US1712765A - Expansion device - Google Patents

Description

May 14, 1929. L. H. HILL EXPANSION DEVI CE Filed D80- 25. 192? INVENTQR Le/and Hf/i/l XLVITNESSES:

Patented May 14, 1929.

UNIT STATES 1,712,765 PATENT OFFICE.

LELAND H. HILL, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

EXPANSION DEVICE.

Application filed December as, 1922. Serial No. 608,792.

My invention relates to expansion devices, and it has particular relation to such 'devices as may be employed in connection with transformers, circuit breakers and electrical apparatus of a similar nature.

One object of my invention is to provide a structure wherein a body of gas is retained above the level of the insulating oil in the tank to constitute a cushion for such shocks as may occur by a sudden evolution of gas within the enclosing casing.

A second object of my invention is to provide an expansion device that is so related to the main tank that the oil in the latter is maintained out of contact with the atmosphere and substantially free from the effects of oxidation.

A further object of my invention is to provide a structure wherein a body of gas above the insulating oil in the tank may be maintained at substantially constant pressure and constant volume during fluctuations in temperature and volume of the insulating oil.

In the operation of transformers, circuit breakers and the like, it has been found that the insulating oil for covering the apparatus deteriorates very rapidly when it is in contact with the atmosphere. Considerable moisture is absorbed, thereby diminishing thev insulating properties of the oil. In addition, the explosive mixtures of air and hydrocarbon gases may form within the tank.

I provide a body of inert gas, such as nitrogen or other suitable gas, which fills the space above the insulating oil in the main tank. An expansion device that is connected to the main tank below the level of the insulating oil is of such capacity and is so disposed relatively to the main tank that increases in the volume of the insulatingoil may occur without materially increasing the pressure applied to the inert gas and without materially diminishing the volume occupied by the gas.

In the accompanying drawing,

Figure 1 is a view, partially in elevation and partially in section, of a tank for electrical apparatus with'my invention applied thereto; and

Fig. 2 is a similar view of a modified form I of my invention.

Referring to Fig.1, a tank 1, which maybe of any conventional form for enclosing a transformer, circuit breaker or other apparatus, illustrated diagrammatically by the reference character 1, is partially filled with insulating oil to a level indicated at 3. The space 4 above the insulating oil is filled with inert gas which may be supplied in any suitable manner. The cover 5 of the casing is attached to the tank in any suitable airtight manner.

An expansion device 6, that is connected to the tank 1 by means of. a pipe 7 at a point considerably below the level of the oil 2, comprises an auxiliary tank 8 that is normally filled with oil, indicated at 9, to the same level as that of the tank 1. The upper portion of the tank 8 is provided with a vent pipe 10. The lower portion of the casing is provided with a drain pipe 11 that is controlled by a suitable valve 12.

When the temperature of the apparatus 1 and th at of the surrounding insulating oil increases, the volume of the oil increases to a corresponding degree. The result is to tend to increase the pressure applied to the-gas in the space 4 by reason of the increased volume of the oil. The oil, accordingly, flows through the pipe 7 into the auxiliary tank 8 to cause the oil in the latter to assume a level above the level 3, at such height as to correspond to the increased pressure in the main tank 1.

If the auxiliary tank 8 is of large capacity relatively to the volume of oil to be transferred from the main tank, the pressure ap plied to the gas in the space 4 is relatively small.- The volume of the gas is accordingly diminished to a correspondingly small degree.

When the temperature decreases, oil flows from the auxiliary tank 8 through the pipe 7 into the main tank 1'. The level of the oil in the auxiliary tank falls in accordance with the changes in pressure. During this operation, air enters through the vent pipe 10 to occupy the space above the oil in the auxiliary tank.

lit will be obvious that, during the operation of breathing or exchanges of oil between the main and the auxiliary tanks, the quantity of inert gas in the space 4 remains the same and that its volume and pressure are not materially afiected by changes in temperature of the nil. It will be understood also that, by reason of the location of the connection of the pipe 7 to the main tank, the external atmosphere is never in contact oxidation or slud'ging as may occur takes.

place in the auxiliary tank. The sludge and any moisture that may have settled in the auxiliarytank may be removed by means of the drain pipe 11 and valve 12.

Reference may now be had to the structure shown in Fig. 2. The apparatus shown therein is similar in principle and operation to that shown in Fig. 1. The expansion device differs in structural details in that it comprises an annular auxiliary tank 14 that surrounds the main tank 1 at its upper portion. The auxiliary tank is connected to the main tank below the level of the insulating oil by suitable openings 15. A vent pipe 16 and a drain pipe 17, with its controlling valve 18, perform functions similar to those described in connection "with the apparatus of Fig. 1. In view of the detailed description of the'operation of the apparatus of Fig; 1, a detailed description of the operation of Fig. 2 is omitted as unnecessary to an understanding of the operation of this form of my invention.

In case of the sudden evolutioniof gases by containing a gaseous medium above the oil level at substantially atmospheric pressure.

4;. The combination with acasing containing insulating oil, of an electrical translating device immersed in said oil, a cushion of inert gas confinedwithin said casing above the oil and in contact therewith, an expansion chamber partially filled with insulating oil, there being communication independent of said gas cushion between the oil in said casing and the oil in said expansion chamber to permit interchange of oil between the casing and exreason of a fault in the electrical apparatus or for any other reason, the body of gas in the space 4 operates as a' cushion to absorb the initial impact of the shock caused thereby.

.This arrangement may diminish the shock sufiiciently to enable the structure of the tank to. withstand the stresses to which it is subjected. This result is a very desirable one because serious damage to life and property may occur if hot or burning oil is permitted to escape from the tank 1.

In addition to providing a cushion for shocks, the body of inert gas prevents the formation of explosive mixtures and the deterioration of the oil by oxidation. The above and other advantages will be apparent to those skilled in the art to which my invention appertains.

I claim as my invention r 1. The combination with a tank for electrical apparatus, a quantity of oil for partially filling said tank, and a quantity of inert gas occupying the space above the oil, of means for permitting the expansion of said oil without correspondingly increasing the pressure applied to said gas, said means comprising an auxiliary tank for containing oil, a connection betwenthe two tanks, below the oil level, said auxiliary tank having a vent opening to the outside air 'above the oil level.

2. The combination with a tank for electrical apparatus, a quantity of oil for partially filling said tank, and a quantity of inert gas occupying the space above the oil, of means for permitting the expansion of said 'oil without affecting the pressure applied to said gas and its volume in said tank, to corresponding degrees, said means comprising an auxiliary tank for containing oil, a connection between the two tanks below the oil level, said pansion chamber due to thermal expansion and contraction of the oil in the casing, and

means for maintaining said expansion chamber substantlally at atmospheric pressure in the region thereof above the level of themsulating oil therein. I

5. The combination with a casing, of a transformer in said casing, an expansion chamber spaced from said casing, a conduit communicating with said expansion chamber and with said casing in a region removed from the top thereof, the cross-sectional area of said conduit being small compared e u with the cross-sectional area of said expansion chamber, aninsulating liquid medium disposed in said expansion chamber, the conduit leading therefrom and in said casing to a level above saidregion, of an inert gas cushion confined within said casing and contacting with the upper surface of said liquid medium, and a connection leading from said expansion chamber and open to the atmosphere.

6. Thecombination with a casing, of a transformer in said casing, an expansion chamber, a conduit'communicatin with said expansion chamber, and with sai casing in a region removed from the top thereof, an insulating liquid medium disposed in said expansion chamber, the conduit leading therefrom and in said casing to a level above said region, a gaseous cushion confined within said casing and contacting with the upper surface of said liquid medium, and a connection leading from said expansion chamber-and open to the atmosphere. I

In testimony whereof, I have herento sub- :SlCIlbed my name this 21st day of December,

LELAND HILL.

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