ANALYSIS OF KATHMANDU GRID DIVISION AND INTREGATED NEPAL POWER SYSTEM WITH OPTIMAL PLACEMENT AND SIZING OF CAPACITOR

Abstract

The lower voltage of transmission system in the Integrated National Power System (INPS) has been a major concern for the Nepal Electricity Authority (NEA). The lower transmission voltage induces the lower voltage in the sub-coordinates (sub-transmission and distribution system) causing reduced voltage and overall higher system loss. The loss in the transmission system has increased from 4.35% to 4.51% in previous year. A total of 97.5km 132kV line and 182km of 220kV line in the FY2076/77 along with 72.5 MVAR of capacitor bank has been augmented in last couple of years. Though such appreciable effort, considering the system enhancement, has been done in the improvement of the transmission system, the problem is still existing. The main reasons for the existing problem can be: the higher increase in demand than the supporting infrastructures. So, this research aims to study the existing system during the system peak and perform an impact analysis in the system with the addition of the optimum sized capacitors in the optimum location for the voltage improvement and overall loss reduction. The study also emphasizes the economic aspect with the addition of the capacitors analyzing the various economic parameters. The sub-objective of the study also includes analysis of the loading status of the transmission lines in the Kathmandu valley. For the acknowledgement of system, the Electrical Transient Analyzer Program (ETAP) has been used as simulation tool. Adaptive Newton-Raphson has been used for the load flow and the Optimum Capacitor Placement (OCP) module inbuilt with Genetic Algorithm (GA) to determine the optimum placement and sizing of the capacitor banks. Moreover, a techno-economic analysis has been performed for the determination of the most suitable voltage level for the capacitor placement. From the analysis it has been found that the system suffers a transmission line loss of 4.16% in the system peak. Also, 6 optimum substations with the total reactive power of 80 MVAR needs to be added in the system for the energy savings of about 16.02 GWh per annum. The economic analysis shows that the implementation of the study has an is economically sustainable with the payback period of 5.97 years and 19.69 % Internal Rate of Return when the capacitors are placed at the most financially suitable voltage level i.e., 11kV determined from the results obtained.