Dynamic Security Assessment On Ethiopian Existing Power Network

Power system security is an important issue in power system operation and hence the operationrnof a power system requires regular security assessment. However, presently dynamic securityrnassessments are not being performed on Ethiopian existing power network. Consequently, thernpower system operators do not have remedial action plans for various contingencies that mayrnoccur in the system.rnIn this thesis work, the dynamic security of the Ethiopian existing power network is assessedrnusing PSS/E software in off-line mode. The Ethiopian existing operational power network modelrnhas been extracted from the 2015 planning model and used for simulation studies. This model isrnvalidated by checking the models of each element one by one. In addition, the history ofrngenerators loading profile has been reviewed and their loading of April 11, 2017 at 19:45 o’clockrnresulting in the peak operational scenario is selected for the analysis.rnThe dynamic simulations have been performed considering sever short circuit faults at the 400rnkV and the 230 kV parts of the system and the outage of a generator at different power plantsrnone by one. The voltage at 132 kV buses like Awassa, Dilla and Boculuguma doesn’t recover torn0.9 pu within 10 seconds for all cases considered in the analysis. In addition, the Sudanesernsystem would be out of synchronism from the Ethiopian system for a short circuit fault on AkakirnII-Kaliti I 230 kV line even if the fault is cleared as per the actual protection setting provided thatrnthe total tie-line flow is above 148MW. These results confirm that the Ethiopian operationalrnpower network was operating at insecure operating point for the operation scenario considered inrnthe analysis.rnThe frequency response plots for outage of a generator at different power plants depict that thernfrequency returns near to the normal value despite the outage. This indicates that the primaryrncontrollers of the generators which are in operation are working properly; and the remainingrngenerators are jointly capable of covering the lost generation.rnReactive power sources like capacitor banks need to be installed in the Southern Region of thernsystem to improve the voltage profile. The generators need to be re-dispatched in such a way thatrnthe total tie-line flow is kept at 148MW and below to keep the Sudanese system in synchronousrnoperation with the Ethiopian system for the operation scenario considered.

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