A procedure to evaluate the risk of failure of distribution transformers insulation due to lightning induced voltages

The aim of the paper is to assess the risk of insulation failure of distribution transformers connected to overhead distribution due to indirect lightning induced voltages. The annual frequencies of occurrence of dangerous voltages are evaluated through a Monte Carlo procedure and by using the LIOV-EMTP code for the calculation of the Lightning Electromagnetic Pulse (LEMP) and its effects on the multiconductor line. The probability of distribution transformers insulation to withstand the stresses caused by lightning overvoltages is inferred from the results of experimental test.