Contamination on outdoor insulators enhances the chances of flashover and can lead to
transmission line outages and reduced system reliability. In practice, various
contaminant types, usually classified as soluble and insoluble, settle on outdoor
insulators and increase the possibility of flashover. The paper assesses the flashover
performance of such insulators in Egypt; in view of the nature and composition of
contaminants accumulated on their surfaces. To quantify these contaminants, numerous
samples are gathered from different regions of the country and subjected to a
comprehensive chemical analysis at the scale analysis laboratory of the Egyptian
Electricity Transmission Company. Measurements of equivalent salt deposition density
(ESDD) surface conductivity (SC), maximum leakage current (MLC) and flashover
voltage (FOV) were conducted and correlated to the contamination constituents. The
study utilized IEC standard cap-pin suspension insulators which were hanged in regions
of different pollution levels and nature. Regression models for predicting the flashover
voltage as related to ESDD and MLC as related to surface conductivity were developed.
The models are validated through statistical analysis as well as comparison with
measured data. The results from this work are useful for utilities to take adequate
measures to improve the efficiency of their transmission systems through scheduling of
their insulator maintenance strategy and selecting the appropriate insulator design for
different system voltages and regions. |
