A Practical Implementation of Statistical Principles to Dimension AC Line Insulators With Respect to Contaminated Conditions

A practical and simplified implementation is presented for the dimensioning of insulators with respect to contamination conditions based on statistical analysis. This simplified statistical method entails the selection of a minimum insulator withstand severity relative to the site contamination severity by making use of a coordination factor. Evidence is presented to show that the proposed dimensioning procedure agrees well with present IEC creepage distance requirements for disc overhead line insulators, based on a commonly used availability requirement and a realistic number of insulator strings on the line. Results from the contamination laboratory test can be used to verify the withstand characteristic of the selected insulators. This simplified method may be used for dimensioning overhead ac line insulation when there is insufficient statistical information available to warrant full risk analysis