Prospective Fault Currents in MVDC Distribution Grids – An Evaluation Methodology

Abstract:
Medium Voltage Direct Current (MVDC) grids are becoming increasingly feasible for the realization of decentralized distribution applications for electrical energy. This is mainly due to cost reduction potential through advances in power electronic technologies as well as grid operation and service advantages with respect to the integration of renewable energy generation. However, the technological penetration of distribution grids on the basis of MVDC technologies is still hindered by a lack of standardization and operational experience. Key elements in this regard are suitable protection equipment and protection strategies. For the adequate design and development of such protection systems, knowledge on prospective fault currents in MVDC distribution grids is necessary. Within this paper an evaluation methodology is presented, which aims at a comparable evaluation of prospective fault currents in diverse MVDC grids by introducing comparable fault current characteristic values. On the basis of these values, the derivation of a current envelope curve is proposed. To demonstrate the applicability of the evaluation methodology, exemplary investigations of fault currents in a simulation test grid are conducted.