US2395886A - Method of filling confined spaces associated with electric apparatus - Google Patents

Description

E. c. LEE

March 5, 1946.

- Filed Oct. 2, 1940 2 Sheets-Sheet 1 m E r E m Mk5 N L R$ aukm$ m C m mums 9s 3 v IE M kYSQS mmkxsttq m 2 E 5 2 Q m Y 3 m 8 P a B 2 m. ,N. 9 wmvn v qmkwkmwkkfi o z E. C. LEE

March 5, 1946.

METHOD OF FILLING CONFINED SPACES ASSOCIATED WITH ELECTRIC APPARATUS Filed Oct. 2, 1940 2 Sheets-Sheet 2 Arm? y Patented Mar. 5, 1946 i l r UNITED STATES. PATENT OFFICE METHOD OF.FILLING CONFINED SPACEs QJSSOCIATED WITH ELECTRIC APPARA- Edwln Charles Lee, London W. C. 2, England, assignor to International Standard Electric Corporation, New York, N. Y.

Application October 2, 1940, Serial No. 359,400 In Great Britain April 10, 1940 9 Claims. (Cl. 174-722) This invention relates to a method of filling Patent No. 2,272,996, issued Feb. 10, 1942 may be confined spaces associated with electric appaused. The most suitable type of plasticiser is one ratus. v which promotes a fiat viscosity temperature char- The invention has particular reference to the acteristic, i. e. the extrudable material must not problem of filling various spaces included within be too hard at 20 C. nor too soft at 100 C. an outer covering with solid material, and is very Filling with plasticised polystyrene or other useful in filling spaces around an electric power p ymers is 'facilitated by wa m the meteflel cable to form a barrier against the flow of insuto a temper ture of t o h this is ot lating fluid, though by no means confined to such generally essential. and a p e 0! up to 1000 use. For such use it has previously been pro- 10 bs. pe q e inch may be required depending posed to effect the filling by using a granular upon the viscosity of the filling material and the moulding powder and converting it into a solid shape of the pa o be fi ed- 'by the application of heat and pressure. With The invention is applicable t t filling 0! such a method, however, considerable heat and spaces within a casing surrounding a Joint or pressure are necessary and it is difilcult to elimtermination of an electric power cable in order inate the air between the particles of moulding to'form a barrier joint or termination, and also powder before applying pressure and to secure a to filling an electric transformer casing with allf f; satisfactory bond between the moulding and the insulant.-' surrounding metal casing. The nature oi, the invention will be better un- It has also been proposed to 1111 the spaces derstood from the following description of cersurrounding an electric power cable joint with a tain embodiments thereof taken in conj c o monomeric material such as monomeric styrene, with the accompanying drawings in which: and thereafter to thicken it by heating to cause Fig. 1 shows across sectional view of a barit to polymerlse. In this method the application rier joint in a single core electric power cable of heat has to be extended over a period of many suitable for use in a 33 kv. cable; hours, since although the originally introduced Fig. 2 shows a cross sectional view of a barstyrene may be partially polymerised, it must rier joint for a 3-core belted type of power cable be thin enough to flow in conveniently and disfor use in a 66 kv. cable system; Fig. 2A shows place all residual air in the spaces to be filled. a detail of Fig. 2; whilst Moreover, there is considerable contraction in Fig.3 shows a barrier type of termination for cooling down from the polymerisation temperan electric power cable.

ature usually 120 C. Referring to the drawings, Fig. 1 shows a form According to the present invention a method of barrier jointfor a Si co e 33 v. cableof filling confined spaces associated with electric The insulation is removed from the ends 3 and apparatus comprises filling the spaces withafiuid 35 4 of the two lengths of cable to be joined and solvent for an extrudable material, and then disa sleeve 1 is slipped over one of the ends. The placing this solvent by forcing in the extrudable lengths-l and 2 are Joined by means of a copper material under pressure to displace the fluid ferrule 5. The insulation from the two lengths solvent. of cable is tapered as shown at I and 2. The

As an example 01 an extrudable material, space shown at 6 is then filled up by building up shellac may be mentioned; a suitable solvent the insulation with paper tapes impregnated with therefor is methylated spirit. We prefer, howpolys y and basting the imp gnated tape ever, to use as the extrudable material a polyw monomeric Styrene at te va s d i the merised material and in particular polystyrene, building up of the insulation to cause them to in which case the preferred solvent is monomeric adhere to one another d i ed. for e ample. styrene. Other monomers may be used such as in British Patent No. 504,720, accepted April 26, methyl methacrylate, so long as they are com- 1939. A layer 8 of metal foil is wound over this patible with the polymer, or alternatively a simbuilt up insulation and electrically connected to ple solvent such as benzene. the lead sheaths 9, ill of the two lengths of cable.

The extrudable material may be rendered more Lappings ll of cotton tape impregnated with a readily extrudable by the addition of plasticisers. mixture of rubber and polystyrene are applied For example, in the case of polystyrene, any wellover the ends of the layer 8 and overlapping the known plasticiser may be used, or in the case lead sheaths 9, III, to prevent oil from flowing in which the material is to be within an electric from the cable into the joint and solvent from field, one of the plasticisers disclosed in U. S. flowing into the cable during the filling. The

sleeve "5 is then slipped back over the joint, lead packing [2 being inserted between the ends of the sleeve 1 and the lead sheaths 9, ill. The sleeve l is joined to the lead sheaths by plumbed wipes l3, [4.

The sleeve 1 is provided with a filling plug H and outlet plugs I5, [6. Monomeric styrene is fed into the plug i7 until the space l8 between the earthed screen 8 and the sleeve 1 is completely filled therewith. Polystyrene, plasticised in accordance with the aforementioned U. S. Patent No. 2,272,996, is then fed under pressure into the filling plug ll. taken that the polystyrene is free from bubbles. Pressure is continued until the material issuing from the outlet plugs l5, i6 is of the thick consistency of the plasticised polystyrene. The joint is then completed by sealing the plugs. In this example it should be noted that the electrical properties are unimportant; the material merely serves as a mechanical barrier.

Fig. 2 shows the invention applied to a barrier joint for a 3-core belted type of cable. The belting is removed from a certain distance from the ends to be joined and a sleeve! slipped over the lead sheath of one of the lengths. The ends of the three cores are joined by copper barrier ferrules 5. The three cores are spaced apart by spacers i9 shaped as shown in Fig. 2A, the cores being bound thereto. The spacers are suitably made of compressed styrenated paper. Cotton tapes 2i impregnated with a mixture of rubber and polystyrene are wrapped around t e cables overlapping the lead sheath in order to prevent egress of oil from the cable and flow of solvent into the cable during formation of the barrier joint. The sleeve 7 is then slid over the joint, spaced from the lead sheaths 9 and ID by lead packing i2 and sealed by wiped joints l3 and M. The sleeve '1' is then filled with monomeric styrene through the plug I! and when it is full the monomeric styrene is displaced by plasticised polystyrene fed into the plug 11 in the same manner as described with reference to Fig. 1. In this example the filling material acts both as a mechanical barrier and as the main insulant of the joint.

Fig. 3 shows a barrier type of termination formed according to the invention. A preformed cylinder 22 of insulating material and of sufficient diameter to be slipped over the insulation 25 of a cable core is provided with metal end caps 23, 24, securely cemented to the cylinder 22 and of sufficient diameter to extend over the lead sheath l8 of a cable. The lead sheath i is removed for some distance from the end of the cable; the metallised paper 26, which usually covers the insulation, is stripped off up to a short distance from the lead sheath in and the insulation 25 is removed for a short distance from the end and bound as shown at 21. A copper end ferrule is soldered to the conducto 28.

The cylinder 22 is then slipped over the cable end, and the metal cap 24 pressed down on the lead sheath in and joined thereto by a wipe 13. The cap 23 is then sweated on to the stall; of the ferrule 5.

The cap 24 is provided with a filling plug l1 and the cap 23 with a vent plug 15. The spaces within the cylinder 22 are then filled as above described with reference to Fig. l or Fig. 2.

It will be evident that the present invention is applicable to a number of different types of joints and terminations in electric power cables. It is, however, to be noted that the invention is Precautions must also be not limited to use with power cables, but is applicable to any case in which confined spaces associated with electric apparatus are to be filled with solid material and only restricted openings are available through which the filling material can be introduced. Thus the invention may be applied to form a body of insulating material within a metal casing surrounding an electric transformer, being particularly useful in the case of a transformer used for high voltages and high frequencies, or to form the dielectric of a multiple plate condenser contained within a casing.

The fluid first fed into the casing acts as a lubricant and also as a Wetting agent which facilitates filling and secures thorough bonding between the plasticised polymerised material, such as polymerised styrene and both metal surfaces and oil impregnated cable papers. The polymerised material then fed in has an excellent barrier action and, more particularly in the case of polystyrene, excellent insulating properties, high breakdown strength and low power factor.

What is claimed is:

1. Method of filling spaces within a container associated with electrical apparatus with insulating material, which comprises filling the said spaces with a fluid solvent for an insulating extrudable material. and then displacing the said solvent by the said extrudable material.

2. Method of filling spaces within a container associated with electrical apparatus with insulating material, which comprises filling the said spaces with a fluid solvent for polystyrene, and then displacing the said solvent by polystyrene.

3. Method as claimed, in claim 2 in which the said solvent is monomeric styrene.

4. Method of filling sptces within a container associated with electrical apparatus with insulating material, which comprises filling the said spaces with a fiuid solvent for polystyrene, and then forcing polystyrene into said spaces under pressure to displace the said fluid solvent.

5. Method of filling spaces within a sleeve surrounding a barrier in an electric power cable, which comprises filling the said spaces with a fluid solvent for polystyrene, and then forcing polystyrene into said spaces to displace the said fluid solvent.

6. Method of forming a barrier joint between two lengths of sheathed electric cable, which comprises joining the cores of the two cables together, building up body of insulation around the joined cores by winding therearound tapes comprising polystyrene, and basting the tapes during the winding with a solvent for polystyrene, surrounding said built-up insulation with a sleeve, welding said sleeve to the cable sheaths, filling spaces within said sleeve with a solvent for polystyrene, and forcing polystyrene into said sleeve until said last mentioned solvent is almost completely displaced.

7. Method of forming a barrier joint between two lengths of multi-core sheathed electric power cable, which comprises joining the several cores I of one length to the several cores of the other sheaths of the two cable lengths, filling the -& od 10; .lUSAIOS a 1mm QAQBIS pres UlqliM eoeds styrene, and forcing polystyrene into said sleeve until said solvent is almost completely displaced.

8. Method of forming a. barrier termination a,sos,see 3 10: on electric power cable, which comprises ioinins the end 0! the core 0! said cable to an end ferrule, surrounding said Joint by a. preformed casing. welding said casing to the sheath of said I cable and to the sold ferrule, filling said casing with a solvent for polystyrene, end iorcing polystyrene into said casing until said solvent is almost completely displaced.

9. Method of forming a barrier Joint between

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