MODELING OF THE TURN OF HIGH VOLTAGE OVERHEAD POWER TRANSMISSION LINES WITH UNDERGROUND CABLE ON FOUR BUSES OF TRANSMISSION LINES FOR IMPROVEMENT THE VOLTAGE PROFILE ON THE SYSTEM (Case Study : Transmission Line 150 kV Region III Sub-system Yogyakarta)

Abstract

Design and operation of electrical power system, economic factor, environmental factor, security factor and reliability factor should considered. Some kinds of electrical power system criterions are voltage drop and power losses caused by peak load. In the study is done two simulations experiments on the transmission line 150 kV sub-system region III Yogyakarta with the help of ETAP power station 7.0.0 using the Newton-raphson method to known the performance of underground cable for improvement the voltage profile on the system.

The result of simulation showed average voltage drop on the system at 1.79% for the mounting 4 branches underground cable or after the turn of overhead lines. This value is smaller than the voltage drop  on the system without the underground cable is 1.83% so underground cable will contribute to the voltage and improvement the voltage profile on the system. Before the turn overhead lines with underground cable, the power losses and reactive power losses respectively 16.983 MW and 49.163 Mvar while after the turn of overhead lines with underground cable, the power losses and reactive power losses respectively 16.809 MW and 48.652 Mvar. Reduction of power losses and reactive power losses respectively 174 MW and 511 Mvar or in percent at 1.02% and  1.03%. The presence of underground cable, power losses on the branches will be smaller due to the supply of capacitive reactive power to the system.