US3444308A - Vapor cooled electrical transformer - Google Patents

Description

May 13, 1969 v p. MRBUT 3,444,308

VAPOR COOLED ELECTRICAL TRANSFORMER Filed July 19, 1967 Sheet of 2 i @136 A2 I 40 I j 44'": I Q 33 ;(.32 3| 42 I v w 5 E 53 X 5 46 S 5| 1 5o 5 s2 gg j l FIG. I.

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WITNESSES: INVENTOR Poul Norbut y 13, 1969 P. NARBUT VAPOR COOLED ELECTRICAL TRANSFORMER Sheet Filed July 19. 1967 United States Patent 3,444,308 VAPOR COOLED ELECTRICAL TRANSFORMER Paul Narbut, Sharpsville, Pa., assiguor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed July 19, 1967, Ser. No. 654,543 Int. Cl. H01b 7/34 US. Cl. 17415 7 Claims ABSTRACT OF THE DISCLOSURE Transformer apparatus comprising a core and coil assembly in a casing and a cooling device connected to the casing. The transformer utilizes a fluid dielectric atmosphere for insulation and cooling. The dielectric atmosphere includes a mixture of condensable vapor and noncondensable vapor. A positive acting liquid operated gate valve is provided for regulating the flow of non-condensable vapor through the casing and cooling device in response to the temperature and pressure, or the tempera. ture or pressure inside the casing.

The Hill Patent 2,561,738 discloses an enclosed electrical apparatus utilizing a relatively small amount of liquid 'fluorocarbon which is sprayed in a thin layer over the electrical windings to cool them by evaporation of the fluorocarbon, the fluorocarbon vapors constituting at least a part of the electrically insulating gas atomsphere. Such apparatus is efficient in operation but has the disadvantage that the vapor pressure developed within the casing varies greatly with load on the electrical apparatus.

An object of this invention is to provide an enclosed electrical apparatus insulated with a mixture of non-condensable gases that dissipate the heat developed in use of the apparatus and controlling the flow of the non-condensable gases through the casing in response to atmospheric conditions within the casing.

Another object of this invention is to provide an enclosed electrical apparatus insulated with a non-condensable gas and a vaporizable liquid coolant which is sprayed thereover and mixes with the non-condensable gas and to control the proportion of vapor gas mixture in accordance with atmospheric conditions within the casing to maintain a predetermined concentration of vapor within the casing.

Another object of this invention is to provide an enclosed electrical apparatus insulated with a non-condensable gas and a vaporizable liquid coolant which is sprayed over the electrical apparatus and mixed with the noncondensable gas to control the proportion of gas vapor in accordance with the atmospheric conditions within the casing by condensing the condensable gas and utilize the condensate to close a liquid seal gate valve for controlling the density of condensable vapor in the casing.

Other objects of this invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of a transformer con structed in accordance with this invention;

FIG. 2 is a fragmentary diagrammatic view illustrating another embodiment of this invention;

FIG. 3 is a fragmentary diagrammatic view illustrating a further embodiment of this invention;

FIG. 4 is a diagrammatic view of a transformer illustrating another embodiment of this invention;

FIG. 5 is a sectional view of the vapor gate valve utilized in the embodiments of FIGS. 1, 2 and 4; and

FIG. 6 is a transverse sectional View of the valve shown in FIG. 5, taken along the line V-V of FIG. 5.

3,444,308 Patented May 13, 1969 Referring to FIGURE 1, this invention is illustrated by reference to a transformer 10 comprising a sealed casing 12 within which is disposed a magnetic core 14 and an electrical winding 16 associated therewith disposed to seat on the bottom of the casing. For the purpose of simplifying the drawings, leads to the winding 16 and the bushings normally carried by the top or cover of the casing 12 are not shown.

As illustrated in FIGURE 1, the bottom of the casing 12 is provided with a sump 18 in which there is disposed a supply 20 of vaporizable liquid coolant. The supply 20 of the liquid coolant is relatively small as compared to the size of the casing 12. A cooling device 26 is connected to the bottom of casing 12 with a conduit 30 and to the top of casing 12 With a conduit 28.

The coolant utilized in this invention may be any of those disclosed in the Hill Patent 2,561,738 or the Narbut Patent 2,875,263.

The space within the casing 12 surrounding the magnetic core 14 and the winding 16 comprises in part a gas 22 which is preferably permanent or non-condensable, that is non-condensable during the conditions of use of the transformer, gas such as nitrogen, argon, neon, carbon dioxide or the like or mixtures thereof, under certain conditions, air may be used as the non-condensable constituent of the gas space. The insulating properties of the non-condensable gas will be greatly enhanced by the pressure of the saturated vapor of the liquid cooling. The dielectric strength of the vapor-gas mixture depends greatly upon the promotion of the coolant vapor, which, in turn depends upon the pressure of the saturated vapor and the pressure of the saturated vapor depends upon the temperature of the vapor-gas space in the casing. It is apparent that in order to maintain a predetermined dielectric strength of the gas vapor mixture, it is necessary to maintain a minimum temperature within the casing 12.

Attempts have been made to maintain this minimum temperature within the casing 12 by controlling the density of non-condensable vapor in the casing 12 with a temperature responsive or pressure responsive valve located directly in the conduit connecting the cooling apparatus 26 to the casing 12. Such an arragement is illustrated in the Narbut Patent 2,875,263. This arrangement works to some degree; however, it has undesirable drawbacks or disadvantages because the valve must be closed tightly for pressures below operating pressures. Although the pressure difference on the two sides of the valve will not be more than about one inch of water, slight seepage of non-condensable gas through the valve occurs which causes faulty operation of the transformer apparatus. The valve must have a large free venting capacity when open; that is, approximately equivalent to a three inch diameter header, or larger if several cooling devices 26 are to be controlled by one valve. This large size diameter further increases the possibility of seepage of non-condensable gas through the valve.

This invention eliminates the objections to the arrangements disclosed in the Narbut Patent 2,875,263 for controlling the flow of the non-condensable gas through the cooler 26 by providing a liquid seal gate valve'40 for controlling the rate at which the hot condensable vapor is admitted to the cooling apparatus, thereby controlling the rate of heat dissipation by the cooling apparatus. The cooling rate is controlled, to be equal to the heat generation rate, to accommodate variable loads while maintaining a nearly constant vapor pressure and temperature in the casing 12.

As illustrated in the drawings the cooler 26 is attached to the upper end of the casing 12 by means of a conduit or header 28 and the lower end of the cooler 26 is attached to the bottom of the casing 12 by means of a conduit or header 30. In normal operation the condensable gas and the non-condensable vapor enter the cooling device 26 through the lower conduit 30. The condensable gas condenses in the cooler 26 and flows back to the casing 12. The non-condensable gas or vapor is returned back into casing 12 through conduit 28, under the control of valve 40.

In order to apply the liquid coolant 20 to the electrical winding 16, a pump 24 is disposed for operation to withdraw the liquid coolant from the sump 18, the pump 24 being connected by a conduit 34 to a suitable spray de vice 36 from which the liquid coolant 28 is distributed in the form of a spray over the core 14 and the winding 16. Other methods of applying the liquid coolant 20 to the core 14 and the windings 16 may be used consistent with the physical arrangement of the apparatus, the only essential requirement being a reasonable uniform distribution of the liquid film over the parts to be cooled. The liquid coolant 20 when sprayed over the core 14 and coil 16 distributes itself as a thin film over the core 14 and coil 16 within the casing 12 and is caused to evaporate freely after the core 14 and coil 16 reaches a sufiiciently elevated temperature to evaporate the liquid, thereby cooling the core 14 and the coil 16. As the liquid coolant 20 vaporizes the vapors thereof mix with the noncondensable gas present in the casing to increase the dielectric strength of the insulating gas within the casing 12.

Since the dielectric strength of the vapor gas mixture depends upon the proportion of the coolant vapor in the casing 12, which, in turn, depends upon the temperature and pressure of the vapor-gas space in casing 12, a liquid seal gate valve 40 is provided in the upper conduit 28 connecting the cooling device to the casing 12 to control the flow of non-condensable gas from the cooling device 26 into the casing 12 and thus control the flow of the hot gas-vapor mixture into the cooler 26, in accordance with the temperature of the pressure in the casing 12, or in accordance with a combination of the temperature and pressure, it being understood that the pressure and temperature within the casing are dependent one upon the other.

The liquid seal gate valve 40 comprises a sump portion 42 and a batfie 44 which extends downwardly from the top of the valve 40 and terminates short of the bottom of the sump 42. The sump 42 of the valve 40 is connected by means of a conduit 46 to a pilot valve 48. The inlet from the pilot valve 48 is connected to the interior of the casing 12 by means of a conduit 50. The pilot valve 48 comprises a gate 51 which is closed by a plug or closure member 52. The closure member 52 is normally held in a closing position in the gate 51 by a spring 43. The closure member 52 is moved to open the gate 51 by a piston 54. The piston 54 is operated by the pressure inside the casing 12.

The liquid seal gate valve 40 is also connected directly to the pump discharge conduit 34 by means of conduit 31, manual valve 32 and conduit 33. This arrangement permits filling of the sump 42 to close the liquid seal gate valve 40 when the transformer is operating under minimum load, simply by opening the valve 32 to permit the pump 24 to deliver enough liquid to the valve to close the valve 40 to the passage of non-condensable vapor.

In the operation of the apparatus shown in FIGURE 1, when the electrical apparatus is operating on low loads or on a low burden it is desired to maintain the density of the condensable vapor in the casing at a maximum in order to maintain the proper dielectric strength of the vapor gas mixture in the casing 12. As seen from FIG- URE 1, the pilot valve 48 is connected to respond to the pressure inside the casing 12. Under low load operating conditions condensable vapor and non-condensable gases will enter the conduit 30 and the cooling device 26. The condensable vapors will condense and fill the sump 42 of the liquid gate valve 40 until the lower end of the baffle 44 is covered. When the lower end of the baflle 44 becomes covered with liquid the valve 40 is completely closed to the passage of non-condensable gas through the valve 40. Thus, the noncondensable gas is trapped in the cooler 26 and a blanket of minimum density of noncondensable gas is maintained in the casing 12. Should the burden or load on the electrical apparatus in the casing increase, the pressure within the casing would increase and this increased pressure acting on the piston 54 of the pilot valve 48, as indicated by the arrows, FIG. 1, would open the pilot valve 48, against the pressure of the spring 53, and the liquid from the liquid gate valve 40 would drain through the conduit 46 through the pilot valve gate 51, opening 55 in valve 48, and the conduit 50 back to the casing 12. As soon as the liquid has drained from the liquid gate valve 40 to a point below the lower end of the baffle 44, then the non-condensable gas starts flowing through the cooling device 26 and into the casing 12 to maintain the predetermined dielectric strength of the gas vapor mixture in the casing with increased load.

The apparatus shown in FIG. 2 is similar to that shown in FIG. 1, except, that instead of the pilot valve 48 being responsive to pressure in the casing 12, the pilot valve 48 is operated by a temperature responsive bulb 60. In this embodiment when the temperature rises above a predetermined limit in the casing 12 liquid in the bulb 60 is forced into the pilot valve 48 to cause the pilot valve 48 to open the gate 51 and dump liquid from the liquid operated gate valve 40 through the conduit 46, the pilot valve gate 51 and the conduit 50 back into the casing 12 and thereby open the liquid gate valve 40 to the flow of non-condensable gases.

The apparatus shown in FIG. 3 is also similar to that shown in FIG. 1, except that a pilot valve 64 is responsive to both the temperature and pressure in the casing 12. In the apparatus shown in FIG. 3, a liquid operated gate valve 66 is shown which comprises a sump portion 68 and a baflle portion 69. The pilot valve 64 comprises a temperature-pressure responsive diaphragm 70 which is biased by a spring 72 and a needle 74 which is operated by the temperature responsive diaphragm 70. The needle 74 opens and closes an opening 75 in the bottom of the sump 68. The opening 75 in the bottom part of the sump 68 is connected to the interior of the casing 12 by a conduit 76. When the apparatus is operating at low load or low burden the condensable gases condense and the sump 68 is filled with liquid until the lower end of the bafile 69 dips into the liquid. When this occurs the liquid operated gate valve 66 is effectively closed to the passage of nonvaporizable gas. However, if the burden or load on the electrical apparatus should increase, the diaphragm 70 responds to the temperature and pressure inside the easing 12 and lifts the needle 74 to open the conduit 76 and permit the liquid to drain from the sump 68 back into the casing 12. As soon as sufficient liquid has drained from the sump 68 to clear the lower end of the bafile 69, the gas-vapor circulation resumes under the control of the pilot valve 64, thus maintaining the predetermined dielectric strength of the vapor-gas mixture in the casing 12.

The apparatus shown in FIG. 4 is similar to that shown in FIGURE 1 except that a diiferent arrangement for providing liquid to the liquid gate valve 40 is provided. This arrangement also uses a pressure operated pilot valve 80. However, it is understood that the pilot valve 80 could be responsive to pressure or temperature or a combination of pressure and temperature. In the apparatus of FIG. 4 the bottom or the sump of the liquid operated gate valve 40 is connected to the pilot valve 80 through a conduit 82 and the bottom 42 of the liquid operated gate valve is also connected directly to the inside of the casing 12 through a conduit 84, having a manually operated valve 86 therein. The outlet from the bottom of the pilot valve 80 is also connected directly to the conduit 34 from the pump 32 by means of a conduit 88.

With the arrangement of FIG. 4, at the minimum load within the controlled operating range, the hand operated valve 86 should be adjusted so as to have the liquid seal gate 40 just closed with a minimum liquid level. Under this condition the cooling apparatus 26 will be filled with non-condensable gas and, hence, be inoperative. As the load is increased, the temperature and pressure in the casing 12 will tend to rise, and cause operation of the pilot valve 80 to reduce the rate of flow of the liquid, thus causing a drop in the liquid level in the gate 40. This will cause circulation of the non-condensable gas-condensable vapor through the cooling apparatus 26 to commence. In this manner, the flow of non-condensable gas-condensable vapor through the cooling apparatus 26 will be controlled by the pressure and temperature within the casing 12, maintaining a desired minimum dielectric strength of the condensable vapor within the control range of the load.

As seen from FIG. 4, as the pump starts pumping liquid dielectric to the spray head 36, some of this liquid dielectric will pass through the conduit 88 through the pilot valve 80 to the conduit 82 and fill the sump 42 of the liquid operated gate valve 40. As soon as the liquid operated gate valve 42 is filled to a level where the bafile 44 dips into the liquid, the manually operated valve 86 is opened to drain off fluid from the sump 42 of the liquid operated gate valve 40 at a rate such that the pump will just keep the liquid in the sump 42 of the liquid operated gate valve 40 up to a level high enough to cover the lower end of the bafile 44 and keep the liquid operated gate valve 40 closed to the passage of non-condensable gas. However, if the pressure in the casing 12 should rise sufiiciently high to require a more rapid rate of flow of non-condensable gas in the casing 12 to maintain the proper dielectric strength in the casing 12, the pressure would be communicated from the casing 12 through the conduit 90 to operate the piston 92 of the pilot valve 80 to close the gate 51 of the pilot valve to the fiow of liquid through the conduit 88, the gate 51, and 82 and with the pilot valve 80 thus closed, the sump 42 of the liquid operated gate valve 40 would soon empty through the conduit 84 and the manually operated valve 86 back into the casing 12, thus opening the liquid operated gate valve 40 to the passage of noncondensable gas through the cooling device 26 and the conduit 28 back into the casing 12. correspondingly when the pressure in the casing again lowers to a value where the rate of flow of non-condensable gases must be reduced in order to maintain the proper dielectric medium in the casing 12, a spring 94 will again open the gate 81 of the pilot valve 80 to permit fluid to again flow through the conduit 88 through the gate 51 and the conduit 82 to again close the liquid operated gate valve 40 to the flow of non-condensable gas from the cooling device 26 into the casing 12.

FIG. 5 merely shows an enlarged detail of the liquid operated gate valve 40 shown throughout the drawings and described herein to illustrate the position and configuration of the sump 42 and the bafile 44.

FIG. 6 is a view of the valve of FIG. 5 taken along the line V--V to show the complete configuration of the liquid operated gate valve 40.

Liquid operated gate valves are described herein for accurately controlling the rate of flow of non-condensable gases from the cooling device 26 into the casing 12. As pointed out hereinbefore, it is important to control the rate of flow of non-condensable gases from the cooling device 26 into the casing 12 in order to maintain a proper dielectric strength of the vapor gas mixture in the casing 12 for most eflicient operation of the apparatus under varying load conditions. It is also pointed out that the liquid operated gate valve described herein eifectively cuts off the flow of non-condensable gases to the casing, but permits the flow of condensed liquid back to the casing 12. As seen from each of the figures of the drawings, if a surplus of condensate is dumped into the sump of the liquid operated gate valve, liquid will merely flow over the edges of the sump and flow back to the casing either directly through the conduit 28 or back through the cooling device 26 and to the casing through the conduit 30. Therefore, it is seen that the liquid operated gate valve described herein provides an effective valve for cutting off the flow of non-condensable gas and permits the condensable vapor to condense and return to the casing 12. It is also seen that the liquid operated gate valves described herein may be operated in response to temperature or pressure in the casing or to temperature and pressure as desired. It is further seen that the liquid operated gas valves provide a positive seal against the passage of non-condensable gas and prevents any leakage of gas through the valve which might cause improper operation of the electrical apparatus, such as may occur in the apparatus shown and described in the Narbut Patent 2,875,263.

From the foregoing it is seen that this invention has provided improved transformer apparatus which is cooled by a mixture of condensable vapors and non-condensable gas wherein the density and mix of the condensable vapors and non-condensable gas is maintained at a predetermined level for maintaining proper dielectric strength for the dielectric medium within the apparatus by providing more reliable means for controlling the density of the noncondensable gas in the casing in response to the temperature or pressure in the casing or both temperature and pressure.

I claim as my invention:

1. Electrical apparatus comprising a sealed casing and an electrical conductor disposed therein which is subject to temperature changes when in use, a non-condensable gas and a vaporizable liquid coolant contained by the casing, means for applying the liquid coolant to the electrical conductor to effect cooling of the electrical con ductor by the vaporization of the applied liquid coolant, vapors of the liquid coolant and the non-condensable gas being intermixed within the casing when the vapors are evolved to provide a dielectric medium for insulating the electrical conductor, a cooling device, conduit means connecting the lower end of the cooling device with the lower end of the casing and the upper end of the cooling device to the upper end of the casing, said conduit means connecting said cooling device to said casing providing for the flow of non-condensable gas and vapors in both directions between the casing and the cooling device, liquid operated gate valve means disposed in the conduit means connecting said cooling device to said casing, second valve means, said second valve means being connected to said liquid operated gate valve and to the inside of said casing, said second valve means being responsive to conditions inside said casing to open and close said liquid operated gate valve to the passage of noncondensable gas.

2. The apparatus as specified in claim 1 wherein said second valve means is responsive to the pressure and temperature in said casing.

3. The apparatus as specified in claim 1 wherein said second valve means is responsive to the pressure in said casing.

4. The apparatus as specified in claim 1 wherein said second valve means is responsive to the temperature in said casing.

5. The apparatus specified in claim 1 wherein said sec ond valve means is connected between said means for supplying liquid coolant to the electrical conductor and said liquid gate valve for supplying liquid to close said liquid gate valve to the passage of non-condensable gas, and means for conducting liquid from said liquid valve means back to said casing to open said liquid gate valve to the passage of noncondensable gas, said second valve being responsive to the pressure in said casing for disconnecting the supply of liquid to said gate valve and permitting said gate valve to open by draining liquid from saidliquid operated gate valve into said casing.

6. The apparaus as specfied in claim 1 wherein said liquid operated gate valve comprises a chamber connected in said conduit means between said casing and said cooling device, said chamber having a partition extending from the top thereof and terminating short of the bottom of said chamber, said chamber having an outlet, said outlet being connected by conduit to drain liquid from said gate valve into said casing, a second valve in the conduit for draining said liquid operated gate valve, said second valve being responsive to conditions in said casing to close said conduit and permit liquid condensate from said cooling device to collect in said chamber to a level above the lower end of said partition and close said liquid operated gate valve to the passage of non-condensable gas, said second valve means being responsive to conditions in said casing to open said conduit and drain the liquid condensate from said liquid gate valve and open said liquid gate valve to the passage of non-condensable gas.

7. The apparatus as described in claim 1 wherein means comprising a conduit and a third valve means connects etween said means for applying the coolant to the electrical conductor and said liquid operated gate valve for supplying liquid to close said liquid operated gate valve.

DARRELL L. CLAY, Primary Examiner.

15 T. J. KOZMA, Assistant Examiner.

US. Cl. X.R. 336-57, 58

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