DETERMINE ELECTRIC FAULTS IN ELECTRICAL ENERGY SYSTEMS WITHOUT GROUND CONNECTION USING A DIRECTIONAL ELEMENT.

摘要

Directional element for detecting ground faults in systems without grounding, comprising: means (30) when activated to calculate a null sequence impedance for a particular protected line, using a null sequence voltage and a current of null sequence in said line; an activation circuit that allows the operation of the calculation means under preselected null current conditions; and means (56, 57) for comparing the null sequence impedance values that come from the calculation means with the selected threshold values appropriate for systems without grounding, in which the means for comparing the null sequence are characterized in that a direct fault indication is provided when the null sequence impedance is above a first sensitivity threshold (26) and an inverse fault indication is provided when the null sequence impedance is below a second sensitivity threshold (28 ).