Application of risk criteria on transmission system insulation upgrade

The traditional criteria for the transmission system insulation specification is based upon recommendations such as that of IEC-815. The minimum specific leakage distance in this pattern is defined for different levels of contamination. Thus, the insulation system is designed according to the average contamination level in the region, and the result of the project depends largely on the average estimation. These deterministic criteria may result in an expensive or cheap system with excellent or poor operation performance. This paper focuses on the need for numerical criteria that can quantify the risk in each solution and help in the most suitable choice. The use of these criteria is just possible if we statistically figure out the main parameters - the pollution and relative humidity levels in the region - that control the insulator performance. Trough the use of these criteria one can accurately define the insulation system and estimate its performance. When the system is operating, the risk criteria can be used to improve the insulation performance by upgrading it. Thus, it is easier to figure out the pollution and humidity levels trough a simple field research. This model also enables us to estimate the natural washing periodicity.