CA1221148A - Glaze to pin connection for a high voltage insulator with embedded metal fitting - Google Patents
Glaze to pin connection for a high voltage insulator with embedded metal fittingInfo
- Publication number
- CA1221148A CA1221148A CA000451347A CA451347A CA1221148A CA 1221148 A CA1221148 A CA 1221148A CA 000451347 A CA000451347 A CA 000451347A CA 451347 A CA451347 A CA 451347A CA 1221148 A CA1221148 A CA 1221148A
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- Prior art keywords
- glaze
- pin
- insulator
- shell
- electrical
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Abstract
ABSTRACT OF THE DISCLOSURE
This disclosure teaches an electrical insulator with improved glaze to pin electrical connection. A
suitably contoured porcelain insulator shell is coated with a glaze for direct current or alternating current applica-tion and has a metal cap and a metal pin each situated at a surface of the insulator shell opposite to the other. The insulator shell forms a recess to receive the pin and Portland cement is poured therein for mechanically securing the pin embedded in the insulator shell. A conductive polymer composition is applied to cover the surface of the Portland cement to connect the pin for non-ionic current flow to the glaze and thus to accommodate passage of leakage current in a manner that generally prevents electrochemical corrosion of the pin with attendant cracking of the por-celain insulator.
This disclosure teaches an electrical insulator with improved glaze to pin electrical connection. A
suitably contoured porcelain insulator shell is coated with a glaze for direct current or alternating current applica-tion and has a metal cap and a metal pin each situated at a surface of the insulator shell opposite to the other. The insulator shell forms a recess to receive the pin and Portland cement is poured therein for mechanically securing the pin embedded in the insulator shell. A conductive polymer composition is applied to cover the surface of the Portland cement to connect the pin for non-ionic current flow to the glaze and thus to accommodate passage of leakage current in a manner that generally prevents electrochemical corrosion of the pin with attendant cracking of the por-celain insulator.
Description
~EB:JS.LO (Foreign~
14 Mar 84 IMPROVED GLA~E TO PI~ CONNECTION
FOR A HIGH VOLTAGE INSULATOR
WITH EMBEDDED METAL FITTING
by William A. Tatem and Edward S. Wheeler This invention relates to electrical insulators and, more particularly, to a high voltage ceramic insulator with a layer of conductive polymer composi~ion to inhibit electro-chemical corrosion of an embedded metal fitting.
BACKGROUND OF THE INVENTION
Ele~trical insulators commohly known as suspension insulators may be used individually, but usually ~orm part of a string to support an electrical conductor from a sup-porting structure. Generally such a suspension insulator comprises two metal hardware members secured to opposite surfaces of a suitable contoured insulator shell, one hard-ware member being embedded by means of cement in a cavity in the porcelain member. By this arrangement the metal hard-ware members are separated and insulated each from the other. The hardware members, typically an upper cap and a lower pin, each are secured to one of the opposite surfaces of the insulator shell usually by a layer of cement or other suitable material. Typically a glaze will cover the exposed porcelain surface.
Head cracking problems have arisen on alternating current lines using suspension insulators coated with a semiconducting glaze. The cracking in that AC case has been attributed to increased leakage current due to the semicon-ducting glaze.
High voltage direct current power transmission lines are known to experience cracked suspension insulators after some pèriod of serviceO This cracking may be caused by an ionic current flow through the moisture in the Portland cement. Because this current flow always is in the same direction in a direct current system, tne resulting electroche~ical reaction causes the pin to corrode and hence to "grow" if the pin is the positive, or anodic terminal in the insulator. This "growth", in turn, leads to tensile stresses within the ceramic insulator that produces the cracking phenomenon. According to one theory developed to explain this cracking phenomenon in direct current insula-tors using standard insulating glazes, adverse environmental
14 Mar 84 IMPROVED GLA~E TO PI~ CONNECTION
FOR A HIGH VOLTAGE INSULATOR
WITH EMBEDDED METAL FITTING
by William A. Tatem and Edward S. Wheeler This invention relates to electrical insulators and, more particularly, to a high voltage ceramic insulator with a layer of conductive polymer composi~ion to inhibit electro-chemical corrosion of an embedded metal fitting.
BACKGROUND OF THE INVENTION
Ele~trical insulators commohly known as suspension insulators may be used individually, but usually ~orm part of a string to support an electrical conductor from a sup-porting structure. Generally such a suspension insulator comprises two metal hardware members secured to opposite surfaces of a suitable contoured insulator shell, one hard-ware member being embedded by means of cement in a cavity in the porcelain member. By this arrangement the metal hard-ware members are separated and insulated each from the other. The hardware members, typically an upper cap and a lower pin, each are secured to one of the opposite surfaces of the insulator shell usually by a layer of cement or other suitable material. Typically a glaze will cover the exposed porcelain surface.
Head cracking problems have arisen on alternating current lines using suspension insulators coated with a semiconducting glaze. The cracking in that AC case has been attributed to increased leakage current due to the semicon-ducting glaze.
High voltage direct current power transmission lines are known to experience cracked suspension insulators after some pèriod of serviceO This cracking may be caused by an ionic current flow through the moisture in the Portland cement. Because this current flow always is in the same direction in a direct current system, tne resulting electroche~ical reaction causes the pin to corrode and hence to "grow" if the pin is the positive, or anodic terminal in the insulator. This "growth", in turn, leads to tensile stresses within the ceramic insulator that produces the cracking phenomenon. According to one theory developed to explain this cracking phenomenon in direct current insula-tors using standard insulating glazes, adverse environmental
-2-conditions, of which moisture and contamination are typical, increase the insulator surface leaka~e current.
In both the alternating current and direct current insulators, when the leakage current reaches the Portland cement, it flows through it, not just over the cement sur-face, inasmuch as moisture from the environment is present in the cement, thereby increasing the cement conductivity and enhancing the undesirable ionic electrochemical process of attack ~pon the galvanized pin.
Thus, there is a need for some means to eliminate ionic current flow through the Portland cement in both alternating current and direct current insulators that have either semiconducting or insulating glazes that are charac-teristic of high voltage insulators, to prevent pin growth and consequent insulator cracking.
STATEMENT O~ INVENTION
The foregoing difficulties cf prior art electrical insulators are solved in a particularly novel, useful and unobvious way through the teaching of the present invention.
~ccording to the present invention, Portland cement, such as neat Portland cement, is positioned in the pin recess formed by the porcelain insulator shell about the pin, thus securing the pin to the insulator shell for mechanical integrity. Then a conductive polymer composition, such as a phenolic polymer composition containing a phenolic resin, having a nonionic electrical conductivity substantially greater than the conductivity of Portland cement, is applied to connect the metal pin electrically to the glaze coating in a manner which substantially prohibits air from con-tacting the Portland cement, The recess forms a mouth and the polymer composition preferably covers that entire rnouth, The polymer composition used in the present inven-tion has reasonably high nonionic electrical conduc~ivity;
is resistant to the effects of weather; bonds well to glaze, cement and metal surfaces; and is relatively inexpensive and appliable conveniently in a factory. One preferred material is a conductive carbon filled phenolic resin manufactured and sold under the trademark CARBO-KOREZ by Atlas Minerals and Chemicals Company.
Therefore, a primary object of this invention is to provide a cementing arrangement, including Portland cement sealed by a conductive polymer composition, for use with alternating and direct current electrical insulators having a glaze coating on their porcelain insulator shells, to establish electrical connection to the hardware, without passage of significant leakage currents through the Portland cement.
It is a further object of this invention to provide a cement arrangement which has low shrinkage, so that suitable bonds are maintained between metal hardware and insulator surfaces.
It is still a further object of this invention to provide electrical insulators oE the type here contemplated which are well suited otherwise to perform their intended functions. The foregoing objects as well as other objects, features and advantages of this invention will be understood more fully from an accompanying drawing, from a detailed description of a preferred embodiment and from claims which are presented herewith.
The drawing and embodiment shown therein are for illustrative purposes only and are not meant to limit or redefine the invention as disclosed and claimed herein.
DESCRIPTION OF THE DRAWING
Fig. 1, the only figure, is a front view of a pre-ferred embodiment of an electrical insulator according to the present invention, the left half of the figure is shown in cross section.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the figure, a typical cap 11 and pin 12 type electrical insulator according to the present inven-tion is designated generally 13; however, it should be understood that the specific form of the ins~lator 13 is not profound so lon~ as features essential to the invention are found therein~ When assembled in a string, cap 11 is attached to a pin of an electrical insulator above it and the pin 12 is connected to a cap of an electrical insulator below it. A contoured porcelain insulator shell 14 is com-posed of a head 16 and a shed 17 and is coated for direct current applications on its exposed and sand band surfaces 19, 22 either with a conventional insulating glaze 18 that is not semiconductive or with a semiconducting glaze 18.
For alternating current insulation purposes, however, the insulating glaze 18 would be typically semicon-ductive,as no general problem exists of head cracking of alternating current conventional glaze insulators. Despite the differences in the electrical characteristics of the glaze 18 applied, either insulating or semiconductive, as mentioned above, nevertheless both glazes permit leakage currents causing the corrosion and cracking problems that the instant invention overcomes. Accordingly, although the balance of this detailed description is addressed to a direct current electrical insulator with insulating or semi-conducting glaze, the concept is equally applicable to alternating current electrical insulators in which the applied glaze 18 has insulating or semiconductive electrical properties.
The cap 11 is metal and is fixed to the sanded sur-ace 19 of the insulator shell 14 at the outer periphery of the head 16 by capping means in the form of cement 21. The pin 12 is metal and is fixed to the sanded surface 22 of the insulator shell 14 (in a pin recess 23 formed in the head 16) by means of cement 24, Both cement 21 and cement 24 preferably are neat Portland cement or silica or other suitable inert material filled Portland cement for securing mechanically and inex-pensively the cap 11 and the pin 12 respectiv~ly to the insulator shell 14D The desired non-ionic electrical con-nectio~ to the pin 12, is achieved by usa of a conductive polymer composition, such as a phenolic polymer composition 26, for example, CARBO-KOREZ preferably placed in a mouth 27 formed in the pin recess 23. It is preferable to have the conductive polymer composition cover the entire mouth 27.
By this arrangement leakage current flow between the glaæe 18 and the pin 12 is shunted around the cement 24. The leakage current will thus be a non-ionic current when carried by the conductive polymer composition 26 which com-position is not affected adversely by the passage of the leakage current therethrough, The conductive organic layer, iE it bonds well to the porcelain and to the pin, which is a prerequisite for its conduction of leakage current~ will also seal off the Portland cement rom the environment and 2~ 8 thus prevent ready replace~nent of the cementls moisture. In this way significant ionic conduction is stopped~ further prevent i ng pi n "growth"~
Various polymer compositions will perform satisfac-torily in this service, including silicone greases, epoxy and silicone rubber layers and phenolic polymers filled with (for example~ carbon particles. As has been mentioned above, an effective (and preferred) low cost commercial product suitable to serve as the conductive polymer composition is available under the tradernark CARBO-KOREZ corrosion proof cement sold by Atlas Minerals and Chemicals Company. The CARBO-KOREZ cement has a resistivity of about 10,000 ohm centimeters.
Accelerated long term tests have shown that direct current electrical insulators according to the present invantion perform extremely well. The units were energized with direct current for up to several years with periodic inspections carried out to observe changes and to measure conductivities. The acceleration was accomplished by increasing the average leakage current per unit time over what would be normal for standard insulating glazes. Signi-ficant current flow over insulating glazes occurs only under wet, cor,taminated conditions, an infrequent situation nor~
mally. Use of a semiconducting glaze permits continual significant leakage current flow without regard to weather or contamination, thus accelerating the DC insulator cracking problem.
Two comparative experiments were conducted in which semiconducting glaze insulators using conductive Portland cement in the conventional fashion were energized over a period of time. In the first experiment five tests of strings of units without the conducting organic cement layer were made with direct current for up to fifteen months with pin polarities and other test conditions and test results as shown:
EFFECTS OF ACCELERATED TESTING OF
DC ENERGIZED DISC SUSPENSION INSULATORS
No. of Polarity Visibly Test Discs of pin Months Cracked Product Type No. Used Electrode Energized Units,~
1 4 Positive 2.5 75 Without Con- 2 4 Positive 6.5 75 duc~ing Organic 3 12 Positive 8.5 67 Cement Layer 4 4 Positive 12 25 4 Negative15 0 In the second experiment, six tests similar to those in the first experiment, except for the application of a con ducting organic cement layer on each disc, were energized with the polarities and other test conditions as shown:
EFFECTS OF ACCELERATED TESTING OF
DC ENERGIzEn DISC SUSPENSION INSULATORS
No~ of Polarity Visibly Test Discs of pin Months Cracked Product Type No. Used Electrode Energiæed Units~
6 4 Negative 4~5 With conduct-7 4 Positive 4.5 0 ing Organic8 4 Negative 19 0 Cement layer9 4 Positive 19 0 10 4 Positive 28 0 11 5 Positive 40 0 . From the foregoing experimental data it can be seen that the preponderance of cracking of porcelains without an applied layer of conducting organic cement in direct current service is unreasonably high, with significant cracking occurring in a period of time cf about two and one-half to about twelve months. The variation in time for a given per-centage of units to crack is dependent upon a number of fac~
tors which vary in outdoor exposure, particularly the level of humidity present in the surrounding air during the expo-sure, In contrast, however, those porcelains in direct current service to which a layer of organic cement had been applied did not show visible cracks after as much as 40 months of testing.
The above experiments involving visually obvious cracking nevertheless do not entirely reveal the physical condition of the apparently intact units. When manufac~
tured, suspenslon units of the type tested have mechanical-electrical strengths well above their rated strength, usually averaging about 120~ or more of rating. The apparently intact units without the applied layer of organic cement were subsequently tested for their ultimate mechanical-electrical strength after the energization period. Of the units tes~ed in this fashion, the measured strength ranged from 74~ to 123~ of the rated strength~ As can be seen, many of the apparently intact uni~s were in fact weakened and might eventually be expected to crack.
To demonstrate the improvement possible by the new method described in the present invention, the four units from test No. 9 were tested for ultimate mechanical and electrical strength and showed 126~ to 154~ of the strength rating after the 19 months energization test.
This last set of results is in strong contrast to those obtained in the preceding experiments and exhibits the marked superiority of this invention.
Although the above accelerated experiments were performed with semiconducting glazed direct current insula-tors, identical cracking has been found to occur in actual service 'on transmission lines. In such service, semicon-ducting glaze alternating current insulators have typically cracked through their heads in periods of two to five years.
Insulating glaze direct current units have similarly cracked in field service within several years under severe con-tamination conditions with consequent high leakage currents.
It will be ev.ident to those skilled in desiyn, manufacture, installation and maintenance of electrical insulators that various deviations may be made from the shown and described preferred embodiment, without departing from a main theme of lnvention set forth in the following claims.
In both the alternating current and direct current insulators, when the leakage current reaches the Portland cement, it flows through it, not just over the cement sur-face, inasmuch as moisture from the environment is present in the cement, thereby increasing the cement conductivity and enhancing the undesirable ionic electrochemical process of attack ~pon the galvanized pin.
Thus, there is a need for some means to eliminate ionic current flow through the Portland cement in both alternating current and direct current insulators that have either semiconducting or insulating glazes that are charac-teristic of high voltage insulators, to prevent pin growth and consequent insulator cracking.
STATEMENT O~ INVENTION
The foregoing difficulties cf prior art electrical insulators are solved in a particularly novel, useful and unobvious way through the teaching of the present invention.
~ccording to the present invention, Portland cement, such as neat Portland cement, is positioned in the pin recess formed by the porcelain insulator shell about the pin, thus securing the pin to the insulator shell for mechanical integrity. Then a conductive polymer composition, such as a phenolic polymer composition containing a phenolic resin, having a nonionic electrical conductivity substantially greater than the conductivity of Portland cement, is applied to connect the metal pin electrically to the glaze coating in a manner which substantially prohibits air from con-tacting the Portland cement, The recess forms a mouth and the polymer composition preferably covers that entire rnouth, The polymer composition used in the present inven-tion has reasonably high nonionic electrical conduc~ivity;
is resistant to the effects of weather; bonds well to glaze, cement and metal surfaces; and is relatively inexpensive and appliable conveniently in a factory. One preferred material is a conductive carbon filled phenolic resin manufactured and sold under the trademark CARBO-KOREZ by Atlas Minerals and Chemicals Company.
Therefore, a primary object of this invention is to provide a cementing arrangement, including Portland cement sealed by a conductive polymer composition, for use with alternating and direct current electrical insulators having a glaze coating on their porcelain insulator shells, to establish electrical connection to the hardware, without passage of significant leakage currents through the Portland cement.
It is a further object of this invention to provide a cement arrangement which has low shrinkage, so that suitable bonds are maintained between metal hardware and insulator surfaces.
It is still a further object of this invention to provide electrical insulators oE the type here contemplated which are well suited otherwise to perform their intended functions. The foregoing objects as well as other objects, features and advantages of this invention will be understood more fully from an accompanying drawing, from a detailed description of a preferred embodiment and from claims which are presented herewith.
The drawing and embodiment shown therein are for illustrative purposes only and are not meant to limit or redefine the invention as disclosed and claimed herein.
DESCRIPTION OF THE DRAWING
Fig. 1, the only figure, is a front view of a pre-ferred embodiment of an electrical insulator according to the present invention, the left half of the figure is shown in cross section.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the figure, a typical cap 11 and pin 12 type electrical insulator according to the present inven-tion is designated generally 13; however, it should be understood that the specific form of the ins~lator 13 is not profound so lon~ as features essential to the invention are found therein~ When assembled in a string, cap 11 is attached to a pin of an electrical insulator above it and the pin 12 is connected to a cap of an electrical insulator below it. A contoured porcelain insulator shell 14 is com-posed of a head 16 and a shed 17 and is coated for direct current applications on its exposed and sand band surfaces 19, 22 either with a conventional insulating glaze 18 that is not semiconductive or with a semiconducting glaze 18.
For alternating current insulation purposes, however, the insulating glaze 18 would be typically semicon-ductive,as no general problem exists of head cracking of alternating current conventional glaze insulators. Despite the differences in the electrical characteristics of the glaze 18 applied, either insulating or semiconductive, as mentioned above, nevertheless both glazes permit leakage currents causing the corrosion and cracking problems that the instant invention overcomes. Accordingly, although the balance of this detailed description is addressed to a direct current electrical insulator with insulating or semi-conducting glaze, the concept is equally applicable to alternating current electrical insulators in which the applied glaze 18 has insulating or semiconductive electrical properties.
The cap 11 is metal and is fixed to the sanded sur-ace 19 of the insulator shell 14 at the outer periphery of the head 16 by capping means in the form of cement 21. The pin 12 is metal and is fixed to the sanded surface 22 of the insulator shell 14 (in a pin recess 23 formed in the head 16) by means of cement 24, Both cement 21 and cement 24 preferably are neat Portland cement or silica or other suitable inert material filled Portland cement for securing mechanically and inex-pensively the cap 11 and the pin 12 respectiv~ly to the insulator shell 14D The desired non-ionic electrical con-nectio~ to the pin 12, is achieved by usa of a conductive polymer composition, such as a phenolic polymer composition 26, for example, CARBO-KOREZ preferably placed in a mouth 27 formed in the pin recess 23. It is preferable to have the conductive polymer composition cover the entire mouth 27.
By this arrangement leakage current flow between the glaæe 18 and the pin 12 is shunted around the cement 24. The leakage current will thus be a non-ionic current when carried by the conductive polymer composition 26 which com-position is not affected adversely by the passage of the leakage current therethrough, The conductive organic layer, iE it bonds well to the porcelain and to the pin, which is a prerequisite for its conduction of leakage current~ will also seal off the Portland cement rom the environment and 2~ 8 thus prevent ready replace~nent of the cementls moisture. In this way significant ionic conduction is stopped~ further prevent i ng pi n "growth"~
Various polymer compositions will perform satisfac-torily in this service, including silicone greases, epoxy and silicone rubber layers and phenolic polymers filled with (for example~ carbon particles. As has been mentioned above, an effective (and preferred) low cost commercial product suitable to serve as the conductive polymer composition is available under the tradernark CARBO-KOREZ corrosion proof cement sold by Atlas Minerals and Chemicals Company. The CARBO-KOREZ cement has a resistivity of about 10,000 ohm centimeters.
Accelerated long term tests have shown that direct current electrical insulators according to the present invantion perform extremely well. The units were energized with direct current for up to several years with periodic inspections carried out to observe changes and to measure conductivities. The acceleration was accomplished by increasing the average leakage current per unit time over what would be normal for standard insulating glazes. Signi-ficant current flow over insulating glazes occurs only under wet, cor,taminated conditions, an infrequent situation nor~
mally. Use of a semiconducting glaze permits continual significant leakage current flow without regard to weather or contamination, thus accelerating the DC insulator cracking problem.
Two comparative experiments were conducted in which semiconducting glaze insulators using conductive Portland cement in the conventional fashion were energized over a period of time. In the first experiment five tests of strings of units without the conducting organic cement layer were made with direct current for up to fifteen months with pin polarities and other test conditions and test results as shown:
EFFECTS OF ACCELERATED TESTING OF
DC ENERGIZED DISC SUSPENSION INSULATORS
No. of Polarity Visibly Test Discs of pin Months Cracked Product Type No. Used Electrode Energized Units,~
1 4 Positive 2.5 75 Without Con- 2 4 Positive 6.5 75 duc~ing Organic 3 12 Positive 8.5 67 Cement Layer 4 4 Positive 12 25 4 Negative15 0 In the second experiment, six tests similar to those in the first experiment, except for the application of a con ducting organic cement layer on each disc, were energized with the polarities and other test conditions as shown:
EFFECTS OF ACCELERATED TESTING OF
DC ENERGIzEn DISC SUSPENSION INSULATORS
No~ of Polarity Visibly Test Discs of pin Months Cracked Product Type No. Used Electrode Energiæed Units~
6 4 Negative 4~5 With conduct-7 4 Positive 4.5 0 ing Organic8 4 Negative 19 0 Cement layer9 4 Positive 19 0 10 4 Positive 28 0 11 5 Positive 40 0 . From the foregoing experimental data it can be seen that the preponderance of cracking of porcelains without an applied layer of conducting organic cement in direct current service is unreasonably high, with significant cracking occurring in a period of time cf about two and one-half to about twelve months. The variation in time for a given per-centage of units to crack is dependent upon a number of fac~
tors which vary in outdoor exposure, particularly the level of humidity present in the surrounding air during the expo-sure, In contrast, however, those porcelains in direct current service to which a layer of organic cement had been applied did not show visible cracks after as much as 40 months of testing.
The above experiments involving visually obvious cracking nevertheless do not entirely reveal the physical condition of the apparently intact units. When manufac~
tured, suspenslon units of the type tested have mechanical-electrical strengths well above their rated strength, usually averaging about 120~ or more of rating. The apparently intact units without the applied layer of organic cement were subsequently tested for their ultimate mechanical-electrical strength after the energization period. Of the units tes~ed in this fashion, the measured strength ranged from 74~ to 123~ of the rated strength~ As can be seen, many of the apparently intact uni~s were in fact weakened and might eventually be expected to crack.
To demonstrate the improvement possible by the new method described in the present invention, the four units from test No. 9 were tested for ultimate mechanical and electrical strength and showed 126~ to 154~ of the strength rating after the 19 months energization test.
This last set of results is in strong contrast to those obtained in the preceding experiments and exhibits the marked superiority of this invention.
Although the above accelerated experiments were performed with semiconducting glazed direct current insula-tors, identical cracking has been found to occur in actual service 'on transmission lines. In such service, semicon-ducting glaze alternating current insulators have typically cracked through their heads in periods of two to five years.
Insulating glaze direct current units have similarly cracked in field service within several years under severe con-tamination conditions with consequent high leakage currents.
It will be ev.ident to those skilled in desiyn, manufacture, installation and maintenance of electrical insulators that various deviations may be made from the shown and described preferred embodiment, without departing from a main theme of lnvention set forth in the following claims.
Claims (5)
1, In an electrical insulator comprising in combination:
a suitably contoured porcelain shell with a glaze thereover;
a metal cap and a metal pin each situated at a surface of the porcelain shell oppo-site to the other, the porcelain shell forming a pin recess receiving the pin;
capping means securing mechanically the cap to the shell; and Portland cement in the recess and about the pin securing mechanically to the shell the pin embedded in the recess; wherein the improvement comprises a conductive polymer composition which bonds to the cement and to the glaze on the porcelain shell and to the pin, the composition having long-term weather resistance and forming an electrical connection bet-ween the pin and the glaze and substantially sealing the Portland cement from contact with moisture in the air, the conductive polymer composition having a nonionic electrical conductivity greater than the conductivity of the Portland cement.
a suitably contoured porcelain shell with a glaze thereover;
a metal cap and a metal pin each situated at a surface of the porcelain shell oppo-site to the other, the porcelain shell forming a pin recess receiving the pin;
capping means securing mechanically the cap to the shell; and Portland cement in the recess and about the pin securing mechanically to the shell the pin embedded in the recess; wherein the improvement comprises a conductive polymer composition which bonds to the cement and to the glaze on the porcelain shell and to the pin, the composition having long-term weather resistance and forming an electrical connection bet-ween the pin and the glaze and substantially sealing the Portland cement from contact with moisture in the air, the conductive polymer composition having a nonionic electrical conductivity greater than the conductivity of the Portland cement.
2. The electrical insulator according to Claim 1 wherein said conductive polymer composition is a carbon-filled phenolic polymer composition.
3. The electrical insulator according to Claim 1 for use on positive polarity direct current transmission lines wherein said porcelain shell glaze further comprises a conventional insulating glaze.
4. The electrical insulator according to Claim 1 for use on alternating current transmission lines wherein said porcelain shell glaze further comprises a semiconduc-tive glaze.
5. The electrical insulator according to Claim 1 for use on positive polarity direct current transmission lines wherein said porcelain shell glaze further comprises a semiconductive glaze.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000451347A CA1221148A (en) | 1984-04-05 | 1984-04-05 | Glaze to pin connection for a high voltage insulator with embedded metal fitting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000451347A CA1221148A (en) | 1984-04-05 | 1984-04-05 | Glaze to pin connection for a high voltage insulator with embedded metal fitting |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1221148A true CA1221148A (en) | 1987-04-28 |
Family
ID=4127588
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000451347A Expired CA1221148A (en) | 1984-04-05 | 1984-04-05 | Glaze to pin connection for a high voltage insulator with embedded metal fitting |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1221148A (en) |
-
1984
- 1984-04-05 CA CA000451347A patent/CA1221148A/en not_active Expired
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