correlate the three measured temperatures to the temperature of the fluid 104, for example, by including the ambient temperature in an equation similar to equations (1) and (2) and deriving a correlation between T3, T4 and the ambient temperature and the temperature of the fluid 104 using known reference measurements such as those described above for the temperature difference or delta T method described with reference to method 4000.

[0068] In method 5000, at 5002, a temperature at the shielded location 108 (corresponding to T3 described with reference to method 4000) is measured. At 5004, a temperature at the exposed area 110 (corresponding to T4 described with reference to method 4000) is measured. At 5006, an ambient temperature is measured. At 5008, an internal temperature of the fluid 104 is estimated based on the measurements of T3, T4 and the ambient environment temperature.

[0069] 9, an exemplary embodiment of a temperature sensor 600 that can be used to estimate the internal temperature of a fluid 104 using a hybrid zero heat flow temperature difference method is shown. The temperature sensor 600 has a body 602 and is configured for attachment to an exterior surface of the housing 102. A first temperature sensing element 604 is attachably disposed adjacent to the exterior surface of the housing 102, and then, similar to the temperature sensor 300, a layer of insulation 608 is disposed outside the first temperature sensing element 604, and then a second temperature sensing element 606 is disposed outside the insulation 608. Thus, heat flows outwardly from the housing 102 along a heat flow path represented by arrows 612.

[0070] Temperature sensor 600 differs from temperature sensor 300 in that the heating element is omitted. Thus, rather than using the heat added from the heating element to calculate the internal temperature of fluid 104 using a zero heat flow method, temperature sensor 600 uses a calibration of the temperature difference between the first temperature sensing element 604 and the second temperature sensing element 606 under a set of known internal temperature conditions to derive an equation that can be used to model and predict the temperature of fluid 104 based on the temperature difference between the first temperature sensing element 604 and the second temperature sensing element 606.

[0071] In some embodiments, a method is provided for estimating the temperature of the fluid 104 using a hybrid zero heat flow method and a temperature difference or delta T method. In some embodiments, such a method may incorporate an additional compensation factor based on the ambient environment temperature, similar to method 5000. An example of such a method 6000 is shown in FIG. 10. Method 6000 may be performed using a temperature sensor 600. In some embodiments, if the ambient temperature is used in estimating the internal temperature of the fluid 104, any suitable device for measuring the ambient environment temperature may be used, such as a thermocouple, a resistance temperature detector (RTD) sensor, a thermistor, a semiconductor-based integrated circuit, or the like.

[0072] At 6002, a temperature T5 of a first temperature sensing element 604 located closest to the housing 102 is measured. At 6004, a temperature T6 of a second temperature sensing element 606 located further from the housing 102 is measured. At 6006, an ambient temperature is optionally measured. At 6008, an internal temperature of the fluid 104 is estimated based on the measurements of T5 and T6 based on coefficients previously derived for an electrical device. In some embodiments, once the ambient environment temperature is measured at step 6006, the internal temperature of the fluid 104 is estimated at step 6008 based on all of T5, T6, and the measured ambient temperature.

[0073] In some embodiments, temperature sensor 300 or 400 may include a light, shown generally as 320 / 320' / 420, or other visual indicator, that indicates that the exterior temperature of the housing has exceeded a predetermined temperature threshold, e.g., a temperature above which it is unsafe for a person to touch the exterior surface of the housing.

[0074] In some embodiments, as shown with respect to the temperature sensor 800 shown in FIG. 11, any of the temperature sensors described herein may also include a wired connection 806, for example, to allow connection to a digital sensor bus or other processor or communication module. The temperature sensor 800 has a head 802 and a stem 804. The wired connection 806 allows the temperature sensor 800 to relay information regarding the sensed temperature to a controller or other processor. In alternative embodiments, a wireless communication module may allow the temperature sensor 800 to relay information regarding the sensed temperature to a controller or other processor equipped with a parallel wireless communication module. In some such embodiments, the wired connection 806 may be omitted.

[0075] example Certain embodiments are further described with reference to the following examples, which are intended to be illustrative rather than limiting in nature.

[0076] Example 1.0 Comparing Estimated Internal Temperature to Actual Internal Temperature The inventors conducted testing using one embodiment of the temperature sensor 400 to estimate the internal temperature of the fluid in the housing using the method 4000. Control measurements of the actual internal temperature of the fluid in the housing were taken to evaluate the accuracy of the estimated temperature. The oil temperature and environmental conditions, such as the ambient temperature and wind speed, could be independently controlled in the experimental setup. At each of the times T1 and T2, the environmental conditions, including the ambient temperature, were changed, but the actual internal oil temperature remained the same throughout the period that T1 and T2 were varied.

[0077] The results are shown in Figure 12. The measured temperature of the fluid in the housing (Actual Oil T) represents a known temperature value. The temperatures of the shielded portion of the tank housing (Shielded Sensor T) and the exposed portion of the tank housing (Exposed Sensor T) were measured and used to estimate the internal temperature of the fluid in the housing (Estimated Oil T) using the transfer function described above.

[0078] As can be seen, the estimated temperature closely tracks the measured temperature (obtained independently using a separate temperature sensor located within the housing), especially after a steady state is reached immediately after a change in environmental conditions (i.e., immediately after the ambient temperature is changed at T1 and T2, respectively). In contrast, neither the shielded nor exposed sensor T is particularly close to the actual oil T, indicating the need for an alternative method of determining the internal oil temperature.

[0079] While a number of exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain modifications, permutations, additions, and subcombinations thereof. It is therefore intended that the following appended claims, and any claims hereafter introduced, be interpreted to include all such modifications, permutations, additions, and subcombinations consistent with the broadest interpretation of the entire specification.

Claims

1. 1. A device capable of non-invasively estimating a temperature inside a housing, comprising: an environmental shielding portion shaped and configured to shield at least a portion of the housing from general environmental conditions to provide an environmentally shielded portion of the housing; a first temperature sensing element disposed within the environmentally shielded portion, the first temperature sensing element being positioned within the environmentally shielded portion of the housing and in thermal contact with the housing when the device is in use; a second temperature sensing element spaced apart from the environmentally shielded portion, the second temperature sensing element positioned so as to be positionable in thermal contact with the housing outside the environmentally shielded portion of the housing when the device is in use; An apparatus comprising:

2. 2. The apparatus of claim 1, wherein the second temperature sensing element is exposed to a majority of prevailing environmental conditions or is exposed to more prevailing environmental conditions than the first temperature sensing element.

3. The device of claim 1 , wherein at least one of the first temperature sensing element and the second temperature sensing element is positioned adjacent to the housing when the device is in use.

4. The device of claim 1 , wherein at least one of the first temperature sensing element and the second temperature sensing element is positioned so as to face the housing when the device is in use.

5. The device of claim 1 further comprising a cartridge portion shaped and configured for insertion into a cartridge housing extending inwardly of said housing, said cartridge portion comprising said second temperature sensing element.

6. The device of claim 5 , further comprising a sensor for determining when the cartridge portion is inserted into the cartridge housing.

7. A method of using the apparatus of claim 6, comprising the steps of: determining whether the cartridge portion is inserted into the cartridge housing; using a third thermal sensing element to directly measure the temperature of a fluid contained within the cartridge housing when the cartridge portion is determined to be inserted within the cartridge housing; or using first and second thermal sensing elements to estimate a temperature of a fluid contained within the cartridge housing when it is determined that the cartridge portion is not inserted within the cartridge housing. The method includes:

8. The method of claim 7 , wherein the second temperature sensing element and the third temperature sensing element are the same temperature sensing element.

9. 1. A method for estimating a temperature of a fluid contained within a housing, comprising: measuring a first temperature at a first external location on the housing, the first external location being protected from environmental conditions; measuring a second temperature at a second external location on the housing, the second external location being exposed to environmental conditions or being more exposed to the environmental conditions than the first external location; correlating a difference between the first temperature and the second temperature to estimate a temperature of a fluid contained within the housing; The method includes:

10. The apparatus of claim 1 , further comprising a sensor for measuring an ambient temperature of an environment outside the housing.

11. 8. The method of claim 7, Measuring an ambient temperature of an environment outside the housing; using the measured ambient temperature as an additional parameter to estimate the temperature of the fluid contained within the housing based on a relationship between the first temperature and the second temperature; The method further comprising:

12. 10. The apparatus of claim 1, further comprising a visual indicator that indicates when the exterior temperature of the housing exceeds a predetermined threshold.

13. 13. A method of using the apparatus of claim 1 to generate calibration coefficients for a particular type of housing, comprising the steps of: measuring an internal temperature of a first housing representative of the particular type of housing; measuring the temperatures recorded by each of the first and second temperature sensing elements to provide the first and second temperatures; deriving a mathematical relationship between the first temperature and the second temperature to obtain the calibration factor; The method includes:

14. The apparatus of claim 1 , wherein the housing comprises a housing for a portion of an electrical device.

15. The method of claim 7 , wherein the housing comprises a housing for a portion of an electrical device.

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