The current paper presents an alternative and innovative technique to predict the severity of pollution of high voltage insulator using a higher harmonics component with up to the 7 th component of leakage current. The leakage current was measured using a current transformer and a shunt resistor. Next, laboratory tests were conducted on glass and porcelain insulators with artificial pollution under salt-fog pollution state which is further represented by three levels, namely light, medium, and high contamination. In this case, the formulation of a new severity of harmonic index refers to a ratio of the sum of 5 th and 7 th to the 3 rd harmonic component. More importantly, the new index managed to provide more accurate results when used as a diagnostic tool for the levels of pollution, compared to the ratio of the total harmonic distortion (THD) to the number of odd harmonics components (n) as the boundaries. In this case, the insulators were found to be in a clean and normal condition when the K (5+7)/3 value was greater than 3%. Contrastingly, the insulators were in an extreme condition when the K (5+7)/3 was lower than 3%. Nevertheless, there is a high probability of a flashover in glass and porcelain insulators if the K (5+7)/3 value is less than 2%. The present study shows the possibility of utilizing the value of strange harmonics up to the 7 th component of leakage current as the parameter for the monitoring of leakage current in overhead insulators in the presence of contamination. Overall, it can be concluded that the 3 rd , 5 th , and 7 th harmonics details extracted from the leakage current act as a good indicator for the level of contamination. INDEX TERMS Polluted insulators, leakage current, harmonic components, total harmonic distortion, fast fourier transform, salt fog.

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In the east-coast of Peninsular Malaysia high voltage insulators of power plants and factories suffered from rapid salt contamination accumulation because of heavy wind coming from the South China Sea. One attempt has been done at one of these plants which is located about 500 meters from the seashore to determine the severity of this kind of contamination and subsequently to determine a suitable mitigation method to overcome this problem. This work describes a mathematical model, which could help to determine the contamination level. It has been proven that the contamination severity predictive model is possible by using regression technique and it is a useful method for determining Equivalent Salt Deposit Density (ESDD).

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