Document jgG8dVD99vYw1VOBdRM4Yx8NO

FILE NAME:McGraw-Edison (ME) DATE: DOC#: ME0 DOCUMENT DESCRIPTION: WD'ZZ/Z ZK Oct. 28, 1969 F. S. SADLER 3,475,546 INSULATING MATERIAL FOR ELECTRICAL APPARATus Filed Aug. 22, 1966 2 Sheets-Sheet l INVENTOR. /7sz S. SaaZeze BY e12zazzas f Szz2% 2172teorizews Oct. 28, 1969 F. S. SAOLER 3,475,546 INSULATING MATERIAL FOR ELECTRICAL APPARATUS Filed Aug. 22, 1966 2 Sheets-Sheet 2 52x8 2 27 2Z s S&NSNNNS S INVENTOR, sa S. Saz2e7? 17az724s 2 Szz7% 172 correys United States Patent Office 3,475,546 Patented Oct. 28, 1969 1. 2 3,475,546 NSULATING MATERAL FOR proved electrical apparatus having insulation which has 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 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 nt. C. H01b. 17/50 U.S. C. 174-137 5 Cains 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 -man 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 in suppressing and extinguishing arcs. allowing a substantial reduction in the overall dimen 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 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 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 insulation. 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 low cost and ability to be easily molded in intricate 45 containing interspersed particles of an organic fluoride. 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 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 vention embodied in an open typefuse 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 equipment are conventionally constructed of porcelain 60 type of fuse cutout embodying the invention; and FIG. 4 is a fragmentary elevational view, partly in which has the disadvantages of: (1) it is heavy; (2) it section, of a magnetic type of circuit interrupter embody fractures into sharp flying pieces under impact; (3) it ing the invention. is difficult to form to close tolerances, and (4) it has Referring now particularly to FIG. 1 of the drawing, a long manufacturing cycle. 65 the invention is illustrated with reference to an open type Further, such ceramic insulators require long creepage 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 come the above disadvantages. will over 70 are secured to insulator 10 by a bolt 6 engaged within It is a further object of the invention to provide im a threaded hole 17 in the upper end of insulator 10. Similarly, a lower resilient arm 8 is mounted against 3,475,546 3 4. terminal 12 and both are secured to insulator 10 by a ly into an arc extinguishing structure comprising a plu bolt 19 engaged within a threaded hole 20 in the lower rality of splitter plates 70 also of the insulating material end of insulator 10. In the preferred embodiment, the 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. 72 and 73 and under the influence of the magnetic field As those skilled in the art will appreciate, the upper between the field pole 22, it will be drawn up into the and lower terminals 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. O 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 0. 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 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. A fuse link 30 including a fusible section, not shown, 20 products be affixed thereto by special cements or be 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, and has a protracted manufacturing cycle due to lengthy connected to flexible conductors 32 which terminate in 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. The organic binder to be used in the insulating ma insulator 10 intermediate the ends thereof. The upper and lower terminals 1 and 12 are inter 30 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 resins such as epoxy resins, polyester resins, phenolic link 30 will melt if an overcurrent occurs in the trans 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 ductor 34 out of insulating member 31 to interrupt the 35 resins, and Epoxide the like can be used. resins to be used are those containing more circuit. than one epoxide group, such as those obtained by the reaction of bis-phenol with epichlorohydrin or aliphatic FIG. 2 shows an insulator 10' according to the instant invention employed with an open type fuse cutout 40. diepoxides, such as diglycidyl ether, or epoxides obtained The details of construction and operation of the fuse cut 40 by the reaction of epichlorohydrin with polyhydric cohols or with polycyclic diepoxide ethers, such as are al de out 40 form no part of the instant invention and accord ingly will not be discussed in detail for the sake of brevity. scribed, for example, in U.S. Patent Nos. 2,582,985; For a detailed description of the fuse cutout 40, refer 2,615,007; 2,615,088; 2,592,560 and 2,581,464. Also epoxides prepared from the reaction of phenol terminated ence is made to U.S. Patent 3,002,070, issued Sept. 26, 1961, and assigned to the assignee of the instant invention. 45 resins which are dihydric phenol prepared by the reaction of an excess of with epichlorohydrin with aliphatic di As seen in FIG. 2, the terminals 11' and 12 of cutout 40 are also secured to the upper and lower ends of in epoxides, or bisphenolepichlorohydrin resins can be used. 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, FIG. 3 illustrates yet another application of the inven action of the amino-bearing material with formaldehyde, 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 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. The polyester resin can be formed by the reaction of FIG. 4 illustrates how the invention can be applied to 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 5 6 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 such as polypropylene and polyethylene; vinyl polymers an alternative method, insulators or arc-suppressing de vices can also be formed by a hot moulding process. In Such as polyvinyl chloride, vinylidrine chloride and the like; polyamide (nylon) resins; acrylic resins; and the this case, a wet mixture of the organic binder, along with 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 diamine and adipic acid. Specific examples of polyamide molding methods. Since fluidity of the hot molded mix ture depends on the viscosity of the binder, the organic resins are polyhexamethylenedipamide methylenesebacamide. and polyhexa O binder of such mixture should preferably be more than Acrylic resins refer to plastics composed of upwards 20% by weight of the molding composition. As previously mentioned, organic materials tend to of about 90% methyl methacrylate, the balance being an ester of methacrylic or acrylic acid, such as ethyl acrylate. decompose upon exposure to conditions which promote Acrylic resins can be modified by co-polymerization with 15 creepage discharges and form carbon tracks and even erode away. Thus, organic materials have not been wide monomers such as acrylonitrile, butadiene styrene, alpha methyl styrene and the like. ly used as insulating materials, even though their low In addition synthetic rubbers can be employed as the cost and ability to be easily molded into intricate shapes 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 20 example, about 98% isobutene copolymerized with about The tendency of an organic insulating material to form 2% isoprene or butadiere; ethylene-propylene terpolymer; a carbon track under polluted conditions is believed to be dependent on two opposing processes, carbon forming silicone polymers in which organic side groups such as methyl, phenyl or vinyl are used along the polymer chain, processes and carbon removal processes. Under a given as for example dimethyl polymers, and the like. polysiloxane; styrene-butadiene 25 Set of conditions, if carbon is formed faster than it is 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, AlF3; hydrated aluminum fluoride lator if the carbon can be removed as it is formed, and (fluellite), AlF3.H2O; hydrated aluminum fluoride, 30 the carbon removal can occur both chemically and me chanically. It is believed that the presence of the fluoride AlF3.3%HO; aluminum oxide Al-O coated with alumi num fluoride; barium fluoride (fluorite), BaF2; calcium compounds at the arcing or scintillation site acts as a fluosiluate, CaSiF6; hydrated calcium fluosilicate, catalyst for the conversion of the carbonaceous materials to gaseous carbon compounds, such as carbon dioxide CaSiF6.2H2O and carbon monoxide. In addition, the fluoride com lead fluoride, PbF; hydrated lead fluosilicate, pounds break down under the arcing conditions and this breakdown results in the mechanical removal of the car PbSiF62HO bonaceous materials from the surface of the organic bind and PbSiF6.4H2O; magnesium fluosilicate, MSiF6; hy er thereby preventing the formation of low resistant paths drated magnesium silicate, MgSiF6.6H2O; magnesium or tracks which are apt to destroy further utility of the fluoride, MgF2; potassium fluosilicate, KSiF6; 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, Na3AIF6; titanium fluo rials on the Surface of the organic binder by both the ride, TiF; lithium fluoride, LiF; hydrated lithium fluo chemical and mechanical action. silicate, LiSiF62HO; barium fluosilicate, BaSiF6; and As a further advantage, when the fluoride compounds tetra titanium fluoride, TiF4. 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 tions 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: Moreover, the fluorides tend to remove the carboneceous Percent material from the surface of the organic binder, thereby eliminating carbon tracks and preventing re-ignition of Inorganic fluoride ----------------------Filler ---------------------------------- 5 to 90 Up to 75 60 the arc on the surface of the shield. In order that those skilled in the art may better under Organic binder -------------------------- Balance 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. inforcement can be substituted for a part of the filler and istics of an insulator composed of an organic binder generally can be employed in an amount up to 35% by 65 containing finely divided particles of an inorganic fluo weight of the composition. Mineral fibers, such as glass, ride. These examples are given by way of illustration asbestos, or synthetic fibers Such as nylon, rayon, Dacron, and not by way of limitation. Orlon and the like can be used as the fibrous reinforce Sample pieces of material suitable for the invention ment. Were evaluated for tracking and using high voltages and The insulator or arc-suppressing shield can be fabri 70 low current 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 reinforcement or filler, are blended with the organic cedure for evaluating insulating materials to be used at resin. This premix is then molded under pressure into 75 high voltages and in contaminating atmospheric condi 3,475,546 7 8 tions. In the Inclined Plane test the sample pieces were the specifically recited examples, but only by the scope mounted at a 45 angle in a test cabinet with electrodes of the appended claims. mounted two inches apart on the sample piece and with Various modes of carrying out the invention are con the upper electrode clamping several layers of filter paper templated as being within the scope of the following to the surface of the sample piece. An alternating current 5 claims particularly pointing out and distinctly claiming potential of 6000 volts was applied across the electrodes the subject matter which is regarded as the invention. for the duration of each test. A contaminant solution con I claim: taining 1% ammonium chloride and 0.02% Triton X 1. In an electrical apparatus, a pair of electrical con 100 wetting agent by weight was fed at a precisely con ducting members between which an arc may form, an trolled rate into the layers of the filter paper adjacent the 10 insulating element having a surface extending adjacent top electrode so that the contaminant solution ran down the arc-path between said members, said element being the bottom surface of the sample piece at a flow rate formed of a composition comprising a synthetic resin or of 0.60 cubic centimeters per minute. The time to failure a synthetic rubber and containing from 5 to 90% by in which carbon tracking occurred between the electrodes weight of finely divided particles of an arc-suppressing was recorded in minutes. inorganic metal fluoride uniformly interspersed in said Example I composition, said fluoride being selected from the group consisting of calcium fluoride, ammonium fluoride, lith Test sample pieces approximately 5' long by 2' wide ium silico fluoride, sodium silico fluoride, and mixtures and approximately 4' thick were molded with heat and thereof. pressure from commercially available polyester resin 2) 2. The apparatus of claim , in which the element con known as Selectron No. 5140 manufactured by the Pitts tains up to 75% by weight of a filler selected from the burgh Plate Glass Company to which was added 1.5% group consisting of asbestos, mica, silica, zircon, fly ash, by weight of benzoyl peroxide, as a catalyst, based upon limestone, barytes, whiting, and mixtures thereof. the weight of the resin, and a mold release agent, zinc 3. The apparatus of claim , in which the organic ma stearate, and mixed with varying percentages by weight 25 terial is a thermosetting resin. of aluminum fluoride and 4' chopped strand glass fiber 4. The apparatus of claim , in which the element manufactured by Johns Manville Company. When tested also contains up to 35% by weight of a reinforcing ma as described above, the results were as follows: terial. TABLE I Binder Material PeCellt All Pittsburgh Plate Glass Selection 5140Polyester Resin------------- { 0 65.3 1 Greater than 200. TABLE II -- Organic Binder Percent Filer filler Allied Chemical Company Plaskon 942 Polyester Resin.----- (As2 60 AlF3 60 Minutes failu. 2.7 (i) Minutes to failure 5.8 6.7 TABLE III - Organic Binder Dupont Lucite (polymethyl-methacrylate).---------------- 1 Greater than 300 minutes, No failure. Petcent fille filler Al2O33H2O 40 AlF3 40 Minutes to failure 9.4 (1) TABLE IV 5. The apparatus of claim 4, in which the reinforcing Minutes 55 material is selected from the group consisting of mineral Percent to fibers and synthetic organic fibers. Organic Binder Filer filler failure None.---- O 8, 2 References (Cited CIBAX8200/103 Epoxy Resin.-------- Sgt.: :: ' 3 UNITED STATES PATENTS 1 Greater than 300, No failure. 3,242,257 3/1966 Jones et al.---------- 174-137 While the invention has been illustrated with respect 2,704,261 3/1955 Comeforo ----------- 106-39 2,938,881 5/1960 Gallagher ---...---- 260-45.7 to a few types of electrical apparatus, those skilled in the art will appreciate that it has application to other 65 LEON D. ROSDOL, Primary Examiner types of apparatus as well. In addition, while a number of organic binders and inorganic fluorides have been re J. D. WELSH, Assistant Examiner cited, these are merely intended as examples, it being U.S. C. X.R. understood that other suitable materials will be suggested 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