JPH0463487B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Field of Application> This invention is applicable to insulators, especially electric fittings for push-in metal fittings.
A high voltage ceramic insulator with a layer of a conductive phenolic polymer composition for inhibiting chemical corrosion. <Prior Art> Although electric insulators, commonly known as suspended insulators, can be used individually, they are usually
Formed as part of a string that supports electrical wires from a support structure. Usually, such suspension insulators are
It includes two metal members fixed to opposing surfaces of a suitably shaped insulator shell, one of which is embedded in a cavity of the porcelain member with cement. With this configuration, the metal members are separated and insulated from each other. The metal members, typically an upper cap and a lower pin, are each typically secured to one of the opposing surfaces of the insulator shell by a layer of cement or other suitable material. . The exposed surfaces of the porcelain shell are usually coated with a glaze. AC lines using suspended insulators coated with semiconductor glazes suffer from head cracking problems. In the case of alternating current, the cracking was thought to be due to an increase in leakage current due to the semiconductor glaze. High voltage DC power transmission lines are known to develop cracks in the suspended insulators after some period of use. This cracking can be caused by ionic currents passing through the moisture in the Portland cement. Since this current is always in the same direction in the DC system, due to the resulting electrochemical reaction, said pin undergoes corrosion and if the pin is the positive or anode terminal of said insulator, it will have a "growth" effect. receive. This "growth" induces tensile stress in the ceramic insulator that causes the cracking phenomenon. One theory developed to explain this cracking phenomenon of DC insulators using standard insulating glazes states that the surface leakage current of the insulator is caused by harsh environmental conditions typified by moisture and contamination. increase In both AC and DC insulators, when the leakage current reaches the Portland cement, it not only flows on the surface of the cement, but also due to the presence of moisture from the environment in the cement. flows through the interior of the This increases the conductivity of the cement and promotes undesirable electrochemical corrosion effects on the energized pins. Therefore, the ionic current passing through the Portland cement for AC and DC insulators includes a semiconductor or insulator glaze that is normally provided on high voltage insulators to prevent pin growth and consequent cracking of the insulator. Some means are needed to eliminate this. <Problems to be Solved by the Invention> The present invention has been made to solve the above-mentioned problems. Provided is an AC and DC insulator, in particular a DC insulator, comprising Portland cement sealed with a glaze covering a porcelain shell and a conductive phenolic polymer composition to establish There is a particular thing. Another object of the present invention is to provide a direct current insulator in which the cement part shrinks less and an appropriate bond is maintained between the metal member and the surface of the insulating part. <Means for Solving the Problem> According to the present invention, this problem is achieved by providing an appropriately shaped porcelain outer shell having a semiconductor glaze on its outer surface, and opposing surfaces of the outer shell. a metal cap disposed thereon and a metal pin, the pin being housed in a pin recess in the outer shell, and further for mechanically fixing the cap to the outer shell; and Portland cement, which is arranged around the pin in the pin recess and mechanically fixes the pin housed in the pin recess to the outer shell, the cement; It is fixed to the semiconductor glaze on the porcelain shell and the pin, exhibiting long-term weather resistance, forming a path for leakage current from the pin through the semiconductor glaze to the cap, and preventing contact with environmental moisture. a carbon-mixed conductive phenolic polymer composition that substantially seals the Portland cement from contact, the phenolic polymer composition having a non-ionic conductivity substantially higher than the conductivity of the Portland cement; The present invention is solved by an insulator for use in a DC power transmission line, which is characterized by exhibiting the following characteristics. The polymer compositions used in accordance with the invention exhibit a reasonably high non-ionic conductivity, are weather resistant, adhere well to glazes, cement and metal surfaces, are relatively inexpensive and easy to use. suitable for A preferred material is Atlas Minerals &
Trademark CARBO− by Chemicals Company
This is a carbon-containing conductive phenolic resin manufactured and sold under the KOREZ brand. <Embodiment> An embodiment of the present invention will be described below with reference to the drawings. In the accompanying drawings, a conventional cap 11-pin 12 type insulator according to the invention is designated generally by the numeral 13. When assembled as a string, cap 11 is attached to the insulator pin above it, and pin 12 is connected to the insulator cap below it. A suitably shaped porcelain insulator shell 14, consisting of a head 16 and a cap 17, is used for direct current;
The exposed, roughened surfaces 19, 22 are covered with a semiconductor glaze 18. As mentioned above, semiconductor glaze 18 tolerates leakage currents that cause corrosion and cracking problems. It is this problem that the present invention seeks to overcome. The cap 11 is made of metal, and the cement 21
It is fixed at the roughened surface 19 of the shell 14 to the outer periphery of the head 16 by covering means in the form of a . The pin 12 is made of metal, and the cement 2
4 (in the pin recess 23 formed in the head 16) by the roughened surface 22 of the shell 14
It is fixed at . The cements 21 and 24 are preferably pure Portland cement or silica or other suitable inert material in order to mechanically and inexpensively fix the cap 11 and pin 12, respectively, to the outer shell 14 via the semiconductor glaze 18. Portland cement mixed with other materials. The desired non-ionic electrical connection with the pin 12 is provided by the CARBO, which is preferably located in a mouth 27 formed in the pin recess 23.
- achieved by the use of electrically conductive phenolic polymer compositions such as KOREZ™. It is desirable to arrange the conductive phenol polymer composition so as to cover the entire mouth portion 27 . With this arrangement, leakage current between glaze 18 and pin 12 is shunted around the cement 24. Thus, the leakage current will become a non-ionic current when carried by the conductive phenolic polymer composition 26 (phenolic polymer composition 26).
is not adversely affected by leakage currents passing through it). This layer of conductive organic material, if it is well bonded to both the porcelain and the pin 12 (this is an essential requirement for conducting leakage currents), will keep the Portland cement away from the environment. seals and thereby prevents rapid displacement of moisture in the cement. This stops the large ionic conduction and better inhibits pin "growth". As mentioned above, a suitable inexpensive commercially available conductive phenolic polymer composition is the corrosion-resistant cement CARBO-KOREZ (trade name) mentioned above. This CARBO-KOREZ cement is approximately
It has a resistivity of 10000 ohms/cm. Accelerated long-term tests have confirmed that the DC insulator according to the invention exhibits very favorable behavior. The unit under test was energized with direct current for several years, during which time changes in condition were observed and
and conducted periodic inspections to measure conductivity. The acceleration was achieved by increasing the average leakage current per unit time above the standard value for standard insulating glazes. High currents on insulating glazes occur only under moist or dirty conditions, but these conditions do not occur frequently, and the use of semiconductor glazes is continuous regardless of weather or dirt. allow large leakage current flows, thereby accelerating the problem of DC insulator cracking. Two types of tests were conducted in which an insulator having the structure depicted in the sent drawings described in the above examples was energized for a certain period of time. In the first test, five tests of a series of units without Phenol Polymer Composition 26 were conducted with direct current for up to 15 months under the pin polarity and test conditions shown in the following table. Got the test results.

[Table] In the second test, phenolic polymer composition 26
The test was conducted six times under the same polarity and other test conditions as in the first test above, except that the following test was used, and the test results shown in the following table were obtained.

【table】

[Table] As can be seen from the test data in the previous table, in the case of direct current use, if phenol polymer composition 26 is not used, the rate of cracking in porcelain will be extremely high.
Large cracks occur over a period of approximately 2.5 to 12 months. Differences over time in the value of a certain percentage of cracks that occur in a unit depend on various factors that vary with outdoor exposure, particularly the level of moisture present in the surrounding air during the exposure period. However, when an insulator containing Phenol Polymer Composition 26 in porcelain was used for direct current use, no cracks were observed visually even after a test period of 40 months. The above test, which includes visually obvious cracks, is also not completely indicative of the physical condition of the apparently intact unit. Suspension units of the type tested, as manufactured, have mechanical and electrical strengths that are significantly higher than their rated strength (usually on average about 120% or more of their rated strength). The apparently intact units without phenolic polymer composition 26 were tested for final mechanical and electrical strength after the energization period described above. The measured strength of units tested in this way is below the rated strength.
It was 74-123%. As is clear, many apparently intact units have been effectively weakened and
It is in a state where it is prone to cracking. Four units from Test No. 9 were tested for ultimate mechanical and electrical strength and exhibited 126-154% of rated strength after 19 months of stress testing. Although the above accelerated test was for a DC insulator with a semiconductor glaze, similar cracking has been found to occur in actual use on power transmission lines. In this use, AC insulators with semiconductor glazes typically develop cracks in their heads within two to five years. Direct current units with insulating glazes also crack in outdoor use within a few years under highly contaminated conditions with the result of high leakage currents. It should be noted that this invention is not limited to the above embodiment, and it will be obvious to those skilled in the art that various deviations can be made from this embodiment without departing from the gist of the invention. <Effects of the Invention> Since the insulator of the present invention includes a semiconductor glaze on the outer shell and a carbon-containing conductive phenol polymer composition with excellent weather resistance fixed to the pin, the insulator of the present invention has a semiconductor glaze on the outer shell and a carbon-containing conductive phenol polymer composition with excellent weather resistance. It is possible to prevent moisture from permeating into the insulator, so that no ionic leakage current occurs, and cracking of the insulator can be prevented. Additionally, since this phenol polymer composition is made conductive by mixing carbon, it is possible to form a current path for nonionic current between the pin and the glaze made of semiconductor material without degrading the semiconductor glaze. . Therefore, during this time, there is no deterioration of the semiconductor glaze or electrochemical corrosion of the pins.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of an insulator according to the present invention, and the left half of the drawing is shown in cross section. 11... Cap, 12... Pin, 13... Insulator, 14... Porcelain shell, 18... Semiconductor glaze, 21, 24... Portland cement,
23...Pin depression, 26...Phenol polymer composition.

Claims (1)

[Scope of Claims] 1. A suitably shaped porcelain shell with a semiconductor glaze disposed on its outer surface; a metal cap and a metal cap disposed on opposing surfaces of the shell; and a fixing means for mechanically fixing the cap to the outer shell, the pin being housed in a pin recess in the outer shell, and a fixing means for mechanically fixing the cap to the outer shell; Portland cement disposed around the pin recess and mechanically fixing the pin housed in the pin recess to the shell; the cement, the semiconductor glaze on the porcelain shell; affixed to the pin, exhibiting long-term weather resistance, forming a path for leakage current from the pin, through the semiconductor glaze, to the cap, and substantially sealing the Portland cement from contact with environmental moisture; Use in a DC power transmission line having a carbon-loaded conductive phenolic polymer composition, the phenolic polymer composition exhibiting a nonionic conductivity substantially higher than the conductivity of the Portland cement. Insulators for