USING THE LABORATORY AGEING METHODS TO ESTIMATE POLLUTION STRENGT OF' COMPOSITE INSULATORS  Fulltext 

[ ZAJAC WIKTOR ] - Technical University Szczecin, Poland
[ SUBOCZ LECH ] - Technical University Szczecin, Poland

خلاصه مقاله:

The salt fog used as one the laboratory ageing factors constitutes the pollution environment having been found in several known pollution testing methods. Thus, it seems interesting to consider the possible estimations of insulator usability for different pollution conditions, basing on ageing test results.
1. General characteristics of pollution tests. The range of high voltage values is defined by IEC standards and Polish standards (81. They precise the way of prepearing the objects to be tested, introducing solid and semi-fluid pollution layers.The requirements for testing equipment define the source short--circuit current to Is > 5-1SA depending on R/X at condition of the alternating voltage of 50-60 ilz.The estimation of insulator being
tested is carried out by detemining theamount of 50% of flashover voltage according to the conductivity of solid and semifluid coating (acc, to IEC 60-1 1989, HD 588.1 S1)- minimum flashover voltage with repect to conductivity value}. When applying heavy salt mist then the cstimat.ton is based on the level of salt water having been withstood. Basing on the tests having been carried out so far it may be concluded that using solid or semi-fluid coatings might be valid enough when the porcelain is considered. However, tests carried out for artificial insulators, where their hydrophobie causes weak adherence of pollution coating it seems more convenient to apply the salt mist insted. Moreover, it seems also more reasonable method, as salt mist pollution allows to observe more non-uniform distribution of surface conductivity that gives the distribution similar to that being found in natural conditions. There is the possibility to correlate the ageing tests with the pollution ones. Using snlld layers seems to show some advantage, i.e. gives the better repeatibility of results and allows to use well known relationship between the layer conductivity and
pollution intensity, considered for natural conditions and pollution zones (9). The considerations lead Lo the attempt of explaining the correlation between testing methods and the results obtained for different foreign coatings, particularly the relation between the salinity having been withstood and the layer conductivity for various pollution zones.
2. Pollutian tests for selected composite insulator models. The pollution tests have been carried out using the composite epoxy insulator of 20 kV, shown at Fig-l, acting as a functional model, with regard to the standards mentioned above,for four different foreign layers:
- semi-fluid coating.
- solid coating.
- salt fog.
The methodology of the tests have complied the standards required [8]. Thus the tests included cyclic restoring of the pollution, layerr after each serles of flashover voltage moacuromoto, The cycle precedurce were adjected acordingly for each kind of pollution coating. The procedure for comifilling coonting inoluded like fil1wing.