Development of Composite Insulators for Overhead Lines

Brittle fractures, on the other hand, occur mostly near the interface between the insulation material and the end-fitting, and provided

Development of Composite Insulators for Overhead Lines

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material, and can on occasion result in breakage of the insulator string. A drop in core strength or holding force of end-fitting can be countered by adopting an appropriate safety factor and using a reliable method of compression.

Brittle fractures, on the other hand, occur mostly near the interface between the insulation material and the end-fitting, and provided this area has been properly manufactured, the probability of their occurrence will be lower than that of electrical aging. To estimate service life from the electrical aspect, actual-scale composite insulators were exposed to electrical stress, and were subjected to an exposure test under a natural environment. A test chamber simulating environmental stress was also constructed, and accelerated tests were carried out according to international standards (IEC 61109 Annex C). Further, by comparing leakage current waveform and cumulative charge, which may be characterized as electrical aging, evaluation of composite insulator service life was carried out. Furthermore, since in Japan, a drop in insulation performance due to rapid pollution during typhoons is a familiar henomenon, an investigation was made based on the characteristics of leakage current obtained during a typhoon into the effect of rapid pollution on electrical aging in composite insulators.

4. CONCLUSION

 

Composite insulators are light in weight and have demonstrated outstanding levels of pollution withstand voltage characteristics and impact resistance, and have been widely used as inter-phase spacers to prevent galloping.

They have as yet, however, been infrequently used as suspension insulators. The composite insulators for suspension use that were developed in this work have been proven, in a series of performance tests, to be free of problems with regard to commercial service, and in 1997 were adopted for the first time in Japan for use as V-suspension and insulators for a 154-kV transmission line. To investigate long-term degradation due to the use of organic insulation material, outdoor loading exposure tests and indoor accelerated aging tests are continuing, and based on the additional results that will become available, work will continue to improve characteristics and rationalize production processes in an effort to reduce costs and improve reliability.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5. WORLD LIST

Conventionally

Outstanding

The Disadvantages

Fractured

To Degradation

Withstand

Polluted

a desire

overcome

drawbacks

appearance

suffered

outdoor

epoxy

tracking

concept

ethylene propylene rubber

ethylene propylene diene methylene

polytetrofluoro ethylene

silicone rubber

a core of fiber-reinforced plastic

to bear the tensile load

remedied

adhesion

penetration of moisture

the end-fittings

silicone rubber

permanent

hydrophobic

engaged

inter-phase spacers

galloping

housing

established

track record

consideration

transportation costs

delivered

Subsequently

trial basis

AC railway service

reinforcing fibers

forged steel

malleable cast iron

adopted

shed

extremely free

acceptance criteria

absence of adequate data

leakage distance

electrical stress

upward(downward)

adhesion

chemically bonded

penetration

electrical weak points

shank

molded

brittle fracturing

raises

hardware

hermetic seal

forth below

Overall performance

Voids

To possess long-term tensile

non-igniting

satisfactory arc

dry

harmful

compressive load

torsional force

leakage

predicting

Involves

Erosion

Occurring

Wet

Flashover

holding force

occasion

electrical aging

To estimate

actual-scale

exposure

environment

chamber simulating

Further

cumulative charge

evaluation

typhoons

familiar henomenon

investigation

obtained

proven

regard

 

 

6. REFERENCES

 

1) Sri Sundhar, Al Bernstorf, Waymon Goch, Don Linson, Lisa

Huntsman: Polymer insulating materials and insulators for high

voltage outdoor applications, IEEE International symposium on

EI, 1992.

2) Composite insulators for a.c. overhead lines with a nominal voltage

greater than 1000V: Definitions, test methods and acceptance

criteria, IEC61109, 1992-03.

3) Guide for the selection of insulators in respect of polluted conditions,

1986.

4) R. Kimata, L. Kalocsai, A. Bognar: Monitoring system for evaluation

of leakage current on composite insulators, 4th

International Conference on Properties and Applications of

Dielectric Materials, No.5125, 1994.

5) Nakauchi et al.: Natural environment exposure tests and accelerated

aging tests of silicone rubber insulators, High-voltage

Symposium, IEEJ, HV-97-41, 1997. (in Japanese)

6) Nakauchi et al.: Studies on pollution of silicone rubber insulators,

High-voltage Symposium, IEEJ, HV-98-73, 1998. (in

Japanese)

7) Nakauchi et al.: Comparison between loading exposure tests and

accelerated aging tests of silicone rubber insulators, Proceedings

of Electric Energy Workshop, No. 431,1997. (in Japanese)

 

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