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
presents an assessment of 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. |
