MXPA01003243A - Fluid filled electrical device with diagnostic sensor located in fluid circulation flow path - Google Patents

Abstract

A fluid filled transformer including a tank (11) for containing at least primary and secondary windings, a radiator (18) connected to the tank via top and bottom headers (20a, 20b), a fluid (50) disposed in the tank, a fluid circulation flow path (25) including passages through the windings, radiator, headers and at least a portion of the tank, and at least one diagnostic sensor (60) disposed within the fluid circulation flow path for measuring properties of the fluid. By positioning the sensor (60) within the circulation flow path (25), measured values are more reliable, accurate and efficiently sensed.

Description

ELECTRICAL DEVICE FULL OF FLUID WITH A DIAGNOSTIC SENSOR LOCATED IN THE FLOW PATH FOR THE CIRCULATION OF A FLUID BACKGROUND OF THE INVENTION The present invention relates to a structure for monitoring the characteristics of a device filled with fluid, and very particularly, to place a diagnostic sensor within a flow path of fluid flow of the device and thus obtain a faster and more representative indication of an observable event. To reduce the cost of maintaining, for example, a high or medium voltage electrical transformer, it is common to monitor certain operating characteristics of the transformer, so that in the case of detecting an anomaly, the transformer can be removed from operation (if necessary ) and / or repair as necessary. Properties that tend to indicate potential problems with a transformer and that can be monitored include the temperature of the tank in which the transformer is housed or the temperature of a refrigerant / insulator fluid, usually oil, placed in the tank. Another property observed is a concentration of gas in the fluid or oil. Gases that provide diagnostic indicators of the state of the transformers include hydrogen, methane, ethane, ethylene, carbon monoxide, carbon dioxide, acetylene, propane and / or propylene. Other observed transformer characteristics include moisture content, dielectric strength of the oil and power factor values. When the measured or observed value of either of these properties exceeds the predetermined levels, it is possible that the transformer is already operating in fault mode, or that it will soon enter this failure mode. Therefore, said transformer must be removed from operation (if necessary) and / or repaired. Generally, changes in the monitorable properties that tend to indicate the general poor condition of a transformer can be described as observable events. Normally, sensors are mounted to monitor the aforementioned characteristics or properties of the fluid in a tank in the external ports existing in the tank, such as drain valves or pressure release means. This procedure takes advantage of pre-existing access to the transformer tank through which the fluid is easily accessible. Another known procedure for monitoring the properties of fluids is to place a sensor at the upper oil level in the tank by means of an internal assembly scheme. The patent of E.U.A. 3,680,359 to Lynch is an example of said procedure. Another known method is to provide a separate access port or port in the tank and from there withdraw an amount of fluid, or oil, that is considered sufficient to operate a sensor that is mounted outside the tank. Examples of this process are described, for example, in the patent of E.U.A. 4,058,373 to Kurz et al., U.S. Patent. 3,866,460 to Pearce, Jr. and U.S. Patent. 5,773,709 to Gibeault and others. However, all of the above-discussed procedures place the sensor in a position that does not result in optimal sensor detection of the observable event. That is, conventional monitoring procedures are inadequate to the extent that the monitoring is performed on fluid or oil that is carried to a region adjacent to a wall of the tank or that is near the upper level of the fluid in the tank. Since the fluid in these regions tends to be more inactive compared to the fluid in other regions of the tank, the sample being monitored does not adequately represent or indicate the manifestations of an observable event.

BRIEF DESCRIPTION OF THE INVENTION The preferred embodiment refers to improving the diagnostic capacity and reliability of transformers by selecting a suitable sensor and locating that sensor, or a variety of sensors in the circulation flow path, i.e., the fluid circulation curve of the electrical device. By placing the sensor in this way, an observable event can be witnessed and detected more efficiently by a sensor, thus producing more reliable, accurate and timely measurements of observable events.

In the context of the present invention, the flow path of fluid circulation is defined as a semi-closed curve where, if an event occurs at a point on the curve, it is most possible that all other sequential points downward will witness that event with some time of delay. In accordance with the exemplary embodiments of the present invention, one or more sensors are placed so that the fluid being detected travels within the circulation flow path, whereby more accurate and efficient measurements of the properties and characteristics of that fluid. In one embodiment, a sensor is preferably placed in a radiator, or in the upper or lower manifolds of the transformer radiator. In another embodiment, a sensor is preferably placed within the transformer tank adjacent to an outlet or an inlet of the radiator manifold. In a third mode, one or more sensors are placed inside the windings of the transformer. In this case, the sensor is bent together with the windings during manufacturing. In a fourth embodiment, a sensor is preferably mounted on one end of a probe whose other end is placed with the windings of the transformer. This procedure reduces the susceptibility of the sensor to electromagnetic interference. In a fifth mode, a sensor is placed next to the inlets or outlets of the flux channels of the windings.

In a sixth modality, multiple sensors are placed within the flow path of circulation and an observable event is monitored with some or all of the sensors, with which a time analysis of the observable event is performed. In all cases, the sensor is preferably positioned within the circulation flow path of the flow circulating in the transformer. As a result, all measurements taken with the sensor are more reliable, efficient and accurate.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a flow path of fluid circulation of an electric transformer that includes the locations of the sensors. Figure 2 shows a sensor mounted on the end of a feeder arranged in the manifold of a radiator. Figure 3 shows a sensor mounted on a square inside the tank of a transformer. Figure 4 shows a sensor at one end of a probe whose other end is disposed within the windings of a transformer.

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described with reference to the figures. Although the following description is directed to transformers, other electrical devices, such as voltage regulators or capacitors, are contemplated as being capable of taking advantage of the present invention. Figure 1 shows a transformer 10 including a tank 11 having a tank base 12 and a tank wall 16. Tank 11 is filled with a fluid 50, preferably oil, which provides the desired cooling and insulation properties for said electrical device. The primary and secondary windings 14 are also shown schematically within the tank 11. For practical purposes, the electrical connections of the primary / secondary windings 14 to the exterior of the tank 11 are not shown. For additional cooling purposes, a radiator 18 is provided outside the tank 11 and connected to the tank by means of the upper and lower manifolds 20a, 20b, respectively. According to Figure 1, a circulation flow path 25 is defined within the transformer 10. There are two main types of circulation flow in the transformers. One type is the forced convection flow that uses a pump to push the oil through the windings or coils 14, and radiator equipment 18. The radiator 18 is used as an example, but any heat exchange apparatus can be used with the teachings of the present invention. The other type of circulation flow is natural convection flow that depends on changes in fluid density to naturally force the flow of circulation. According to a preferred modality, the circulation flow path 25 for the forced convection type can be defined starting at a pump 27 and following to a flow channel 25a to the primary / secondary windings 14. The windings 14 are preferably wound with key separators (which are not show) that direct the flow through the windings 14 in a reciprocal pattern. That is, the windings 14 in combination with the key spacers result in zigzag-shaped flow channels 25b. After leaving the windings 14, the fluid 50 moves to the radiator 18 through the flow channel 25c. Once the fluid 50 enters the upper manifold 20a it is flowed through individual panels of the radiator 18 and then to the lower manifold 20b. After the fluid 50 leaves the lower manifold 20b it returns to the pump 27 and circulation is repeated. In the case of natural convection, the flow path is a little less definitive at certain points. In this case, the fluid 50 in the windings 14 is heated, forcing itself to rise. Once the fluid 50 leaves the flow channels 25b defined by the windings 14 and key separators the fluid 50 is mixed. At the top of the fluid level 50a, the fluid 50 enters the well-defined flow path 25 including the radiator 18 and the manifolds 20a, 20b. After leaving the lower collector 20b the fluid 50, by natural convection it re-enters the flow channels 25b in the windings 14 to repeat the process.

In either flow, forced or by natural convection, there is a difference between the fluid 50 circulating in a defined circulation flow path 25 and the comparatively stagnant fluid 50 outside the circulation flow path 25. For example, the fluid 50 in a region 11a of tank 11 does not have the same kinetic energy as fluid 50 within flow channels 25b. This kinetic energy exists as a result of the pumping action in the type of forced convection flow and / or as a result of natural convection currents. The circulation flow path can also be considered, generally, as a traditional closed curve in which once the curve is traversed the first time, the measurement of the characteristics or properties of the fluid in a second or subsequent step does not produce results considerably different unless the properties of the fluid have changed in the interim. The circulation flow path can also be defined with respect to the fluid velocity. Moving fluid in the circulation flow path typically has the property that the highest velocity is present at the center of the circulation flow path and the lower velocities are at increased distances taken perpendicular to the flow direction. The boundaries of the circulation flow path, ie, the point at which the fluid ends in the flow path and the stagnant fluids begin, is defined as the point at which the fluid is flowing to approximately one tenth or 10th. % of the maximum velocity present at the center of the flow path. Similarly, the circulation flow path can be defined with respect to fluid density. The outgoing fluid with the lowest density will typically match the fluid that has the highest velocity. Therefore, the distribution of the densities measured in the flow path of circulation is similar to the distribution of velocities. The temperature of the fluid is also interrelated. Generally speaking, the highest temperature coincides with the lowest density, which in turn, matches the highest velocity. In many fluid-filled electrical devices, such as electric transformers, the fluid in the circulation flow path comprises only a fraction of the total amount of fluid present in the device. This fraction can be calculated by determining the mass of the fluid in the circulation flow path against the mass of all the fluid in the device. The mass of the fluid in the circulation flow path can be calculated by multiplying the average density of the ppromed.o fluid, by the cross-sectional area of the circulation flow path (based on the 10% limit factor discussed above) by the length of the flow path. Of course, the values of these variables depend on the particular type and size of the device. As noted above, the conventional transformer monitoring schemes depend on the measurement of the properties and characteristics of the fluid 50 that typically resides, for example, near the wall of the tank 16, since the measurement is made in the fluid that is located adjacent to existing access holes or even to a hole specially provided in the wall of the tank. In this way, the fluid under examination is outside the circulation flow path and, therefore, the results obtained are not so reliable. On the other hand, as shown in Figure 1, sensors 60 are placed in a variety of points, each point being within the well-defined circulation flow path 25 of the transformer 10, whereby an observable event in the path of Circulation flow 25 can be monitored and / or detected more accurately, reliably and effectively. The sensors 60 can be physically mounted in different ways depending on where they are placed. Some preferred ways to mount the sensors 60 in the circulation flow path 25 include, as shown in Figure 2, make a hole 80, for example, in the upper manifold 20a and weld a connector 81 over the hole 80. The sensor 60 is mounted on the end of a through feeder 70 which is screwed preferably in the soldered connector 81. In this case, the cables 62 for the sensor 60 remain outside the tank 11. It is noted that a hole could also be made with the described connector in a panel of the radiator 18 or the lower manifold 20b. The through feeder 70 is preferably long enough for the sensor at its end to be placed within the circulation flow path 25. The cables 62 are preferably connected to a processor 65 to process the power of the sensor 60. The processor 65 it is preferably capable of storing the power of the sensor (or multiple sensors) and determining when a power exceeds a predetermined threshold, thus indicating an imminent or actual failure condition. Preferably, the processor 65 is also capable of analyzing the powers of a variety of sensors both with respect to the magnitude of the relative power of the sensor and the relative and absolute time between the readings. These data are preferably used to analyze an observable event for a particular period resulting in more accurate and useful data regarding the state of the transformer. Another preferred way to mount a sensor 60 in the circulation flow path 25 is by means of a square within the tank 11 adjacent to an inlet or an outlet of the lower upper manifold c, 20 a, 20 b, respectively. Figure 3 shows a U-shaped square 72 with a sensor 60 mounted on its upper part. The square 72 is of a height and position with respect to the outlet of the manifold (in the shown case) so that the sensor 60 is placed within the circulation flow path 25 of the transformer 10. In this case the wires 62 are internally for the tank and, therefore, must be removed by means of a feeder through 85. Of course, this feeder through 85 preferably maintains a strong seal for fluid and maintains the pressure inside the tank 11. Therefore, the feeder through 85 is preferably attached or screwed to the wall of the tank 16 or to the base 12 or to the cover (not shown) of the tank 11. In any case the assembly may allow the replacement of the sensor by removing the upper or lower collector 20a, 20b, as required, to access the sensor 60. While the through-mounted feeder 70 externally described above with a sensor at its end (FIG. 2) is relatively easy to replace under conditions In the field, the internally mounted sensor that has just been described has the advantage of avoiding the need to provide additional access holes in the walls of the tank. In another embodiment of the present invention, a sensor is preferably mounted very close to the primary / secondary windings 14. This position is convenient since many fault conditions come from this part of a transformer. Figure 1 schematically illustrates sensors 60 that are wound with the windings 14, preferably during the manufacture of the windings. Although this position of the sensors is adequate due to the proximity of potential observable events, this procedure may involve certain problems. For example, the sensor and the associated cables are electrically isolated, preferably from the winding conductors, but the sensor or cables can be destroyed by breakage or abrasion during manufacturing, shipping or operation. This can lead to other physical phenomena that greatly affect the location and mounting mechanism of the sensor in the windings 14. A transformer operates by magnetic field lines joining between the primary and secondary coils. And, the intensity of the magnetic bonding field is generally large enough to be able to generate electrical disturbance in the sensor cables. Unfortunately, the disturbance level may be higher than the normal signal level produced by the sensor, thus leaving the sensor practically unusable. To alleviate this problem, armored cable is preferably used for the sensor cables. In addition, the magnetic field generated by the windings 14 induces voltage in the windings 14. The induced voltage levels are generally high enough to result in capacitive coupling between the windings and the sensor, thus raising the voltage level of the sensor over Earth. This problem is preferably solved by implementing the electronic capacitance decoupling. Again, although it is convenient to have a sensor located within the flow path of circulation with the primary and / or secondary windings, this procedure can become more expensive compared to the other embodiments described herein. Another place to place the sensor, as shown in Figure 4, is at one end of a probe 90, where the other end of the probe is placed inside the windings 14. In this embodiment the fluid 50 in the windings 14 it is preferably extracted by means of the probe and passed to the sensor 60 which is outside the windings 14. This method considerably reduces the magnetic and electric field limitations described above with respect to the sensors arranged within the windings. In another embodiment of the present invention invention, a sensor 60 is preferably mounted at a small distance, either from the inlet or outlet of the winding flow channel 25b, as shown in Figure 1. This procedure allows the sensor 60 to be in the circulation flow path. and achieve reduced sensor susceptibility for electrical / magnetic interference. The sensors 60 operable with the teachings of the present invention are not limited in any way. That is, according to the present invention, any known sensor can be placed in a flow path of a transformer or any other type of electrical device that includes cooling and / or insulating fluid. Temperature sensors, gas concentration sensors, whose sensor gases are soluble in oil (for example hydrogen, methane, ethane, ethylene, carbon monoxide and carbon dioxide, acetylene, propane, propylene), humidity sensors, sensors can be used of dielectric strength and power factor sensors with the present invention. The following list is intended only to exemplify and in no way limit the type of sensor that may be implemented in the present invention. In accordance with the embodiments described herein it is possible to more accurately and effectively monitor an observable event that may occur in a transformer or any fluid-filled electrical device. By placing at least one sensor in the fluid flow path of the transformer, a faster and more representative indication of an observable event can be obtained. Although specific embodiments have been described, those skilled in the art will understand that several changes can be made and equivalences substituted by elements thereof without departing from the scope of the invention. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from its essential field. Thus, it is intended that the invention is not limited to the particular embodiments shown as the best mode contemplated for carrying out the invention, but that the invention includes all modalities that fall within the scope of the appended claims.

Claims (33)

NOVELTY OF THE INVENTION CLAIMS

1. - An electrical device filled with fluid, comprising: a tank (11) for containing parts of an electrical device; a fluid (50) placed in said tank (11); heat exchange means (18) connected to the tank to cool the fluid; a fluid circulation flow path (25) including passages to the heat exchange means (18) and at least a portion of the tank (11); and at least one diagnostic sensor (60) disposed in said fluid circulation flow path (25).

2. The electrical device according to claim 1, further characterized in that it comprises an upper collector and a lower collector (20a, 20b) respectively connected to the heat exchange means (18), further characterized in that the passages to said collectors (20a, 20b) comprise a part of the fluid circulation flow path (25).

3. The electrical device according to claim 2, further characterized in that at least one diagnostic sensor (60) is placed inside at least one of the heat exchange means (18) and collectors (20a, 20b) ).

4. - The electrical device according to claim 3, further characterized in that it comprises a feeder (70) having at least one diagnostic sensor (60) connected to it at one of its ends and connecting at the other end to one of the heat exchange means (18) and collectors (20a, 20b).

5. The electrical device according to claim 2, further characterized in that it comprises a connector (81) connected to one of the heat exchange means (18) and to the collectors (20a, 20b).

6. The electrical device according to claim 2, further characterized in that at least one diagnostic sensor (60) is placed adjacent to an inlet or outlet of the collectors.

7. The electrical device according to claim 6, further characterized in that at least one diagnostic sensor is supported by a bracket (72).

8. The electrical device according to claim 1, further characterized in that it comprises primary and secondary windings (14) placed in the tank (11), and further characterized in that said diagnostic sensor (60) is placed within at least one of the windings (14).

9. The electrical device according to claim 8, further characterized in that the cables (62) connected to at least one diagnostic sensor (60) are armed.

10. - The electrical device according to claim 1, further characterized in that it comprises primary and secondary windings (14) placed in the tank (11), and further characterized in that one end of a probe (90) is placed inside at least one of the windings and a sensor (60) is connected to the other end of the probe that is placed outside the windings (14).

11. The electrical device according to claim 8, further characterized in that at least one diagnostic sensor (60) is placed next to the bottom or top of the windings and within the circulation flow path (25).

12. The electrical device according to claim 1, further characterized in that at least one diagnostic sensor (60) is a temperature sensor, gas concentration sensor, humidity sensor, dielectric force sensor or factor sensor. of power.

13.- The electrical device in accordance with the claim 1, further characterized in that a variety of diagnostic sensors (60) are placed in the circulation flow path (25) of the electrical device.

14. The electrical device according to claim 1, further characterized in that the circulation flow path (25) is defined by at least one of a forced fluid flow and a natural convection fluid flow.

15. - The electrical device according to claim 1, further characterized in that the fluid comprises oil.

16. The electrical device according to claim 1, further characterized in that the electrical device is one of an electric transformer, a voltage regulator and a capacitor.

17. The electrical device according to claim 1, further characterized in that the heat exchange means (18) is one of a radiator and a heat exchanger.

18. The electrical device according to claim 1, further characterized in that it comprises a processor (65) connected to at least one diagnostic sensor (60).

19. The electrical device according to claim 1, further characterized in that the circulation flow path (25) is a traditional closed curve.

20.- The electrical device in accordance with the claim 1, further characterized in that the fluid which is in the central part of the circulation flow path has a maximum velocity and the rest of the fluid in the circulation flow path has less than 10% of said maximum velocity.

21.- The electrical device in accordance with the claim 18, further characterized in that the processor analyzes at least one of the magnitudes of a power of at least one sensor and a time related to this power.

22. - A transformer filled with fluid, comprising: a tank (11) for containing at least the primary and secondary windings (14) of the transformer; a radiator (18) connected to the tank (11) by means of upper and lower collectors (20a, 20b); a fluid (50) placed in the tank (11), radiator (18) and manifolds (20a, 20b); a flow path of fluid flow (25) including passages through the radiator windings (14), manifolds (20a, 20b) and at least a portion of the tank (11); and at least one diagnostic sensor (60) disposed within the fluid circulation flow path (25).

23. The transformer according to claim 22, further characterized in that at least one diagnostic sensor (60) is one of a temperature sensor, gas concentration sensor, humidity sensor and dielectric force sensor.

24. The transformer according to claim 22, further characterized in that the fluid is oil.

25. The transformer according to claim 22, further characterized in that the circulation flow path is defined by at least one of a forced fluid flow and a natural convection fluid flow. .

26. The transformer according to claim 22, further characterized in that it comprises a processor (65) connected to at least one sensor (60).

27. - The transformer according to claim 22, further characterized in that the fluid in the central part of the circulation flow path has a maximum velocity and the rest of the fluid in the circulation flow path has less than 10% of said velocity. maximum.

28. The transformer according to claim 26, further characterized in that the processor (65) analyzes at least one magnitude of a power of at least one sensor (60) and a time related to that power.

29. A method for monitoring an electrical device filled with fluid, comprising the steps of: placing at least one sensor (60) in a circulation flow path (25) of the electrical device; monitoring with at least one sensor (60) the properties of the fluid in that circulation flow path (25) and recording the detected properties; and process those detected properties.

30. The method according to claim 29, further characterized in that it comprises determining if the detected properties exceed a predetermined threshold.

31. The method according to claim 29, further characterized in that it comprises generating, with a pump, a circulation flow path. 32.- The method according to claim 29, further characterized in that it comprises placing at least one sensor (60) together or inside a tank (11) of the electrical device, a radiator (18), radiator manifold (20a, 20b) of the electrical device and windings of the electrical device. 33.- The method according to claim 29, further characterized in that the processing step includes at least one step of analyzing at least one of the magnitudes of a power of at least one sensor (60) and a time related to that power.