Browsing by Author "Salum, Salum Kombo"

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    Assessment of geomagnetically induced currents in the power grid system in Dar es salaam, Tanzania
    (University of Dar es Salaam, 2014) Salum, Salum Kombo
    The purpose of this study was to estimate the range of magnitude of GIC and its effect on the voltage in the power grid in Dar es Salaam, Tanzania. The data used in this study were real-time geomagnetic field components and recorded by a fluxgate-type magnetometer installed at the University of Dar es Salaam. The plane wave geoelectric field model was used to estimate the horizontal geoelectric field components during minor geomagnetic storms that occurred on 30th August and 08th November, 2009 and major geomagnetic storms that occurred 02nd October 2008,11th October, 2008 and on 04th February, 2009. This model was coupled with power grid coefficients to estimate the range of GIC at the Kipawa, Ilala, and Ubungo substations in Dar es Salam. The results show that the ranges of magnitude of GIC were between 3.71 ± 0.02 A and 11.31 ± 0.04 A for Ubungo substation, 8.21 ± 0.04A and 19.17 ± 0.07A for Ilala substation, and for Kipawa substation it was between 8.33 ± 0.04 A and 21.01±0.07 A. The corresponding fluctuations of voltage show that, Kipawa substation experienced a rise of voltage by as much as 2.50 % of the base voltage and a drop of voltage by 2.30 %. Ilala and Ubungo substations experienced maximum voltage rise of 2.05 % and 0.99%, and minimum voltage drop of 2.10 % and 0.93 %, respectively. In conclusion, these ranges of GIC are considered to be significant, and the level of fluctuation of voltage was highest at Kipawa followed by Ilala and Ubungo substation. These results suggest that, Kipawa and Ilala substations are at high risk due to relatively high level of GIC. It is recommended that future research should incorporate long term data to determine periodicity in storm occurrence and assess the effects of GIC through simulation studies. It is also recommended to design a mechanism to monitor, block and protect power grid systems from GIC impact.