Mousalreza Faramarzi Palangar - Golestan Electric Power Distribution Co. gorgan,Golestan Province, Iran
Sina Mohseni - Golestan Electric Power Distribution Co. gorgan,Golestan Province, Iran.
Mohammad Mirzaie - Golestan Electric Power Distribution Co. gorgan, Golestan Province, Iran.

In this paper, a new method is proposed for prediction of critical conditions on porcelain and glass insulators. In this regard, a variety of experiments were conducted on various kinds of porcelain and glass insulators under different environmental conditions and on their leakage current harmonic analysis. Then, the third to fifth harmonic ratio of the insulator’s leakage current (R3/5) has been proposed as the indicator of detection of critical conditions on the porcelain and glass insulators. Results of these experiments indicated that above harmonic ratio has a definite and constant trend against the changes in pollution type and the humidity rate. The performed experiments indicated that the increase of index R3/5 to more than one is indicative of critical conditions on the insulators and the high probability of flashover. Hence, a device is also designed and built for critical conditions detection and flashover prediction by using harmonic components of the leakage current and the defined index (R3/5). Application of this index can obtain the proper data of the insulators’ functional status and offer the suitable planning for duration of insulators to the repair and maintenance teams of the power transmission and distribution companies and thence increase the line reliability.

critical condition, pollution insulator, flashover,harmonic analysis