Dr.Sridevi Tirunagari born in India in 1978. she received B.Tech in EEE from Nagarjuna University in 1999, M.Tech in Power systems from Jawaharlal Nehru Technological University, Anantapur, India in 2005 and Ph.D from J.N.T.U Hyderabad India in 2016.She is working as assistant professor in GNITS Hyderabad.
For the power system overvoltage studies, modeling of frequency dependent transmission lines have been developed since the early 1970′s. Only a 3–Φ model, which includes coupling and impedance unbalance can accurately assess the effect of current injection unbalance . Modeling of transmission lines can be carried out in time domain analysis as well as in phase domain analysis. Highly accurate results can be obtained for overhead & underground cables from phase domain transmission line models . So, In the present work phase domain modeling was considered. For electrically short transmission lines, lumped parameters and nominal–π representation is sufficient to perform fundamental frequency analysis. When long line effects have to be included, distributed parameter concept needs to be considered to analyze higher order harmonic frequencies. A bundled conductor equivalent π model considering skin effect, utilizing Model transformation and Eigen value analysis, reduces the problems associated with cascaded π such as computational complexity, accuracy & storage. or frequency dependent transmission lines, a number of parallel impedance branches can be computed by the concept of complex depth with earth return. The evaluation of transmission line frequency dependent effects can be obtained by different methods. Previous methods need the solution of either Bessel function (or) infinite integrals. The calculation of transmission line parameters for wide range of frequencies with the help of infinite series (or) infinite integrals are associated with long simulation times. Longer simulation times triggered research into closed form solution methods which are based on complex penetration concept. The infinite series by using closed form solution methods reduces the time to converge. The effect of earth return may be included by adding a correction term. Earlier for the correction term, Carson′s equations [formed with the help of Maxwell′s equations and basic concepts of circuit theory] are used. Disadvantages associated with this are