Study and Analysis of Geomagnetic Induced Current in Ethiopian Electric Power System
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Date
2021-07
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Addis Ababa University
Abstract
In this master thesis the effect of GIC on Ethiopian electric power system is investigated using the power world simulator software and python coding.
GIC flowing in the transformers core lead to a higher magnetizing peak current, which produce a higher flux, that also contains a lot of harmonics. This leads to a large increase of eddy and circulating current in both windings and structural parts of the transformers, causing unnecessary heat generation. Such unnecessary heat generation causes tripping of transformers components like relays, SVC, capacitor bank controllers and burning of transformer sheet cores. GIC not only affect transformers but also affect transmission lines. The effect of GIC on power transmission lines is a high voltage drops at the receiving end due to the varied geo-magnetic and geo-electric field value.
The equatorial electro-jet magnetic field ( GIC Max-H and GIC Max-L) undergoes variability in the high latitude region of Ethiopia and low latitude region of Ethiopia. The equatorial electro-jet magnetic field value for high latitude region of Ethiopia is 192 nT and the equatorial electro-jet magnetic field value for low latitude region of Ethiopia is 100 nT. The GIC is propagated from 45 degree to 315 degree eastward in the high latitude region of Ethiopia and from 135 degree to 225 degree westward in the low latitude region of Ethiopia. It is also found that the percentage of GIC flowing in the transformers core is approximately 1000 percent greater than the rated peak magnetizing current of the transformers. And finally, a GIC value of 34kA is measured in the high latitude region of ethiopia. For this GIC value of 34kA, an 80 MVAR of reactive power is absorbed by a transformers located in high latitude region of Ethiopia.
The result showed that the Impact of GIC on transformers and transmission lines is severe in High latitude region of Ethiopia compared to the low latitude region of Ethiopia. The reactive power consumptions of transformers located in high latitude region of Ethiopia is high compared to low latitude region of Ethiopia. One of the primary reasons for such difference in reactive power consumption is that, the differences in the geomagnetic fields of the two region which is 360 T in high latitude region compared to 150 T for low latitude region. Therefore, it is recommended that EEP should re-arrange the position of the transmission lines and transformers with respect to GIC propagation to minimize the effect caused by GIC.
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Keywords
Geomagnetic Induced Current, Ethiopian Electric Power System