APPLICATION OF THYRISTOR CONTROLLED SERIES CAPACITOR FOR PERFORMANCE IMPROVEMENT OF NIGERIA POWER TRANSMISSION NETWORK

Abstract

ABSTRACT The population and industrial growths coupled with the limited capacity of the power transmission grid in Nigeria has created a wide margin between electricity supply and demand, with attendant high power loss and voltage instability. The desire for efficient power quality delivery to electricity customers has led to emergence of flexible alternating current transmission systems (FACTS). This study examined the effect of thyristor-controlled series capacitor (TCSC), a series FACTS compensator, on the performance of the Nigerian 330 kV, 30-bus electric power transmission grid. The static response of power system without and with TCSC compensation was modelled using Newton-Raphson based load flow equations. The NEPLAN software was employed for the simulation of the system response without and with compensation. The voltage magnitudes and line loadings of the system were determined and compared with appropriate operating limits to identify possible violations. The system active power loss was also evaluated. The obtained resultsrevealedthatbefore the compensation, six buses which are Gombe,Kano, Jos,NewHaven,CalabarandOnitsha withvoltagemagnitudesof0.6608,0.8138,0.8141,0.9002, 0.9319 and 0.9466 p.u., respectively, violated statutory voltage limit of 0.95 to 1.05 p.u. The system overallactive power loss was219.08MW. TwobranchesOkapi-CalabarandAlaoji-Calabar also exceededthe recommended voltage-ampere limit of 80% with 101.69and 84.19 % loadings, respectively. The installation of TCSC in the system mitigated all thevoltagemagnitudeviolations with constrained bus voltages improved to 0.9715,0.9777, 1.0022, 1.0247, 1.0043 and 1.0312 p.u., respectively; the values which are now within the statutory limit. The overall active power loss of the system decreased to 174.06 MW, giving an improvement of 20.55% in the active line flow. However, Alaoji-Calabar branch with a loading of 80.61% was still overloaded. The installation of TCSC and an additional line across the branch further improved the overall voltage profile of the system and eliminated the line loading violations. The overall active power loss further reduced to 161.54 MW, leading to an improvement in the active line flow by 26.26%. The results showed that the combined use of TCSC and line expansion produced a better impact on the system bus voltage and power profiles along the transmission network. The compensation provided by the thyristor controlled series capacitor together with the line expansion improved the performance of the Nigerian electric power grid and system bus voltages.