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Several methods are being used to evaluate the site pollution severity (SPS). The degree of pollution is generally determined by measuring equivalent salt deposit density (ESDD) on the insulators surfaces which are removed from existing transmission lines and/or field testing stations. Non-soluble material deposit density (NSDD) is also measured, especially in case that much dust or sand is expected to accumulate on the insulator surface. Moreover, pollution level or pollution index (PI) is assessed using directional dust deposit gauge (DDDG). In this paper, the pollution severity and pollution performance of porcelain insulators are measured in different areas with different degrees of pollution by measuring the ESDD and NSDD values. The measurements are conducted on three longrod porcelain insulators with alternating sheds that were removed from three existing towers. Moreover, seven DDDG stations are mounted in several locations with different topographies to evaluate the pollution severity. Based on the values of the ESDD and PI, the field measurements show that some zones are classified as light, others as medium and others as heavy zones of pollution. Accordingly, the corresponding specific creepage distances of the insulators for each zone are determined.