Transient Stability Analysis Of Nigeria Power System: Multimachine Approach

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ABSTRACT 

The recent power sector reform in Nigeria has thrown up enormous challenges in this sector, ranging from the construction of more power stations, construction of new transmission lines and substations. The existing network of 8-plants and 26 bus-bars expanded to the proposed network of 16 generating plants with 49 bus-bars. This network expansion requires reappraisal for power evacuation capabilities, relay systems setting and establishment of stability margins for adverse system fault conditions on the network. Power flow evaluations of the existing and proposed 330KV networks were done using the Newton-Raphson technique. The transient stability analysis of the two networks was also simulated by direct method using ode45 MATLAB programmed functions. The critical clearing time of 0.21second and stability margin of 0.238 were established for a three-phase fault at bus 16, line 13 – 16 of the existing Grid. In the proposed  Grid, the critical clearing times and stability margins for three-phase faults at buses 3 (line 3 – 44) and 31 (line 2 – 31) were established as 0.21second, 0.238 and 0.29second, 0.448 respectively. The results provided a suite of specifications and standards for the proposed grid system. An algorithm for coherent generators was developed with which the 16 machines in proposed network were reduced to 13 machines system. The network reduction was carried out through coherent generators aggregation and construction of dynamic equivalents representing the aggregated generators. 

Key words: existing network, proposed network, power flow, transient stability, coherent generators, dynamic equivalents, clearing time, stability margin, swing curve

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