Comparison of transmission losses and voltage drops of GIL(Gas Insulated transmission line ) and overhead transmission lines Danish Khan, Muhammad Rafiq, Syed Furqan Rafique, Idris Khan and Farukh Abbas North China Electric Power University Beijing, China danishjadoon90@gmail.com Abstract—In a power system the loads are connected to the generation plants through transmission lines. The transmission lines are overhead and underground cables. From last forty years the new technology is included in the underground cable GIL. GIL has lot of advantages on underground cables and overhead transmission lines such as low transmission losses, less capacitive load, reliability, personal safety , same operation as overhead lines and with negligible electric aging. GIL can handle much more power than overhead lines due to his large conductor area. GIL is best for high voltages.GIL can be our future lines specially in big cities due to increasing population and size of big cities. In this paper the losses and voltage drops of same voltage rated overhead lines are compared to GIL lines. The simulation in PSCAD is done using the parameters of overhead and GIL lines of same rated voltages (230 KV, 345KV, 500KV, 765KV,1100KV) . The length of line is taken as 100km in both cases. The comparison graphs of percentage losses and voltage drops are plotted using MATLAB. Keywords—GIL(Gas Insulated transmission line), OHL(over head lines) I. INTRODUCTION GIL is best option for high voltages due to high power rating. Due to large area it can pass lot of current than overhead lines. The area is inversely proportional to the resistance. In this way the resistance of GIL is much more lower than overhead lines. The diameter of 500KV GIL is at about 500mm, and 1100KV GIL has diameter at about 760mm[1]. On the other hand in overhead line the kiwi code conductor with four layers has diameter at about 17.37mm and falcon with three layers has 15.91mm[2]. GIL power rating is much higher than overhead lines.The transmission losses of GIL are much lower than overhead transmission lines. To build a high voltage line is a difficult task due to public obstacles and Right of way. In future GIL lines can be installed over the long distances. The GIL in Japan is 3.25km is the longest GIL line[3]. Due to high installation cost GIL is not used over the long distances. II. CALCULATION OF LOSSES A. Calculation of overhead transmission line losses Simulation is done in PSCAD. Three phase circuit is taken having power measurements on both sides. The parameters are taken from below table 1. TABLE I. PARAMETERS OF OVERHEAD TRANSMISSION LINES Voltages level Line parameters per km Resistance per km Inductance per km Susceptance per km 230kv 0.050 0.488 3.371 345kv 0.037 0.367 4.518 500kv 0.028 0.325 5.2 765kv 0.012 0.329 4.978 1100kv 0.005 0.292 5.544 The voltage source, line parameters and load are simulated. The capacitors are connected on both sides because transmission line is taken as medium 100km line.The multimeters are connected for measuring power at sending end and receiving end.The parameters for 100km lines are taken for each of voltage levels.The result obtained from the simulation are following. 16th International Power Electronics and Motion Control Conference and Exposition Antalya, Turkey 21-24 Sept 2014 PEMC 2014 1151 978-1-4799-2060-0/14/$31.00 ©2014 IEEE