US2103816A - Electrical apparatus - Google Patents

Description

Dec. 28, 1 937. w. J R 2,103,816

A ELECTRICAL APPARATUS Filed Oct. 31, 1933 4 Sheets-Sheet l WITNESSES: v INVENTOR M/flamfHar/f W. I BY ATTORNEY DOC. 28, w H RT ELECTRICAL APPARATUS Filed Oct. 31, 1933 4 Sheets-Sheet 2 INVENTOR M'///'am J'f/a/f ATTO WITNESSES:

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Dec. 28, 1937. .w. J. HART ELECTRICAL APPARATUS Filed Oct. 31, 1933 4 Sheets-Sheet 5 m m 51 m .WY W

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Dec. 28, 1937. w HART 2,103,816

ELECTRI CAL APPARATUS Filed Oct. 51, 1933 4 Sheets-Sheet 4 WITNESSES:

c INVENTOR 5% M fl/bmff arf aim. W BY 5' ATTOFQNEY Patented Dec. 28, 1937 UNITED STATES ELECTRICAL APPARATUS William J. Hart, Sharon, Pa., assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa.,

sylvania a corporation of Penn- Application October 31, 1933, Serial No. 696,049

6 Claims.

My invention relates to a protective device for electrical apparatus, such as oil immersed transformers, and particularly to means for interrupting a circuit through the apparatus upon the occurrence of predetermined conditions of the circuit or of the apparatus.

Such electrical apparatus is subject to different types of disturbances, one of which results in the flow of a heavy fault current through the circuit of the apparatus, another of which results in temperatures that are too high for the safe operation of the apparatus, such as may be produced by a continuing overload on the apparatus, and another of'which causes a slow disintegration of the insulating material and the generation of gases from the decomposition products thereof, which may be. explosive in character, and which tend to build up a pressure within the transformer casing that will eventually open up the gaskets under the transformer cover and permit the gas to fill the space above the transformer. This is particularly undesirable in certain locations, for example, particularly when the transformer is installed in a vault within a building where no proper facilities exist for ventilating the vault. It is possible under such circumstances for the vault to become filled with an explosive gas which, if ignited by a spark, may do considerable damage.

In the usual type of transformer the pressure developed from the sudden flow of heavy fault current may be so high as to force oil and gas out under the cover of the tank or even to open the welded tank seams. Such. disturbances, however, usually originate as minor faults, or stewing arcs, between local parts of the apparatus and become progressively worse if not checked. Such anarc causes decomposition of the oil and solid insulation of the apparatus and results in explosive gaseous products that build up a gas pressure inside the tank which may finally become sufilcient to force the gas past the gaskets or into the vault or chamber containing the transformer where a secondary explosion may occur. When, as a result of such stewing arc, enough oil is decomposed to uncover the transformer terminal board a heavy arc may occur between the terminals.

If the transformer is disconnected from its power circuit with the pressure when the transformer tank due to gases formed by a stewing arc has reached a value just below that which might force the gas past the gaskets, a secondary explosion in the vault containing the transformer, or the likelihood of a heavy are between terminals as a result of uncovering the terminal board within the transformer may be prevented.

The possibility of an are inside the transformer casing and of the accompanying gas pressure becoming severe is reduced if the transformer is disconnected from its power circuit within a few cycles after the occurrence of a heavy fault current, which is quicker than it ordinarily would be disconnected if it were necessary to wait for a circuit breaker at a station or in the power feeder system to trip the circuit.

It is, therefore, desirable .in electrical apparatus, such as transformers, that the apparatus be disconnected from the line upon the sudden flow of a heavy fault current such as may result from short circuited windings, upon the breakdown of the insulating material, such as may be caused by a continued or stewing are between adjacent turns of the winding, or upon prolonged overloads resulting in excessive oil temperatures.

In accordance with my invention, I have provided a circuit interrupting mechanism for preventing explosions that occur as the result of short circuited windings, prolonged overloads, or stewing arcs in electrical apparatus and that will minimize or prevent explosions from gases given off as a result of a heavy arc fault occurring suddenly.

In the accompanying drawings:

Figure 1 is a view partly in elevation and partly in section of a transformer embodying apparatus containing the protective features of my invention;

Fig. 2 is an enlargedcross-sectional View of a detail of the embodiment of a pressure and temperature release device comprising a part of the apparatus illustrated in Fig. 1;

Fig. 3 is a cross-sectional view of one embodiment of the pressure and temperature release device comprising a part of my invention;

Fig. 4 is a cross-sectional view taken along the line IVIV of Fig. 3;

Fig. 5 is a view partly in elevation and partly in cross-section of an auxiliary chamber or fuse box containing three circuit-interrupting devices for use with a three-phase circuit;

Fig. 6 is a cross-sectional view taken along the line VI-VI of Fi 5;

Fig. '7 is an enlarged cross-sectional view of a detail of part of the tripping mechanism illustrated in Fig. 5;

Fig. 8 an end view of the part of the apparatus shown in Fig. 7 taken along the line VIII-V1II; I

Fig. 9 is a detail of the switch mechanism illustrated generally in Figs. 5 and 6;

Fig. 10 is a cross-sectional view taken along the line X-X of Fig. 9;

Fig. 11 is a schematic view showing the electrical and mechanical connections of the three circuit interrupting devices shown in Figs. 5 and 6 to three transformers of a bank; and

Fig. 12 is an enlarged cross-sectional view of the interrupting device shown in Fig. 1.

Referring to the drawings, and particularly to Figs. 1 and 2 thereof, a transformer l is shown veniently located casing 8, and an explosion type -fuse or switch 9 suitably mounted within the casing.

The circuit interrupting device indicated generally at 9 is illustrated as a boric acid type switch such as is covered generally in a copending application of Joseph Slepian, Serial No. 568,554, filed October 13, 1931, now Patent No. 2,077,276, patentedv April 13, 1937 and assigned to the same assignee as this application.

The circuit interrupter 9 as illustrated comprises a tubular enclosing casing l3 of fibre or other suitable insulating material that extends between metal terminal members 04 and I5 which electrically connect the circuit interrupting switch between cable conductors l6 and I? through terminals l8 and I9 respectively. The casing member I3 is lined on the inside with solid blocks or washers of boric acid 2! having openings through the central portions thereof. A movable switch element or plunger rod 22, having a fusible portion 23 therein, extends through the opening in the boric acid blocks and is actuated by a biasing member 25 to move through the openings in the blocks and draw a circuit interrupting are upon the fusing of the portion 23 thereof. The are is thus drawn in contact with the walls of the boric acid blocks causing the boric acid to be decomposed and give off water vapor which flows longitudinally through the arc and out the end of the explosion chamber formed by the openings through the boric acid blocks.

The circuit closing, or movable plunger member 22, is normally held in its illustrated or circuit closing position by a latch 25 that engages a. notch 25 at one end of the member 22. The terminal It is formed in the shape of a cap suitably secured to the tube l3 and provided with an opening 2'6 in the central portion thereof which provides for discharge of the arc gases from the explosion chamber. rod 22 is electrically connected to the terminal cap It by some suitable connecting means as, for example, a wire 20 fastened to the cap it and contacting with the rod 22. The mechanical strength of the connection between the Wire 20 and the rod 22 is such that it will rupture when the rod is actuated toward the right by the spring 24. The other end of the rod 22 is connected through the pin 28 to an angle or collar 29. The compression spring 26 is positioned between the collar 29 and a washer 3! at the end of the series of boric acid blocks or discs 2!. The collar 29 is electrically connected to the terminal 15 through a conductor 32 with which it slidably engages and through a disc 33 which is secured between the end of the terminal 85 and a cap 34.

A pressure and temperature actuated release device 35 is provided, the interior of which is connected by means of pipes 36 and 37 with the interior of the transformer casing below the level of the oil, thus permitting the oil to circulate One end of the through the release device. A wire-operating means 38 is provided operatively connecting the release device 35 to the latch 25 for tripping the same under certain predetermined conditions. The pressure release deviceis better shown in Fig; 2 and comprises a casing 39, the interior of which is connected by means of the pipes 36 through an opening in the end plate 4| and terminates in a piston Q5 that is biased by a compression spring 46 that extends from the piston 45 to the wall of the end plate M tending to force these two members apart. A sylphon bellows t! extends between the end plate 4! and the piston 45 surrounding the spring 46 for the purpose of making an oil-tight joint between these members.

A quartz bulb 48, that is designed to rupture at a predetermined temperature, is positioned between the piston 45 and a piston 49 and acts as a compression member to prevent movement of the piston 65, in a direction away from the end plate M so long as the toggle or link mechanism to be described is in its illustrated position. The piston 49 is slidablymounted within a guide 50 that extends from one side-wall of the casing 39 and is connected by means of pivotally connected links-5i and 52 to an abutment 53. In the position illustrated in Fig. 2 the biasing action of the spring 55, tending to move the pistons 45 and 69 toward the right forces the ends of the links 5i and 52 that are pivotally connected at 56 downwardly against an abutment 55 that prevents further movement of the pistons. A rod 56 is pivotally connected to the links 5| and 52 at the point 54 and extends upwardly therefrom, the upper end being attached to a piston 57 from'which a sylphon bellows 58 extends downwardly to a plate 59 that is suitably attach, d to the casing 39 and between which a gasket 55 is provided to form a tight joint. An

opening in the plate 59, the'gasket SI, and the a vided extending upwardly from the casing 39 and enclosing the sylphon bellows 58.

The purpose of the pressure release device is to operate to trip the circuit interrupting device 9 whenever the oil temperature within the transformer becomes excessive or whenever the pressure produced by gases given 015 by the oil and entrapped above the oil level in the transformer reaches a predetermined value. The actuating force of the mechanism is the spring 66 which, when released, forces the piston 45 away from the end wall ll and pulls the wire 38 through the flexible cable 413, thus tripping the latch 25 and permitting the fuse mechanism to operate and interrupt the circuit through the transformer winding.

The oil from the transformer casing flows into the casing 39 through the pipe 35 and returns to the transformer casing through the pipe 3?. It thus surrounds the quartz bulb 48 which is designed to burst at a predetermined temperature, allowing the compression spring to force the piston 45 toward the right and trip the boric acid fuse by means of the steel wire 38. This operation does not disturb the position of the pressure release element of the mechanism comprising the bellows 58, piston 49 and links 5| and 52.

When the internal pressure within the transformer tank exceeds the same minimum operating value permitted, this pressure, which also exists within the sylphon bellows 58, exerts a pressure on the piston 51 forcing it upwardly and moving the toggle mechanism comprising the links 5| and 52 away from the abutment 54, thus permitting the piston 49 to be moved by the pressure of the spring 46, the links and piston assuming the positions shown in dotted lines. In this operation of the mechanism the quartz bulb remains in its illustrated position between the pistons 45 and 49 and is moved bodily toward the right, as viewed in Fig. 2.

Referring to Figs. 3 and 4 of the drawings, an embodiment of the temperature and pressure release device is illustrated that is suitable for mounting on the cover of a transformer and that extends downwardly below the oil level. In Fig. 3 a portion 65 of the transformer cover is shown above which is mounted a base plate 68 supporting the release mechanism and which is connected by means of a nipple 81 to a flexible cable 68 through which an operating wire 89 extends for actuating the tripping mechanism of the circuit interrupting device. The wire 89 is connected by means of a rod II that extends through the base plate 68 to a piston 12 that is forced downwardly by a compression spring I3 extending between the piston I2 and the base plate 68 and which is surrounded by a sylphon bellows I4. A rod 15 extends downwardly from the piston I2 and carries a piston I6 on the lower end thereof. A supporting tube 11 is provided, the upper end of which is attached to the base plate 66 that extends downwardly about the pistons I2 and I8, and to the lower end of which is attached a supporting frame I9 for the temperature and pressure release responsive mechanism. To the lower end of the frame a casing I9 is attached surrounding and enclosing a piston 8| and pressure responsive sylphon bellows 82 connected therewith, the interior of which is filled with oil, and is responsive to the oil pressure. The piston 8| is attached, by means of links 83 and 84, to a bell crank lever, 85 that is mounted upon a support 88 and connected by means of link 81 to a piston 88 that slides within the support 89 carried by the frame I8. A temperature responsive quartz bulb 9| is positioned between the pistons I8 and 88 for normally holding them apart against the pressure of the spring I3, and an abutment 92 is provided for preventing a counter-clockwise rotation of the bell crank lever 85 beyond the illustrated position thereof.

In the embodiment of the release mechanism illustrated in Fig. 3, whenever the internal pressure within the transformer, exceeds the safe minimum amount, the pressure within the bellows 82 forces the piston 8| downwardly causing the bell crank lever 85 to rotate in a clockwise direction and the connecting link 81 to move accordingly, thus permitting the entire mechanism from the piston 8| to and including the rod II and the wire 69 to be moved downwardly and operate the fuse tripping mechanism.

Upon a predetermined temperature of the oil the bulb 9| will burst allowing the spring I3 to operate the pistons 12 and I8 downwardly and also to trip the fuse mechanism.

One temperature and pressure release device is required for each single-phase transformer to be protected and one for a three-phase transformer unit mounted in a single tank. Where a three-phase circuit is connected to three singlephase transformers operating as a bank, it is desirable to provide a pressure and temperature release device for each transformer, and three fuse mechanisms connected in circuit with the three transformers which may be mounted in an auxiliary fuse box compartment as illustrated in Figs. 5 and 6. A plurality of connections may be made, one to each over-temperature and overpressure release device of the several transformers so that, upon the occurrence of abnormal conditions in any one of the three transformers, the several latching mechanisms of the fuses will be tripped, thus disconnecting the three trans formers from the circuit upon a fault in any one of them.

Referring to Figs. 5 and 6, an auxiliary fuse box IOI is provided within which a support I02 is fastened for mounting the three circuit interrupting fuses I03, I04 and I05 that are respectively provided with latch operating mechanisms I08, I01 and I08 that may be connected together through connecting links I09, H0 and III to a common junction box II2 for the three fuse mechanisms shown in greater detail in Figs. 7 and 8.

Referring to Fig. '7, the junction box comprises a casing II3 mounted in the fuse box casing IOI and extending therethrough. A movable piston H4 is provided within the junction box casing and connected by means of a rod II5 to the link I09 which is operatively connected to the three fuse tripping mechanisms. A bellows H6 is provided between the piston H4 and the end of the junction box that is within the fuse box casing. A connecting lug II! is suitably attached to the piston H4 and to which three wires H8, H9 and I2! are connected and extend through separate openings in an end cap I22 attached to the casing II3 of the'junction box. The several wires H8, H9 and I2| extend through their respective flexible cables to the pressure and temperature release devices associated with the three transformers in the circuits of which the fuses I03, I04 and I05 are respectively connected.

The fuses illustrated in Figs. 5 and 6 and the tripping mechanism therefor may be similar to that illustrated in Figs. 9 and 10 which is for the same general purpose as the fuse I illustrated in Fig. 1. The fuse comprises a boric acid cartridge I25 within a fibre tube I26 mounted within an insulating container I21, one end of which extends within and is attached to a metallic casing I28, one end of which is connected to a casing I29 containing the condenser mechanism for the fuse, and also acts as a terminal for the device. A flange I3| extends inwardly from the central portion of the casing I28 and abuts against a metallic ferrule I32 that is screw-threadedly attached to the fibre tube I26 and is conductively connected to the casing I29 and to the latching mechanism comprising latches I33 and I34 pivotally mounted thereon at I35 and I36 respectively, the unpivoted or free ends of which are held in the closed position (illustrated in Fig. 10) by a bifurcated member I31 attached to the end of a rod I38 extending upwardly to a piston I39 within a casing I that is attached to and extends upwardly from the central portion of the casing I28. A spring I42, about which a sylphon bellows I43 is positioned, extendsfrom the raised portion of the casing I28 to the piston I39 which is provided with a projection I45 that extends into an opening I46.in the upper end of the casing MI,

and is normally prevented from moving through 5 the opening by a shoe I41 attached to the end of a bell crank lever I48 that is pivotally mounted at I 49 on a supporting bracket I5I extending upwardly from the casing I 4|. The upper end of'the lever I48 is provided with a bifurcated member I52 for connection to the junction box I I 2 and to the operating wire of the pressure and temperature release mechanism.

In the closed ,or illustrated position of the latches I33, I34, a conical or wedge shaped terminal member I53, that may also be the fusible link of the device is held between the latches I33 and I34 and is operatively connected to the conducting rod or plunger I54. The connecting rod I54 is operatively connected to any suitable spring actuating mechanism for biasing it away from the latches through which it is connected to the terminal I29 of the fuse. The spring actuating mechanism will, in general, be similar to that illustrated in Fig. 1, the particular details thereof not being a part of this invention. One arrangement of such details is illustrated and described in an application by Herbert L. Rawlins, Serial No. 665,132 filed April 8, 1933, now Patent No. 1,976,634, patented October 9, 1934, and assigned to the same assignee as this application. The end of the tube I21 containing the fuse mechanism, that is remote from the latching and tripping mechanism, is provided with a ferrule I55 of electrically conducting terminal.

Fig. 11 illustrates schematically the arrangement of three transformers I50, I51 and I58, the illustrated circuits of which are shown connected in delta, from which extend circuit conductors I59, I60 and IBI that connect, respectively, to the 40 fuses I03, I and I that are tripped by latching mechanisms I06, I01 and I08, respectively,

that are connected to the common junction box into which extend the several operating wires II 8, H9 and I2I that connect respectively to pressure and temperature release mechanisms I62, I63 and I04, thatmay be similar in construction to the mechanism illustrated in Figs. 3 and 4.

In the tripping mechanisms illustrated generally in Figs. 5, 6, 7, 8 and 11 and in detail in Figs. 9 and 10, when any one of the wires H8, H9 and I2I are actuatedby the pressure and temperature release mechanism of the transformer to which the wire is connected the mechanism in the junction box illustrated in Figs. 5, 6 and 7 is actuated to rotate the lever I 48 (Fig. 9) to remove the shoe I41 from the end of the projection I45, permitting this projection to be forced through the opening I46 by the spring I42, and thus moving the bifurcated member I31, that normally holds the latches I33 and I34 in their closed position, away from engagement with these latching members, thus permitting the connection rod I54 of each of the fuses I03, I04 and I05 to be operated to its open circuit position.

It will be apparent that other modifications of the structures shown and described and within the spirit of my invention will readily suggest themselves to those skilled in the art, and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

1. In a protective system for electrical apparatus, a circuit interrupting device, the circuit interrupting device comprising a spring actuated plunger, a latch for holding the plunger in its circuit closing position, means responsive to a predetermined current flow through said plunger for releasing said plunger, means responsive to an unnormal temperature within said apparatus and to an unnormal pressure within said apparatus for independently tripping said latch to release said plunger.

2. In a circuit interrupting device, a circuit closing rod biased to a circuit opening position, a latch for holding said rod in its circuit closing position, said rod including a fusible link for interrupting the circuit therethrough upon the occurrence of a predetermined current flow, means independent of said fusible link for tripping said latch to permit the operation of said rod to its circuit opening position, a pressure device and a temperature responsive device for independently actuating said last named means.

3. In a protective system for electrical apparatus adapted to be connected in a circuit. a circuit interrupting device, means for normally holding said circuit interrupting device in a circuit closing position, a fuse connected in the circuit interrupting device responsive to a predetermined current flow for interrupting the circuit through said circuit interrupting device, and means responsive to an unnormal pressure and to an unnormal temperature for independently releasing said holding means to interrupt the circuit through said circuit interrupting device.

4. In a protective system for a transformer, in combination, a circuit closing member biased to a circuit opening position, a latch for holding the circuit closing member in its circuit closing position, means connected in the circuit closing member responsive to a predetermined current flow in the transformer for interrupting the circuit through the circuit closing member, and means independently responsive to predetermined pressures and predetermined temperatures within the transformer for releasing the latch to interrupt the circuit through the circuit closing member.

5. In a protective system for a transformer, in combination, a circuit closing member biased to a circuit opening position, a latch for holding the circuit closing member in its circuit closing position, means connected in the circuit closing member responsive to a predetermined current flow in the transformer for interrupting the circuit through the circuit closing member, and means cooperative with the circuit closing member for interrupting the circuit, the cooperative means being disposed to actuate the latch and being independently responsive to the temperatures and pressures within the transformer.

6. In a protective system for a transformer, in combination, a circuit closing member biased to a circuit opening position, means for holding the circuit closing member in its circuit closing position, means in the circuit closing member responsive to a predetermined current flow therethrough for interrupting the circuit, and means cooperative with the circuit closing member and being independently responsive to predetermined pressures and temperatures in the transformer for releasing the holding means to interrupt the circuit. WM. J. HART.

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