EP0410644A2 - Surge arrester with improved weatherseal - Google Patents
Surge arrester with improved weatherseal Download PDFInfo
- Publication number
- EP0410644A2 EP0410644A2 EP90307888A EP90307888A EP0410644A2 EP 0410644 A2 EP0410644 A2 EP 0410644A2 EP 90307888 A EP90307888 A EP 90307888A EP 90307888 A EP90307888 A EP 90307888A EP 0410644 A2 EP0410644 A2 EP 0410644A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- arrester
- housing
- adhesive
- bracket
- insulative
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
- H01C7/12—Overvoltage protection resistors
Definitions
- This invention relates to high voltage surge arresters that include disconnectors, insulative mounting brackets, metal oxide varistors, and polymeric housings.
- metal oxide surge arresters for protecting outdoor overhead high voltage electrical systems against lightning have been advantageously provided with polymeric weathershed housings, disconnectors, and with insulative brackets.
- Metal oxide varistor blocks are sealed within the polymeric housings, which protect and insulate the varistor blocks against the damaging effects of rain, snow and airborne contamination, for example.
- the insulative brackets have provided electrical insulation to allow for proper operation of the ground lead disconnector.
- Prior art surge arresters have also included fiberglass tubes or wrappings supporting the varistor blocks. Also, the inner diameter, or bore, of the polymeric housings have been bonded to the outer peripheral surfaces of the tube or wrapping.
- U.S. Patents Nos. 4,656,,555 and 4,404,614 disclose some embodiments of these, constructions and methods of construction. Methods of bonding a polymeric housing along its bore directly to varistor blocks, or to layers or coatings surrounding the blocks, are also disclosed in U.S. Patent No. 4,161,012. Polymer housings molded directly onto the peripheral surfaces of an arrester element as well as to flat end surfaces are disclosed in U.S. Patent No. 4,833,438.
- Each of the methods and embodiments referred to in the aforementioned U.S. patents involves a relatively expensive process for achieving a seal between the inner surfaces of an arrester housing and the outer or peripheral surfaces of arrester components enclosed within the housing.
- a method of achieving an air free, sealed, moisture excluding interface between peripheral surfaces of arrester components and inner surfaces of an elastomeric housing that includes the use of silicone grease at the interface is also described with reference to FIG. 8 in U.S. Patent No. 4,161,012.
- the elastomeric or polymeric housing surrounding the arrester components has been also compressed between flat surfaces disposed at the opposing flat ends of the housing.
- silicone oil from the silicone grease has escaped, along the flat surfaces, to outer surfaces of the housing.
- the oil has accumulated objectionable quantities of airborne dust and dirt.
- a surge arrester insulative bracket is shown in FIG. 3 of U.S. patent No. 4,609,902. Others are identified as the insulating base shown on pages 10 and 11 of Ohio Brass Catalog 94. The method of bolting the insulating base to a metallic arrester mounting bracket is shown in detail on Ohio Brass Instruction Sheet No. 17-5113, whereon the recommended mounting torque for the one-half inch (12.7 mm) fastener is forty ft-lbs (54 newton-metres). Torque greater than forty ft-lbs has cracked the insulating base in the area of the bolt hole ex tending through the insulating base. Restricting the applied torque to forty ft-lbs (54 N.m) places the burden of not cracking the insulating base, i.e., the insulative bracket, upon the skill, knowledge and diligence of the installer.
- a lockwasher on a mounting bolt of the metallic bracket is compressed against a flat surface of an insulative bracket, the flat surface being perpendicular to the bolt hole extending through the bracket.
- the tightening of a threaded nut against the lockwasher transmits a mechanical force through the lockwasher to the flat surface.
- the flat surface yields and the insulative material under the lockwasher is crushed into the clearance that had surrounded the bolt in the bolt hole. Further tightening of the nut against the lockwasher then produces radial cracks extending from the damaged bolt hole through the insulative material, thereby weakening the bracket and drawing complaints from users.
- the metallic mounting bracket may also be connected to a source of ground potential.
- the full voltage of the power system exists across the arrester, from the top end of the arrester to the bottom end; and little voltage, if any, is impressed across the insulative bracket.
- the internal components of surge arresters have been known to become damaged, in which case the disconnector will automatically disconnect the ground wire from the arrester.
- the power line voltage may be impressed across the insulative bracket, as is known to those skilled in the art, until such time as the damaged arrester is discovered and replaced. Damaged arresters may not be discovered and replaced for hours, days, or even months, during which time the insulative bracket must withstand the voltage across it, without regard for weather conditions or atmosphere borne contaminants that may become deposited on the insulative bracket.
- the contaminants and moisture combine on the broad upper surfaces of prior art insulative brackets and conduct electrical leakage current across those upper surfaces as well as up and down the vertical surfaces of interposed baffles formed on the insulative brackets.
- the electrical current flowing across those surfaces, including the baffle surfaces may damage the insulative bracket and/or cause it to fail to withstand the impressed voltage, thereby causing an outage of the electrical system.
- Baffles are known to be raised portions of insulative material disposed transversely to a leakage current path along an insulative bracket as a means to increase the length of the creepage distance, and thereby to decrease the magnitude of the leakage current.
- an object of the present invention is to provide a metal oxide surge arrester having an improved weatherseal that is relatively easy to manufacture.
- Another object of the invention is to prevent the rotation of a surge arrester element with respect to a surge arrester insulative bracket.
- Yet another object of the invention is to provide an improved method for sealing a surge arrester.
- Still another object of the invention is to provide a method for providing a seal for a surge arrester while at the same time bonding the arrester components together to prevent their relative rotation with respect to the insulative bracket component of the arrester.
- the present invention comprises a surge arrester that is sealed and locked together by the bonding of readily accessible flat end surfaces of an elastomeric arrester housing and/or of the arrester element to readily accessible flat surfaces of other components of the arrester.
- the bonding is achieved by applying adhesive between opposing flat surfaces, or to one or the other of opposing flat surfaces. All opposing surfaces are then pressed together, while at the same time compressing the elastomeric housing. The compression of the housing spreads a line of adhesive into a continuous thin layer, covering the entire end surfaces of the housing, and/or holds the adhesive in place until cured and firmly bonded.
- FIG. 1 depicts a surge arrester 1 that includes a conventional clamping device 2 and threaded nut 4 for connecting the arrester 1 to an outdoor electric power distribution system.
- a ground lead disconnector 6 includes a clamping device 9 and threaded nut 8 for connecting a metallic wire to ground or earth.
- the body 18 of the arrester, the disconnector 6 and the insulative arrester bracket 21 are interconnected firmly together by means of a threaded conductive stud 10.
- the arrester 1 is shown mounted to a portion of a conventional metallic bracket 22 that includes a carriage bolt 23 that extends through the insulative bracket 23, a threaded nut 24, a helical spring lockwasher 25 and an external tooth lockwasher 26.
- the metallic bracket 22 may be electrically grounded by conventional means, not shown; and a ground wire, not shown, will be connected in the clamp 9.
- a conductive wire not shown, will be connected in the clamp 2 and its other end to the high voltage wires of the electric power system.
- the body 18 of the arrester 1 includes an arrester element 13 enclosed within a polymeric weathershed housing 19.
- Arrester element 13 includes metallic spacers 15, 16 and metal oxide varistor element 17, which may consist of one or more varistor blocks disposed between and in electrical series contact with the metallic spacers 15, 16.
- the flat series contact surfaces, e.g., 17a and 17b, as well as similar flat series contact surfaces that may exist between varistor blocks forming varistor element 17, may be bonded together by soldering or by the use of a conductive cement, such as a mixture of silver and epoxy, as is known in the art.
- the arrester element 13 may also include a relatively rigid insulative tube or wrapping 14, firmly attached to the spacers 15, 16 and retaining the spacers 15, 16 and the varistor element 17 together in series electrical contact.
- the spacers 15, 16 are centrally threaded to receive and engage the threads of the threaded studs 3, 10, which pass through central holes of the metallic discs 11, 12.
- a first layer of adhesive is placed between the metallic disc 12 and the adjacent flat end surfaces, namely, 19a of the housing 19 and 15a of the spacer 15.
- a second layer of adhesive is placed between the metallic disc 11 and the end surface 19b of the housing 19 and of the end surface 16a of the spacer 16.
- a third layer of adhesive is placed between the disc 11 and the adjacent flat surface of the insulative bracket 21.
- the task of applying the adhesive is relatively simple, since all of the surfaces to which the adhesive is to be applied are end surfaces, fully exposed prior to assembly of the surfaces together.
- the adhesive may be PLIOBOND #20, made by the Goodyear Tire Rubber Co., or another suitable adhesive.
- the polymeric housing 19 may also be elastomeric, made of EPDM rubber, for example. It is made longer In length than is the arrester element 13, by a predetermined amount; just as it is in prior art arresters where silicone grease has been used to maintain an atmosphere excluding interface at the end surfaces of an elastomeric housing as well as along the entire internal bore of the housing.
- adhesive need not be applied to the bore of the housing 19, nor along the peripheral surface of the arrester element 13, but merely at the end surfaces referred to above.
- the elastomeric housing be as long, and preferably longer, than the arrester element. Compression of the elastomeric housing then assures that the adhesive will then bond to the entire end surface of the housing and to the opposing flat surface to be bonded.
- PLIOBOND #20 is readily applied as a continuous bead which spreads to fully cover the housing end when compressed, and it cures at room temperature, though elevated temperature may be used. For wafers, elevated temperatures are usually required.
- any of the opposing flat surfaces that are to be bonded need only be substantially flat; this is, adequately flat so that the compression of the housing 19 will cause its end surfaces 19a, 19b to adequately conform to an opposing substantially flat surface to form a moisture excluding seal when bonded.
- either or both of the opposing flat surfaces to be bonded may include concentric annular grooves or bosses and still be considered as being substantially flat.
- the housing 19 When the threaded studs 3, 10 have been fully tightened, the housing 19 will be compressed to the same length as the arrester element 13. The force then exerted by the housing 19 will assure that the adhesive at the end surfaces 19a and 19b has been spread into a thin continuous layer, and that the adhesive layer will not be disturbed during the time required for the adhesive to set up and bond the housing surfaces 19a, 19b to the respective discs 11 and 12. When all three layers of adhesive have set up to bond their respective surfaces, the arrester body 18 will be permanently sealed against the ingress of moisture and permanently bonded to the insulative bracket 21.
- the arrester 1 of FIG. 1 may be assembled without inclusion of the metallic disc 11.
- the third layer of adhesive would also be deleted, the second layer of adhesive therefore bonding the housing end surface 19b, and the end surface 16a of the spacer 16, directly to the adjacent surface of the insulative bracket 21.
- the disc 12, electrically connected to the clamp 2 is energized at high voltage.
- the disc 11, in contact with the threaded stud 10 and metallic cup or cap 5, are all at near ground or earth potential, as is the conductive metallic bracket 22. Therefore, little or no voltage is impressed across or along the insulative arrester bracket 21, between the disc 11 and the metallic bracket 22. It is well known and understood that varistor block or blocks 17 within the arrester body 18 may eventually become damaged, causing the disconnector 6 to automatically separate the clamp 9, and the attached ground wire, from the arrester 1, thereby causing the metal disc 11, together with the metallic cap 5 to which the flange 10a is firmly attached, to become energized at high voltage.
- the disc 11 may remain energized at high voltage until the damaged arrester 1 is replaced, or until the insulative bracket 21 itself is unable to withstand the high voltage, flashes over electrically from the energized disc 11 to the grounded metallic bracket 22, and causes an outage of the electrical system.
- the amount or magnitude of the leakage current flowing along the creepage distance surfaces e.g., the horizontal surfaces 27-32a, added together with the horizontal and vertical surfaces of the baffles 33-38 of the insulative bracket 21, will depend on the amount of the moisture and contaminants deposited on those surfaces.
- leakage current increases with increased moisture and contaminants, e.g., rain water, dust, dirt, salts, etc., and electrical flashover is more likely to occur with increased leakage current.
- FIGS. 1-7 the same numbers have been used to identify the same portions of the insulative bracket 21 and of the metallic bracket 22.
- FIG. 2 illustrates a preferred embodiment of the present invention, wherein a mass of insulative material has been molded to form insulative bracket 21 which includes end portions 39, 40 and baffles 33- 38. Also included are the horizontal surfaces 28-32 and 28a-32a, each of which is less than one quarter as wide as the end portions 39, 40, since their width is interrupted by the width of the included apertures 41-45.
- the apertures 41-45 reduce the mass of the insulative material required to form the insulative bracket 21, thereby reducing the weight and cost of bracket 21. Further, liquids, including rain; and contaminants such as airborne dirt; can readily drain or fall entirely through the apertures 41-45, thus reducing the amount of liquid, moisture or contaminants that will remain on the insulative bracket 21. As a consequence, the creepage path can dry quickly, leakage current flow trirough the moisture and contaminants is reduced; and the probability that the bracket 21 will flashover and cause an electrical outage is reduced.
- FIG. 3 depicts the baffle 35 that is also typical of the baffles 33, 34, 36 and 37, all of which have been necked down at their centers to even further reduce the amount and cost of the mass of insulative material used to form the insulative bracket 21.
- the surfaces 30, 30a are the top surfaces of the stringers 46, 47 that may be construed as extending from and between the end portions 39, 40.
- the stringers 46, 47, the baffles 33-38 and the end portions 39, 40 are all rigidly interconnected as one single mass of molded insulative material, a fiberglass reinforced polyester, for example.
- the baffle 35 may also be construed as having been formed of three parts, l.e., one baffle formed around stringer 46, a second baffle formed around stringer 47, and with the two separate baffles being aligned for interconnection by the necked down portion 48 of baffle 35, thereby forming the single baffle 35.
- This construction increases the rigidity and strength of the insulative bracket 21, particularly with all baffles 33-37 being formed in this manner as single baffles, each enclosing both stringers 46, 47.
- FIG. 4 is a detailed enlargement of the portion of the prior art insulating base or bracket depicted on the aforementioned Ohio Brass Instruction Sheet No. 17-5113, whereon the recommended tightening torque for nut 24 is shown as 40 ft-lbs. (54 N.m).
- the concavities 51, 52 of FIG. 4 are shown, without written description, on the aforementioned Sheet No. 17-5113.
- Each concavity 51, 52 defines a flat surface 51a, 52a at opposing ends of bolt hole 53.
- lockwasher 25 is shown fully compressed against the flat surface 51a.
- the teeth of lockwasher 26 are shown at least partially embedded or biting into the surface 54 of the partially shown insulative bracket 55, as it might be with 40 ft-lbs of torque applied to the nut 24.
- FIG. 5 is the same as FIG. 4 except that the nut 24 has been tightened beyond 40 ft-lbs to further embed the teeth of lockwasher 26 into the surface 54, and the insulative material forming the bracket 55 has been cracked, crushed and displaced into the upper portion of the bolt hole 53 and into the threads of the bolt 23, as depicted by the dashed lines at 53a.
- the wedgelike form of the crushed material 53a can cause radial cracks to then form and extend through the insulative material from the bolt hole 53.
- the full embedment of the teeth of the lock-washer 26 tends to exacerbate the cracking, as evidenced by cracks that have been found extending in line with the teeth of the lockwasher 26.
- FIG. 6 depicts the portion 40 of insulative bracket 21 shown in FIGS. 1 and 2, except that the convexity 49 together with the concavity 50 have been deleted.
- a radiused surface 56 joins the flat surface 27 and the bore surface 53 to form the concavity 57.
- the concavity 57 causes the washer 25, when compressed against the insulative bracket 21 by the tightening of threaded nut 24, to contact the insulative bracket 21 only at contact surfaces that are nearest or adjacent the outer diameter of the washer 25.
- the crushing of the insulative material surrounding the bolt hole 53 has been alleviated, and greater torque may be applied to the nut 24 before crushing or cracking of the insulatlve material surrounding the bolt hole 53 may occur.
- the concavity 57 alleviates the cracking of the insulative bracket 21 that is due to compressing of the washer 25 against the bracket 21, the cracking due to penetration of the surface 54 by the teeth of the lockwasher 26 is not alleviated.
- Such alleviation is achieved by the preferred embodiment of the invention as depicted in FIG. 1, and in greater detail in FIG. 7.
- the insulative bracket 21 includes annular convexities or bosses 49, 49a that define annular concavities 50, 50a formed as a countersink at the predetermined angle A.
- the convexitles 49, 49a and the defined or surrounded concavities 50, 50a are formed substantially concentrically to bolt hole 53.
- the height of the convexities 49, 49a have been chosen so as to limit the penetration of the teeth of the lockwasher 26 into the surface 54 to approximately one-half of the penetration that can occur against the flat surface 54 as shown in FIG. 5. Any further penetration of the teeth of washer 26 into the surfce 54, FIG. 7, is prevented when the central flat portion of the metallic lockwasher 26 impacts the convexity 49a as the nut 24 is tightened.
- convexities 49, 49a so as to form concavities 50, 50a has been found to raise the resistance to the cracking of insulative surge arrester brackets, the cracking being due to the compression of a flat washer or a helical spring washer against one side of an insulative bracket as well as that due to the compression of an external tooth lockwasher against an opposing side.
- any embodiment that includes an annular convexity or concavity or spacing means substantially concentric to a bolt hole through an arrester insulative bracket is considered to be within the teachings of the invention if it causes an insulative bracket to contact a washer surface at surfaces substantially adjacent the outer diameter of that washer surface rather than at surfaces substantially adjacent the inner diameter of that washer surface, when that washer surface is being compressed against the insulative bracket by the tightening of a threaded means.
- the insulative material forming the bracket and the washer surface itself may have been mechanically deformed during the tightening, without deleterious effect, so that contact between the washer surface and the bracket may then also exist at the surfaces substantially adjacent the inner diameter of the washer surface.
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Thermistors And Varistors (AREA)
Abstract
A metal oxide surge arrester (18) and a method of making a metal oxide surge arrester that is sealed and locked together by the bonding of readily accessible flat end surfaces (15a, 16a 19a, 19b) of an elastomeric arrester housing (19) and/or of the arrester element (13) to readily accessible flat surfaces of other components (11, 12,21) of the arrester. The bonding is achieved by applying adhesive between opposing flat surfaces, or to one or other opposing flat surface. All opposing surfaces are then pressed together, while at the same time compressing the elastomeric housing (19).
Description
- This invention relates to high voltage surge arresters that include disconnectors, insulative mounting brackets, metal oxide varistors, and polymeric housings.
- In recent years, metal oxide surge arresters for protecting outdoor overhead high voltage electrical systems against lightning have been advantageously provided with polymeric weathershed housings, disconnectors, and with insulative brackets. Metal oxide varistor blocks are sealed within the polymeric housings, which protect and insulate the varistor blocks against the damaging effects of rain, snow and airborne contamination, for example. The insulative brackets have provided electrical insulation to allow for proper operation of the ground lead disconnector.
- Prior art surge arresters have also included fiberglass tubes or wrappings supporting the varistor blocks. Also, the inner diameter, or bore, of the polymeric housings have been bonded to the outer peripheral surfaces of the tube or wrapping. U.S. Patents Nos. 4,656,,555 and 4,404,614 disclose some embodiments of these, constructions and methods of construction. Methods of bonding a polymeric housing along its bore directly to varistor blocks, or to layers or coatings surrounding the blocks, are also disclosed in U.S. Patent No. 4,161,012. Polymer housings molded directly onto the peripheral surfaces of an arrester element as well as to flat end surfaces are disclosed in U.S. Patent No. 4,833,438. Each of the methods and embodiments referred to in the aforementioned U.S. patents involves a relatively expensive process for achieving a seal between the inner surfaces of an arrester housing and the outer or peripheral surfaces of arrester components enclosed within the housing.
- A method of achieving an air free, sealed, moisture excluding interface between peripheral surfaces of arrester components and inner surfaces of an elastomeric housing that includes the use of silicone grease at the interface is also described with reference to FIG. 8 in U.S. Patent No. 4,161,012. In a prior art embodiment using silicone grease at the above-described interface, the elastomeric or polymeric housing surrounding the arrester components has been also compressed between flat surfaces disposed at the opposing flat ends of the housing. However, in this embodiment, silicone oil from the silicone grease has escaped, along the flat surfaces, to outer surfaces of the housing. Here, the oil has accumulated objectionable quantities of airborne dust and dirt.
- A surge arrester insulative bracket is shown in FIG. 3 of U.S. patent No. 4,609,902. Others are identified as the insulating base shown on
pages 10 and 11 of Ohio Brass Catalog 94. The method of bolting the insulating base to a metallic arrester mounting bracket is shown in detail on Ohio Brass Instruction Sheet No. 17-5113, whereon the recommended mounting torque for the one-half inch (12.7 mm) fastener is forty ft-lbs (54 newton-metres). Torque greater than forty ft-lbs has cracked the insulating base in the area of the bolt hole ex tending through the insulating base. Restricting the applied torque to forty ft-lbs (54 N.m) places the burden of not cracking the insulating base, i.e., the insulative bracket, upon the skill, knowledge and diligence of the installer. - In the prior art devices, a lockwasher on a mounting bolt of the metallic bracket is compressed against a flat surface of an insulative bracket, the flat surface being perpendicular to the bolt hole extending through the bracket. The tightening of a threaded nut against the lockwasher transmits a mechanical force through the lockwasher to the flat surface. At a level of mechanical force predetermined by the characteristics of the insulative mass of material forming the insulative bracket, the flat surface yields and the insulative material under the lockwasher is crushed into the clearance that had surrounded the bolt in the bolt hole. Further tightening of the nut against the lockwasher then produces radial cracks extending from the damaged bolt hole through the insulative material, thereby weakening the bracket and drawing complaints from users.
- Thus there is a need for an improved insulating base that can withstand greater torque during installation.
- After a surge arrester has been bolted to a metallic mounting bracket, a threaded nut must be tightened against a clamp at the top end of the arrester to connect the arrester to an electrical power system. Similarly, a threaded nut at the bottom end of the arrester must be tightened to connect the ground lead disconnector of the arrester to a source of ground potential. During the tightening of either of these threaded nuts, there has been a tendency for the arrester housing, including the varistor blocks within the housing, to rotate with respect to the arrester insu lative bracket thereby drawing complaints from users. Thus, there is a need to prevent such rotation.
- In use, the metallic mounting bracket may also be connected to a source of ground potential.
- With all connections made as described above, the full voltage of the power system exists across the arrester, from the top end of the arrester to the bottom end; and little voltage, if any, is impressed across the insulative bracket. However, the internal components of surge arresters have been known to become damaged, in which case the disconnector will automatically disconnect the ground wire from the arrester. Now the power line voltage may be impressed across the insulative bracket, as is known to those skilled in the art, until such time as the damaged arrester is discovered and replaced. Damaged arresters may not be discovered and replaced for hours, days, or even months, during which time the insulative bracket must withstand the voltage across it, without regard for weather conditions or atmosphere borne contaminants that may become deposited on the insulative bracket.
- Under damp or rain conditions, the contaminants and moisture combine on the broad upper surfaces of prior art insulative brackets and conduct electrical leakage current across those upper surfaces as well as up and down the vertical surfaces of interposed baffles formed on the insulative brackets. Eventually, in the course of wetting and drying, the electrical current flowing across those surfaces, including the baffle surfaces, may damage the insulative bracket and/or cause it to fail to withstand the impressed voltage, thereby causing an outage of the electrical system. Baffles are known to be raised portions of insulative material disposed transversely to a leakage current path along an insulative bracket as a means to increase the length of the creepage distance, and thereby to decrease the magnitude of the leakage current.
- Accordingly, an object of the present invention is to provide a metal oxide surge arrester having an improved weatherseal that is relatively easy to manufacture.
- Another object of the invention is to prevent the rotation of a surge arrester element with respect to a surge arrester insulative bracket.
- Yet another object of the invention is to provide an improved method for sealing a surge arrester.
- Still another object of the invention is to provide a method for providing a seal for a surge arrester while at the same time bonding the arrester components together to prevent their relative rotation with respect to the insulative bracket component of the arrester.
- Briefly, the present invention comprises a surge arrester that is sealed and locked together by the bonding of readily accessible flat end surfaces of an elastomeric arrester housing and/or of the arrester element to readily accessible flat surfaces of other components of the arrester. The bonding is achieved by applying adhesive between opposing flat surfaces, or to one or the other of opposing flat surfaces. All opposing surfaces are then pressed together, while at the same time compressing the elastomeric housing. The compression of the housing spreads a line of adhesive into a continuous thin layer, covering the entire end surfaces of the housing, and/or holds the adhesive in place until cured and firmly bonded.
- The above and other objects and advantages and novel features of the present invention will become apparent from the following detailed description of the embodiments of the invention illustrated in the accompanying drawings wherein:
- FIG. 1 is a side elevation, in partial section, of a preferred embodiment of a surge arrester constructed in accordance with the principles of the present invention, shown attached to a portion of a metallic mounting bracket;
- FIG. 2 is a top plan view of the insulative bracket shown assembled in the surge arrester depicted in FIG. 1;
- FIG. 3 is a cross-sectional view of the device of FIG. 2 taken along the line 3-3 of FIG. 2;
- FIG. 4 is a side elevation in partial section, of an end portion of a prior art insulatlve arrester bracket shown bolted to a metallic mounting bracket;
- FIG. 5 is a side elevation, in partial section, of an end portion of a prior art insulative arrester bracket shown damaged by assembly to a metallic mounting bracket;
- FIG. 6 is a side elevation, in cross-section, of a portion of an insulative bracket in accordance with an embodiment of the invention, shown attached to a portion of a metallic mounting bracket; and
- FIG. 7 is a side elevation, in cross-section, of the portion of the insulative bracket in accordance with FIG., 1, shown attached to a metallic mounting bracket.
- FIG. 1 depicts a surge arrester 1 that includes a
conventional clamping device 2 and threaded nut 4 for connecting the arrester 1 to an outdoor electric power distribution system. Aground lead disconnector 6 includes aclamping device 9 and threadednut 8 for connecting a metallic wire to ground or earth. Thebody 18 of the arrester, thedisconnector 6 and theinsulative arrester bracket 21 are interconnected firmly together by means of a threadedconductive stud 10. The arrester 1 is shown mounted to a portion of a conventionalmetallic bracket 22 that includes acarriage bolt 23 that extends through theinsulative bracket 23, a threadednut 24, ahelical spring lockwasher 25 and anexternal tooth lockwasher 26. When the surge arrester 1 is placed into service to protect an outdoor electric power distribution system, it is mounted firmly to thebracket 22 by the tightening of thenut 24. Themetallic bracket 22 may be electrically grounded by conventional means, not shown; and a ground wire, not shown, will be connected in theclamp 9. One end of a conductive wire, not shown, will be connected in theclamp 2 and its other end to the high voltage wires of the electric power system. - The
body 18 of the arrester 1 includes anarrester element 13 enclosed within a polymericweathershed housing 19.Arrester element 13 includesmetallic spacers oxide varistor element 17, which may consist of one or more varistor blocks disposed between and in electrical series contact with themetallic spacers varistor element 17, may be bonded together by soldering or by the use of a conductive cement, such as a mixture of silver and epoxy, as is known in the art. Thearrester element 13 may also include a relatively rigid insulative tube or wrapping 14, firmly attached to thespacers spacers varistor element 17 together in series electrical contact. - The
spacers studs metallic discs 11, 12. - During assembly of the arrester 1, a first layer of adhesive, not shown, is placed between the
metallic disc 12 and the adjacent flat end surfaces, namely, 19a of thehousing spacer 15. Similarly, a second layer of adhesive is placed between the metallic disc 11 and theend surface 19b of thehousing 19 and of theend surface 16a of thespacer 16. A third layer of adhesive is placed between the disc 11 and the adjacent flat surface of theinsulative bracket 21. The task of applying the adhesive is relatively simple, since all of the surfaces to which the adhesive is to be applied are end surfaces, fully exposed prior to assembly of the surfaces together. The adhesive may be PLIOBOND #20, made by the Goodyear Tire Rubber Co., or another suitable adhesive. - The
polymeric housing 19 may also be elastomeric, made of EPDM rubber, for example. It is made longer In length than is thearrester element 13, by a predetermined amount; just as it is in prior art arresters where silicone grease has been used to maintain an atmosphere excluding interface at the end surfaces of an elastomeric housing as well as along the entire internal bore of the housing. However, adhesive need not be applied to the bore of thehousing 19, nor along the peripheral surface of thearrester element 13, but merely at the end surfaces referred to above. Whether the adhesive is applied as a wafer cut to the shape of the opposing ends to be bonded, or is spread or painted on, or is applied as a continuous bead or line, it is advantageous that the elastomeric housing be as long, and preferably longer, than the arrester element. Compression of the elastomeric housing then assures that the adhesive will then bond to the entire end surface of the housing and to the opposing flat surface to be bonded. PLIOBOND #20 is readily applied as a continuous bead which spreads to fully cover the housing end when compressed, and it cures at room temperature, though elevated temperature may be used. For wafers, elevated temperatures are usually required. - It is to be understood that any of the opposing flat surfaces that are to be bonded need only be substantially flat; this is, adequately flat so that the compression of the
housing 19 will cause itsend surfaces - Thus, when the adhesive has been appropriately applied in a manner as described above, and when the threaded
stud 3, which includes acentral flange portion 3a, and the threadedstud 10, which includes anend flange 10a, are screwed into thespacers flange 3a will bear against thedisc 12, which, in turn, through the adhesive, will bear against thehousing end surface 19a and finally against theadjacent end surface 15a of thespacer 15. Similarly theflange 10a will bear against the adjacent portion of theinsulative bracket 21, and theinsulative bracket 21 will in turn, through the adhesive, bear against the disc 11, which in turn, through the adhesive, will bear against thehousing end surface 19b and against theadjacent end surface 16a of thespacer 16. When the threadedstuds housing 19 will be compressed to the same length as thearrester element 13. The force then exerted by thehousing 19 will assure that the adhesive at the end surfaces 19a and 19b has been spread into a thin continuous layer, and that the adhesive layer will not be disturbed during the time required for the adhesive to set up and bond thehousing surfaces respective discs 11 and 12. When all three layers of adhesive have set up to bond their respective surfaces, thearrester body 18 will be permanently sealed against the ingress of moisture and permanently bonded to theinsulative bracket 21. Thus, when torque is applied to thenuts 4, 8, to connect the arrester 1 to a high voltage electrical system and to a ground wire, respectively, the torque thereby transmitted will not cause thearrester body 18 to be rotated with respect to theinsulative bracket 21, as may occur when thebody 18 is not bonded or otherwise locked to theinsulative bracket 21. - In another embodiment, the arrester 1 of FIG. 1 may be assembled without inclusion of the metallic disc 11. In this instance, the third layer of adhesive would also be deleted, the second layer of adhesive therefore bonding the
housing end surface 19b, and theend surface 16a of thespacer 16, directly to the adjacent surface of theinsulative bracket 21. - When the arrester 1 is electrically connected in service, the
disc 12, electrically connected to theclamp 2, is energized at high voltage. The disc 11, in contact with the threadedstud 10 and metallic cup or cap 5, are all at near ground or earth potential, as is the conductivemetallic bracket 22. Therefore, little or no voltage is impressed across or along theinsulative arrester bracket 21, between the disc 11 and themetallic bracket 22. It is well known and understood that varistor block or blocks 17 within thearrester body 18 may eventually become damaged, causing thedisconnector 6 to automatically separate theclamp 9, and the attached ground wire, from the arrester 1, thereby causing the metal disc 11, together with the metallic cap 5 to which theflange 10a is firmly attached, to become energized at high voltage. The disc 11 may remain energized at high voltage until the damaged arrester 1 is replaced, or until theinsulative bracket 21 itself is unable to withstand the high voltage, flashes over electrically from the energized disc 11 to the groundedmetallic bracket 22, and causes an outage of the electrical system. - When the
interconnected spacer 16, the disc 11 thestud 10 and the cap 5 are energized at high voltage, the amount or magnitude of the leakage current flowing along the creepage distance surfaces, e.g., the horizontal surfaces 27-32a, added together with the horizontal and vertical surfaces of the baffles 33-38 of theinsulative bracket 21, will depend on the amount of the moisture and contaminants deposited on those surfaces. In general, leakage current increases with increased moisture and contaminants, e.g., rain water, dust, dirt, salts, etc., and electrical flashover is more likely to occur with increased leakage current. - The manner in which the
insulative bracket 21 has been improved to reduce its weight and cost and to reduce the amount of moisture or liquid and contaminants deposited along its creepage path or leakage distance is best explained with respect to FIGS. 2 and 3. - In FIGS. 1-7, the same numbers have been used to identify the same portions of the
insulative bracket 21 and of themetallic bracket 22. - FIG. 2 illustrates a preferred embodiment of the present invention, wherein a mass of insulative material has been molded to form
insulative bracket 21 which includesend portions end portions - The apertures 41-45 reduce the mass of the insulative material required to form the
insulative bracket 21, thereby reducing the weight and cost ofbracket 21. Further, liquids, including rain; and contaminants such as airborne dirt; can readily drain or fall entirely through the apertures 41-45, thus reducing the amount of liquid, moisture or contaminants that will remain on theinsulative bracket 21. As a consequence, the creepage path can dry quickly, leakage current flow trirough the moisture and contaminants is reduced; and the probability that thebracket 21 will flashover and cause an electrical outage is reduced. - FIG. 3 depicts the
baffle 35 that is also typical of thebaffles insulative bracket 21. Thesurfaces stringers end portions stringers end portions - In FIG. 3, the
baffle 35 may also be construed as having been formed of three parts, l.e., one baffle formed aroundstringer 46, a second baffle formed aroundstringer 47, and with the two separate baffles being aligned for interconnection by the necked downportion 48 ofbaffle 35, thereby forming thesingle baffle 35. This construction increases the rigidity and strength of theinsulative bracket 21, particularly with all baffles 33-37 being formed in this manner as single baffles, each enclosing bothstringers - As shown in FIG. 1, when the
nut 24 has been tightened on thebolt 23 to compress thehelical spring lockwasher 25 as shown, thelockwasher 25 restrains the nut from vibrating loose while the teeth of theexternal tooth lockwasher 26 bite into the adjacent surfaces of themetallic bracket 22 and theinsulative bracket 21 to prevent rotation of thebracket 21 around thebolt 23. The configuration and function of theconvexity 49 are hereinunder explained with reference to FIG. 7. - FIG. 4 is a detailed enlargement of the portion of the prior art insulating base or bracket depicted on the aforementioned Ohio Brass Instruction Sheet No. 17-5113, whereon the recommended tightening torque for
nut 24 is shown as 40 ft-lbs. (54 N.m). - The
concavities concavity flat surface 51a, 52a at opposing ends ofbolt hole 53. On FIG. 4,lockwasher 25 is shown fully compressed against the flat surface 51a. The teeth oflockwasher 26 are shown at least partially embedded or biting into thesurface 54 of the partially showninsulative bracket 55, as it might be with 40 ft-lbs of torque applied to thenut 24. - FIG. 5 is the same as FIG. 4 except that the
nut 24 has been tightened beyond 40 ft-lbs to further embed the teeth oflockwasher 26 into thesurface 54, and the insulative material forming thebracket 55 has been cracked, crushed and displaced into the upper portion of thebolt hole 53 and into the threads of thebolt 23, as depicted by the dashed lines at 53a. When thenut 24 is then further tightened, the wedgelike form of the crushedmaterial 53a can cause radial cracks to then form and extend through the insulative material from thebolt hole 53. This weakens the bracket and renders it non-reusable, since any attempt to remove thebracket 55 from thebolt 23 requires the removal of the crushedmaterial 53a that extends into the threads of thebolt 23. The full embedment of the teeth of the lock-washer 26 tends to exacerbate the cracking, as evidenced by cracks that have been found extending in line with the teeth of thelockwasher 26. - FIG. 6 depicts the
portion 40 ofinsulative bracket 21 shown in FIGS. 1 and 2, except that theconvexity 49 together with theconcavity 50 have been deleted. Instead, in accordance with another embodiment of the invention, aradiused surface 56 joins theflat surface 27 and thebore surface 53 to form theconcavity 57. Theconcavity 57 causes thewasher 25, when compressed against theinsulative bracket 21 by the tightening of threadednut 24, to contact theinsulative bracket 21 only at contact surfaces that are nearest or adjacent the outer diameter of thewasher 25. As a result, the crushing of the insulative material surrounding thebolt hole 53, as explained hereinabove with respect to FIG. 5, has been alleviated, and greater torque may be applied to thenut 24 before crushing or cracking of the insulatlve material surrounding thebolt hole 53 may occur. - While the
concavity 57 alleviates the cracking of theinsulative bracket 21 that is due to compressing of thewasher 25 against thebracket 21, the cracking due to penetration of thesurface 54 by the teeth of thelockwasher 26 is not alleviated. Such alleviation is achieved by the preferred embodiment of the invention as depicted in FIG. 1, and in greater detail in FIG. 7. Here theinsulative bracket 21 includes annular convexities orbosses annular concavities convexitles concavities hole 53. The height of theconvexities lockwasher 26 into thesurface 54 to approximately one-half of the penetration that can occur against theflat surface 54 as shown in FIG. 5. Any further penetration of the teeth ofwasher 26 into thesurfce 54, FIG. 7, is prevented when the central flat portion of themetallic lockwasher 26 impacts theconvexity 49a as thenut 24 is tightened. - Because of large variations in the actual configurations of washers, i.e.,
lockwasher 25, due to material thicknesses, forming methods, and corrosion protective coatings of washers, a chamfer angle A of 4 to 8 decrees has been found to be most advantageous. - The provision of
convexities concavities - While certain advantageous embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that any embodiment that includes an annular convexity or concavity or spacing means substantially concentric to a bolt hole through an arrester insulative bracket is considered to be within the teachings of the invention if it causes an insulative bracket to contact a washer surface at surfaces substantially adjacent the outer diameter of that washer surface rather than at surfaces substantially adjacent the inner diameter of that washer surface, when that washer surface is being compressed against the insulative bracket by the tightening of a threaded means. When the tightening has been properly completed, it is to be understood that the insulative material forming the bracket and the washer surface itself, may have been mechanically deformed during the tightening, without deleterious effect, so that contact between the washer surface and the bracket may then also exist at the surfaces substantially adjacent the inner diameter of the washer surface.
Claims (8)
1. A high voltage surge arrester comprising:
an elastomeric arrester housing (19) having a bore and first and second substantially flat end surfaces (19a,19b) disposed at opposing ends of said bore;
a rigid arrester element (13) disposed within the bore, comprising at least one metal oxide varistor block (17) and at least one metallic connector (15,16);
an arrester component (11 or 21) having a third substantially flat surface large enough to at least substantially cover said first end surface (19b) of said housing; and CHARACTERIZED IN THAT
a layer of adhesive is disposed between said first surface (19b) and said third surface,
said arrester housing (19) being compressed against said adhesive layer; no adhesive being disposed between the bore of the housing (19) and the arrester element (13).
an elastomeric arrester housing (19) having a bore and first and second substantially flat end surfaces (19a,19b) disposed at opposing ends of said bore;
a rigid arrester element (13) disposed within the bore, comprising at least one metal oxide varistor block (17) and at least one metallic connector (15,16);
an arrester component (11 or 21) having a third substantially flat surface large enough to at least substantially cover said first end surface (19b) of said housing; and CHARACTERIZED IN THAT
a layer of adhesive is disposed between said first surface (19b) and said third surface,
said arrester housing (19) being compressed against said adhesive layer; no adhesive being disposed between the bore of the housing (19) and the arrester element (13).
2. A high voltage surge arrester as defined in claim 1, further comprising a metallic disc (12) having a fourth substantially flat surface large enough at least substantially to cover the second end surface (19a) of the housing, wherein a second layer of adhesive is disposed between the second surface (19a) and the fourth surface, the arrester housing (19) being compressed against the second adhesive layer.
3. A high voltage surge arrester as defined in claim 1 or claim 2 wherein said arrester component is a metallic disc (11).
4. A high voltage surge arrester is defined in claim 1 or claim 2 wherein said arrester component is an insulative bracket (21).
5. A high voltage surge arrester as defined in claim 4, further comprising means for preventing the relative rotation of said arrester element (13) with respect to said insulative bracket (21), said preventing means comprising a layer of adhesive disposed between said arrester element and said insulative bracket.
6. A method of bonding and sealing a high voltage surge arrester comprising the steps of:
forming a rigid arrester element (13), comprising at least one metal oxide varistor block (17) and at least one metallic connector (15,16);
forming an elastomeric housing (19) having a bore and first and second substantially flat end surfaces (19a, 19b) disposed at opposing ends of said bore, said housing also being formed to a length between said end surfaces that will exceed the length of said arrester element (13) when said arrester element is disposed within said bore;
forming an arrester component (11 or 21) having a third substantially flat surface large enough to at least substantially cover said first end surface (19b) of said housing;v inserting said arrester element (13) into said bore;
placing an adhesive between said first surface (19b) of said housing and said third surface of said arrester component; and
forcing said first surface (19b) and said third surface against said adhesive while compressing said housing (19), to form a bond and seal between said first surface and said third surface.
forming a rigid arrester element (13), comprising at least one metal oxide varistor block (17) and at least one metallic connector (15,16);
forming an elastomeric housing (19) having a bore and first and second substantially flat end surfaces (19a, 19b) disposed at opposing ends of said bore, said housing also being formed to a length between said end surfaces that will exceed the length of said arrester element (13) when said arrester element is disposed within said bore;
forming an arrester component (11 or 21) having a third substantially flat surface large enough to at least substantially cover said first end surface (19b) of said housing;v inserting said arrester element (13) into said bore;
placing an adhesive between said first surface (19b) of said housing and said third surface of said arrester component; and
forcing said first surface (19b) and said third surface against said adhesive while compressing said housing (19), to form a bond and seal between said first surface and said third surface.
7. The method of bonding and sealing a high voltage surface arrester as defined in claim 6 further including the step of placing an adhesive between said arrester element (13) and said arrester component (21) and forcing said arrester element and said arrester component against said adhesive.
8. The method defined in claim 7, further comprising the steps of:
forming a metallic disc (12) having a fourth substantially flat surface large enough at least substantially to cover the second end surface (19a) of the housing;
placing an adhesive between the second surface (19a) of the huusing and the fourth surface of the metallic disc (12); and forcing the second surface (19a) and the fourth surface against the adhesive while composing the housing (19) to form a bond and seal between the second surface and the fourth surface.
forming a metallic disc (12) having a fourth substantially flat surface large enough at least substantially to cover the second end surface (19a) of the housing;
placing an adhesive between the second surface (19a) of the huusing and the fourth surface of the metallic disc (12); and forcing the second surface (19a) and the fourth surface against the adhesive while composing the housing (19) to form a bond and seal between the second surface and the fourth surface.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US38427889A | 1989-07-24 | 1989-07-24 | |
US384278 | 1989-07-24 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0410644A2 true EP0410644A2 (en) | 1991-01-30 |
EP0410644A3 EP0410644A3 (en) | 1991-10-23 |
Family
ID=23516680
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19900307888 Withdrawn EP0410644A3 (en) | 1989-07-24 | 1990-07-19 | Surge arrester with improved weatherseal |
Country Status (1)
Country | Link |
---|---|
EP (1) | EP0410644A3 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001047078A2 (en) * | 1999-12-23 | 2001-06-28 | Mcgraw Edison Company | Compliant joint between electrical components |
US8085520B2 (en) | 2004-01-23 | 2011-12-27 | Cooper Technologies Company | Manufacturing process for surge arrester module using pre-impregnated composite |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3334533A1 (en) * | 1983-09-23 | 1985-04-04 | Transformatoren Union Ag, 7000 Stuttgart | Surge arrester |
US4609902A (en) * | 1985-10-03 | 1986-09-02 | Harvey Hubbell Incorporated | Arrester support and disconnector structure |
US4779162A (en) * | 1987-03-16 | 1988-10-18 | Rte Corporation | Under oil arrester |
-
1990
- 1990-07-19 EP EP19900307888 patent/EP0410644A3/en not_active Withdrawn
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3334533A1 (en) * | 1983-09-23 | 1985-04-04 | Transformatoren Union Ag, 7000 Stuttgart | Surge arrester |
US4609902A (en) * | 1985-10-03 | 1986-09-02 | Harvey Hubbell Incorporated | Arrester support and disconnector structure |
US4779162A (en) * | 1987-03-16 | 1988-10-18 | Rte Corporation | Under oil arrester |
Non-Patent Citations (1)
Title |
---|
IEEE TRANSACTIONS ON POWER DELIVERY. vol. 3, no. 2, April 1988, NEW YORK US pages 584 - 590; D. W. LENK ET AL.: "A NEW APPROACH TO DISTRIBUTION ARRESTER DESIGN" * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001047078A2 (en) * | 1999-12-23 | 2001-06-28 | Mcgraw Edison Company | Compliant joint between electrical components |
WO2001047078A3 (en) * | 1999-12-23 | 2002-01-03 | Mc Graw Edison Co | Compliant joint between electrical components |
US6483685B1 (en) | 1999-12-23 | 2002-11-19 | Mcgraw Edison Company | Compliant joint between electrical components |
US8085520B2 (en) | 2004-01-23 | 2011-12-27 | Cooper Technologies Company | Manufacturing process for surge arrester module using pre-impregnated composite |
Also Published As
Publication number | Publication date |
---|---|
EP0410644A3 (en) | 1991-10-23 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4161012A (en) | High voltage protection apparatus | |
KR100264938B1 (en) | Surge arrester | |
US4467387A (en) | Combination strut insulator and lightning arrester | |
JP3058883B2 (en) | High voltage insulator and method of manufacturing the same | |
US6441310B1 (en) | Moisture activated barrier for electrical assemblies | |
US5444429A (en) | Electrical assembly with surge arrester and insulator | |
US6225567B1 (en) | Polymeric weathershed surge arrester and method | |
JPS63312602A (en) | Lightning arrester | |
US4972291A (en) | Surge arrester with improved insulative bracket | |
EP0410642B1 (en) | Surge arrester with draining insulative bracket | |
CN105788775A (en) | Needle type composite insulator for 10 kV transmission line | |
EP0410644A2 (en) | Surge arrester with improved weatherseal | |
US5684665A (en) | Modular electrical assembly with conductive strips | |
CN211150222U (en) | Novel lightning arrester | |
CN110993219A (en) | Rain and snow prevention bird damage prevention multifunctional lightning protection porcelain insulator with safety cover | |
JPS645305Y2 (en) | ||
US2539749A (en) | Open type valve arrester | |
CN211907115U (en) | Rain and snow prevention bird damage prevention multifunctional lightning protection porcelain insulator with safety cover | |
JPS6321082Y2 (en) | ||
JP4169126B2 (en) | Arrester with gap | |
JPH0338794Y2 (en) | ||
JPS645774Y2 (en) | ||
JPH0515013B2 (en) | ||
JPH0229626Y2 (en) | ||
JPS6131454Y2 (en) |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE ES FR GB IT |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): DE ES FR GB IT |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
18D | Application deemed to be withdrawn |
Effective date: 19920424 |