Improving Voltage Profile and Loss Reduction Of Distribution Substation Using Capacitor Banks Case Study: Kotebe Distribution Substation

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Addis Ababa University


Electric transmission and distribution system are the intermediate stages in the transfer of electrical power from the central generating station to the consumers. Minimization of power losses and improvement of voltage profile are the most essential concerns of any electric utility to support increased load requirement. The voltage at buses reduces due to insufficient amount of reactive power in the network and consequently power losses increases. There are many numerous activities which have been tried to minimize distribution loss like upgrading MV and LV distribution conductors, taps changing and installing new capacitor. In this thesis work, optimal placements of the capacitors have been suggested. A methodology to determine the optimal capacitor locations and their sizes to improve voltage profile and to minimize the line loss of the distribution system has been developed. The study has been carried out on COTEBE Substation having 42 buses radial distribution system. The optimal capacitor placement is determined by the repetitive load flow to achieve the total minimum system loss. DIGSILENT Powerfactory software is used for Power flow analysis to determine the power loss and voltage profile of the system. The location of reactive power support allocation has been studied according to the highest reactive power flow which has been observed. Loss sensitivity method has been used to determine the optimal capacitor location. The results of the loss sensitivity are used for the optimal capacitor size selection. The proposed objective function is the minimization of the total investment cost due to reactive power support for loss reduction and voltage profile improvement. Different available capacitors values are used for the test cases, starting from 10KVAr to 10MVAr and the capacitor sizes of 2.2MVAr and 3.3MVAr are selected as an optimization solution. The selected test case result make that the total grid loss to decrease from 0.583MW to 0.413MW and the minimum voltage level to increase from 0.905(p.u) to 0.959(p.u). Due to this, the Ethiopian Electric Utility can save 26,132.33$ per annum with the payback period of Fifteen months.



Capacitor Placement, DIGSILENT Powerfactory, Loss Minimization, Voltage Improvement, Cost benefit analysis, Distribution Network in Ethiopia