Study on the difference of chemical composition of insulator contamination on UHV‐AC and ‐DC transmission lines

Abstract

For the ultra high voltage (UHV)-DC and UHV-AC transmission lines, their contamination characteristics are different. Thus, researching the contamination polluted degree of UHV-AC and UHV-DC lines by geoaccumulation index and enrichment factor method is an ingenious method. This study analyses and compares the chemical composition of contamination on parallel energised UHV-DC (800 kV) and UHV-AC (1000 kV) overhead transmission lines. The results indicate that the major cations of insulator contamination are Ca2+ , and NH4 +, and the major anions of insulator contamination are SO4 2− and NO3 − both on UHV-DC and UHV-AC lines. For the UHV-DC line, the concentrations of the same cations on the insulator bottom surface are higher than that of on the top surface. However, on the UHV-AC line, the same cation concentrations on the bottom surface close to the one on the top surface. The metallic elements of Ca2+ and Zn2+ are in seriously polluted degree. Also, the polluted degree of contamination on UHV-DC insulator is more serious than UHV-AC insulator. This study considers that field charging plays an important role in accumulating contamination.