US1868605A - Potential transformer - Google Patents

Description

July 26, 1932. G. E. .JANssoN lPOTENTIAL TRANSFORMER Filed Deo. l, 1930 Patented July 26, 1932 UNITED STATES PATENr orrie- GUSTAV E. JANSSON, OF ATLANTIC, MASSACHUSETTS, ASSIGrNOR` TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPORA- TION OF MSSACHUSETTS POTENTIAL TRANSPORT/IER Application led December 1, 1930. Serial No, 499,142.

This invention relates to high tension power distribution systems, and particularly to means for taking power at a low potential from a high tension circuit of the system.

The usual inductive potential transformer, when employed for very high voltages, becomes very costly since it must be insulated to withstand the full potential of the line, and it constitutes an object of this invention to provide a very simple and inexpensive potential transformer of the capacitive type suitable for deriving low tension power from very high potential lines which also provides a greater security against breakdown of insulation than is possible with the usual high tension inductive transformer without excessive provisions for insulation of the primary winding thereof.

Capacitive transformers have been used where it was desired to obtain very small amounts of low tension power to operate electrostatic volt meters, synchroscopes and the like; but heretofore, it has not been considered possible to obtain any sizeable current from a capacitive transformer without the use of very large condensers which are prohibitive because of space limitations and expense.

It is a further object of the invention to provide a potential transformer ofthe capacitive type in combination with an inductive stepdown potential transformer of moderate voltages as unitary apparatus which is inexpensive and economical ofspace and which is capable of providing adequate low voltage power to perform all the operations ordinarily required of the presentinductive potential transformers, and which is also capableV of Vsupplying suicient power to permit phaseangle correction of the secondary voltage according to any of the well-known methods in use.

A further object of the invention is the provision of a potential transformer as above outlinedwhich does not present any difficultproblems of insulation and which does not require the use of expensive high potential insulating; bushings.

A still further object is generally to improve the methods and apparatus for deriving low tension power from high potential electrical` systems.

Fig. 1 is a sectional elevation of a capacitive potential transformer embodying the present invention.

Fig. 2 is a cross section taken along line 2-2 of Fig. 1.

Fig. 3 is a diagrammatic showing of the potential transforming elements of the transformer.

As here shown, the potential transformer embodying the invention comprises an outer upstanding tubular casing including a lower metal base portion 10, an intermediate metal portion 12, and an upper insulating portion 14 having annular insulating capes 16 formed integral therewith. Said lower base portion 10which is cylindrical in configuration, is provided at its bottom edge with an annular collar 18 which has an outstanding flange 20 that provides a supporting base for the casing. Said base. portion 10 is further provided with an integral outstanding flange 22 at the top which provides an annular horizontal base for the support of said intermediate casing portion 12 which is also cylindrical but somewhat smaller in diameter than the base portion 10 and which has an integral outstanding flange 24 at its bottom edge that overlies the flange 22 of said base por-tion, whereby to support the intermediate portion 412 concentric with the base portion 10. Clamping bolts 26 extend through said flanges 22 and 24 to secure said casing portions together, a gasket 28 being provided between said lianges to provide a fluid tight joint thereat. Said intermediate casing portion 12 is pro-vided with an annular collar 30 on the outer surface thereof below its top edge. Said collar, which may be welded toV the casing, has an outstanding flange 32 which is provided with an upstanding inte-4 gral annular flange 34 that is lconterminous with the upper end of the casing12 whereby to provide an annular open top recess at the upper end thereof in which the lower end of thevuper cylindrical insulating portion 14 is received. A packing 36 is provided be tween the annular flange 32 and the bottom edge of the insulating shell 14 against which mit packing said insulating portion 14 is permanently held in a fluid tight manner by a body of cement 38 which permanently connects the intermediate and upper casing portions l2 and 14. An external metal collar 40 is secured by a body of cement 42 to the upper end of said insulating portion 14 and has an inwardly directed annular flange 44 which overlies the upper end of said insulating portion 14. Said collar also has an outstanding annular flange 46 at its upper end to which a dome-shaped metal cap y48 is detachably secured by means of peripheral clamping screws 50. The cap 48 has an annular horizontal rim 49 which overlies the attaching flange 46X and is provided with an annular downturned lip 52`which extends below the attaching flange 46 and thus provides a weather proof cover fo-r the tubular casing. Preferably a gasket 54 is provided between the confronting surfaces of the attaching flange 46 and the rim 49 of said cover to prevent the entrance of moisture to the casing,

the cap screws 50, however, constituting a good electrical connection between said cover 48 and the collar 40. The cap 48 is provided with a central terminal clamping screw 56 which is adapted to be connected electrically by a lead 58 with the high tension line from which power is to be derived.

The base portion 10 of said casing is further provided with an annular internal bracket 60 which is spaced below the upper end thereof and which forms the support for the ycapacitive unit of the transformer. Said unit includes a vertical cylindrical insulating tube 62 which is supported at its lower end by said bracket 60 andwhich extends upwardly to a point just beneath the cap 48 of said cas`- ng and is concentric with and has its sidewall spaced apart a substantial distance from said outer casing. Said tube 62 is formed with a reduced lower end portion 64 on which an annular supporting collar 66 is secured. Said collar 66 has an outstanding` flange 68 that overlies the supporting bracket 60 of the casing and is secured removably thereto by means of clamping screws 70. The outstand-A ing flange 68 is provided with a series of spaced peripheral passages 7 2 which provide for fluid communication between the portions of the casing above and below said flange.

In accordance with the present invention the insulating tube 62 is preferably built up of bakelized paper or some similar insulatingr material which can be built up in layers. Spaced cylindrical condenser plates of metal foil or gauze are interposed between successive layers of insulating material to provide a plurality of serially connected parallel condensers which are arranged along the length of the tube and are supported by and are in` sulated from each other and from the surrounding casing by said tube. The disposition of the condenser plates within the insulation of the tube is more clearly illustrated in Fig. 8, which shows somewhat diagrammatically a lon gitudin al section through a wallv of the tube 62 in which three sets of vertically spaced concentric inner and outer cylinders a, b, c, are 1provided between which three intermediate vertically aligned cyliir ders el, e, f, are arranged which overlie the proximate ends of the adjacenI sets of said inner andvoute'r cylinders. As thus arranged each intermediate cylinder in conjunction with each set of inner and outer cylinders constitutes two .condensers in parallel which are designated at C1, C2, C3, C4 and C5. The intermediate plates (Z and c which are common to two sets also constitute means for connecting the parallel condensers in series.`

The inner and outer cylinders a of the upper set areelectrically connected together at their upper ends by means of a metal plate having the downturned side wall 7 4 which isembedded-in the material of the tube- 62 and overlies the outermost condenser cylinder a, and the horizontal bottom wall .7 6 which overlies the upper end of the insulating tube 62 and is in electrical contact with the innermost cylinder a. Said bottom wall 76 is provided with a large central passage 78, whereby to leave the insulating tube open at the top. The bottom wall 76 of said tube also carries a plurality of radially outstanding resilient strips 8O having the horizontal end portions 82 which overlie and are in pre. sure engagement with the inwardly directed flange 44 of the upper collar 40, thus establishing electrical connection between the two upper condenser cylinders a and the casing terminal 56 through said collar 40 and cap 48. The'base portion 10 of said outer casing is provided near the lower end thereof with a'raised bottom 84 having a peripheral downwardly refleXed flange 86 which is secured in av fiuid tight manner to the inner side of said base portion, as by welding. Said bottom 84- also constitutes the support for an inductive potential transformer. Said transformer includes a laminated core frame 88 which suitably fiXed to said bottom wall 84 on a base 90. The upper leg of said core frame carries a secondary winding 92 having the low tension leads 94, and a primary winding 96 whichvis disposed about and is insulated from said secondary winding having one of its leads 98 connected electrically with the lowermost intermediate condenser cylinder f, and its other lea-d 100 connected wfth a ground terminal 102 of the base portion 10. As thus connected the primary winding 96 of said transformer is connect-ed in series with the condensers of the tube 62 to ground. The lowV tension leads 94 are molded in an insulating bushing 104 which is suitably connected in a fluid tight manner with the side wall of said casing.

Preferably the cuter enclosing casing is completely lills the casing.

filled with an insulating fluid, as an insulating oil or gas, to a point above the top of the insulating tube 62. As herein shown a body of oil 106 is provided Which substantially The oil is, therefore, free to circulate by thermal action due to the heat-ing of the tube 62 resulting from the dielectric losses in the insulating material thereof. By the provision of the open passage 78 at the top of the tube and the peripheral passages 7 2 in the supporting iiange G8 at the bottom thereof, the heated oil in the interior of said tube is free to rise, being replaced by oil from outside said tube which is cooler by reason of its contact with the outer casing of the transformer.

The combined use of inductive and capacitive transformer units, as above described, has definite advantages. If the potential transformer is to be used, for example, on a 110,000 volt line With a normal potential to ground of approximately 63,500 volts, by designing the inductive transformer with a ratio of 13,500 to 110 volts, a lovv voltage poiver of approximately 100 volts amperes can be obtained with a primary current of only .03 amperes which, With the arrangement of condensers shown, is commercially feasible.

The transformer above described provides a very simple and inexpensive arrangement for deriving lovv voltage power from a high voltage line and one Which presents no difficult problems of insulation and is consequently relatively inexpensive. By enclosing the inductive and ,capacitive transformer units in a single casing it is possible to entirely eliminat-e expensive terminal bushings and to provide a very compact and troublefree apparatus.

Certain features of the present invention are described in my concurrently filed application Serial No. 499,143.

The construction and arrangement of the capacitive transformer may be widely varied Without departing from the scope of the invention.

I claim:

1. In a voltage transformer, the combination of an upstanding enclosing casing having a terminal at its upper end for connection to a .high potential line, an insulating shell vertically extended in said casing having plates of conducting material Within the insulating material thereof comprising .seri-V ally connected condensers, means electrically connecting the uppermost plate with. said casingT terminal, means electrically connecting the loivermost plate of said shell to ground including the primary Winding of an inductive transformer, and a secondary Winding for said transformer having loiv tension terminals that are extended externally of said casing.

2. In a'voltage transformer` the combinaing.

tion of an outer tubular casing having` an insulated high tension terminal at its upper end, an insulating shell extended vertically in said casing having concentric overlapping metal plates embedded in and insulated from each other by the insulation of said tube, means electrically connecting the uppermost plate with said high tension terminal, .and means electrically connecting the lowermost plate to ground'including the primary Winding of an inductive potential transformer, said transformer also having a lovv tension secondary Winding, a terminal of which is extended exteriorly of said casing.

3. In a voltage transformer, the combination of an enclosing casing comprising a lower metallic base portion and an upper insulating portion havinga high tension terminal at the top thereof, a tube of insulating material vertically extended in said casing and spaced apart from the side Walls thereof, said tube having a series of concentric spaced and overlapping metallic plates embedded in the insulating material thereof which comprise serially connected condensers disposed along the length of said tube, an inductive transformer located in the base portion of said casing including a primary Winding Which is connected in series with said condenser plates to ground, anda secondary Winding havinga low tension terminal thereof extended exteriorly of said cast. In a voltage transformer, the combination of an outer tubular casing having a base portion and an upper insulating portion, a cover for the upper open end of said casing having a high tension terminal, a capacitive transformer located in the upper insulating portion of said casing and extended down- Wardly into said base portion, said transformer comprising` a tubular insulating shell having concentric overlapping metal inserts which are embedded in and are spaced apart by the insulating material of said tube, and a step-down potential transformer of relatively lovv voltage located in the base portion of said casing having its primary Winding connected in series With said capacitive transformer and having a lovv tenson secondary a terminal of which is extended exteriorly of said casing.

`5. In a voltage transformer, the combination of an upstandinfy tubular casing comprising a lower metallic base portion and an upper insulating portion, a capacitive transformer located in the upper portion of said casing comprising a tubular insulating shell having spaced concentric and overlapping metal inserts embedded in and insulated by the material. thereof, an inductive transformer of relatively lovv potential located in the base portion of said casing having a primary vvinding which is electrically connected in series with said capacitive transformer and having'a low tension secondary Winding, a terminal of which is extended eX- teriorly of said casing.

6. In a voltage transformer, the combination of an upstanding tubular enclosing casing having a lower metal base portion and an upper insulating portion, a cap forming a closure for the upper end of said casing having a high tension terminal, a base plate forming a fluid tight closure for the bottom end of said casing, an inductive transformer located in said base portion on said base plate having primary and secondary windings, a capacitive transformer located in said casing above said inductive transformer comprising a cylindrical tube of insulating material which is concentric with and is spaced apart from the side wall of said casing, said tubey having concentric cylindrical metal inserts arranged in staggered and overlapping relation along said tube and insulated from each other by the material of said tube, means connecting the uppermost cylinder of said tube electrically with said casing terminal and Ineanselectrically connecting the lowermost cylinder of said tube in series with the primary winding of said transformer7 said transformer having secondary low tension terminals one of which is extended to the outside of said casing.

7. In a voltage transformer, the combination of an outer tubular enclosing casing comprising a lower base portion, an upper 1nsulating portion and an intermediate connecting portion, closures for the upper and lower ends of said casing, a high tension terminal at the upper end of said casing, a capacitive transformer located in said insulating and connecting portions comprising a vertically extended insulating tube having serially connected condenser plates embedded in and insulated from each other by the material of said tube, means electrically connecting the uppermost plate of said condensers with said casing terminal, means connecting the lowermost condenser plate to ground including the primary winding of a step-down transformer, said step-downtransformer having a secondary winding and having terminals which constitute the low tension terminals of said voltage transformer, and a fluid insulating m-edium occupying said casing and in which said capacitive and step-down transformers are immersed.

8. In a voltage transformer, the combination of an upstanding tubular enclosing casing comprising a lower base portion, an upper insulating portion and an intermediate connecting portion, said base portion and intermediate portion having a breakable connection therebetween, an inductive transformer located in said base portion having primary and secondary windings, a capacitive transformer located mainly above said base portion comprising an insulating vertically extended tube which is spaced apart from said casing and is conterminous with the Lipper end thereof having a series of concentric and overlapping condenser plates vertically spaced along the length thereof and insulated from each other by the material of said tube, means supporting said tube removably in said casing, a metal collar carried by the upper end of said insulating portion, a cap secured to said collar constituting a closure for the upper end of said casing having a high tension terminal carried thereby, a metal plate carried by the upper end of said tube which is electrically connected with the uppermost condenser plate thereof, means arranged to connect said plate with said casing terminal including resilient abutment contact members and means electrically connecting the lowermost condenser plate of said tube through the primary of said inductive transformer to ground.

"9. A voltage transformer comprising the combination of an inductive transformer of relatively low voltage having primary and secondary windings, a capacitive transformer including an insulating supporting member which upstands above said inductive transformer and which has overlapping metallic inserts comprising condenser plates carried by the material thereof, a high tension terminal electrically connected with the uppermost plate of said transformer, and means connecting the lowermost plate of said condenser electrically with the primary winding of said inductive transformer, the terminals of said secondary winding constituting the low tension terminals of the voltage transformer.

10. A voltage transformer comprising as a unitary apparatus the combination of an inductive transformer having primary and secondary windings which are insulated for relatively low voltages, a capacitive transformer including an insulating support upstanding above said inductive transformer having a high tension terminal at the top and a low tension terminal at the bottom which is connected to said primary winding, the terminals of said secondary winding constituting the low tension terminals of the Voltage transformer.

11. A voltage transformer comprising as a unitary apparatus the combination of an inductive vtransformer having primary and secondary windings which are insulated for relatively low voltages, a capacitive transformer comprising an insulating shell vertically extended above said inductive transformer and having plates of conducting material carried thereby comprising serially connected condensers, means for electrically connecting the uppermost condenser plate with a high tension line, and means electrically connecting the lowerinost plate to ground including the primary Winding of said inductive transformer, the terminals of the seconary winding of said transformer constituting the low tension terminals of the voltage transformer.

12. In a voltage transformer, the combination of an enclosing casing, an insulated high tension line terminal at the top of said casing, an inductive transformer located in the hase of said casing having primary and secondary windings, and a capacitive transformer located in said casing intermediate said high tension terminal and said inductive transformer, and connected electrically in series with said primary winding, the terminals of the secondary winding of said inductive transformer constituting the low tension terminals of the voltage transformer.

13. In a voltage transformer, the combination of an enclosing casing having an insulating side wall, a high tension terminal located at the upper end of said casing, an inductive transformer located in the base portion of said casing having primary and secondary windings, and a capacitive transformer located in said casing intermediate said terminal and inductive transformer and having its upper terminal electricallyconnect ed with said high tension terminal and its lower terminal electrically connected inseries with the primary winding of the inductive transformer, the terminals of said transformer secondary constituting the lower tension terminals of the voltage transformer.

14. In a voltage transformer, the combination of an enclosing casing adapted to contain oil, an insulated high tension line terminal at the top of said casing, an inductive transformer contained in the lower portion of said casing having primary and secondary windings which are insulated for relatively low voltages, and a capacitive transformer located in said casing intermediate said terminal and inductive transformer having one terminal thereof electrically connected to -said line terminal and another terminal electrically connected with the primary winding of said inductive transformer, the terminals of said secondary winding constituting the low tension terminals of the voltage tra-nsformer.

15. In a voltage transformer, the combination of an upright enclosing casing adapted to contain an insulating fluid, an insulated high tension line terminal carried by said casing at its upper end, an inductive transformer located in the lower portion of said casing having primary and secondary windings which are insulated for relatively low voltages, a capacitive transformer located in said casing intermediate said inductive transformer and said high tension terminal having an upper terminal electrically connected with said high tension terminal and a lower terminal which is connected to one end of said primary winding, the secondary ter- GUSTAV E. JANSSON.

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