Study on Natural Contamination Depositing Characteristics of Insulator of EHV Transmission Line in High Altitude Salt Lake Area

In order to study the natural contamination deposited characteristics of insulators in salt lakes of Qinghai, China, sampling of insulator contamination was carried out on 750kV Chai-Yu I, II line and 330kV Ge-Yan line in Chaerhan Salt Lake area. The characteristic values such as equivalent salt density (ESDD), gray density (NSDD), gray salt ratio, coefficient on uneven distribution of upper and lower surfaces (K
E
,K
N
) were obtained from the test point, and the difference of pollution accumulation where inside and outside the salt lake area was compared. Furthermore, the chemical composition of the salt lake and saline-alkali land was measured, and analyzed the composition and content of soluble salt and insoluble substances in pollution layer on insulator Surface. The results show that the pollution level reaches above d and e both in salt lake and its vicinity, and the contamination on the surface of the insulator is rapidly accumulated in the salt lake environment. The ratio of gray to salt tends to be concentrated and less than 1, and the ratio on composite insulator is 2 to 3 times than porcelain. The degree of contamination on bottom surface of each shed is much larger than that of the top surface, and the average values of K
E
and K
N
are 2.33 and 1.42 respectively. The components of the pollution are mainly composed of CaSO
4
, NaCl and CaCl
2
, the insoluble matter are mainly CaO, SiO
2
, Fe
2
O
3
, and the coefficient of effective ESDD in this area can be taken as 0.8.