Operation of the Integrated Nepal Power System on Injection of the Upper Tamakoshi Hydroelectric Power Station

Abstract

The goalmouth of this dissertation is to develop operating models on the injection of the Upper Tamakoshi Hydroelectric power plant within the Integrated Nepal power grid. It gives a constructive idea to assist power grid system planners. It suggests the concept of regional and sub-regional control of an Integrated Network together with addressing transmission expansion plan for the long-term operation. The possible mapping of demand and supply management for power flow study based on the current real scenario is presented by taking necessary data from the Load Dispatch Centre and System Planning Department, NEA. Upper Tamakoshi Hydroelectric power plant, which is approximately one-third of the installed capacity of generated power, is going to operate in fiscal year 2077/078. An optimal evacuation of such a power plant of 456 MW requires a secure and reliable transmission grid for the stable operation of the integrated network. Nepalese power grid still has poor voltage supply and occasional system collapse due to insufficient and poor planning of transmission links. The proposed network of an integrated system is subjected to various analysis techniques for secure and stable operation including import and export scenarios with the optimum utilization of the generators by minimizing transmission loss. Especially, steady-state power flow analysis is conceded and simulated within the computer model to find out the most effective optimal operation. It identifies the finest optimal operating state by understanding the operation of the Integrated Nepal power grid and recommends a brand-new approach to the robust and reliable transmission line expansion plan for providing the national peak demand. Also, the integrated system can supply electrical power to the neighbouring countries. The results obtained from the predicted model for the different scenarios shows that the voltages of all major substations and line loading of all major transmissions lines are inside the set restrictions as prescribed by the grid code. Initially, almost all the 66 kV existing transmission line conductors displayed unstable voltage supply, but later on, has a stable voltage profile when existing conductors are replaced by the BEAR conductor. Also, it is recommended that using MOOSE conductor instead of DEER conductor for the 220 kV high voltage transmission line conductors for the stable and reliable operation. Mahendranagar, Ramnagar, Raxual, Dhalkebar, and Kusaha are the most central five, substations that are used for the cross border power exchange. About 135 MW power is exported to India through three cross borderlines. Among them, about 53 MW power through Dhalkebar 220 kV, 40 MW through Katiya, and 42 MW power through Ramnagar 132 kV substations are going to be delivering the power to Indian Grid. Kathmandu valley, Hetauda, Butwal, Duhabi Kholpur are the major load centers through which large electric power has been consumed. The overall analysis shows that the Integrated Nepal power grid has stable operation on clustering whole integrated system into three different zones, i.e. Eastern, Central, and Western zone, which are capable of self-generation and self-consumption. The largest central zone has the load demand of approximately 1125 MVA and also the smallest western zone has a load demand capacity of 100 MVA. Also, the eastern zone incorporates a load demand of about 385 MVA. This study has concluded that after injection of Upper Tamakoshi Hydroelectric power plant provides stable operation to the integrated network on improving system voltage profile. It advises power system planners to follow regional control for the long run operation after the injection of Upper Tamakoshi onward. Due to the synchronization difficulties, and transmission line infrastructures available, sub-regional control is essential for the stable operation of the power system network. Additionally, such a power control mechanism is significant for radial power exchange in the context of cross border power trade.