This International Standard specifies the procedure for a radio interference (RI) test carried out in a laboratory on clean and dry insulators at a frequency of 0,5 MHz or 1 MHz or, alternatively, at other frequencies between 0,5 MHz and 2 MHz. This standard applies to insulators for use on a.c. or d.c. overhead power lines and overhead traction lines with a nominal voltage greater than 1 000 V. In service the RI characteristics of an insulator may be modified by the ambient conditions, particularly rainfall and other moisture, and by pollution. It is not considered feasible to specify reproducible test conditions to simulate a range of ambient conditions. Hence only tests on clean and dry insulators are specified in this standard. NOTE The effects of insulator surface conditions, including pollution, are presented in CISPR 18-2:2017 clause 6.3