Dielectric Fundaments of k-Factor Function to Determine the Test Voltage of Lightning Impulses with Overshoot Used in the IEC 60060-1 and IEEE 4 Standards

The IEC 60060-1 (2010) and IEEE 4 (2013) Standards establish the k-factor function to determine the test voltage value of lightning impulses (LI) with superimposed oscillations. The test voltage function is included in these Standards to enable a more accurate and consistent determination of the test voltage and the time parameters, of LI with superimposed oscillations of any frequency content. The experimental k-factor function was determined by five research European institutes, but no dielectric fundaments were given to justify the k-factor function. This paper presents a specific study that was performed to validate the k-factor approach by checking its compatibility with the disruptive physic phenomenon. The same testing data used for determining the k-factor function for the air dielectric medium were used to determine the disruptive effect area model proposed by Kind in 1958. The results obtained ratify the compatibility between the k-factor function and the disruptive effect area model. The results presented in this paper are considered a valuable information for future research related to the test voltage k-factor function to improve the current International Standards.