The behavior of high voltage insulators during the up-and-down procedure

Industrial tests of high voltage equipment insulation at impulse voltages are carried out following rigorously described procedures and require, as a rule, long time duration and, implicitly, significant costs. Reducing the duration of these tests, as well as the possibility of disruptive voltage prediction has been always an objective of interest. This paper involved the rigorous statistical processing of a large number of recordings made during the testing of high-voltage insulator strings (with composite insulators and having rated voltage of 110 kV, 220 kV and 400 kV), fully equipped, using the up-and-down method. The aim was to describe the behavior of such equipment during lightning impulse tests, to know characteristic parameters of disruptive discharges, as well as to estimate the 50% voltage value based on previously recorded data, in order to reduce the number of voltage applications which do not provide relevant information.