Thesis (M.Eng.)--Chulalongkorn University, 2008

This thesis presents the development of two software programs, STPM and I-EMTP, for estimating the lightning outage rates of overhead transmission lines. Both programs apply the different methods for determining the critical lightning current required to cause a flashover. The STPM program uses a simplified two-point method, while the I-EMTP program gets the critical lightning current from the simulation with Electromagnetic Transients Program (EMTP). However, both software programs have the same procedure for calculating the outage rate with the obtained critical lightning current. The STPM program is easier to use and saves time, while the user of I-EMTP program must model the power system to simulate the critical lightning current which wastes time. However, it is easier to develop models in EMTP program for more accurate result. The STPM program is implemented to study the parameters that have effects on the lightning outage rates of overhead transmission lines, i.e. tower configuration, tower footing resistance, shielding angle, insulation level, ground flash density and probability distribution of lightning current.