Abigail Chidimma Odigbo1, Obinna Kingsley Obi2, Chinedu Chigozie Nwobu3, Kingsley Idiode4
1, 2, 3, 4 Nnamdi Azikiwe University, Awka, Nigeria.
Abstract
Distribution networks were originally designed to operate as passive radial systems supplied from a single upstream source, with protection and equipment ratings selected under the assumption of predictable and unidirectional fault current contribution. The increasing penetration of distributed generation (DG) has fundamentally altered these assumptions by introducing additional fault current sources within the feeder. This paper presents a detailed investigation of the impact of distributed generation penetration on short-circuit levels in the 33/11 kV Enugu Electricity Distribution Network, Nigeria. A comprehensive network model was developed in ETAP and analyzed using the IEC 60909 short-circuit calculation method. DG penetration was defined as the ratio of total DG capacity to feeder peak load and simulated at multiple buses. The results show significant increases in fault current across all locations following DG integration. For three-phase faults, current levels increased from 1.842 kA to 2.508 kA at 9th Mile (36.1% rise), from 2.655 kA to 3.254 kA at Agbani (22.6%), from 4.120 kA to 5.012 kA at Kingsway (21.6%), and from 5.240 kA to 6.120 kA at New Haven (16.8%). Single line-to-ground fault currents similarly increased by up to 35.8% at weaker buses. The findings indicate that DG penetration significantly reduces network short-circuit margins and may push existing equipment toward their interrupting limits. The study highlights the necessity of mandatory short-circuit assessment and location-sensitive DG evaluation prior to interconnection in active distribution networks.
Keywords: Distributed generation, Short-circuit analysis, Fault current, Distribution network, ETAP, Enugu distribution system
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