Abstract
Protection coordination of distribution network has been one of the issues with the distributed generators integration. The reason is that the distribution network is radial in nature by which energy flow is unidirectional. The research aim is to investigate how the location or placement of DG affects the protection setting of the existing network. The healthiness of the test distribution system used in this work is investigated with and without DG connection by use of load flow analysis using Neplan software. The results confirm that the location or placement of DG with the distribution system connection improves the voltage profiles at each bus and active power load loss. The DG placed 1km away from point of common coupling (PCC), the voltage profiles is 10.448Kv with DG connection, and 10.442kV without DG connection, while active power load loss is 69kW with DG connection and 71kW without DG connection. Also, DG placed 6km away from point of common coupling the voltage profiles is 10. 404kV with DG connection 10.372Kv without DG connection, while the active power load loss is 110kW with DG connection and 131kW without DG is connected. Moreover, with the DG placed 1km away from the point of common coupling (PCC) the fault current 17.596kA with DG connection and 3.286kA without DG connection, while 6km away from the PCC is 17.543kA with DG connection and 3.286kA without DG connection. It can be concluded that as the distance of the DG from the PCC increases, the fault current also increases which affects the protection scheme of the existing distribution system.
Highlights
The electric power system is generated from the generating station, transmit via a transmission station, to the power injection substations of the distribution network, and to the consumers
From the one-line diagram of the test distribution network in Figure 1, the distribution system is being fed from the Transmission Company of Nigeria (TCN) grid Alagbon with data of real power 17.362MW and reactive power 0.308Mvar connected to 33kV bus1
Figure 3: one-line diagram of the test distribution system with distributed generators (DGs) connected The load flow analysis results done on the test distribution network with or without DG connection to 33Kv bus3 of Fowler injection substation with 9MW load obtained from the Neplan software shows how the placement of DG affects the voltage profile, load loss, and the fault current of the distribution network when two-phase and three-phase fault are simulated into the network
Summary
The electric power system is generated from the generating station, transmit via a transmission station, to the power injection substations of the distribution network, and to the consumers. The distribution system is designed to extract power from the injection substations, supply the loads but not designed to have distributed generators DGs connected to it directly because of its unique radial or unidirectional flow of energy. The placement of DGs into the conventional radial distribution networks has an adverse effect on the coordination of the overcurrent protection relay between downstream and upstream overcurrent protective devices [2], [3]. Integration of the DGs into distribution system, the network will no longer operate as unidirectional but operate as bi-directional which will cause a loss of coordination among system over current protection schemes [4]. The main purpose of this research work is to investigate how placement or locations of DGs into the distribution network affects the protection schemes and to determine the fault current flow in the system
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