Relationship between Leakage Current and Diameter of Composite Insulators during the Early Period of Tracking Wheel Test

Summary

The tracking wheel test described in IEC Technical Report 62730 provides a method for composite insulators to assess their resistance to tracking and erosion in order to reject materials or designs which are inadequate. However, the method is only suitable for long rod insulators and some other insulators with relatively small diameters. Because for large-diameter composite insulators, such as post insulators and cross-arms used in ultrahigh voltage systems, hollow core insulators etc., their surface resistivity is smaller than that for small-diameter ones, therefore leakage current is larger under the same test conditions, which may cause tracking and erosion of large diameter composite insulators to appear earlier, and more serious. In addition, it's rather difficult to make the large and heavy test samples to rotate around the shaft. In order to conduct tracking wheel teats on large-diameter composite insulators, some parameters and test arrangement in IEC Technical Report 62730 should be adjusted. In this study, a tracking wheel test device was designed and constructed in accordance with IEC Technical Report 62730. Some adjustments were made in order to adapt the test requirement of the heavy large-diameter insulators. Leakage current was measured during the whole period of test. Some exploratory work was carried out firstly and the relationship between leakage current and diameter of insulators under different concentration of NaCl solutions ionized during the early period of tracking wheel test was discussed in detail. The results show that under the same NaCl content of the solution, different diameter composite insulators have different peaks of leakage current, furthermore, the peaks of leakage current were approximately proportional to the equivalent diameters of composite insulators. Leakage current would be too large for the insulator with the largest diameter according to the original test parameters in IEC Technical Report 62730, it means that one or more of the test parameters should be adjusted in a certain way.

Additional informations

Authors

Tamus Zoltán Ádám, Sarfi Vahid, Khan Umer Amir, Lee Jong Geon, Csányi Gergely Márk, Vahidi Farzaneh, Roesner Michael