A Detection Method for Double Line-To-Ground Faults in DC-AC Systems

The insertion of power electronics to control electrical drives is nowadays essential. However, the protection against electric ground faults is a difficult task. In this paper, a new method is developed to provide support to already existing single line-to-ground fault detection devices versus double line-to-ground faults, which can provoke malfunctions in these devices. The method is based on the voltage measurement in terminals of a grounding resistor placed in the midpoint of the DC side of a power converter and on the voltage measurement at the AC side phases. Analyzing the phasors’ phase differences or the DC behavior, the double line-to-ground fault location can be estimated. The method has been verified through simulations, obtaining satisfactory results.