Procecdings of 2005 Inicmational Symposium on Electrical Insulating Materrals. June 5-9, 2005, Kiiakyushu. Japan ES-6

ENVtRONMENTAL AGING OF POLYMERIC INSULATORS IN PAHSTAN

Mohammad Amin Univ. of Engg. And Tech. Taxila, Pakistan

Polymeric materials in electric power applications has increased rapidly. Special intcrest has been paid on the use of polymeric materials for high voltage outdoor insulators. Some of the major advantages of the polymeric insulators over the traditional ceramic ones are their light weight and lower cost. They are easier and cheaper to store, transport and install. However, the polymeric materials are more prone to deterioration and chemical alterations which can seriously reduce the reliability and life-time of the insulator in service. The features of the weather, Chemical Pollutants and Others that degrade polymers are ,

1. Heat, Light and Moisture. 2. Sulpherdioxide,Ozone.Oxygen., 3. Wind/Dust/Microbiological

0rganism.Rain & precipitation. The weather exposed part of the polymeric Insulators should possess high hydrophobicity in order to give maximum performance. Necessary demands on materials for such usage are non- polarity and an ability to withstand discharges in wet, salty, acidic, tropical or arctic environment. Difficult environmental conditions can, however, causc a permanent or temporary loss of hydrophobicity. Polymeric insulators are therefore today often pessimistically

designed for an assumed hydrophilic state. This means that the benefits of using polymeric material instead of porcelain and glass are not utilized to their full potential. Properly used, these materials can offer advantages such as more compact design, reduced maintenance and lower total operating costs. Recently, polymeric materials. Such as silicone rubber, EPDM, EP/silicone alloy have become the materials of choice for insulators, surge arrester housing, cable terminations and bushings. Industry has adapted from ceramic to polymeric insulators when opportunity presented itself in the form of light weight, aesethic and hydrophobic materials, with superior performance against contamination. Because of these reasons many countries like America Sweden Saudi Arabia Japan etc. are now using composite insulators .In Pakistan no composite insulators are being used

.By this research feasibility of use of composite insulators in Indutrial /coastal/clean areas of Pakistan under Energised and unenergised conditions will be studied according to following Plan.

Field Research program

Three sites: (i) Coastal (ii) Industrial, and (iii) Inland are being considered. At each site, we plan to test (4) different types of insulators . In addition, a few rectangular plats and cylindrical samples will also be exposed at the three sites for natural aging.

Exposures at a coastal site Test voltage ; 10 kV Source capacity : 2 kVA Creepage distance : 50 mm / kV

Insulator type :4 (these could be of different design or of different material formulations). Insulating Plates:

2 (Rectangular 150x300~5 mm). 2 (Cylindrical I x @ = 300x 26 mm).

Parameters to be recorded : Leakage current (to see the effect of electrical stress).

Un-energized aging (excluding electrical SWESS).

ESDD / NSDD measurements. Metrological parameters (data of the nearest station to be utilized).

Un-energized exposure of insulating plates.

Exposure at industrial site

Test voltage : 10 kV Test source capacity : 2 kVA Test creepage : 3 5 4 0 mm / kV Insulator type @om different design

and or different material formulations). Type and size of insulating plates :

a) Rectangular 150x300~5 mm

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b) Cylindrical Ix@ 300x26 mm

Parameters to be measured Leakage current (to see the effect of

eIearical stress).

Un-energized aging (excluding electrical stress). ESDD I NSDD measurements. Metrological parameters (data of the nearest station to be utilized).

Un-energized exposure of insulating plats.

Exposure at Inland test site

This test site will be located on the premises of UET, Taxila. The test station will have a similar design as given for industrial and coastal test

sites. However, the test creepage will be 25-30 mm / kV. The requirements of insulators and insulating plates will be similar.

Laboratory Investigation

Test voltage : IO kV Source capacity : 5 kVA Insulators to be studied : 4 types x 3 of

4 types x 3 of

(SO mm / kV.

(30 mm / kV)

Parameters to be measured : ESDD / NSDD Leakage Current Artificial aging through different means.

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