US1523891A - Transformer for high voltagb - Google Patents

Description

Jan. 20, 1925.

W. PETERSEN ET AL TRANSFORBER FOR HIGH VOLTAGE Filed April 20. 1921 2 Shoots-Sheet. 1

I Fig I.

Jan. 20, 1925.

w. PETERSEN ET AL TRANSFORMER FOR HIGH VOLTAGE Filed April 20. 1921 2 Sheen-Sheet 2 Patented Jan. 20, 1925.

UNITED STATES PATENT OFFICE.

WALDEMAR PETERSEN, OF DARMSTADT, GERMANY, AND XVILHELM HESS, OF BASEL, SWITZERLAND, ASSIGNORS TO' THE SOCIETY EltIIL EAEFELY & CO. A. G., OF BASEL,

SWITZERLAND.

Application filed April 20, 1921.

To all whom it may concern: I

Be it known that we, WALDEMAR PETER- SEN, acitizen of the Republic of Germany, and resident of Darmstadt, Germany, and VVILHELM HESS, a citizen of the Swiss Republic, and resident of Basel, Switzerland, have invented new and useful Improvements in Transformers for High Voltages, of which the following isa full, clear, and exact specification.

It has hitherto been customary to con- .struct transformers for voltages above approximately 30,000 v'olts with oil insulation, on the ground that the high insulating propertiesof a' good specialoil permit the design of the insulation to be reduced to a minimum. On the other hand oil insulation causes difiicultics, inasmuch as the incipient discharges from the solid insulating material, which in time'cause perforation, can only be obviated with great difficulty and at considerable cost. A further objection with oil transformers is the impossibility of detecting such discharges in time to obviate them. In the case of testing transformers for very high voltages in particular, on ac,- count of the usually brief period of operation, the heating of the upper layers of oil is too slight ensurea natural circulation of oil; as alresult when at any point in the transformer an incipient discharge has been formed, this tends to increase in intensity owing to the-want of a fresh supply of oil, and finally causes break down or perforation of the insulation.

According to the present invention an air transformer is employed in which the incipient discharges which are harmful in oil are utilized for obtaining a graduated electric field distribution as the ionized insulating material (air) is continually renewed, whilst the solid insulating material with a suitably proportioned field density isnct at;- tacked by what may be called streamer discharges. This condition is attained in an air transformer having coaxial high and low tension windings according to the invention, by the fact that an insulating hollow body surrounding the low tension winding. and a second insulating hollow body surrounded .by the high tension winding, are separated from one another by a large, entirely free air space which is so proportioned that in the high tension field brush discharges or sparks cannot occur .but only Serial No. 462,931.

Figures 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12 show by partial vertical sections different forms of a discharge ring or shield for protecting the high tension winding.

Referring now to Figures 1 and 2 the low tension winding (1 is usually placed over the arms of the iron core I). A hollow insulating cylinder 0 composed of material having a high dielectric coetlicient surrounds "the winding a and provides for a uniform dis-,

tribution of the lines of force of the electric field in the air space hereinafter referred to. By providing an earthed metal lining d for the hollow insulating cylinder 0 this equalizing effect is increased. The air space f extends around the hollow insulating cylinder 0 and is enclosed externally by the outer hollow insulating cylinder 9 the air space thus enclosedbetween said cylinders o and f/ being of relatively large dimensions and entirely free, that is without any subdivision or intermediate subdividing elements. The latter cylinder, which is also composed of material having a high dielectric coefficient and is of a considerably larger internal diameter than the cylinder 0, ensures the uniformity of distribution of the electric Held in the air space f due to the high tension winding 11 surrounding the outer cylinder g. The uppermost coil or coils of highest potential of the high tension winding hare protected by a conducting protecting ring In with internal insulation m.

The electric stress in the air at the points of highest potential of the high tension winding h is such that far below the highest voltage of the transformer streamer discharges occur on the outer cylinder g, the uniformity of which is assured by the provision of a conducting discharge ring or shield i located on the outer cylinder g, which simultaneously protects the uppermost coilor coils of highest potential of the high tension winding against sparking, and by a conducting end ring or shield p at the upper end of the cut er insulating cylinder These streamer discharges,which as has been ascertained. do not become transformed around an air spa-ce into brush orflash discharges, proide"for--a'unifornrdropof potential in axial direction of the outer crlinderaud therefore permit. of very short. direct spacing het'w en the high tension winding and the core. in this case the end ring I which is connect d to the yoke of the iron core is of great 2dvantag .-e sit prov icles ,for a uniform distribution of the leakage" or creeping cur cuts on the surface of the cuter cylinder g.

In order toremore entirely electric stresses between the high tension winding It and the outer cylinder g, the separate coils of the i i hightension winding the potential distribution'iina radial direction in theair space may be, influenced as desired, as will be readily fIthasbeenstatedabbve that the high tension en'diof the high tension winding IL is protected, afdisoharge ring'i surrounding thehollow insulating 'body g. 'Such a .discharge ring mayha've various for ns. Whereas in the Figures 1 and 2, this ring has a substantially circular cross section near 'it'scontactin ,edge, the discharge ring 5 according to-l' igures 3 and 4 lies by a sharp ed e lperpendlcu'larly in contact with the be low insulating body g. According to Figures 5 and 6, it is provided with a sharp contacting edge i turned upwards or downwards, respectively. In the modifications of Figs. 7, 8, 9 and 10, the connection of the discharge ring i" with the insulating body 7 is effected by means of an auxiliary connecting ring 1? placed either inside themain ring i (Fi pro 7), or above it. (Figure 8), or below 1t v(Figure 9), the auxiliaryring 2' being provided with a circular groove in the form of Figure 10. In the examples of Figures 11 and .12 the discharge ring i isprovided with .an upwardly directed, sharpened discharge edge i at some distance from the insulating body 9. Obviously,

rman other forms inay beconccived for the disc ar e ring.

'In a these modifications, the discharge rmgrs provided as above with the depending protection shell n fonuppermost coils of the high tension winding. At its outer end itmay be curved downwards for a favorable electric fielddistribution (Figures 3, 4, 5, 6, 11 and 12'), but it inay also have the purpose specified. high tension winding may. also be connected hollow insulating bodies being separated by a large, free air space without any subdivision and of such dimensions that streamer discharges only can occur within the electric high tension field, while spark or brush discharges are prevented, for the 2. An air insulated high voltage transformer having an iron, core, coaxially arranged high and low tension windin "sthe-reon, a hollow insulatingbody forthed ow tension winding and a larger hollow insulating bodyfor the high; tension winding, said hollow insulating bodies being separated by a. large, free air .-spa.ce without any subdivision and of such dimensions that streamer discharges only can occur within the electric high tension'field, while spark or brush discharges are prevented, adischargering being arranged around the 1101- low insulating body for the high tension thereon, a hollow,insulating body for the low tension "windin and a larger hollo'w'insulating body fort ie high tension winding, said hollow insulating bodies being separated by a large, free-air space'without any subdivision and of such dimensions that streamer discharges only can occur within the electric high tension field, while spark or brush discharges are prevented, a discharge ring being arranged around the hollow insulating body for the high tension winding, adjacent to the high potential end thereof, and an end ring electrically connected with the iron core. being provided around the hollow insulating body for the high tension winding, for the p'hrpose specified.

4. An air insulated high voltage transformer having an iron core, ahlow tension winding thereon, a hollow insulating body for said Winding, a high tension winding coaxially arranged with said low tension winding, a hollow insulating body for said hi h tension winding, said. two hollow insu ating bodies being separated by a large, entirely free air space, metal rings being -arranged on the hollow insulating body of the high tension winding and electricallv connected to the coils thereof, for the purpose specified.

iii

An air insulated high voltage transformer having an iron core, a low tension winding thereon, a hollow insulating body for said low tension winding provided with an earthed sheath of conducting material, a high tension winding coaxially arranged with said low tension winding, a hollow insulatin body for said high tension winding, said two hollow insulating bodies being separated by a large, entirely free air space, for the purpose specified.

6. An air insulated high voltage transformer having an iron core, a low tension winding thereon, a hollow insulating body surrounding said winding, a high tension winding coaxialh arranged with said low tension winding, a hollow insulating body placed within said high tension winding,v said two hollow insulating bodies being separated from each other by a large, entirely free air space, substantially as and for the purpose described.

In witness whereof we have hereunto signed our names this 30th day of March,

1921, in the presence of two subscribing wit- HGSSGS.

WALDEMAR PETERSEN. WILHELM HESS. Witnesses:

FREDERICK BEEns; AMAND FRANCE.

Images