Impact of the Arc Resistance Occurring in Short-Circuit Point on Success of Remote Backup Protection in 0,4 Kv Power Grids

0,4 kV grids play an important role in ensuring the functioning of industries and own needs systems of powerhouses and substations. Their reliable operation depends on sustainability of 0,4 kV networks. In considering grids there is an acute problem in maintenance of remote backup protection due to a significant decrease of fault current values moving away from power source. During the research of protection sensitivity assessment, the essential issue connected with influence of arc resistance occurring in a damage site on short-circuit current values is arisen. In the article the calculation both of symmetrical and asymmetrical fault through an arc currents is given considering remoteness from power source in the distributed grid of 0,4 kV with «delta-grounded wye» connection. Moreover, graphs of fault current dependence on transformer power and cable length and recommendations for the choice of considering short-circuit point for protection sensitivity testing are presented.