Omówiono znaczenie parametrów konstrukcyjnych izolatorów oraz procedurę doboru izolatorów przeznaczonych do pracy w warunkach zabrudzeniowych. Na tle rozwoju izolatorów napowietrznych przedstawiono koncepcję schodkowego kształtowania kloszy, podkreślając jej walory wynikające z analizy mechanizmu przeskoku zabrudzeniowego. Podano sposób wykonania badań porównawczych izolatorów gładkich LP 75/12, LSs 75/21 i schodkowych LPZS 75/12, LPZS 75/15. Wykazano, że napięcie przeskoku izolatorów schodkowych jest wyższe niż izolatorów gładkich zarówno w warunkach laboratoryjnych, jak i naturalnych.
Pollution flashover is complicated physical process. The existing mathematical models describe this phenomenon by means of a very simplified, flat, 2-dimensional model. Taking the 3-dimensional shape of insulator is very difficult. Due to the difficulties and problems related to experimental research during the study of this problem our knowledge is insufficient and the number of publications - small. The guiding principles introduced by IEC concerning the insulator shape are based rather on intuition than on reliable scientific basis. There are limited number of interesting insulator constructions, such as Spirelec (France) and Stair Insulator designed by prof. Skowroński. These insulators were patented in the sixties. At that time in Poland the interest of industry in applying special constructions was rather small. Technological and other problems caused the stopping of promising research in this direction. Nowadays, due to strong competition on the insulator market, better forming possibility of porcelain, digital data acquisition the study on the anti-pollution insulators can be applied in practice. The paper summarises of pollution performance of stair insulators conducted in Poland from 1966 to 1980 and explains theoretical fundamentals of pollution flashover. The insulators were tested in the laboratory and under natural conditions. The measurements showed that the pollution flashover voltage of stair insulator is higher by 20-30% than the flashover voltage of insulators with flat sheds.