Composite Insulators development history

Composite Insulators development history is not as longer as ceramic insulators. The composite insulators were widely used from the 1980's and the usage increased rapidly in the 1990's. Now, it is a common choice.

Composite Insulators

Composite Insulators development history:
The history of insulators began together with the development of electrical communications. Ceramic materials and rubber have been used in insulators from 1800 onward. In 1850, the first porcelain post insulators were introduced. A few years later, in 1858, glass pin-type insulators appeared. At the beginning of the 20th century, suspension insulators became available, and by 1910, cap and pin insulators already had geometrical designs very similar to those seen today. Between 1920 and 1950, there was an almost explosive development of different insulator types and designs with the overall goal to increase performance under contaminated conditions. The concepts employed to achieve this were different and sometimes quite unexpected. Most often, designers developed geometry of the insulator so as either to enlarge creepage or to increase the self-washing property. Other approaches involved the search for a means to actively combat dry-band arcing. Among the different proposals in this regard were included oil-bath insulators, water-repellent insulators, insulators with built-in heaters, and semi-conducting glaze insulators. In parallel, various efforts concentrated on improving the quality of the different materials and the effectiveness of manufacturing technologies.

The history of polymeric insulators began in the 1940s when organic insulating materials were used to manufacture high voltage indoor electrical insulators from epoxy resins. These materials were light weight, impact resistant, and could be used to form large complex parts [27]. Polymeric insulators for outdoor use were made feasible by the discovery in the 1950s that alumina trihydrate filler increases the tracking and erosion resistance of the polymer material. However, polymeric insulators for outdoor application on transmission lines were not developed until the late 1960s and 1970s. Polymeric insulators finally came into general use on transmission lines in the 1980s.

The first polymers used for electrical insulation were bisphenol and cycloaliphatic epoxy resins. Introduced commercially in the mid 1940s, bisphenol epoxy resins were the first polymers used for electrical insulation, and are still used to make electrical insulators for indoor applications. Cycloaliphatic epoxys (CE) were introduced in 1957, and were introduced in England for outdoor insulation in 1963. They are superior to bisphenol because of their greater resistance to carbon formation. However, the first commercial CE insulators in the U.S. failed shortly after installation in outdoor environments. Since then, new CE formulations have resulted in improved electrical performance.

In the early 1960s, distribution class (CE) insulators were first sold commercially in the U.S. under the name GEPOL. These units failed due to surface damage and punctures. CE was used later in experimental 500 kV station breaker bushings, and in 115 kV bushings in the 1970s, and for suspension insulators by Transmission Development Limited (TDL) of England. The TDL suspension insulators used slant sheds to provide natural washing of contamination. From the mid 1960s on, CE insulators were tested at up to 400 kV service voltage as suspension/strain insulators and cross-arms in the United Kingdom. For various reasons, including poor cold temperature performance and insufficient weight reduction, CE did not gain acceptance in the US for outdoor high voltage suspension insulators. But today, CE is used in indoor and even semi-enclosed power systems.

In the 1960s an insulator having porcelain sheds supported by an epoxy resin fiberglass rod was developed. It was not widely used because of developments in lighter weight polymeric insulating materials.

Polymeric outdoor insulators for transmission lines were developed as early as 1964 in Germany, and by other manufacturers in England, France, Italy, and the U.S. In Germany, units for field testing were provided in 1967. In the late 1960s and early 1970s, manufacturers introduced the first generation of commercial polymeric transmission line insulators.

The composite insulators were widely used from the 1980's and the usage increased rapidly in the 1990's. In 1980, Furukawa Electric was engaged in the development of inter-phase spacers to prevent galloping in power transmission lines, and at that time developed composite insulators that had the required light weight and flexibility. In 1991 the first composite insulators having a SIR housing were used as inter-phase spacers for 66 kV duty, and in 1994 their use was extended to 275 kV service with a unit 7 m in length. Excellent contamination and wetting performance, high ratios of strength to weight, vandalism resistance, easy transport and installation and obvious cost advantages over conventional ceramic insulators, especially in extra HV and ultra HV lines, are great attractions for utilities.


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