GB2157094A - Improved glaze to pin connection for a high voltage insulator with embedded metal fitting - Google Patents
Improved glaze to pin connection for a high voltage insulator with embedded metal fitting Download PDFInfo
- Publication number
- GB2157094A GB2157094A GB08408220A GB8408220A GB2157094A GB 2157094 A GB2157094 A GB 2157094A GB 08408220 A GB08408220 A GB 08408220A GB 8408220 A GB8408220 A GB 8408220A GB 2157094 A GB2157094 A GB 2157094A
- Authority
- GB
- United Kingdom
- Prior art keywords
- glaze
- pin
- polymer composition
- shell
- electrical insulator
- 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.)
- Granted
Links
- 239000002184 metal Substances 0.000 title claims abstract description 14
- 239000012212 insulator Substances 0.000 title abstract description 34
- 239000000203 mixture Substances 0.000 claims abstract description 20
- 239000011398 Portland cement Substances 0.000 claims abstract description 18
- 229910052573 porcelain Inorganic materials 0.000 claims abstract description 15
- 229920001940 conductive polymer Polymers 0.000 claims abstract description 11
- 229920000642 polymer Polymers 0.000 claims abstract description 8
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims abstract description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 4
- 239000004568 cement Substances 0.000 claims description 23
- 239000000615 nonconductor Substances 0.000 claims description 19
- 230000005540 biological transmission Effects 0.000 claims description 5
- 230000007774 longterm Effects 0.000 claims description 2
- 238000007789 sealing Methods 0.000 claims 1
- 238000005336 cracking Methods 0.000 abstract description 14
- 238000006056 electrooxidation reaction Methods 0.000 abstract description 2
- 229920001296 polysiloxane Polymers 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 13
- 239000010410 layer Substances 0.000 description 10
- 238000002474 experimental method Methods 0.000 description 7
- 239000000725 suspension Substances 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 238000011109 contamination Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000001965 increasing effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 229920001568 phenolic resin Polymers 0.000 description 2
- 239000005011 phenolic resin Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000012935 Averaging Methods 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000013065 commercial product Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000012044 organic layer Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B17/00—Insulators or insulating bodies characterised by their form
- H01B17/42—Means for obtaining improved distribution of voltage; Protection against arc discharges
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B17/00—Insulators or insulating bodies characterised by their form
- H01B17/50—Insulators or insulating bodies characterised by their form with surfaces specially treated for preserving insulating properties, e.g. for protection against moisture, dirt, or the like
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Insulators (AREA)
Abstract
A contoured porcelain insulator shell 14 is coated with a glaze 18 for direct current or alternating current application and has a metal cap 11 and a metal pin 12 which is secured with Portland cement 24. A conductive polymer composition 26 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 porcelain insulator. The glaze may be semiconducting. The polymer composition is preferably phenolic filled with carbon; silicones may also be used. <IMAGE>
Description
SPECIFICATION
Improved glaze to pin connection for a high voltage insulator with embedded metal fitting
This invention relates to electrical insulators and, more particularly, to a high voltage ceramic insulator with a layer of conductive polymer composition to inhibit electro-chemical corrosion of an embedded metal fitting.
Electrical insulators commonly known as suspension insulators may be used individually, but usually form part of a string to support an electrical conductor from a supporting structure. Generally such a suspension insulator comprises two metal hardware members secured to opposite surfaces of a suitable contoured insulator shell, one hardware member being embedded by means of cement in a cavity in the porcelain member. By this arrangement the metal hardware 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 semiconducting glaze.
High voltage direct current power transmission lines are known to experience cracked suspension insulators after some period of service. 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, the resulting electrochemical 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 insultors using standard insulating glazes, adverse environmental conditions, of which moisture and contamination are typical, increase the insulator surface leakage 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 surface, 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 upon 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 characteristic of high voltage insulators, to prevent pin growth and consequent insulator cracking.
The foregoing difficulties of prior art electrical insulators are solved in a particularly novel, useful and unobvious way through the teaching of the present invention. According 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 contacting the Portland cement. The recess forms a mouth and the polymer composition
preferably covers that entire mouth.
The polymer composition used in the present invention has reasonably high nonionic electrical conductivity; 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 of 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.
Figure 1, the only figure, is a front view of a preferred embodiment of an electrical insulator according to the present invention, the left half of the figure is shown in cross section.
Referring to the figure, atypical cap 11 and pin 12 type electrical insulator according to the present invention is designated generally 13; however, it should be understood that the specific form of the insulator 13 is not profound so long 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 composed 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 semiconductive, 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 semiconducting 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 surface 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 inexpensively the cap 11 and the pin 12 respectively to the insulator shell 14. The desired non-ionic electrical connection to the pin 12, is achieved by use 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 glaze 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 composition is not affected adversely by the passage of the leakage current therethrough.The conductive organic layer, if 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 from the environment and thus prevent ready replacement of the cement's moisture. In this way significant ionic conduction is stopped, further preventing pin "growth".
Various polymer compositions will perform satisfactorily 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 trademark 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 invention 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. Significant current flow over insulating glazes occurs only under wet, contaminated conditions, an infrequent situation normally. 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
ducting Organic 3 12 Positive 8.5 67
Cement Layer 4 4 Positive 12 25
5 4 Negative 15 0
In the second experiment, six tests similar to those in the first experiment, except for the application of a conducting organic cement layer on each disc, were energized with the polarities and other test conditions 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,%
6 4 Negative 4.5 0
With conduct- 7 4 Positive 4.5 0
ing Organic 8 4 Negative 19 0
Cement layer 9 4 Positive 19 0
10 4 Positive 28 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 of about two and one-half to about twelve months.
The variation in time for a given percentage of units to crack is dependent upon a number of factors which vary in outdoor exposure, particularly the level of humidity present in the surrounding air during the exposure.
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 manufactured, suspension units of the type tested have mechanical-selectrical 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-selectrical strength after the energization period. Of the units tested in this fashion, the measured strength ranged from 74% to 123% of the rated strength. As can be seen, many of the apparently intact units 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 insulators, identical cracking has been found to occur in actual service on transmission lines. In such service, semiconducting 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 fieldsservice within several years under severe contamination conditions with subsequent high leakage currents.
It will be evident to those skilled in design, 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 invention set forth in the following claims.
Claims (6)
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 opposite 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 comprising 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 between 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 semiconductive 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.
6. An electrical insulator substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08408220A GB2157094B (en) | 1984-03-30 | 1984-03-30 | Improved glaze to pin connection for a high voltage insulator with embedded metal fitting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08408220A GB2157094B (en) | 1984-03-30 | 1984-03-30 | Improved glaze to pin connection for a high voltage insulator with embedded metal fitting |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8408220D0 GB8408220D0 (en) | 1984-05-10 |
| GB2157094A true GB2157094A (en) | 1985-10-16 |
| GB2157094B GB2157094B (en) | 1988-03-02 |
Family
ID=10558913
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08408220A Expired GB2157094B (en) | 1984-03-30 | 1984-03-30 | Improved glaze to pin connection for a high voltage insulator with embedded metal fitting |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2157094B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007120076A1 (en) * | 2006-04-14 | 2007-10-25 | Zakrytoe Akcionernoe Obschestvo 'armaturno-Izolyatornyi Zavod' | High-voltage suspended insulator |
| CN104733139A (en) * | 2015-02-27 | 2015-06-24 | 南方电网科学研究院有限责任公司 | Organic protective sleeve for extremely severe corrosion area of insulator metal accessory |
| CN104733137A (en) * | 2015-02-27 | 2015-06-24 | 南方电网科学研究院有限责任公司 | Direct-current disk-shaped suspension type porcelain and glass insulator for metal accessory corrosion extreme region |
| CN104733136A (en) * | 2015-02-27 | 2015-06-24 | 南方电网科学研究院有限责任公司 | DC disk-shaped suspension porcelain and glass insulator |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1398306A (en) * | 1972-05-10 | 1975-06-18 | Doulton & Co Ltd | Electrically conductive cement |
-
1984
- 1984-03-30 GB GB08408220A patent/GB2157094B/en not_active Expired
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1398306A (en) * | 1972-05-10 | 1975-06-18 | Doulton & Co Ltd | Electrically conductive cement |
Non-Patent Citations (1)
| Title |
|---|
| ERRI DC WORKSHOP, NOVEMBER 1985 E.S. WHEELER & A.C. BAKER }A PRACTICAL SOLUTION TO ELIMINATION OF CERAMIC SUSPENSION INSULATOR HEAD CRACKING UNDER LONG TERM DC ENERGISATION * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007120076A1 (en) * | 2006-04-14 | 2007-10-25 | Zakrytoe Akcionernoe Obschestvo 'armaturno-Izolyatornyi Zavod' | High-voltage suspended insulator |
| CN104733139A (en) * | 2015-02-27 | 2015-06-24 | 南方电网科学研究院有限责任公司 | Organic protective sleeve for extremely severe corrosion area of insulator metal accessory |
| CN104733137A (en) * | 2015-02-27 | 2015-06-24 | 南方电网科学研究院有限责任公司 | Direct-current disk-shaped suspension type porcelain and glass insulator for metal accessory corrosion extreme region |
| CN104733136A (en) * | 2015-02-27 | 2015-06-24 | 南方电网科学研究院有限责任公司 | DC disk-shaped suspension porcelain and glass insulator |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2157094B (en) | 1988-03-02 |
| GB8408220D0 (en) | 1984-05-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PE20 | Patent expired after termination of 20 years |