Abstract： AS 4436:1996 pdf download.Guide for the selection of insulators in respect of polluted conditions. The evaluation of the pollution severity can he made with an increasing degree of confidence: — qualitatively from indications given in Tab...

AS 4436:1996 pdf download.Guide for the selection of insulators in respect of polluted conditions.

The evaluation of the pollution severity can he made with an increasing degree of confidence:

— qualitatively from indications given in Table I,

— from information on the behaviour of insulators from lines and substations already in service on that site (see Appendix A), for evaluation by experts in this held.

— from measurements in situ.

For measurements in situ, different methods are generally used. They arc:

1) volume conductivity for the pollutant collected by means of directional gauges:

2) Equivalent Salt Deposit Density on the insulator surface (ESDD method):

3) total number of flashovers of insulator strings of various lengths:

4) surface conductance of sample insulators:

5) leakage current of insulators subjected to service voltage (highest current values during subsequent time intervals.

The first two methods do not require expensive equipment and can he easily performed. The volume conductivity method gives no

direct information by itself on the frequency and on the severity of the contamination events on a natural site. The ESD method

characterlies the pollution severity of the site. Information on wetting shall be separately obtained.

The accuracy of these methods depends upon the frequency of measurement. However, for the FSDI) method, an automatic measuring

system has been developed and therefore pollution severity can be measured continuously, in order to hind, for example. the

suitable timing of washing.

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