A Ground Fault Location Method for DC Systems Through Multiple Grounding Connections

Direct current (dc) systems have an increasingly important role in electrical systems, especially photovoltaic (PV) solar power plants and battery storage systems as they are essential for the development of more sustainable, efficient, and reliable electrical systems. PV panels and batteries are generally composed of multiple series-parallel cells. This fact makes their fault diagnosis challenging, especially against ground faults as these systems are generally ungrounded. In this article, a ground fault location method for dc sources with multiple series-parallel cells is proposed. It estimates the faulty branch, the faulty cell location inside this branch and its fault resistance. The method is based on the output current measurement of each branch and on the voltage measurement on a grounding resistor, which is switched between three positions: the positive, the midpoint and the negative terminals of the protected dc system. To validate it, several computer simulations and experimental tests on a battery pack have been carried out. The results obtained proves an excellent performance for faulty cell location and fault resistance estimation, although further investigations are required to better discern the faulty branch.