AN ASSESSMENT OF TRANSMISSION CAPACITY CONTROL OF CRITICAL POWER LINES OF NIGERIAN GRID USING TCSC FACTS DEVICE

Abstract

Transmission capacity control has been one of the major challenges to the Nigerian transmission network resulting from its complexity and fast-growing power demands with limited expansion options from generation and transmission ends due to inadequate resources, environmental and political constraints. This has characterized some load buses with voltage instability and excessive line loading. In this research, the obtained system data of the Nigeria’s transmission grid were utilized to create power flow simulator (PFS) using a Power System Analysis Toolbox (PSAT) in Matlab/Simulinks environment to perform power flow analysis and voltage control across the Nigerian 330kV network. The PSAT deploys Newton-Raphson (NR) computation technique to test for steady state stability. The initial power flow simulation showed that some load buses experienced excessive voltage violations from the statutory limit of ±5 tolerance; these buses are Maiduguri (+16.3%), Damaturu (+13.1%), Gombe (+9.45%), Yola (+8.23%), B’Kebbi (–9.81%) and Sakete (–5.34%). Some critical transmission lines were identified to be excessively overloaded towards the southern part of the network – Benin-Sapele (159.39%), Delta-Sapele (131.66%), Afam-Alaoji (139.28%), Onitsha- Asaba (107.52%), Onitsha-Alaoji (103.84%), Asaba-Benin (101.42%), Benin-Onitsha (93.45%) and Benin-Omotosho (97.58%) transmission lines. The metrics considered in determining the critical lines on the network are thermal capacity, transmission capacity and power loss. Three case scenarios were used to test the performance of the network under steady state. Case 1 is when the troubled lines are reinforced with additional transmission lines, Case 2 is when the troubled lines are reinforced with Thyristor Controlled Series Capacitors (TCSC) FACTS devices, Case 3 is the integration of Cases 1 and 2. TCSC were deployed to the identified critical transmission lines in the network to regulate percentage line loading and voltage profile at these buses. The total power vii losses across the network were mitigated by 34.67%, 76.73%, and 77.97% in Cases 1, 2 and 3 respectively. Economic considerations were made for the proposed solutions and Case 1 is observed to be most technically viable and economically profitable; a payback of two years at a total profit of 212.18 billion Naira would be realized at the end of 2021. The return on investment (ROI) would be realized at the mid of the 3rd year.