Tomsk Polytechnic University

Electrotechnical Institute

Electrical Systems and

Networks Departments

Development of Composite Insulators for Overhead Lines

Made by

Group

Checked by

Tomsk

Contentss

1.	Introduction & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; .	3
2.	Design of composite dielectrics & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; … .	4
2.1.	Structure of composite dielectrics & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; …	4
2.2	Planing composite dielectrics & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; …	5
3.	Predicting service life & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; ..	8
4.	Decision & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; ..	10
5.	Wordss list & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ;	11
6.	Mentions & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; & # 8230 ; … …	13

1. Introduction

Overhead power transmittal lines require both overseas telegrams to carry on the electricity and dielectrics to insulate the overseas telegrams from the steel towers by which they are supported. The dielectrics have conventionally been made of ceramics or glass. These stuffs have outstanding insulating belongingss and weather opposition, but have the disadvantages of being heavy, easy fractured, and capable to debasement of their withstand electromotive force belongingss when polluted. There was hence a desire to develop dielectrics of a new construction utilizing new stuffs that would get the better of

these drawbacks.

The 1930s and ’40s saw the visual aspect of the first dielectrics to replace inorganic stuffs with organic, but these suffered jobs of conditions opposition, and their features were unsatisfactory for out-of-door usage. In the 1950s epoxy rosin dielectrics were developed, but they were heavy, suffered from UV debasement and trailing, and were ne’er put into existent service. By the mid-1970s a figure of new insulating stuffs had been developed, and the construct of a composite construction was advanced, with an dielectric lodging made of ethylene propylene gum elastic ( EPR ) , ethylene propene diene methylene ( EPDM ) linkage, polytetrofluoro ethene ( PTFE ) , silicone gum elastic ( SR ) or the similar, and a nucleus of fiber-reinforced plastic ( FRP ) to bear the tensile burden.

Since these stuffs were new, nevertheless, there were many proficient troubles that had to be remedied, such as adhesion between stuffs and incursion of wet, and the end-fittings, which transmit the burden, had to be improved. Since the 1980s, greater usage has been made of silicone gum elastic due to its conditions opposition, which is virtually lasting, and its hydrophobic belongingss, which allow betterment in the maximal withstand electromotive force of pollution, and this had led to an explosive addition in the usage of composite dielectrics.

In 1980, Furukawa Electric was engaged in the development of inter-phase spacers to forestall galloping in power transmittal lines, and at that clip developed composite dielectrics that had the needed visible radiation weight and flexibleness. In 1991 the first composite dielectrics holding a silicone gum elastic lodging were used as inter-phase spacers for 66-kV responsibility, and in 1994 their usage was extended to 275-kV service with a unit 7 m in length — the universe ‘s largest.

Therefore as composite dielectrics have established a path record in stage spacer applications and their advantages have been recognized, greater consideration has been given to utilizing them as suspension dielectrics with a position to cutting transit costs, simplifying building work and cut downing the cost of dielectrics in order to take down the costs of puting and keeping power transmittal lines.

Recently Furukawa Electric developed composite dielectrics for suspension and delivered, for the first clip in Japan, 154-kV tenseness dielectrics and V-type suspension dielectric strings. Subsequently they were besides used on a test footing as tension-suspension devices in 77-kV applications. Work is besides under manner on the development of composite dielectrics for 1500-V DC and 30-kV AC railroad service.

2. Design OF COMPOSITE INSULATORS

2.1 Structure of Composite Insulators

Figure 1. Structure of composite dielectric.

Typically a composite dielectric comprises a nucleus stuff, end-fitting, and a gum elastic insulating lodging. The nucleus is of FRP to administer the tensile burden. The reenforcing fibres used in FRP are glass ( E or ECR ) and epoxy rosin is used for the matrix. The parts of the end-fitting that transmit tenseness to the overseas telegram and towers are of bad steel, ductile dramatis personae Fe, aluminium, etc. The gum elastic lodging provides electrical insularity and protects the FRP from the elements. For this ground we at Furukawa Electric have adopted silicone gum elastic, which has superior electrical features and weather opposition, for usage in the lodging. Figure 1 shows the construction of a composite dielectric.

2.2 Designing Composite Insulators

An of import characteristic of the composite dielectrics developed here is that the design of the caducous constellation is highly free, owing to the usage of silicone gum elastic for the lodging. Based on past experience, IEC 60815 “ Guide for the choice of dielectrics in regard of contaminated conditions ” was adopted. Electrical and mechanical features were designed to fulfill the demands set Forth in IEC 61109 “ Composite dielectrics for a.c. overhead lines with a nominal electromotive force greater than 1000 V: Definitions, trial methods and credence standards ” .

With respect to pollution design, it has been suggested that because of the hydrophobic belongingss of silicone gum elastic, composite dielectrics can be designed more compactly than in the past, but because of the absence of equal informations it was decided in rule to supply as great or greater surface escape distances. The design value for escape distance was referenced to the value per unit electrical emphasis as determined in IEC 60815, adjusted upward or downward harmonizing to client demands.

Tensile breakdown strength was determined by using a safety factor to the long-run debasement in tensile breakdown strength.

The gum elastic and FRP of the lodging were required non merely to hold sufficient mechanical adhesion but to be chemically bonded, so as to forestall incursion of H2O at the interface. And because in general a big figure of interfaces may ensue in electrical weak points, Furukawa Electric has adopted a composite dielectric design in which the sheds and the shank are molded as a unit, ensuing in higher dependability.

The end-fittings comprise three elements, and have the greatest consequence on dielectric dependability. Specifically the incursion of wet at this point raises the danger of brickle fracturing of the FRP and the electrical field becomes stronger. For this ground the hardware is of field relaxing construction and the silicone gum elastic of the lodging is extended to the end-fitting to organize a hermetic seal. The end-fitting is connected to the FRP nucleus by a compaction method that maintains long-run mechanical features.

The design demands for composite dielectrics for 154-kV service are set away below.

& # 8226 ; Overall public presentation

( 1 ) To hold satisfactory electrical features in outdoor usage, and to be free of debasement and snap of the lodging.

( 2 ) To be free of the incursion of wet into the interfaces of the end-fitting during long-run outdoor usage.

( 3 ) To possess long-run tensile withstand burden feature

s.

( 4 ) To be free of nothingnesss and other defects in the nucleus stuff.

( 5 ) To be non-igniting and non-flammable when exposed to flare for short periods.

& # 8226 ; Electrical public presentation ( insulator entirely )

( 1 ) To hold a power-frequency moisture withstand electromotive force of 365 kilovolts or greater.

( 2 ) To hold a lightning impulse withstand electromotive force of 830 kilovolts or greater.

( 3 ) To hold a shift impulse withstand electromotive force of 625 kilovolts or greater.

( 4 ) To hold a withstand electromotive force of 161 kilovolts or greater when polluted with an tantamount salt deposition denseness of 0.03 mg/cm2.

( 5 ) To hold satisfactory discharges withstand features when exposed to a 25kA short-circuit current discharge for 0.34 sec.

( 6 ) Not to bring forth a aureole discharge when prohibitionist and under service electromotive force, and non to bring forth harmful noise ( insulator twine ) .

& # 8226 ; Mechanical public presentation ( insulator entirely )

( 1 ) To hold a tensile breakdown burden of 120 kN or greater.

( 2 ) To hold a flexing breakdown emphasis of 294 MPa or greater.

( 3 ) To demo no abnormalcy at any point after being subjected to a compressive burden equivalent to a bending minute of 117 N.
m for 1 min.

( 4 ) To demo no dielectric abnormalcy with regard to torsional force bring forthing a turn in the overseas telegram of 180 & # 176 ; .

( 5 ) To be for practical intents free of harmful defects with regard to repetitive strain caused by oscillation of the overseas telegram.

Table 1 shows the features of an dielectric

designed to fulfill these specifications.

3. PREDICTING SERVICE LIFE

The service life of a composite dielectric involves both electrical and mechanical facets. Electrical aging involves harm from eroding or tracking due to the thermal or chemical effects of discharge happening when the insularity stuff is polluted or wet, and may even ensue in flashover.

Mechanical aging includes long-run bead in the strength of the nucleus stuff or in the keeping force of the end-fittings, every bit good as brickle breaks of the nucleus stuff, and can on juncture consequence in breakage of the dielectric twine. A bead in nucleus strength or keeping force of end-fitting can be countered by following an appropriate safety factor and utilizing a dependable method of compaction.

Brittle breaks, on the other manus, occur largely near the interface between the insularity stuff and the end-fitting, and provided this country has been decently manufactured, the chance of their happening will be lower than that of electrical aging. To gauge service life from the electrical facet, actual-scale composite dielectrics were exposed to electrical emphasis, and were subjected to an exposure trial under a natural environment. A trial chamber imitating environmental emphasis was besides constructed, and accelerated trials were carried out harmonizing to international criterions ( IEC 61109 Annex C ) . Further, by comparing escape current wave form and cumulative charge, which may be characterized as electrical ripening, rating of composite dielectric service life was carried out. Furthermore, since in Japan, a bead in insularity public presentation due to rapid pollution during typhoons is a familiar henomenon, an probe was made based on the features of escape current obtained during a typhoon into the consequence of rapid pollution on electrical aging in composite dielectrics.

4. Decision

Composite dielectrics are light in weight and have demonstrated outstanding degrees of pollution withstand electromotive force features and impact opposition, and have been widely used as inter-phase spacers to forestall galloping.

They have every bit yet, nevertheless, been infrequently used as suspension dielectrics. The composite dielectrics for suspension usage that were developed in this work have been proven, in a series of public presentation trials, to be free of jobs with respect to commercial service, and in 1997 were adopted for the first clip in Japan for usage as V-suspension and dielectrics for a 154-kV transmittal line. To look into long-run debasement due to the usage of organic insularity stuff, out-of-door burden exposure trials and indoor accelerated aging trials are go oning, and based on the extra consequences that will go available, work will go on to better features and apologize production procedures in an attempt to cut down costs and better dependability.

5. WORLD LIST

Conventionally

Outstanding

The Disadvantages

Fractured

To Degradation

Withstand

Polluted

a desire

overcome

drawbacks

visual aspect

suffered

outdoor

epoxy

tracking

construct

ethylene propene gum elastic

ethylene propene diene methylene

polytetrofluoro ethylene

silicone gum elastic

a nucleus of fiber-reinforced plastic

to bear the tensile burden

remedied

adhesion

incursion of wet

the end-fittings

silicone gum elastic

permanent

hydrophobic

engaged

inter-phase spacers

galloping

lodging

established

path record

consideration

transit costs

delivered

Subsequently

test footing

AC railroad service

reenforcing fibres

forged steel

ductile dramatis personae Fe

adopted

shed

highly free

credence standards

absence of equal informations

escape distance

electrical emphasis

upward ( downward )

adhesion

chemically bonded

incursion

electrical weak points

shank

molded

toffee fracturing

rises

hardware

hermetic seal

Forth below

Overall public presentation

Nothingnesss

To possess long-run tensile

non-igniting

satisfactory discharge

prohibitionist

harmful

compressive burden

torsional force

escape

foretelling

Involves

Erosion

Happening

Moisture

Flashover

keeping force

juncture

electrical aging

To gauge

actual-scale

exposure

environment

chamber imitating

Further

cumulative charge

rating

typhoons

familiar henomenon

probe

obtained

proven

respect

6. Reference

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

Hunter: Polymer insulating stuffs and dielectrics for high

electromotive force outdoor applications, IEEE International symposium on

EI, 1992.

2 ) Composite dielectrics for a.c. overhead lines with a nominal electromotive force

greater than 1000V: Definitions, trial methods and credence

standards, IEC61109, 1992-03.

3 ) Guide for the choice of dielectrics in regard of contaminated conditions,

1986.

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

of leakage current on composite dielectrics, 4th

International Conference on Properties and Applications of

Dielectric Materials, No.5125, 1994.

5 ) Nakauchi et Al. : Natural environment exposure trials and accelerated

aging trials of silicone gum elastic dielectrics, High-voltage

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

6 ) Nakauchi et Al. : Surveies on pollution of silicone gum elastic dielectrics,

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

Nipponese )

7 ) Nakauchi et Al. : Comparison between lading exposure trials and

accelerated aging trials of silicone gum elastic dielectrics, Proceedings

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