Fault current calculation

Smart grid is an advancement of the existing electrical grid. The key feature of the future smart grid is the decentralization of the main power grid into number of smaller grids (known as micro grids). Interconnection of the distributed generating (DG) sources is required with the existing electrical grid to enhance the reliability of the power system. Extensive integration of DG sources within a smart grid causes failure of a successful implementation of smart grid due to the presence of enormous fault current. Superconducting Fault Current Limiter (SFCL) has the capability to reduce the fault current level within the first cycle of the fault current resulting in an increased transient stability of the power system. In this paper an application of a resistive type SFCL, designed in Simulink / SimPower System has been proposed to limit the fault current that occurs in an interconnected power system. A resistive type SFCL model has been developed in Simulink and the performance of SFCL at different locations has been analysed in the proposed system considering wind farm (10 MVA) as a distributed generating (DG) source with the conventional power plant, to reduce the fault current in micro grids. The feasible location of the SFCL having no negative effect on the DG source has been evaluated in three phase and single line to ground faults at various positions in the smart grid. Index Terms-conventional power plant, wind farm, micro grid, smart grid, superconducting fault current limiter, fault current.

Hybrid AC–DC networks are transforming high-voltage transmission and medium-voltage distribution grids by embracing the advantages of both AC and DC systems, which facilitates the inclusion of renewable energy sources and distributed generation. As modular multilevel converters (MMCs) are vastly employed in such hybrid networks, determining their maximal fault current in worst-case scenario is a critical design factor for planning and implementation of a reliable protection scheme. This study develops a novel mathematical framework that applies a Lagrangian energy method to calculate the maximal fault magnitude. This method allows to account for converter's internal energy and compute its impact on the amplitude of the fault current. It is shown when the converter is interfacing weak AC sources with high internal impedance such as wind farms or solar farms, dumping the internal energy of the converter into the fault is the salient contributing factor of the fault magnitude. Furthermore, to distinguish and classify the output overcurrent as either ignorable transients or destructive faults, a perceptron with sigmoid threshold is employed. The model is verified using a simulated medium-voltage hybrid AC–DC distribution network.

The consumption increase, generating capacities
and electric grid development in Moscow region and especially on Moscow-City territory in short-term and long-term perspective will lead to the short circuit current increase to ultrahigh values which exceed the disconnection capability of the serial equipment. The present article covers the issues of short circuit current limitation in megalopolis power system taking Moscow Power System as an example. The issues of consumers’ power supply reliability were considered. The foreign experience of short circuit current limitation in megalopolis was analyzed.
The system approach for solving this problem was proposed. The future recommendations for energy companies were developed.

Smart grid is an advancement of the existing electrical grid. The key feature of the future smart grid is the decentralization of the main power grid into number of smaller grids (known as micro grids). Interconnection of the distributed generating (DG) sources is required with the existing electrical grid to enhance the reliability of the power system. Extensive integration of DG sources within a smart grid causes failure of a successful implementation of smart grid due to the presence of enormous fault current. Superconducting Fault Current Limiter (SFCL) has the capability to reduce the fault current level within the first cycle of the fault current resulting in an increased transient stability of the power system. In this paper an application of a resistive type SFCL, designed in Simulink / SimPower System has been proposed to limit the fault current that occurs in an interconnected power system. A resistive type SFCL model has been developed in Simulink and the performance of S...