US3898404A

US3898404A - Sudden pressure relay having a plurality of flow restricting baffles

Info

Publication number: US3898404A
Application number: US445506A
Authority: US
Inventors: Paul W Martincic
Original assignee: Westinghouse Electric Corp
Current assignee: ABB Inc USA
Priority date: 1974-02-25
Filing date: 1974-02-25
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05
Also published as: JPS50115124U; JPS5529329Y2

Abstract

A relay responsive to sudden changes in internal transformer pressure and unresponsive to ordinary temperature responsive pressure changes. A bellows is disposed in communication with the gas cushion in the transformer and is enclosed by a housing. The housing is in communication with the gas cushion through an orifice. The orifice retards quick pressure build-up in the housing and permits the bellows to expand and activate a switch. The orifice includes a plurality of baffles each having an opening therein with the openings in adjacently located baffles being offset from each other to provide a tortuous path for any gas flowing through the orifice.

Description

United States Patent [191 Martincic SUDDEN PRESSURE RELAY HAVING A PLURALITY OF FLOW RESTRICTING BAFFLES [75] Inventor:

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

22 Filed: Feb. 25, 1974 21 Appl. No.: 445,506

Paul W. Martincic, Sharpsville, Pa.

138/42; 200/153 T, 82 R, 82 C, 83 C, 83 D, 83 R, 83 A, 83 T, 83 W [56] References Cited UNITED STATES PATENTS 2,275,472 3/1942 Samiran 251/127 Aug. 5, 1975 Attorney, Agent, or Firnz-J. R. Hanway [57] ABSTRACT A relay responsive to sudden changes in internal transformer pressure and unresponsive to ordinary temperature responsive pressure changes. A bellows is disposed in communication with the gas cushion in the transformer and is enclosed by a housing. The housing is in communication with the gas cushion through an orifice. The orifice retards quick pressure build-up in the housing and permits the bellows to expand and activate a switch. The orifice includes a plurality of baffles each having an opening therein with the openings in adjacently located baffles being offset from each other to provide a tortuous path for any gas flowing through the orifice.

7 Claims, 5 Drawing Figures 1 SUDDEN PRESSURE RELAY HAVING A PLURALIT'Y OF FLOWRESTRICTING BAFFLES BACKGROUND OF THEINVENTION 1. Field of the Invention 1 I a This invention relates, in generaLto electrical inductive apparatus and, more specifically, topower transformers having a-sudden-pre'ssure' relay.

2. Descriptionof the Prior Art Sudden pressure relays are used in conjunction with power transformers-to indicate the occurrence of an internal are within the transformerenclosure. The relay is connected to appropriate alarm or control devices which provide suitable indicating or control functions;

The sudden pressure relay monitors the pressure in the gas cushion. which is located above the oil level in the transformer. w T i The sudden pressure relay must be suitably constructed todistinguish between gas pressure rises due to temperature variations within the transformer enclosure and due to internal arcs occ urring 'between components of the transformer structure, A n orifice may be used to provideapath through whicha gas at arela tively low pressurelmay p ass without significant restriction. The orifice provides some restriction to' the flow of gases when under relativlylhigh pressure. Thus, a suitably positioned o'rifice may' be iised in a sudden pressure relay .to help distinguish between sudden 'and longer term gas piessureincre'ases.

One of the mostsimple orificearrang ements, and the arrangement usually'used according tothe prior art, consist of a' single; smal ldiarnet'er' bore extending through a plate'or'other memberlwhi'ch restricts the flow of gases. While this type of orifice arrangement has been used satisfactorily in the past, there are some problems associated therewith which it is desirable to remedy. A single bore or opening type orifice requires that the opening be of relatively small diameter to provide the desired-"flow characteristics during thenonlaminar flow due to hi g h'gay'pressures. When used in conjunction witlr'p'ower transformers containinga liquid dielectrici-fsuc 'h asoil, c'o'ntamina-nts'in' the dielectric and m-oistu're' containe d thereinterid t'o accumulate in and aroundthe's'inall' op'enihgand change the diameter thereof. The'overall result is a decrease in the effectiveness of thes'u'dden'pressurerelay after a period of time and possible-failureof the sudden pressure relay to recognize a sudden increase in gas pressure within the transformer'enclosuref i m H Other types of-orificesrhave been used'according to the prior art, but 'eaeh has some-drawback when used in a sudden pressure relay which is associated with a power transformer. Thereforefit is desirable, and it is an object of this. invention to provide a sudden pressure relay for power transformers having an orifice which is conveniently and inexpensively .constructed in such a manner that the problems associated with prior art orifices are substantially solved.

SUMMARY OF ue INVENTION There is disclosed herein a new and useful sudden pressure relay for use with power transforrners fThe relay includes a housing which'is suitably attached over an opening in the transformer ericlosurer Gas communication between the inside of thehousing and the inside of the'transformer enclosure. is, p'rov ided by an orifree. The gas ,within the" enclosure also, communicates with, the interior of an expandable bellows which is located within the housing. When the differential pressure between the gases on the inside and outside of the expandable bellows is greater than a predetermined amount, the bellows expands sufficiently to activate a switch which is connected through a sealing connector to. the appropriate indicating or control circuitry located outside of the relay housing. The orifice contains a plurality of disc-shaped baffles each separated from eachother by an O-ring. Each baffle contains an opening therein which is suitably offset from the openings in the adjacent baffles'to provide a tortuous path for any gas passing through the orifice. With this arrangement, the openings in the baffles may be sufficiently larger than the opening in a single opening orifice.

BRIEF DESCRIPTION OF THE DRAWING 'Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing, in which:

FIG. 1 is a view of a power transformer having a sudden pressure relay mounted thereon;

FIG. 2 is a partial cut-away view of the sudden pressure relay illustrated in FIG. I and constructed according to this invention;

FIG. 3 is a sectional view of the orifice in the sudden pressure relay shown in' FIG. 2;

FIG. 4 is a view of the baffle in the orifice illustrated in F103; a d,

FIG. 5 is a view of baffle positioned adjacent, in the orifice,'to the baffle illustrated in FIG. 4.

- DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description, similar reference characters refer to similar elements or members in all of the figures ofthe drawing.

Referring now to'the-drawing, and to FIG. I in particular, there is shown a power transformer constructed according to thisinvention. The transformer includes the'tank' l0 which contains the oil dielectric 12 and a gas cushion 16 located above the oil level 14. Although not illustrated, the tank I0 encloses the core and coil assembly of the transformer which is connected to appropriate bushings, such as the bushing 18. A sudden pressure relay 20 is attached to the top of the tank 10 and is connected by the electrical cable 21 to the indicator 22. The indicator 22 may be attached to the tank 10 or it may be located at a remote location. In addition, the indicator 22 may provide suitable indications or alarms to indicate the activation of the sudden pressure relay 20, or it may control circuits or components which mayrde-energize the transformer when the sudden pressure relay 20 is activated.

FIG. 2 is a cut-away view of the sudden pressure relay 20 shown in FIG. 1 illustrating the major components thereof. The sudden pressure relay 20 includes the housing 26 which is attached to the plate 28. The plate 28 is sealingly attached to the flange 30 by the bolts 32 andthe gasket 34. The flange 30 is positioned above the opening 24 in the transformer tank 10 and is suitably connected therearound.

The pressure exerted by the gas cushion 16 contained within the transformer tank 10 extends into the expandable bellows 36 through the opening 38. The bellows 36 is rigidly attached to the plate 28 by the coupling 40. The housing 26 defines a gas chamber 42 which is in communication with the gas cushion 16 through the orifice 44. The orifice 44 prevents a sudden increase in pressure in the gas cushion 16 from providing a similar rate of gas pressure increase in the gas chamber 42. A switch 46 is secured to the housing 26 by the bracket 48 and is activated when the expandable bellows 36 expands sufficiently to push the plunger 47 a predetermined distance within the switch 46. Electrical connection between the switch 46 is extended through the gas tight connector 50 to the cable 21 and the associated indicating and/or control circuitry.

The orifice 44 contains a tortuous path across which gas from the gas cushion 16 must flow to enter into the gas chamber 42. When the pressure of the gas in the gas cushion 16 increases at a relatively slow rate, such as caused by normal temperature increases during ordinary transformer operation, the pressure in the gas chamber 42 is substantially equal to the pressure in the gas cushion 16. Thus, the pressure on the inside of the expandable bellows 36 is substantially equal to the pressure in the gas chamber 42 and expansion of the bellows does not occur. Therefore, the switch 46 is not activated and the sudden pressure relay effectively does not recognize this relatively slow increase in gas pressure. When the pressure in the gas cushion 16 increases rapidly, such as an increase caused by an internal are within the transformer tank 10, the tortuous path for the gas provided by the orifice 44 prevents the build-up of pressure in the gas chamber 42 as quickly as the build-up of gas pressure within the inside of the expandable bellows 36. Thus, the bellows 36 expands in a direction toward the plunger 47 of the switch 46. When the gas pressure differential is sufficiently large enough, the switch 46 is activated and the appropriate indicating and/or control functions are initiated.

The various components located within the housing 26 of the sudden pressure relay 20 must be compatible for use with the atmosphere provided by the gases entering the openings to the bellows 36 and to the gas chamber 42. The switch 46 preferably is enclosed within an explosion proof housing, and the bellows preferably is constructed of a suitable metallic material, such as stainless steel which is strong enough to withstand the differential pressures to which it is subjected.

FIG. 3 is a sectional view showing, in detail, the construction of the orifice 44. The orifice 44 includes a substantially cylindrical tube 70 which includes the

openings

72 and 74, and which is suitably shaped to extend through an opening in the plate 28. A plurality of baffles, such as the

baffles

76 and 78, are disposed within the tube 70 and are separated by O-rings 81. The combination of baffles and O-rings is secured in place by a retainer ring 83. Each baffle contains an opening, such as the

openings

80 and 82 in the

baffles

76 and 78, respectively, which are aligned to provide a tortuous path for any gas passing from one opening of the tube 70 to the other opening.

The baffles are constructed of disc-shaped elements of a suitable material, such as stainless steel, and have suitably sized openings which the desired amount of flow restriction. Due to the tortuous path provided by the offsetting of the openings in adjacent baffles, the diameter of the openings may be substantially larger than an opening in an orifice which contains one long, substantially straight opening.

FIG. 4 is a view of the baffle 76 shown in FIG. 3. Every other baffle spaced alternately within the orifice 44 is similar to the baffle 76. As can be seen in FIG. 4, the opening 80 is substantially located at the center of the disc-shaped baffle 76. By placing the opening 80 at the center of the baffle 76, and in similar baffles, it is not important to rotationally align the baffles when assembling the orifice 44, since the opening 80 remains at the same position regardless of the orientation of the baffle 76.

FIG. 5 is a view of the baffle 78, and of similar baffles, which illustrates the placement of the opening 82. The opening 82 is located at a position which is offset from the center of the disc-shaped baffle 78. The amount of offset may be changed to establish the restrictive charisterics of the orifice, and different offset distances from that shown in FIG. 5 may be used within the scope of the invention. With the arrangement of the baffles having openings as indicated in FIGS. 4 and 5 alternately throughout the orifice 44, orientation of any of the baffles during assembly of the orifice 44 is not required since the three dimensional tortuous path provided by the openings is substantially the same regardless of the orientation of any of the baffles. Thus, the orifice 44 may be constructed conveniently and inexpensively by using the baffle arrangement and construction disclosed herein.

Since numerous changes may be made in the above described apparatus, and since different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.

I claim as my invention:

1. A sudden pressure relay for electrical apparatus, comprising:

a housing which defines a gas chamber, said housing being mounted on an electrical apparatus enclosure which contains a gas cushion;

a plurality of baffles each having an opening therein,

said baffles being aligned with the opening in adjacent baffles offset from each other thereby forming a tortuous path for gas passing through the openings in the baffles, said baffles being located between the housing and the electrical apparatus enclosure;

expanding means which is located substantially withinthe gas chamber and which is in relatively unrestricted communication with the gas cushion, said expanding means increasing at least one of its dimensions when the gas pressure in the gas cushion is larger than the gas pressure in the gas chamher; and,

sensing means for detecting when a predetermined amount of expansion of the expansion means has occurred.

2. The sudden pressure relay of claim 1 wherein the baffles are disc-shaped members containing an opening therein, with adjacent baffles being separated from each other by an O-ring.

3. The sudden pressure relay of claim 2 wherein the opening in every other adjacent baffle is located substantially in the center of the baffle.

4. The sudden pressure relay of claim 2 wherein the openings in the baffles which are not substantially in the center of the baffles are offset from the center of the baffles by substantially the same distance.

5. The sudden pressure relay of claim 1 wherein the expanding means includes a bellows with the inside thereof communicating through a relatively largediameter opening with the gas cushion.

6. The sudden pressure relay of claim 1 wherein the sensing means includes a switch disposed in close proximity to the expanding means and which is activated by the movement of the expanding means when the predetermined amount of expansion has occurred.

7. A sudden pressure relay for electrical apparatus, comprising:

a plurality of baffles each having an opening therein,

said baffles being aligned with the openings in adjacent baffles offset from each other thereby forming a tortuous path for gas passing through the openings in the baffles, said baffles being located between the housing and the electrical apparatus enan expandable bellows disposed within the gas chamber, with said bellows connected to said housing in such a manner that the gas pressure on the inside of said bellows has the same value as the pressure of the gas in the gas cushion;

a switch positioned within the housing, said switch being activated when the bellows expands beyond a predetermined amount; and,

means for sealingly extending an electrical conductor from said switch to the outside of said housing.

Claims

1. A sudden pressure relay for electrical apparatus, comprising: a housing which defines a gas chamber, said housing being mounted on an electrical apparatus enclosure which contains a gas cushion; a plurality of baffles each having an opening therein, said baffles being aligned with the opening in adjacent baffles offset from each other thereby forming a tortuous path for gas passing through the openings in the baffles, said baffles being located between the housing and the electrical apparatus enclosure; expanding means which is located substantially within the gas chamber and which is in relatively unrestricted communication with the gas cushion, said expanding means increasing at least one of its dimensions when the gas pressure in the gas cushion is larger than the gas pressure in the gas chamber; and, sensing means for detecting when a predetermined amount of expansion of the expansion means has occurred.

5. The sudden pressure relay of claim 1 wherein the expanding means includes a bellows with the inside thereof communicating through a relatively large-diameter opening with the gas cushion.

7. A sudden pressure relay for electrical apparatus, comprising: a housing which defines a gas chamber, said housing being mounted on an electrical apparatus enclosure which contains a gas cushion; a plurality of baffles each having an opening therein, said baffles being aligned with the openings in adjacent baffles offset from each other thereby forming a tortuous path for gas passing through the openings in the baffles, said baffles being located between the housing and the electrical apparatus enclosure to provide relatively restricted communication therebetween, the openings in the baffles being suitably dimensioned to permit the pressure of the gases in the gas chamber and in the gas cushion to be equal when the rate of pressure increase in the gas cushion is below a predetermined value, and to cause the pressure of the gas in the gas chamber to be lower than the pressure of the gas in the gas cushion when the rate of pressure increase in the gas cushion is above said predetermined value; an expandable bellows disposed within the gAs chamber, with said bellows connected to said housing in such a manner that the gas pressure on the inside of said bellows has the same value as the pressure of the gas in the gas cushion; a switch positioned within the housing, said switch being activated when the bellows expands beyond a predetermined amount; and, means for sealingly extending an electrical conductor from said switch to the outside of said housing.