Document YLng0jOzN870MapXD0xMQRk8

FILE NAME: McGraw-Edison (ME) DATE: 1966 Aug 22 DOC#: ME018 DOCUMENT DESCRIPTION: Patent [McGraw-Cooper] - Insulating material for electrical apparatus [Approved - 1969 Oct 28] Oct. 28,1969 f . s. SAD LER 3,475,546 INSULATING MATERIAL FOR ELECTRICAL APPARATUS Filed Aug. 22, 1966 2 Sheets-Sheet I INVENTOR. Free/ S. Sadler BY c/fnafrus $ S ta rv e o F tto rre y's Oct. 28, 1969 F. s. SAD LER 3,475,546 INSULATING MATERIAL FOR ELECTRICAL APPARATUS Filed Aug. 22, 1966 2 Sheets-Sheet 2 P - E r if INVENTOR. Fred S: Sadler BY crfradras # S ta rv e c /p tC o r n e y e United States Patent Office 3,475,546 Patented Oct. 28, 1969 1 2 3,475,546 proved electrical apparatus having insulation which has INSULATING MATERIAL FOR high resistance to both arc tracking and creepage tracking. ELECTRICAL APPARATUS Another object of the invention is to provide improved Fred S. Sadler, Zanesville, Ohio, assignor to McGraw- electrical apparatus having insulation characterized by Edison Company, Milwaukee, Wis., a corporation of 5 high resistance to both arc tracking and creepage track Delaware ing and which can be molded to intricate shapes and to Filed Aug. 22, 1966, Ser. No. 574,098 close tolerances. A further object is to provide improved Int. Cl. HOlb 17/50 U.S. Cl. 174--137 5 Claims electrical apparatus having insulation which does not permit low resistance carbonaceous deposits to form and ----- 10 acts as a catalyst to promote oxidation and removal of ABSTRACT OF THE DISCLOSURE the carbon. Still another object of the invention is to provide improved electrical apparatus having insulation _-An insulating element for an electrical apparatus which which has high resistance to both arc tracking and creep- aids in supporting and extinguishing arcs. The insulating age tracking and can be cast or molded at low tempera material is formed of a synthetic resin or synthetic rub- 15 tures into insulating members having high strength and ber containing from 5% to 90% by weight of finely durability. divided particles of an inorganic metal fluoride. Another object of the invention is to provide improved electrical apparatus having insulation which reduces the tendency to form carbonaceous deposits and thus permits This invention relates to insulation for electrical ap- 20 reduction in the distance between conductive members paratus and in particular to such insulations which are having a given potential difference therebetween, thereby exposed to contaminated atmospheric conditions and aid allowing a substantial reduction in the overall dimen in suppressing and extinguishing arcs. sions of the electrical apparatus. . Failure of electrical apparatus exposed to contaminat . A still further object of the invention is to provide ing _atmospheric conditions such as dust, dirt, salt and 25 improved electrical apparatus having insulation which moisture due to electrical creepage discharges between permits a greater creepage distance to be readily op spaced conductors at different potentials is well known. erated for a given air strike distance because intricate Accumulation of dust, dirt, rain or other contaminants configurations can easily be formed in the insulating ma on the surface of molded insulation separating two con terial and which will not chip when subject to flashover. ductors at different potentials may form a high resist- 30 Still another object of the invention is to provide im ance path between the conductors and promote random proved electrical apparatus having insulation which pre surface discharges or arcing known as surface creepage. vents formation of carbonaceous deposits under exposure The creepage discharges cause the formation of car to contaminating conditions which promote creepage bonaceous deposits in the insulation which ultimately re with conventional organic insulation and which also pre sult in low resistance paths, or tracks, that cause electri- 35 vent erosion due to discharge between electroconductive cal failure of the apparatus. Tracks due to creepage are members at different electric potentials embedded in the random in effect and produce a tree-like path, and creep- msulation. age type of electrical failure can occur not only due It is a further object of the invention to produce an in to surface failure but also due to tracking beneath the sulating shield or enclosure having improved arc-sup surface of the insulating material. Organic insulating ma- 40 pressing properties and which can be molded to intricate terials particularly tend to decompose upon exposure to shapes without the use of high temperatures. conditions which promote creepage discharges and form The electrical insulator or arc-suppressing shield em carbon tracks and even erode away, thus preventing use bodying the invention comprises an organic resin binder of such organic insulating materials even though their containing interspersed particles of an organic fluoride. low cost and ability to be easily molded in intricate 45 The fluoride co-acts with the organic material under arcing shapes and to close tolerances makes them otherwise conditions to reduce the formation of carbonaceous mate ideal for use in electrical apparatus. rial on the surface of the insulator as well as generating Organic insulating compounds are also subject to elec arc-quenching gaseous reaction products which aid in sup trical failure due to carbon tracking caused by power r - pressing or quenching arcs. arcing which is distinguished from creepage discharges . These and other objects and advantages of the inven in that the arc track formed by decomposition of the tion will be more readily apparent from the following organic material forms a direct path along the line of detailed description when taken in conjunction with the the arc between the conductors at different electrical accompanying drawing wherein: potentials. FIG. 1 is an elevational view of one form of the in The low tracking resistance of organic insulating ma- 55 vention embodied in an open type fuse cutout; terials has, in general, prevented their use for insulators FIG. 2 is an elevational view of an expulsion type fuse in electrical power protective equipment such as lightning cutout embodying the invention; arresters and fuse cutouts used to protect electrical power FIG. 3 is an exploded elevational view of a closed distribution lines, and the insulators of such protective rn type of fuse cutout embodying the invention; and equipment are conventionally constructed of porcelain which has the disadvantages of: ( 1 ) it is heavy; (2) it fractures into sharp flying pieces under impact; (3 ) it FIG. 4 is a fragmentary elevational view, partly in section, of a magnetic type of circuit interrupter embody ing the invention. is difficult to form to close tolerances, and (4) it has a long manufacturing cycle. Referring now particularly to FIG. 1 of the drawing, the invention is illustrated with reference to an open type . Further, such ceramic insulators require long creepage 65 fuse cutout which includes an elongated insulator 10 hav distances for a given air strike distance, and also flashover ing upper and lower conductive terminals 11 and 12 re may chip the petticoats of the porcelain insulators. spectively mounted adjacent opposite ends thereof. A con It is an object of the invention to provide improved ductor arm 15 is mounted against terminal 11 and both electrical apparatus having insulation which will over- 7n are secured to insulator 10 by a bolt 16 engaged within come the above disadvantages. u a_threaded hole 17 in the upper end of insulator 10. It is a further object of the invention to provide im- Similarly, a lower resilient arm 18 is mounted against terminal 12 and both are secured to insulator 10 by a bolt 19 engaged within a threaded hole 20 in the lower end of insulator 10. In the preferred embodiment, the ly into an arc extinguishing structure comprising a plu rality of splitter plates 70 also of the insulating material according to the invention. On separation of the contacts threaded holes 17 and 20 for bolts 16 and 19, respec 62 and 63, the resulting arc transferred to arcing horns tively, are molded within insulator 10. As those skilled in the art will appreciate, the upper 5 72 and 73 and under the influence of the magnetic field between the field pole 22, it will be drawn up into the and lower terminals 1 1 and 12 carry suitable means, not arc extinguishing splitter plate structure where it will be shown, for engaging an electrical distribution power line extinguished in the manner well known in the art. conductor, not shown, and a contductor from a distri The insulating structure of the invention comprises an bution transformer, not shown. 10 organic binder containing finely divided particles of an The conductor arm 15 terminates in an upper hook inorganic fluoride. The composition is characterized by like fuse link holding means 23 extending upwardly rela high resistance to both arc tracking and creepage tracking tive to insulator 10. The resilient arm 18 comprises a and can be cast or molded at low temperatures into in pair of elongated resilient wire members 24 having loop sulating members and arc-suppressing shields of high portions 25 therein and joined at their ends to a lower 15 strength and durability. hook-like fuse link holding means 26. The wire members As discussed hereinbefore, prior art insulators for fuse 24 are prevented from spreading outwardly relative to cutouts are usually of porcelain which is heavy, tends to each other by a clamp 27, and the ends of wire members fracture into sharp flying pieces upon impact, cannot be 24 are bent upwardly for being secured to the terminal held to close tolerances, required that metal mounting 12 by the bolt 19. 20 products be affixed thereto by special cements or be A fuse link 30 including a fusible section, not shown, clamped thereto by special fittings, requires long creepage surrounded by an insulating tubular member 31 may be distance for a given strike distance, chips under flashover, connected to flexible conductors 32 which terminate in and has a protracted manufacturing cycle due to lengthy contacts 33 engaged within the upper and lower hook pre-firing, firing, and cooling stages. Organic insulating like fuse link holding means 23 and 26. Contacts 33 may 25 materials have heretofore been unsatisfactory for such in be secured to flexible conductors 34 by solder and may sulators because they are subject to the problem of car carry tool engaging eyes 35. bonaceous residue formation, an accumulation occasioned A metallic hanger 36 adapted to be secured to a cross by randon electrical discharges which are likely to occur arm of a power line pole, not shown, is molded within under adverse climatic conditions in outdoor installations. insulator 10 intermediate the ends thereof. 30 The organic binder to be used in the insulating ma The upper and lower terminals 11 and 12 are inter terial of the invention can be any conventional synthetic connected by fuse link 30, and the fusible section of fuse resin or synthetic rubber. For example, thermosetting link 30 will melt if an overcurrent occurs in the trans resins such as epoxy resins, polyester resins, phenolic former and the ends of the fuse link will be separated resins, ureaformaldehyde resins, melamine-formaldehyde by resilient arm 18 which will flip the lower flexible con 35 resins, and the like can be used. ductor 34 out of insulating member 31 to interrupt the Epoxide resins to be used are those containing more than one epoxide group, such as those obtained by the circuit. FIG. 2 shows an insulator 10' according to the instant reaction of bis-phenol with epichlorohydrin or aliphatic invention employed with an open type fuse cutout 40. diepoxides, such as diglycidyl ether, or epoxides obtained by the reaction of epichlorohydrin with polyhydric al Touhte 4d0etfaoilrsmofnocopnasrttruocftitohne ainndstaonpterinavtieonntioofnthanedfuascecocrudt 40 cohols or with polycyclic diepoxide ethers, such as are de ingly will not be discussed in detail for the sake of brevity. scribed, for example, in U.S. Patent Nos. 2,582,985; 2,615,007; 2,615,088; 2,592,560 and 2,581,464. Also For a detailed description of the fuse cutout 40, refer ence is made to U.S. Patent 3,002,070, issued_Sept._26, epoxides prepared from the reaction of phenol terminated 1961, and assigned to the assignee of the instant invention. 45 resins which are prepared by the reaction of an excess of dihydric phenol with epichlorohydrin with aliphatic di As seen in FIG. 2, the terminals 11' and 12' of cutout epoxides, or bisphenolepichlorohydrin resins can be used. 40 are also secured to the upper and lower ends of in The melamine-formaldehyde and urea-formaldehyde sulator 10' by bolts 16' and 19', respectively. However, polymers are the reaction product of either melamine or in this embodiment the bolts 16 and 19 are received in urea with formaldehyde. Urea and melamine share in threaded metallic inserts 41 which are molded within the 50 common the amino group --NH2, and in each case re insulator 10. action of the amino-bearing material with formaldehyde, FIG. 3 illustrates yet another application of the inven under suitably catalyzed conditions forms a reactive mono tion, i.e., to a housed fuse cutout 45 having a housing mer. By condensation polymerization, the reactive mono 46 of the insulating material according to the instant mer forms polymeric intermediates which in turn are invention. The cutout 45 also includes an upper contact 55 readily converted to more highly polymerized forms which 48 and a lower contact 49 which are respectively secured are infusible. by upper and lower mounting studs 50 and 52 which are Phenolic resins are the reaction product of a phenol molded within the housing 46. and an aldehyde. The most common phenolic resin is that The housing 46 is also adapted to receive a door 54 based on phenol and formaldehyde. However part of the composed of the insulating material according to the in 60 phenol can be replaced with substituted phenols such as vention and pivotally mounted on the housing 46 at 55. cresols, xylenols, or butyl phenol. For example, p-t-butyl The door 54 carries a fuse tube 56 having a terminal phenol, p-phenyl phenol and resorcinol can be used as a 57 at its upper end for engaging the contact 48. An eye replacement for phenol in the reaction. While formalde let 58 is formed on the door for receiving a hookstick so hyde is the most widely used aldehyde others such as that it can be opened and closed in the manner well known 65 furfural can be used. in the art. _ FIG. 4 illustrates how the invention can be applied to The polyester resin can be formed by the reaction of a polyhydric saturated or unsaturated polybasic acid an air magnetic type circuit interrupter 60. The circuit either with or without a modifying unsaturated monomer interrupter 60 includes a pair of arcing contacts 62 and such as styrene or the like. Specific examples of the basic 63 disposed within a casing comprising wall portions 64 70 material are, for instance, diethylene glycol maleate, di which may be prepared from sheets or panels of the in propylene glycol maleate, diethylene glycol fumarate, and sulating material according to the invention. A magnetic the like. The basic materials are readily polymerized by coil 66, adapted to be energized when contacts 62 and 63 peroxy catalysts such as benzoyl peroxide, tertiary butyl are separated, is associated with a magnetic core 67 and perbenzoate, and the like. magnetic field pole plates 68 for drawing an arc upward 75 Thermoplastic resins can also be used as the organic 3,475,546 S S S s s w s binder in the insulating material. Examples of common the desired shape and cured at elevated temperatures. As thermoplastic resins which can be used are polyolefins an alternative method, insulators or arc-suppressing de such as polypropylene and polyethylene; vinyl polymers vices can also be formed by a hot moulding process. In such as polyvinyl chloride, vinylidrine chloride and the this case, a wet mixture of the organic binder, along with like; polyamide (nylon) resins; acrylic resins; and the the fluoride and any other fillers or reinforcing materials, like. are molded into an article of the desired form under Polyamide resins are formed by the reaction of straight pressure and/or heat as in conventional compression chain diamines and dibasic acids such as hexamethylene- molding methods. Since fluidity of the hot molded mix diamine and adipic acid. Specific examples of polyamide ture depends on the viscosity of the binder, the organic mreesitnhsyleanreesebpaoclaymheidxea.methylenedipamide and polyhexa- 10 b2i0n%debr yowf esiugchht omf itxhteurmeosldhionugldcopmrepfoesriatibolny. be more than Acrylic resins refer to plastics composed of upwards As previously mentioned, organic materials tend to of about 90% methyl methacrylate, the balance being an decompose upon exposure to conditions which promote ester of methacrylic or acrylic acid, such as ethyl acrylate. creepage discharges and form carbon tracks and even Acrylic resins can be modified by co-polymerization with 15 erode away. Thus, organic materials have not been wide monomers such as acrylonitrile, butadiene styrene, alpha ly used as insulating materials, even though their low methyl styrene and the like. cost and ability to be easily molded into intricate shapes In addition synthetic rubbers can be employed as the and close tolerances makes them otherwise ideal for use organic binder. Synthetic rubbers include butyl rubber as electrical insulators. composed of butenes copolymerized with diolefins, as for 2n The tendency of an organic insulating material to form example, about 98% isobutene copolymerized with about a carbon track under polluted conditions is believed to 2% isoprene or butadiene; ethylene-propylene terpolymer; silicone polymers in which organic side groups such as be dependent on two opposing processes, carbon forming processes and carbon removal processes. Under a given methyl, phenyl or vinyl are used along the polymer chain, set of conditions, if carbon is formed faster than it is as for example dimethyl polysiloxane; polymers, and the like. styrene-butadiene 25 removed, then tracking will occur. Where an organic ma The inorganic, arc-suppressing fluoride distributed terial has a tendency to form carbon as a result of pyrol ysis, the organic material may still be of use as an insu throughout the organic binder can take the form of aluminum fluoride, A1F3; hydrated aluminum fluoride lator if the carbon can be removed as it is formed, and the carbon removal can occur both chemically and me- . ' ' Kl C / J ------------- ---- --* ^ .1. *'-*-**-'' A1F3.3J/iH 20; aluminum oxide A120 3 coated with alumi num fluoride; barium fluoride (fluorite), BaF2; calcium fluosiluate, CaSiF6; hydrated calcium fluosilicate, CaSiF6.2H20 compounds at the arcing or scintillation site acts as a catalyst for the conversion of the carbonaceous materials to gaseous carbon compounds, such as carbon dioxide and carbon monoxide. In addition, the fluoride com lead fluoride, PbF2; hydrated lead fluosilicate, PbSiF6.2H20 35 pounds break down under the arcing conditions and this breakdown results in the mechanical removal of the car bonaceous materials from the surface of the organic bind and PbSiF6.4H20; magnesium fluosilicate, MgSiF6; hy er thereby preventing the formation of low resistant paths drated magnesium silicate, MgSiF6.6H20; magnesium or tracks which are apt to destroy further utility of the fluoride, MgF2; potassium fluosilicate, K2SiF6; silicon 40 apparatus. Thus, the fluoride coacts with the organic bind fluoride absorbed on silica gel; sodium fluoride, NaF; sodi ing material to aid in reducing the carbonaceous mate um fluosilicate, Na2SiF6; cryolite, Na3AlF6; titanium fluo rials on the surface of the organic binder by both the ride, TiF3; lithium fluoride, LiF; hydrated lithium fiuo- chemical and mechanical action. silicate, Li2SiF6.2PI20; barium fluosilicate, BaSiF6; and As a further advantage, when the fluoride compounds tetra titanium fluoride, TiF^. 45 breaks down, fluoride gases are formed which ionize un The amount of the inorganic fluoride used in the com der the conditions of the arc and serve to quench any position is not critical and may vary widely depending small arcs or scintillas on the surface of the insulator. on the particular binder used, the desired structural In addition to its use as an electrical insulator, the strength and other factors. Generally, the inorganic fluo composition of the invention can also be employed in the ride comprises about 5 to 90% by weight of the composi- 50 molding of switch enclosures, fuse enclosures, and other tion, and preferably 40 to 70%, with the organic binder arc-suppressing shields. In an arc quenching application, being the balance. the shield does not prevent arcing but tends to quench In some cases finely divided fillers such as asbestos, any arc that forms, thereby reducing the energy repre mica, silica, zircon, fly ash, limestone, barytes, whiting sented by the existence of the arc. Under arcing condi- and the like can be incorporated in the composition. If a 55 *10ns.the fluoride breaks down to form arc-extinguishing filler is used, the composition will generally have the fol fluoride gases which serve to quench or suppress the arc. lowing formulation in weight percent: Percent Inorganic fluoride______________________ 5 to 90 Filler-------------------------------------------------- Up to 75 Organic binder_________________________ Balance Moreover, the fluorides tend to remove the carboneceous material^ from the surface of the organic binder, thereby e lmmatmg carbon tracks and preventing re-ignition of 60 the arc on the surface of the shield. In order that those skilled in the art may better under stand how the present invention may be practiced, the To increase the strength of the insulator 10, fibrous re following examples are given to illustrate the character liinifiouricememnt can boe subostiintutieda rfor a part orf tnhe mfililer anda istics of ainl uin^suuilaatuor composeda otf an organic binder generally can be employed in an amount up to 35% by 65 c? 1ntairnr->vng finely di, vided ^pa---r--t-i--c- l-es of "a-1n-1 liunuoirsgaaunAic- nfluuuo-weigeht of the comnposition. lMVTinireifrtraal fihbpercs, s<umcrh nas galpacscs, riiddee.. TThheessee eexxaammtpllleess aarrep. gcritvuepnn by w7a0y.. of i:lili.u--sjt.rat.ion asbestos, or synthetic fibers such as nylon, rayon, Dacron, ana not by way of limitation. Orion and the like can be used as the fibrous reinforce ment. Sample pieces of material suitable for the invention were evaluated for tracking and using high voltages and The insulator or arc-suppressing shield can be fabri 70 . f!urrent between the electrodes wherein the "end cated by either conventional cold molding or hot mold point of tracking is defined as the time required to con ing techniques. In cold molding insulators or arc-sup tinuously track between the electrodes at a given applied pressing devices, the inorganic fluoride and any fibrous voltage. The Inclined Plane test is well recognized pro reinforcemen_t o_r -f-il-l-e-r7, --are -b-l-e--n-d--e-d- w...i--th t--h^e organic cedure ufonr wevcaiiluucaiLtiiniig minasuilcautimngs umuauterniails to boe used at resin. This premix is then molded under pressure into 75 high voltages and in contaminating atmospheric condi tions. In the Inclined Plane test the sample pieces were mounted at a 45 angle in a test cabinet with electrodes mounted two inches apart on the sample piece and with the upper electrode clamping several layers of filter paper to the surface of the sample piece. An alternating current potential of 6000 volts was applied across the electrodes for the duration of each test. A contaminant solution con taining 1% ammonium chloride and 0.02% Triton X 100 wetting agent by weight was fed at a precisely con trolled rate into the layers of the filter paper adjacent the top electrode so that the contaminant solution ran down the bottom surface of the sample piece at a flow rate of 0.60 cubic centimeters per minute. The time to failure in which carbon tracking occurred between the electrodes was recorded in minutes. Example I Test sample pieces approximately 5" long by 2" wide and approximately 14" thick were molded with heat and pressure from commercially available polyester resin known as Selectron No. 5140 manufactured by the Pitts burgh Plate Glass Company to which was added 1.5% by weight of benzoyl peroxide, as a catalyst, based upon the weight of the resin, and a mold release agent, zinc stearate, and mixed with varying percentages by weight of aluminum fluoride and 14" chopped strand glass fiber manufactured by Johns Manville Company. When tested as described above, the results were as follows: 546 B the specifically recited examples, but only by the scope of the appended claims. Various modes of carrying out the invention are con templated as being within the scope of the following g claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention. I claim: 1. In an electrical apparatus, a pair of electrical con ducting members between which an arc may form, an jo insulating element having a surface extending adjacent the arc-path between said members, said element being formed of a composition comprising a synthetic resin or a synthetic rubber and containing from 5 to 90% by weight of finely divided particles of an arc-suppressing 15 inorganic metal fluoride uniformly interspersed in said composition, said fluoride being selected from the group consisting of calcium fluoride, ammonium fluoride, lith ium silico fluoride, sodium silico fluoride, and mixtures thereof. 20 2. The apparatus of claim 1, in which the element con tains up to 75% by weight of a filler selected from the group consisting of asbestos, mica, silica, zircon, fly ash, limestone, barytes, whiting, and mixtures thereof. 3. The apparatus of claim 1, in which the organic ma 25 terial is a thermosetting resin. 4. The apparatus of claim 1, in which the element also contains up to 35% by weight of a reinforcing ma terial. TABLE I Binder Material Pittsburgh Plate Glass Selection 5140Polyester Eesin....... 1 Greater than 200. TABLE II Organic Binder Piller Allied Chemical Company Plaskon 942 Polyester E e sin ........./AI2O3 \AIF3 Percent A1F? J 0 \65.3 Percent finer 60 60 Minutes to failure 21.7 G) Minutes to failure 15.8 61.7 TABLE III Organic Binder Petcent filler filler Dupont Lucite (polymethyl-methacrylate)....................... - /A12033H2C> 40 IAIF3 40 ` Greater th an 300 minutes, No failure. Minutes to failure 9.4 C1) TABLE IV Organic Binder Percent Filler fifier [None......... 0 CIBAX 8200/103 Epoxy Eesin........ ___-{Quartz____ 58.5 (AIF3 62.2 Minutes to failure 8.2 12.3 0) 5. The apparatus of claim 4, in which the reinforcing material is selected from the group consisting of mineral fibers and synthetic organic fibers. References Cited UNITED STATES PATENTS ' Greater than 300, No failure. While the invention has been illustrated with respect to a few types of electrical apparatus, those skilled in 3,242,257 2,704,261 2,938,881 3/1966 Jones et al___________ 174--137 3/1955 Comeforo 106--39 5/1960 Gallagher_________ 260--45.7 the art will appreciate that it has application to other LEON D. ROSDOL, Primary Examiner types of apparatus as well. In addition, while a number 65 of organic binders and inorganic fluorides have been re J. D. WELSH, Assistant Examiner cited, these are merely intended as examples, it being understood that other suitable materials will be suggested U.S. Cl. X.R. to those skilled in the art once the invention is known. 252--63.2, 63.5; 260--37, 41 Accordingly, it is not intended to limit the invention by 70